Horticulture – Page 25 – Naturehydro Horticulture Grow

Various types of markers have been mapped on the 1S arm of wheat and rye

The root biomass among these translocation lines ranked as follows: Pavon 1RS.1AL > Pavon 1RS.1DL > Pavon 1RS.1BL > Pavon 76. On the other hand, in Colorado, the ‘Amigo’ 1RS.1AL translocation from a different rye source in wheat cv. ‘Karl 92’, showed 23% yield increase under field conditions over its winter wheat check, Karl 92 . In 1RS.1BL translocation wheats grown in acid soils, roots were thinner and there was a higher root length density, and this likely enhanced the root surface area . The yield advantage of 1RS translocation lines may be partly attributed to the increase in root biomass that increases uptake of water and nutrients from the soil . To elucidate the mechanisms responsible for increase in root biomass in 1RS wheats, it is necessary to genetically map and identify loci responsible for enhanced root traits. The objective of this study was to develop a consensus genetic map of the 1RS- 1BS chromosome arms using a population of induced homoeologous recombinants, and subsequently use the genetic map to tag the 1RS chromosomal region responsible for increased root traits. Molecular linkage maps of cereals are being improved rapidly by adding new types of markers, merging different species-specific maps and comparative mapping of markers between related genomes. Efficient use of resulting dense maps requires detailed insights into the relationship between genetic and physical distances.PCR-based markers were developed for 1RS.1AL and 1RS.1BL wheat-rye translocations in wheat .

However,stackable planters these translocations have not been used extensively to generate consensus map of wheat and rye chromosomes which would be a useful tool to study different agronomic characters influenced by the presence of rye chromatin. Recombination mapping has an advantage over deletion-bin mapping in generating higher resolution maps. In deletion mapping, the number of available breakpoints, hence the number of bins, limits the resolution, and after the set developed by Endo there have been no further efforts to generate new breakpoints. In genetic mapping, resolution is limited primarily by the number of available markers, and these increase steadily. Another advantage of recombination mapping is the ability to study the genes on rye chromosomes, where, because of diploidy, it is difficult, if not impossible, to practice deletion bin mapping. In this study, using a set of recombinants, we generated a consensus map of 1RS-1BS that integrates physical and molecular markers and attempted to narrow the regions containing major QTL for root characteristics. Experimental material was provided by Dr. A.J. Lukaszewski, University of California, Riverside. It consisted of a set of rye-wheat recombinant lines in a nearisogenic background of bread wheat cv. Pavon 76. Pavon 76 is a spring hard wheat from the breeding program at Centro Internacional de Mejoramiento de Maíz y Trigo , Mexico. The set includes centric translocation 1RS.1BL in Pavon 76, where the 1RS arm is from cv. Kavkaz and 1BL arm is from Pavon 76 and a set of 68 recombinants of the 1RS arm with 1BS in Pavon 76 . 1RS-1BS recombination was induced by the absence of the Ph1 locus. All recombinants are single breakpoints; therefore, the short arm of each recombinant chromosome contains one segment of 1RS and a complementary segment of 1BS. Each recombinant has a normal 1BL long arm. Since they were produced by crossing over, they can be used to generate a genetic map.

However, since recombination in wheat is predominantly in the distal portion of each arm , physically, these recombination breakpoints cover only the terminal 40% of the arm’s length. A phenotyping experiment to study root characters was set up in the glasshouse in sand-tube cultures in PVC tubes, 80 cm long and 10 cm in diameter during 2006, 2007 and 2008. The study involved five lines: Pavon 76 and Pavon 1RS.1BL as the parents, and recombinants T-14, 1B+38, and 1B+2 . The three recombinant lines were chosen from the set of 68 lines to subdivide the recombining portion of the arms into three segments of roughly equal lengths. Seed of these five lines were surface sterilized with 5% commercial bleach for 5 min, washed for 10 min in distilled water, soaked in water for 24 hrs and then germinated on wet filter paper in Petri dishes. Five day old seedlings were transplanted to 80 cm PVC tubes containing 1 m polythene tubing, closed at one end, with 8.5 kg of silica sand #30. Two small holes were made at the bottom of polythene tube to allow drainage of excess water. The PVC tubes were supported in metal frames and arranged in a randomized complete block design with four replicates. Plants were harvested 45 days after germination when the differences for root characters could be efficiently measured among different recombinant lines. Data for different shoot characters were recorded and the tubes containing roots were stored at 4oC until processing. Roots were washed and recovered without damage using a floatation technique . The shoot characters measured were longest leaf length , maximum width of the longest leaf , leaf area , plant height , number of tillers , and dry shoot biomass .

The root characters measured were number of roots greater than 30 cm , longest root length , total length of roots greater than 30 cm , shallow root weight , deep root weight , dry root biomass , and root biomass to shoot biomass ratio . The shoot and root data were subjected to the analysis of variance for each year . The combined ANOVA across years was performed for each measured and calculated trait. The overall rooting ability of each genotype was calculated by ranking each genotype for individual root traits in each replication in each of the three years. Genotypes with the highest values were ranked 5 and those with the lowest values were ranked 1. Subsequently, all the ranks of root characters for each genotype were summed providing a measure of the rooting ability index for each genotype at different replications . The genotypic rank sums averaged across the years were subjected to the non-parametric Quade analysis developed for randomized complete block designs to differentiate genotypes for overall rooting ability. A calculative approach was used to generate a genetic map of the 1RS-1BS arms. The 1RS-1BS map from the previous study , based on twelve markers and 103 recombinants, was enriched by eight additional molecular markers and recalculated using 68 lines. The population of recombinants was divided into two configuration groups, 1B+ lines with distal 1RS, and T- lines with distal 1BS, comprising 34 lines each. Both groups were scored seperately for the presence/absence of each of the 20 markers, with the presence of a marker denoted as a score of 1 and the absence as 0. Each line was then ranked according to its total score for all markers and each group was further divided into 11 subgroups on the basis of its ranking. Thus,stacking pots the entire mapping population was divided into 22 subgroups . In this fashion, the 20 markers subdivided the genetic maps of the arms into 15 intervals . Phenotyping of recombinants was necessary to test the general applicability of the consensus 1RS-1BS map in locating a 1RS region showing better rooting ability. Various shoot and root traits were studied using two parents and three recombinants covering the whole 1RS-1BS map. There were significant differences among years for all shoot characters measured, except for the maximum width of the longest leaf . Significant differences were found among the genotypes for shoot characters, except for maximum width of the longest leaf and leaf area. Genotype × year interaction was significant only for the number of tillers per plant . This interaction was due to changes in the magnitude of the genotypic means across different years rather than changes in ranking of the means. Therefore, shoot characters in Table 2 are represented by means averaged across years. Pavon 1RS.1BL was taller, had longer leaf length and a greater root to shoot ratio than Pavon 76. Since Pavon 1RS.1BL and Pavon 76 had similar shoot biomass , greater root to shoot biomass ratio in the former genotype indicated greater root biomass in 1RS.1BL than Pavon 76 . Leaf area in 1B+2 was the highest followed by Pavon 1RS.1BL .

Despite significant differences observed among the genotypes for shoot characters, the differences were relatively small, except for the shoot biomass in 1B+2 in the third year which was due to greater number of tillers per plant and plant height . Otherwise, the rest of the genotypes did not show large differences for combined as well as for individual years for most of the shoot traits. There were significant differences among years for all root characters measured . Significant differences were found among the genotypes for all the root characters measured, except for longest root length. The genotype × year interaction was significant only for the number of roots greater than 30 cm. Therefore, means for root characters were averaged across three years . The number of roots greater than 30 cm and root biomass in Pavon 1RS.1BL were greater than those in Pavon 76 which confirmed the results reported earlier . Number of roots greater than 30 cm in Pavon 1RS.1BL, 1B+2 and 1B+38 were similar, but greater than those in Pavon 76 and T-14 . A similar trend was observed for the total length of roots greater than 30 cm. Shallow root weight was highest in Pavon 1RS.1BL followed by 1B+2 , and 1B+38 . The lowest shallow root weight belonged to T-14 . Deep root weight in Pavon 1RS.1BL, 1B+2, and 1B+38 were similar, but greater than those in Pavon 76 and T-14. Greater dry root biomass observed in Pavon 1RS.1BL compared to Pavon 76 was due to a combination of greater shallow and deep root weight in the former than the later genotype . Quade analysis was used to compare the rooting ability index of the examined genotypes based on the mean rank sums of root characters. The Quade statistic ranged from -11.0 for T-14 to 11.5 for Pavon 1RS.1BL . Differences among Sj were statistically significant at P< 0.10 . Pavon 1RS.1BL had the highest RAI followed by 1B+2 and 1B+38 . Pavon 76 and T-14 had the lowest RAI . Genetic mapping in wide hybrids has been performed for many plant species, particularly in diploids including barley , chickpea , lentils , onion , Nicotiana species , and tomato . In the early days of genetic mapping with molecular markers, wide hybrids were the approach of choice, for it guaranteed much higher levels of polymorphism than in intra-specific hybrids. Despite notable instances of non-Mendelian segregation and skewed distribution of recombination, wide hybrids produced useful genetic maps with higher marker saturation at considerably less cost and effort . Use of wide hybrids in allopolyploids is more complicated than in diploids as allopolyploids tend to have some kind of chromosome pairing control system in place that limits crossing over to homologues. Hence, homoeologous pairing may be low or even non-existent. In this study, 68 recombinants produced by crossing over were used. These recombinants were selected at random from a population of 103 such recombinants developed by Lukaszewski . The entire recombinant population was selected from a population of ca. 17,000 progeny with the Ph1 system disabled. If the assumption is made that crossing over in the Ph1+ and Ph1- wheats is the same, and they appear to be, except for the absence of multiple crossovers per arm then the sample analyzed here would be equivalent to a population of 136 back cross progeny, a sensible number giving the maximum resolution level of 0.7 cM. Physical distribution of 68 recombinant breakpoints used in the present study is shown in Figure 3. With a total of 20 physical and molecular markers, we constructed the combined genetic map of 1RS-1BS recombinant breakpoints in Pavon 76 background. The genetic map produced here has an average density of 2.5 cM. The maps shown in Figures 2 and 4 represent only the physical 40% of the distal ends of the 1S arms as no recombination took place in the proximal 60% of the arm. Any loci in this region would show complete linkage with the centromere.

These phenomena are further examined in the following sections

Several applications have been discovered, such as for wastewater treatment, fish farming, shrimp breeding, and hydroponics. These are further substantiated by Agarwal and coworkers , for such specific issues as the disinfection of infected surfaces, the degradation of organic compounds, and the disinfection of the water itself. The effects of increased yield of fish due to higher dissolved oxygen content are summarised by Endo et al. . The usage of hydrogen nanobubbles in gasoline to improve the calorific yield is also reported by Oha et al. . Other projected uses include the use of nanobubbles as contrast agents for the ultrasound imaging of tumours, as reported by Cai and co-workers, as well as reduction and removal of deposits of calcium oxalate, which is similar to the composition of kidney stones in rat kidneys, as presented by Hirose et al. Another application of the nanobubble’s ability to permit salts to crystallize is the design of self-cleaning membranes for desalination of water, which use nanobubbles as electrically conductive spacers and pass current through them to force the salts to crystallize on the nanobubble surface,nft channel which will permit easy removal of the accumulated salts. This was demonstrated and presented by Abida et al.

The pressure balance of the nanobubble is considered to be given by the Young-Laplace equation, which, as explained above, equates the internal pressure, external pressure and the surface tension. The first of the four forces that we consider in the Young-Laplace equation is internal pressure. It is proportional to the surface area of the nanobubble, and is assigned a positive sign since it acts to increase surface area. The second is the external pressure, given by the hydrostatic pressure acting on the surface of the bubble, which also decreases the surface area and is negative. The third is the surface tension, which acts along the surface area at the molecular level. The surface tension acts to decrease the surface area, hence the radius and size, and can also be assigned the negative sign. However, a fourth force which is thought to be integral to the stability is the electrostatic repulsion between hydroxide ions adsorbed to the surface of the nanobubble, or, possibly in the cloud surrounding the surface. This repulsion seeks to reduce the contact between the ions on the surface of the bubbles, which also acts to increase the distance between the ions, thus increasing the surface area, and therefore results in a positive pressure. The nature of the interaction between ions can be characterized by the expression for Coulombic repulsion. Since one hydroxide ion is of the order of 1 nanometre in diameter, and most nanobubbles are two orders of magnitude greater in size, we can ignore the curvature of the distance between them and take it to be linear.

The repulsion should, in theory, affect all neighbouring hydroxide ions, but is assumed to be insignificant beyond the nearest neighbours. We also assume the spatial arrangement of these ions over the surface to be close-packed in nature, since the repulsion is equal in all directions, and they would ideally assume a close-packed formation. This arrangement of ions is shown schematically below, in Fig. 1a, and as shown in Fig 1b it is assumed, due to close-packing, that they assume the formation of a rhomboidal unit cell, of side and diagonal length denoted by x, which will be referred to subsequently as the inter-ionic distance. That the nanobubble shrinks due to outward diffusion of the gas contained within is, of course, undisputed, but the precise methods and the rate of diffusion are highly debated. Previous theoretical studies have always assumed a model with a higher mass transfer coefficient, or longer time scales for the process to account for the reduced rate and the high lifetime of the nanobubble. However, it is reasonable to suggest that the change in the rate of diffusion can be attributed to two things: the velocity due to the Brownian motion of the nanobubble, and the inhibition of the diffusion due to the adsorbed hydroxide ions on the surface. In this chapter, the possible effects of Brownian motion are examined for the effect on the rate of diffusion that they may possess. Earlier studies have shown that nanobubbles can be formed by supersaturation, where the solubility limit of the gas, when surpassed will permit the gas to precipitate and form bulk nanobubbles as reported by Matsuki and co-workers .

The shrinkage of nanobubbles has so far been thought to be governed by Fick’s Laws, since it is a case of how fast the gas can dissolve into the surrounding fluid. Thus, according to the first law, it must be directly proportional to the outward gas flux, but the constant is still the diffusion constant D0 for the diffusion of the gas into water. However, this only holds true where the surface area of the nanobubble remains constant. It is, however, possible, that the outward diffusion is a case of Fick’s second law, since the surface area that is available to the gas to diffuse outward also changes according to size, and that this surface area determines the rate of shrinkage and thus the lifetime of the bulk nanobubble. It is then reasonable to suppose that the cause of the change of surface area available for diffusion is the change in the surface area occupied by hydroxide ions combined with the decreasing radius of the bulk nanobubble. The rationale for the assumption that the hydroxide ions adhere to and are released the nanobubble surface is based on two observations, as mentioned before. Firstly, the observation that all interfaces formed by water are negatively charged, and we consider nanobubbles to be a special case of a gas-water interface which may be charged in the same way. Secondly, the zeta potentials measured for nanobubbles are all negative, indicating that a negative ion present in pure water is responsible for the negative charge, which by elimination is the hydroxide ion. Further observations also indicate higher negativepotentials for more electronegative gases, such as oxygen and nitrogen, than for other reported gases such as argon and xenon as reported by Ushikubo et. al.. That nano- and micro-bubbles release hydroxide ions as they shrink is a well-known phenomenon. The stabilization and the shrinkage can be considered to be related to the same phenomenon; thus, the ideal case can be taken to be a nanobubble that is newly formed with no hydroxide ions at the surface at the instant of its formation of an interface. Here, the hydroxide ions present in the water immediately surrounding the bubble, in the hydrodynamic layer, adhere almost instantaneously, the time taken for the adsorption to occur being too small in comparison to the overall timescale to be important. As a concentration gradient is then formed between the water layers at the nanobubble surface and the bulk fluid,hydroponic nft more hydroxide ions begin diffusing from the bubble through this diffusion layer to the surface of the bubble. The thickness of this layer can be found by Prandtl’s equation, where the fluid velocity is the velocity of the Brownian motion of the bubble as predicted by the Langevin equation, using the Ornstein-Uhlenbeck process. The same layer also acts a diffusion region for protons, which diffuse in from the bulk layer once they are depleted or their concentration changes, and must also be affected by the distance they must diffuse through to reach the nanobubble surface.At the same time, protons from the diffusion layer also reach the hydroxide ion-rich surface, but much more slowly, at a rate about five times slower than the hydroxide ions. Upon reaching the surface, they start eliminating the hydroxide ions into water molecules, which further increases the dilution of both ions, and encourages diffusion from the bulk layer to the interface, which is probably a monolayer.

When the three processes, of hydroxide diffusion, proton diffusion, and hydroxide elimination by protons, are in steady state or in dynamic equilibrium, we have a fixed amount of area which is not covered by hydroxide ions, however temporarily and will allow the diffusion of gas into the water. Taking an average, we can define a percentage of surface area of the nanobubble, which will remain available for diffusion, which will be in proportion to the radius of the bubble. This can be done by taking the size of one hydroxide ion, then finding the capacity of a nanobubble’s surface to adsorb hydroxide ions, correlating it with the number of ions being eliminated, and taking a ratio with the capacity which is a function of area, which is a function of radius. The rate at which the adsorption of the hydroxide ion takes place would then depend on two separate phenomena: firstly, the repulsion by the hydroxide ions already physisorbed onto the surface, which would force the ion to move along the surface until it finds a location that is unoccupied, and secondly, the velocity of the hydroxide ion as it travels through the hydrodynamic layer of the nanobubble. The velocity can be found by calculating the surface charge on the nanobubble, and using it and the initial distance between a particular ion to find the potential that drives it to move. The potential for the hydroxide ion to move to the nanobubble surface decreases as the surface charge increases, and thus the rate will eventually dwindle down to zero as the bubble achieves stability, and the potential will reach a constant value. The rate for the elimination of the physisorbed hydroxide ions, on the other hand, will only increase the surface charge density increases, since the elimination is accomplished by positively charged protons attracted to a negatively charged surface. The same equations for ionic mobility can be used to calculate the velocity of travel for the protons, but there is no equation needed for the rate of adsorption, as they simply react with the adsorbed hydroxide ion to give two molecules of water. The balance between these two rates thus depends on the time at which the reactions are taking place, which will ultimately determine the area needed for the diffusion of the gas into the water. To find the ion mobility, we first consider an ideal case where a newly-formed and shrinking bubble has no hydroxide ions physisorbed onto its surface, and is formed in pure water with a pH of 7. This gives us, assuming a perfectly uniform distribution of ions in the water, a concentration of 10-7 moles of hydroxide and protons each in the surrounding hydrodynamic layer. Thus, the amount of both available to be physisorbed can be found by simply taking a section of the hydrodynamic layer up to the distance from the surface where we wish to find the concentration and time needed to reach the surface for the ions present at that distance from the surface. We take the volume of this section and multiply by molarity and Avogadro’s number to get the actual number of ions present, as shown below. In the derivation of the force balance presented in section 3.2, the formula takes into account the contribution of the repulsion between hydroxide ions adsorbed to the surface of the nanobubble. This section estimates the number of the ions adsorbed to the surface of the nanobubble, and uses the terms associated wit their arrangement to calculate this contribution and to examine the possibility that they can, indeed help to balance the inward and outward pressures exerted on the nanobubble surface and thus provide an explanation for their stability. Both possibilities of stationary and nanobubbles in motion are assumed and calculated to provide estimates for the repulsive force, and are substituted along with representative values in the derived equation for the force balance, and the result is presented. However, the stationary nanobubble is an ideal case, and in actual situations the bulk nanobubble is usually in motion due to Brownian motion, which also prevents it from rising to the surface. Thus, it can be established that the bulk solvent for a bulk nanobubble in motion, only consists of the boundary layer that moves with the nanobubble as it moves through the solvent. It also must supply the ions needed to stabilise it, and must contain the ions that are adsorbed.

The fraction of NO converted to N2 increases with the increase of reaction temperatures

The BJH average pore size initially increases with the increase in time, but decreases with prolonged activation. Prolonged activation results in an increase in burn off. The BJH average pore size of rice hulls char activated at 600°C was 25.1 A, 67.1 A, and 45.1 A with an activation time of 0.5 hr, 1.0 hr, and 2 hr, respectively. It is imperative that the larger the BET surface area and the larger the BJH cumulative pore areas, the higher the adsorption efficiencies must be. Typical BJH adsorption cumulative pore areas for different samples are shown in Fig.3. From the graph, it can be inferred that activated carbon made from rice hulls has a large BJH adsorption cumulative pore area, close to that of coconut shell , but significantly larger than two other biomass samples shown. Because of the superior surface area and average pore size measured for rice hulls activated carbon than those of wheat straw and peanut shells, this study concentrates on rice hulls carbon. Optimal pyrolysis and activation temperatures and times for carbon preparation were determined based on the amount of NOx that can be adsorbed by the activated carbon. The adsorption capacities of rice hull activated carbons generated by different pyrolysis and activation temperatures are shown in Fig.4.

A simulated flue gas containing 250 ppm NO, 5% O2, 10% CO2,maceta de plastico cuadrada with N2 as the balance was passed through the tubular reactor containing 2 g of activated carbons at a flow rate of 250 ml/min at 25°C. It is evident from the plots that the NO removal efficiency increases in the order of RH-2- 300-1-350, RH-2-400-2-450, RH-2-500-1-550, RH-2-600-1-650, RH-2-700-1-750, and RH-2-800-1-850. Activated carbon derived from the highest tested pyrolysis and activation temperatures exhibited the best adsorption efficiency. The better adsorption efficiency is attributed to higher micro-porosity obtained at higher carbonization temperatures. But samples carbonized above 700°C have a higher burn off rate than those carbonized at lower temperatures. In order to obtain a better production yield of activated carbon, 700°C and 750°C for pyrolysis and activation, respectively are chosen as optimum for the preparation of rice hull activated carbon. The NO adsorption efficiencies of samples carbonized by differing pyrolysis and activation times are shown in Figure 5. It is evident from the plots that activated carbons carbonized by prolonged pyrolysis and activation times have better adsorption efficiencies than those carbonized by shorter times due to higher pore count and BET surface area. It can be seen from these figures that the micropore count and the surface area of activated carbon increases with longer preparation time, thus explaining why the samples with the longest pyrolysis and activation times have the best adsorption efficiencies. However, prolong activation results in more burn off and the production of ash.

A balance must be reached when setting reaction parameters; one that will generate the largest surface area without a significant burn off. We found that the optimal pyrolysis and activation times are two and one hour, respectively. The removal efficiency of NO by carbon was studied at various temperatures: 10°C, 100°C, 300°C, 400°C, and 500°C. A gas mixture containing 250 ppm NO in N2 was passed through a column of carbon with a W/F of 15.4 g-min/L. Fig.6 shows that NO removal efficiency decreases with increased temperatures, when kept below 100°C. However, further increases in temperature beyond 100°C reversed the course, causing an increase in NO removal efficiency. This phenomenon is attributed to the reduction of NO by activated carbon, which results in the formation of nitrogen gas. The results from this set of experiments indicate that at the condition of W/F employed, NO can be completed reduced to N2 at temperatures equal to or above 500°C, while only some of the inlet NO is reduced to N2 at temperature below 500°C.It is expected that the high temperature flue gas will be cooled down before passing to the carbon bed to avoid the combustion of carbon due to the presence of flue gas oxygen. This cooling down results in the condensation of water vapor. Flue gas can contain up to 3.0 % v/v H2O even after cooling down to room temperature, thus it is important to study the effect of water vapor on the removal efficiency of NO by carbon. Fig. 8 shows that moisture causes a significant decrease in NO removal efficiency by carbon.

The more water vapor present in the flue gas, the lower the NO removal efficiency exhibited. This is due to the fact that water vapor competes effectively with NO for the adsorption sites on carbon particles. The detrimental effect of water vapor on NO adsorption can be overcome by the removal of water vapor either by drying agents or by cooling flue gas to low temperatures prior to adsorption. The adsorbed NO can be desorbed from activated carbon if temperature of the carbon bed is raised. Further increases of temperature results in the reduction of NO by activated carbon to produce N2. Simultaneously, the activated carbon is regenerated as a result of the reduction of NO to N2. Experiments on the reduction of the adsorbed NO by the activated carbon were performed by heating the NO saturated carbon under anaerobic conditions. In order to evaluate the behavior of the process over time, a purge gas flow of 1.0 L/min N2 was passed through the carbon bed and subsequently directed to the NOx analyzer. Desorption was conducted with a temperature ramp rate of 40°C/min from room temperature to 600o C. As the temperature of the carbon bed was increased, NO was desorbed from the surface of the activated carbon. Further increase of the temperature results in the reduction of NO by the activated carbon to N2. The fraction of the adsorbed NO that is reduced to N2 can be calculated by subtracting the NO coming out of the carbon bed from the total amount of NO adsorbed. The fraction of the adsorbed NO that is reduced depends on the temperature and the flow rate of N2 gas. Fig.10 shows the fraction of the desorbed NO integrated over the temperatures as the temperatures of the carbon bed was raised. As can be seen, the fraction of the total NO desorbed as NO reaches the maximum at 550°C and that this fraction was less than 100% of the total NO adsorbed, the difference of which being attributed to the reaction of NO with the activated carbon to form N2. The fraction of the adsorbed NO desorbed as NO is 48.2% in the case when NO adsorption was done without the presence of H2O vapor, and 64.5% in the case when NO adsorption was performed with 2% H2O. This result indicates that NO reduction by activated carbon is inhibited by the presence of water vapor. Water vapor can compete with NO for the reaction with activated carbon. From the desorption curve as a function of temperature, the NO desorption mainly took place at temperature below 300°C, while the NO reduction by carbon occurred at temperature above 300°C, the higher the temperature the more effective the reduction is. Since the ramp rate was 40°C per min., it would take 7.5 minutes to raise from 300°C to 600°C, the temperature range when most of the NO reduction takes place. During the 7.5 min. time interval, about 50% of the adsorbed NO was reduced to N2. Consequently,fabrica de macetas plasticas it can be concluded that the complete reduction of NO to N2 at 550°C can be done within 15 minutes in a closed system. Another set of experiments were performed to study the reduction of NO by activated carbon as a function of temperature and W/F, the ratio of the amount of carbon to flow rate of N2. In this study, temperatures were varied between 300 and 550°C and W/F between 10 and 40 g.min/L. Fig. 11 shows that with a feed gas containing 250 ppm NO with the balance N2, the fraction of NO reduced by activated carbon increases with the increase of temperature at a given W/F, and the fraction also increases with the increase of W/F at a given temperature.

All of NO was reduced to N2 at 550°C with a W/F above 20 g.min/L, and at 500°C with a W/F 40 g.min/L. It would require a W/F larger than 40 g.min/L to convert all of NO to N2 at temperature below 500C. The NO reduction efficiency also depends on the concentration of NO in the system. Fig 12 shows NO reduction at 500°C for two inlet NO concentrations, 250 ppm and 1000 ppm. As can be seen, higher inlet NO concentrations cause less fraction of NO to be reduced. Only 55% of inlet NO was reduced at 500°C with an inlet NO concentration of 1000ppm and a W/F of 40g.min.L-1. Experiments were conducted at room temperature using rice hull activated carbon to determine at what conditions it would prolong efficient adsorption of NO and that outlet concentrations would be less than SMAC . The principle variables manipulated were inlet oxygen concentration, ranging from 5% to 20%, and weight to flow rate ratio , ranging from 15 to 45 g.min/L . The time that the carbon bed can hold before the NOx concentration exiting the bed exceeds the SMAC, will be called SMAC time. Fig.13 shows SMAC time at different oxygen concentrations. The SMAC time increases along with increases in O2 concentrations. The SMAC time was longer than 6 hours with oxygen concentration of 10% and W/F of 45 g.min/L, while about 10 hours were obtained with an 15% oxygen and W/F of 45 g.min/L. As previously mentioned, oxygen presence enhances NO adsorption, thus allowing the SMAC time to be longer. Increasing W/F, especially above 20g.min/L, also increases the SMAC time. Experiments were conducted to determine the effects of the regeneration on activated carbon in terms of NO removal efficiency, as assessed by the carbon’s SMAC time. Fig.14 shows the SMAC time after different numbers of regeneration cycles. The results indicate that regeneration improves the removal efficiency of NO. This phenomenon is attributed to the increase of surface area and micropores of the activated carbon. However, it was observed that additional carbon burns off occurs during regeneration, which causes the overall amount of activated carbon to decrease after each regeneration cycle. The loss of mass was determined to be about 0.16% of activated carbon per cycle of regeneration. The SMAC time was 163 minutes and 372 minutes for the first and the 8thcycle run, respectively. The larger the activated carbon adsorption efficiency, the longer the SMAC time will be. The production and use of carbonaceous nanomaterials , including carbon nanotubes and graphene, have rapidly increased.Annual global production of CNTs has attained several thousand metric tons,1 and graphene production is predicted to exceed 1000 metric tons annually by 2019. Once released into the environment, CNMs may accumulate in soils.CNM-containing bio solids are applied to agricultural lands,while CNM containing products are used both to remediate soils and to fertilize and protect crops.Given the potential for terrestrial plant and herbivore exposures, there is a need to understand hazards of CNMs to crop plants.Thus far, widely varying effects of CNMs on plants have been reported,possibly owing to disparate study conditions including types and concentrations of CNMs, plant species and developmental stages, toxicity metrics, and exposure conditions. Hydroponic conditions have been used to study CNM effects at relatively high CNM concentrations .However, fewer studies simulate field conditions including using CNM concentration ranges that are predicted to occur in soils.Many complex soil components can interact with CNMs and thereby affect CNM bio-availability.Therefore, dose– response relationships for soil-grown plants cannot easily be inferred from hydroponic study results.To assess CNM hazards to agricultural plants, more soil-based research using a wider range of CNM concentrations is needed. In agricultural settings, plants not only root in the complex environment of soils, but plants also develop over time, including the maturation of root symbioses. Some CNM phytotoxicity studies have emphasized acute toxicity on seed germination and seedling growth.However, while such phytotoxicity assays offer the convenience of being standardized, they are performed over exposure periods that are too short to assess full agricultural impacts and are relatively insensitive for indicating nanotoxicity.

How To Make Drainage Holes In Plastic Pots

One must also consider the potential for the formation of metabolites and the consequences of exposure to all non-target organisms in order to better understand the fate and risks of CECs in terrestrial environments. The results have potential implications for policy makers and other stakeholders attempting to assess the risks for the land application of treated wastewater and bio solids.The results presented in this dissertation suggest the highly chemical-, species-, and research technique- specific nature of the environmental fate of CECs. For example, cell cultures often form amino acid conjugates while whole plants form sugar conjugates during xenobiotic metabolism. The differences in CEC metabolism imposed by treatments or species warrant further investigation. Additionally, more toxicological data are needed on the effects of these and other compounds in terrestrial invertebrates, especially for those of agricultural importance. From the research conducted in this dissertation, future research should focus on the impacts of exposure and the potential for transformation of CECs under different conditions and in multiple species. Future studies should place emphasis on experimentation using bio solids and TWW with inherent compounds and field conditions to improve environmental relevance.

Future risk assessments should be conducted by taking into account the formation of biologically active and conjugated metabolites,arandano azul cultivo and with regard to the potential toxicity of CECs in non-target terrestrial organisms. Excessive soil salinity is an important constraint limiting the distribution of plants in natural habitats, and is an increasingly severe agricultural problem in arid and semi-arid regions . In Tunisia, the arid Mediterraneanan bio-climatic regions are frequently irrigated with water leached in salt. Consequently, about 10% of the whole territory area and 20% of the cultivated lands are salinized . Enhancing salt tolerance in plants has major implications in agriculture. Salicylic acid is now considered as a hormone-like endogenous regulator, and its role in the defence mechanisms against biotic and abiotic stressors has been well documented . SA has been suggested to be physiologically important in stress tolerance since exogenous SA brought about plants tolerance to various abiotic stress including drought and salt . The ameliorative effects of SA has been well documented in inducing salt tolerance when applied as a soil drench in bean and tomato, addition to hydroponic culture in tomato, and seed treatment in tomato and barley . The aim of this work was to study the responses of growth and mineral nutrition in tomato plants, cv Marmande to the interactive effects of salicylic acid 0.01 mM and NaCl treatment 100 mM. But this reduction was suppressed when adding SA 0.01mM to the culture medium.

Salicylic acid-treated tomato plants exhibited an increase in tolerance to salt treatment. In fact, exogenous applied SA increased dry weight of the 3 organs significantly both in saline and non-saline conditions. In saline conditions, with the applicatoin of SA , dry yield increased almost up to the yield obtained from the non-saline control treatment. We observed stimulation of about 38% compared to the control medium. The improvement of the tolerance to salt by SA can be related to two factors: the stimulation of the activity of growth of the roots and the attenuation of the depressive effect of NaCl on the shoots. Salinity decreased leaf area of tomato plants significantly . The reduction was about 80% at the 5 stage and 40% at the 3 stage. Exogenous applied SA increased leaf area significantly both in saline and non-saline conditions. At the 5 stage, we noted stimulation about 63% in the leaf area compared to the control medium. Salinity treatment significantly affected total chlorophyll contents . Whereas, the addition of SA in the culture medium induced a significant increase in this parameter . The stimulation was about 50% compared to the plants treated only by NaCl 100 mM. Tomato , one of the important and widespread crops in the world, is sensitive to moderate levels of salt in the soil. So many authors have reported large variation among tomato genotypes in their response to salinity. The salt concentrations we have used are within the range found in water used for irrigation purposes in regions with a Mediterranean climate . This salt concentration caused significant reductions in all growth parameters , so Marmande was considered as a sensitive variety to salt.

This reduction of growth does not relate to the roots, but is explained by the strong sensitivity to salt of the aerial parts. Similar results were found in the tomato varieties Marmande and Rio Grande . Salinity stress results in a clear stunting of plant growth, which results in a considerable decrease in the dry weights of leaves, stems and roots . The immediate response of salt stress is reduction in the rate of leaf surface expansion leading to cessation of expansion as salt concentrations increases . Our results showed a significant decrease in leaf area of tomato plants. The reduction was about 80% at the 5 stage and 40% at the 3 stage . Salinity stress also induced a reduction in total chlorophyll contents . The decreased in chlorophyll content under salinity stress is a commonly reported phenomenon in various studies, because of its adverse effects on membrane stability . The chlorophyll contents of leaves of different tomato cultivars decreased by NaCl stress . Under salinity stress, leaf pigments, studied in nine genotypes of rice, reduced in general . The development of methods and strategies to ameliorate deleterious effects of salt stress on plants has received considerable attention. Salicylic acid has been shown as an important signal molecule for modulating plant responses to environmental stress . Exogenous application of SA may influence a range of diverse processes in plants, including seed germination , ion uptake and transport , membrane permeability , and photosynthetic and growth rate . In addition to facilitating the growth of plant, SA has been shown to play a role in mitigating the deleterious effects of some environmental stresses including low temperature, salinity, and cadmium stress . Our results showed that exogenous application of SA through the rooting medium had an ameliorative as well as growth promoting effect under both non-saline and saline conditions . It was shown in a previous work that 0.5 mM of SA added in the hydroponics solution of maize increased its tolerance to salt stress . Dhaliwal et al. attributed this amelioration in growth production to an increase in photosynthesizing tissue of leaves. This was in agreement with our results. In fact, application of 0.01 mM SA through the rooting medium increased pigments chlorophyll in salt stressed plants . This effect of SA application on photosynthetic pigments was expected in many studies that showed increased or decreased photosynthetic pigments following SA application, depending on type of species . Greenway and Munns suggested that the susceptibility of many glycophytes to salt is due to an insufficient ion supply. Indeed, in tomato, salt reduces K+ supply and induces Ca2+ and Mg2+ deficiency . Salt has a depressive effect on the whole plant growth of Marmande. Tomato plants grown in the presence of NaCl accumulated large amounts of both Na+ and Cl- ions . In the other case, the presence of salt in root medium causes disturbances in the essential mineral nutrition of the plant. NaCl severely reduces K + , Ca2+, and Mg2+ uptake and translocation from roots to shoots . Consequently,macetas 25 litros selectivity in favour to potassium decrease with salinity . Whereas SA addition ameliorates this parameter. In fact, at salinity level 100 mM NaCl, the K/ ratio in leaves was equal to 0.38. Applied SA in the culture medium significantly decreased the Na+ and Cl- concentrations in saline conditions. Whereas K+ , Ca2+, and Mg2+ uptake increased with the addition of SA in saline medium.

Thus K/ ratio was enhanced when adding SA 0.01mM to the saline medium . Thus SA ameliorate the aptitude of whole plant to ensure a sufficient supply K + by maintaining a high selectivity for this essential nutriment, in spite of excess of Na+ in the medium. This result is in agreement with those of Gunes, et al. , who demonstrated that salicylic acid strongly inhibited Na and Cl accumulation, but stimulated N, Mg, Fe, Mn, and Cu concentration of stressed maize plants. According to these authors, the increase in dry matter content might be attributed to the increased mineral uptake by stressed plant with SA. Furthermore, it has been reported that SA applications increase carbon dioxide assimilation and photosynthetic rate, thus increasing dry matter . This improvement in growth yield might also be related to the effect of SA on membrane permeability. The cellular membrane dysfunction due to stress is well expressed in its increased permeability for ions and electrolytes which can be readily measured by the efflux of electrolytes . NaCl treatment induced significant increases in electrolyte leakage in tomato plants compared with the control . Similar results were obtained by Lutts et al. who reported that salinity increased the membrane permeability of sensitive rice varieties. Addition of salicylic acid in the culture medium decreases permeability of membrane in salt treated plants . This agrees with the findings of Stevens and Senaratna who demonstrated that SA application reduced electrolyte leakage by 44 and 32% in tomato plant growing respectively under 150 and 200 mM NaCl, compared to untreated plants. One important strategy of several species to tolerate salinity was to use NaCl as an osmoticum and to compartmentalize the Na+ and Cl- ions primarily in the leaf vacuoles. The appreciation of the capacity of plant to compartmentalize the Na+ in the leaf vacuoles was possible by correlating the water contents of the leaves with the Na+ contents of these organs . The data in Figure 5, correlating leaves water content with its Na+ content, showed that the presence of salt in the medium induce a sodium accumulation in the photosynthetic organs of tomato.As an essential macro-nutrient for plant growth and development, potassium nutrient status in soils has direct consequences on crop yield and quality . Since soluble K+ in most arable fields is low, crop production relies on extensive use of K+ fertilizers . However, heavy use of fertilizers is not sustainable because fertilizers are costly and cause environmental pollution . To support sustainable agriculture, a key strategy is to breed crops with improved K+ use efficiency so that they can produce more with less input of fertilizers, which requires a thorough understanding of molecular mechanisms that allow plants to respond and adapt to limited K+ availability in the soil. While cellular K+ concentration in plants is maintained at approximately 100 mM, the typical K+ concentration in natural soils fluctuates between 0.1 and 1 mM. After the uptake of K+ from the soil into the root symplast and subsequent release into the xylem apoplast, K+ is translocated from root to shoot and distributed throughout the plant. Once arrived in sink cells, K+ is utilized for cellular metabolism and osmoregulation with excess K+ sequestered into the vacuole. K+ efflux from plant cells is also involved in the adjustment of intracellular K+ homeostasis in response to altered environment conditions. To deal with K deficiency, plants have evolved two major mechanisms to maintain K+ homeostasis in plant cells, one is K+ acquisition from the soil and another is K+ remobilization from vacuolar stores. In Arabidopsis roots, the high-affinity K+ transporter HAK5 and the inward-rectifier K+ channel AKT1 are two major contributors to K+ uptake under K-limiting conditions in the natural soil. The vacuolar K+ -pool is stocked up in times of sufficiency, but under K+ limited environments, several tonoplast K+ -permeable channels, including two-pore K+ channels, facilitate K+ remobilization from the vacuole to support a stable concentration in the cytoplasm. An interesting question arises: how does a plant cell balance the demand and supply of K+ by connecting K+ status with the activity of channels and transporters ? This question has been addressed by studies on a calcium-dependent signaling mechanism consisting of calcineurin B-like calcium sensors and CBL-interacting kinases . A typical CBL-CIPK signaling module is activated by elevation in free cytosolic Ca2+ that binds to CBLs through their EF hand motifs and trigger conformational changes. Activated CBLs interact with CIPKs that transphosphorylate and modulate the activity of downstream targets such as ion transporters. In the case of low-K+ response, K+ deficiency has been shown to triggers distinct Ca2+ changes in Arabidopsis roots, which may activate CBL-CIPK signaling pathways that in turn promote K+ -uptake and/or vacuolar remobilization.

¿Cuál es la durabilidad de las macetas plásticas y su resistencia a condiciones climáticas adversas?

La durabilidad de las macetas plásticas puede variar según la calidad del plástico utilizado y el diseño de la maceta. En general, las macetas plásticas son conocidas por ser duraderas y resistentes, pero su longevidad puede depender de varios factores. Aquí hay algunos puntos a considerar:

Calidad del plástico: Las macetas plásticas de alta calidad tienden a ser más duraderas. Los plásticos más resistentes a la intemperie y a los rayos UV son preferibles, ya que resistirán mejor la exposición constante al sol y las condiciones climáticas adversas.
Diseño de la maceta: El diseño de la maceta también puede influir en su durabilidad. Las macetas con paredes más gruesas tienden a ser más resistentes,macetas de 10 litros especialmente en áreas donde pueden estar expuestas a golpes o impactos.
Condiciones climáticas: En general, las macetas plásticas son resistentes a una variedad de condiciones climáticas, incluyendo lluvia, sol y temperaturas extremas. Sin embargo, las temperaturas extremadamente altas pueden hacer que algunos plásticos se vuelvan más frágiles con el tiempo, mientras que las temperaturas extremadamente bajas pueden hacer que se vuelvan más quebradizos.
Exposición al sol: La exposición prolongada al sol puede afectar la durabilidad del plástico y su color. Algunos plásticos pueden volverse quebradizos o descoloridos con el tiempo debido a la radiación ultravioleta.
Cuidado y mantenimiento: La durabilidad de las macetas plásticas también puede depender del cuidado y mantenimiento que se les dé. Evitar dejarlas al sol durante períodos prolongados cuando no están en uso y limpiarlas regularmente puede ayudar a preservar su aspecto y resistencia.

En general, las macetas plásticas son una opción duradera y resistente, especialmente si se eligen macetas de alta calidad y se les brinda el cuidado adecuado. Sin embargo, es importante tener en cuenta que, con el tiempo y la exposición constante a los elementos, cualquier material puede experimentar desgaste.

¿Existen proveedores confiables de macetas plásticas a granel?

Sí, existen proveedores confiables de macetas plásticas a granel. Sin embargo, es importante realizar una investigación cuidadosa antes de elegir un proveedor para asegurarte de obtener productos de calidad y un servicio confiable. Aquí hay algunos pasos que puedes seguir para encontrar proveedores confiables:

Investigación en Línea: Utiliza motores de búsqueda y plataformas de comercio electrónico para encontrar proveedores de macetas plásticas al por mayor. Lee reseñas de otros compradores para tener una idea de la reputación del proveedor.
Directorios de Proveedores: Consulta directorios de proveedores en línea que se centran en la industria de productos para jardinería y hogar. Estos directorios a menudo clasifican a los proveedores según la calidad de sus productos y servicios.
Referencias y Recomendaciones: Pregunta a otros en tu industria o red de contactos si tienen recomendaciones de proveedores confiables. Las referencias de personas de confianza son valiosas.
Ferias Comerciales y Eventos: Participa en ferias comerciales y eventos de la industria donde puedas conocer a proveedores en persona. Esto te permite establecer conexiones directas y evaluar la calidad de los productos.
Verificación de Antecedentes: Investiga la historia del proveedor, su tiempo en el mercado y su reputación. Verifica si tienen certificaciones de calidad y cumplen con los estándares de la industria.
Contacto Directo: Ponte en contacto directo con los proveedores que estás considerando. Haz preguntas sobre sus productos, términos de venta, políticas de devolución y cualquier otro detalle relevante.
Muestras de Productos: Si es posible, solicita muestras de los productos antes de realizar una compra a gran escala. Esto te permitirá evaluar la calidad de las macetas por mayor plastico antes de hacer un compromiso financiero significativo.
Revisar Condiciones de Pago y Envío: Asegúrate de comprender las condiciones de pago y envío. Verifica los costos de envío, los plazos de entrega y cualquier cargo adicional.
Comentarios en Redes Sociales y Foros: Examina las redes sociales y foros relacionados con jardinería y suministros para el hogar. A menudo, encontrarás comentarios y experiencias compartidas por otros compradores.

Tomarte el tiempo para realizar una investigación exhaustiva te ayudará a encontrar proveedores confiables que satisfagan tus necesidades y expectativas.

Efectos de las macetas de plástico en la temperatura del suelo y el crecimiento de las plantas

En el ámbito de la jardinería, la elección de los recipientes puede influir significativamente en el bienestar de las plantas. Las macetas de plástico, muy utilizadas por su durabilidad y versatilidad, desempeñan un papel crucial no sólo para proporcionar un entorno propicio a las raíces de las plantas, sino también para influir en la temperatura del suelo. En este artículo, analizaremos cómo pueden influir las macetas cuadradas plastico en la temperatura del suelo y sus consecuencias para el crecimiento de las plantas.

Propiedades aislantes del plástico:

El plástico tiene propiedades aislantes, lo que significa que puede ayudar a regular la temperatura del suelo actuando como barrera entre éste y el entorno exterior. Este aislamiento puede ser especialmente beneficioso en regiones con temperaturas extremas, ya que ofrece protección a las raíces de las plantas contra el calor del sol o el frío.
Retención de la temperatura:

Las macetas de plástico pueden retener el calor absorbido durante el día, liberándolo lentamente durante las noches más frescas. Esta liberación gradual del calor almacenado ayuda a mantener una temperatura del suelo más estable, evitando fluctuaciones bruscas de temperatura que pueden estresar las raíces de las plantas.
Calentamiento del suelo en climas más fríos:

En climas más fríos o durante las estaciones más frías, las macetas de plástico pueden contribuir a calentar el suelo. El efecto aislante del plástico ayuda a atrapar el calor generado por la luz solar, creando un microambiente dentro de la maceta que es más cálido que el suelo circundante. Esto puede ser ventajoso para las plantas que prosperan a temperaturas ligeramente elevadas.
Protección contra el sobrecalentamiento:

Por otro lado, en condiciones de calor y sol, las macetas de plástico pueden proteger las raíces de las plantas del calor excesivo. Actúan como una barrera, reduciendo el impacto directo de la luz solar en el suelo. Esta protección es crucial para evitar el sobrecalentamiento del suelo, que puede ser perjudicial para la salud de las plantas.
Impacto en el desarrollo de las raíces:

La temperatura del suelo desempeña un papel vital en el desarrollo de las raíces. Una temperatura del suelo constante y moderada favorece el crecimiento sano de las raíces. Las macetas plastico cuadradas, al regular la temperatura del suelo, crean un entorno propicio para el desarrollo óptimo de las raíces, contribuyendo en última instancia al vigor general de la planta.
Consideraciones para plantas específicas:

Las necesidades de temperatura de cada planta varían. Algunas prefieren un suelo más cálido, mientras que otras prosperan en condiciones más frescas. Los jardineros deben tener en cuenta las preferencias de temperatura de cada especie de planta a la hora de elegir macetas de plástico y controlar el impacto en el crecimiento.
Posibles inconvenientes:

Aunque las macetas de plástico ofrecen ventajas aislantes, puede haber casos en los que la retención excesiva de calor se convierta en un inconveniente, sobre todo en climas extremadamente cálidos. Los jardineros deben ser conscientes de ello y considerar materiales alternativos o aplicar medidas adicionales, como el sombreado, para evitar que la temperatura del suelo aumente hasta niveles perjudiciales para la salud de las plantas.
Conclusión:

En conclusión, las macetas de cultivo de plástico pueden tener un impacto notable en la temperatura del suelo, influyendo en el crecimiento y desarrollo de las plantas. Las propiedades aislantes del plástico contribuyen a regular la temperatura, proporcionando un entorno estable y propicio para los sistemas radiculares. Los jardineros deben tener en cuenta las necesidades específicas de sus plantas, las condiciones climáticas locales y los posibles efectos del plástico en la temperatura del suelo para fomentar un crecimiento óptimo y el bienestar general de las plantas. Al comprender estas dinámicas, los jardineros pueden aprovechar las ventajas de las macetas de plástico y tomar decisiones con conocimiento de causa para crear entornos prósperos y saludables para las plantas.

Grow Year-Round with Ease: Hydroponic Systems for Indoor Gardens

Environmentally relevant concentrations of three antibiotics, lincomycin, ciprofloxacin, and oxytetracycline increased mortality and development time in cabbage loopers when reared on an artificial diet and treated tomato plants . Further, the three antibiotics altered the microbiome inside cabbage loopers and mosquitos but did not impact development time of mosquitoes . However, antibiotic exposure did not induce toxicity in aphids reared on bell peppers . Antibiotic toxicity in terrestrial invertebrates, therefore, appears to depends upon the specific antibiotics, concentrations, bio-availability, invertebrate species, and environmental conditions.Exposure to NSAIDs caused acute and sub-acute adverse effects in terrestrial invertebrates, including earthworms . Pino et al. assessed lethality of E. fetida cultivated in artificial soil as a result of exposure to 18 pharmaceuticals. Ibuprofen had the lowest LC50 at 64.8 mg kg-1 followed by diclofenac at 90.5 mg kg-1 . Exposure to diclofenac resulted in a dose-dependent decrease in survival and reproduction of Folsomia candida in spiked soils . However, it should be noted that these LC50 values were much higher than what may be expected in the real environment. At sub-acute concentrations ,gardening pots plastic diclofenac induced significant genotoxicity in Folsomia candida, including induction of the up-regulation of transcriptional processes and genes associated with the immune response .

Acetaminophen increased E. fetida mortality along both a dose-dependent curve and over time [7-28 d ]. In the mosquito species Culex quinquefasciatus, exposure to water contaminated with an environmentally relevant concentration of acetaminophen resulted in increased susceptibility to Bacillus thuringien israelensis and increased larval development time . Acetaminophen at environmentally relevant concentrations also significantly increased days to adulthood in cabbage loopers reared on an artificial diet. However, a similar effect was not observed when cabbage loopers were reared on acetaminophen-treated tomato plants . Similarly, the development time for aphids reared on acetaminophen treated bell pepper was not affected by acetaminophen . Therefore, like for other CECs, effects of NSAIDs on terrestrial invertebrates are species, compound, and environment specific.Many antimicrobials and preservatives, including the common environmental contaminants triclocarban, triclosan, and parabens are amongst the most frequently detected in TWW and bio solids . Partitioning of these CECs into bio-solids suggests that soil-dwelling organisms are at greater risks of exposure as they preferentially consume organic matter rich soils and bio-solids . Triclocarban, triclosan, and methyl-triclosan have been detected in the tissues of earthworms collected from field sites that were amended with bio solids 4 years prior to the worm collection . After 28-d exposure to triclosan at ≥50 mg kg-1 in soil E. fetida had significantly increased SOD and CAT activities and increased concentrations of malondialdehyde , a chemical indicative of lipid peroxidation and DNA damage in E. fetida . Lin et al. reported negative impacts of triclosan exposure on E. fetida reproduction including decreases in the number of cocoons and juveniles.

Triclosan also decreased the biomass, shell diameter, and food intake in a terrestrial snail at concentrations ≥ 40 mg kg-1 . Further, triclosan exposure increased CAT and SOD activities and MDA concentration in A. fulica in a dose-dependent manner . However, no adverse effects were observed in E. fetida cultivated in triclosan-amended bio solids at environmentally relevant concentrations . Triclocarban is more persistent in the environment than triclosan and is known to bio-accumulate in earthworm tissues . However, information on its toxicity to terrestrial invertebrates remains limited. For example, in Synder et al. exposure to triclocarban at concentrations ≥ 77 mg kg-1 for 2-4 weeks resulted in a trend towards increased mortality; however, the variations in data were too high to discern any statistically significant trend. Exposure ≥ 400 mg kg-1 to methyl paraben in soil resulted in increased abnormalities in earthworms where a normal survival-EC50 value of 397 mg kg-1 was estimated . An acute exposure to methyl paraben in soil at ≥ 60 mg kg-1 increased F. candida mortality and chronic exposure at concentrations ≥150 mg kg-1 decreased the reproductive rate . However, methyl paraben is often detected at concentrations ranging from 15.9 – 203.0 µg kg-1 in sewage sludge, levels that are well below the concentrations where toxicity was observed .Terrestrial invertebrates are more likely to be exposed to complex mixtures of CECs in the environments, including agricultural soils . However, studies addressing the effects of CEC mixtures on terrestrial invertebrates are scarce. E. fetida reared in bio solid-amended soils suffered a decrease in cocoon counts and a decrease in adult survival at 8 weeks with 4% bio solids amendment rates .

High, but environmentally relevant, rates of bio solids application also caused mortality in E. fetida and F. candida; even lower application rates hindered reproduction in both species . However, bio solids are extremely complex in composition with numerous other constituents, including metals and salts, and it is difficult to attribute their effects solely to CECs. Environmentally relevant concentrations of mixtures of antibiotics, hormones, acetaminophen, and caffeine were found to extend development time, increase mortality, and alter the microbiome of mosquitos and cabbage loopers . Collectively, the aforementioned studies suggest that CECs may have increased toxicity when present in mixtures, and adverse effects at environmentally relevant concentrations are likely, but need to be further confirmed.Currently, knowledge on the fate and toxicity of CECs in terrestrial invertebrates is still very preliminary. The limited studies conducted so far shown chemical-specific and species-specific effects of CECs in the environment. It is known that the bio-availability of these compounds and environmental conditions will play a large role in the overall accumulation and toxicity of the CECs in terrestrial invertebrates . However, information on bio-availability under differing environmental conditions is still lacking for most CECs. Similarly, the potential for trophic transfer warrants further investigation. Overall, more research involving a wider range of compounds, especially in the context of environmental relevance, is needed to more accurately assess the fate and toxicity of CEC in terrestrial invertebrates. The studies highlighted above suggest that CECs are ubiquitous in the environment and that exposure, even at environmentally relevant concentrations, these contaminants may be hazardous for terrestrial organisms. However, studies also suggest that these organisms can metabolize, transform and detoxify these CECs. The interplay between the toxicological effects of CEC exposure and an organism’s ability to take up and metabolize these contaminant is poorly understood and serves as significant knowledge gaps in understanding the fate and risks of CECs in terrestrial environments. These gaps must be addressed to gain better risk assessments of CECs during the use of bio solids and treated wastewater in the agro-environment. To address these gaps, we carried out a series of experiments utilizing plant cell cultures, hydroponic cultivations, earthworm incubations, high-resolution mass spectrometry, 14C-tracing, and enzyme assays to systematically evaluate the fate, metabolism, and biological effects of sulfamethoxazole, diazepam, naproxen,plastic pots with drainage holes and methyl paraben and their major metabolites in terrestrial organisms under laboratory conditions. The four CECs were selected based on their detection in TWW and bio solids, their range of physicochemical properties and uses, and the paucity of information about their fate and impacts in the literature . The study systems included Arabidopsis thaliana cells cultures, radishes, cucumbers, and E. fetida. Organisms were selected due to their extensive use in the literature, commercial availability, and worldwide agricultural relevance. Over the past two decades, pharmaceuticals and personal care products have emerged as contaminants of environmental concern due to their extensive use and continuous emission into the environment .

PPCPs are released into the environment primarily through the disposal of treated wastewater and bio solids from wastewater treatment plants . As climate change and population growth places an increasing stress on freshwater resources, especially in arid and semi-arid regions, communities have turned to utilizing municipal treated water for agricultural irrigation, which may result in soil contamination by PPCPs . Furthermore, the heavy use of some pharmaceuticals, particularly antibiotics, for disease control and growth promotion in intensive animal farming also contributes to contamination of agricultural fields when animal wastes are used for fertilization . The presence of PPCPs in irrigation water and soil can lead to contamination of food crops if plants can substantially accumulate these compounds. Various studies over the last decade have sought to quantify plant uptake of PPCPs, and in general, only low levels of PPCPs have been found in edible tissues . The majority of studies to date have only targeted the parent form of PPCPs for analysis. However, plants have a cascade of enzymes that may extensively transform xenobiotics such as PPCPs after uptake . Recently several published studies have explored the metabolism of pharmaceuticals in plants . Therefore, consideration of metabolism and biologically active metabolites is much needed for a better understanding of the fate and risks of PPCPs in the soil-plant system. Higher plants have many detoxification enzymes similar to those in animals. These enzymes function in plants as a ‘green liver’ . In general, metabolism of xenobiotics includes three phases. Phase I involves modification reactions such as oxidation, hydrolysis, and dealkylation reactions introducing reactive sites to the molecule. Phase II is characterized by conjugation with large polar bio-molecules, such as sugars and amino acids, to further increase the polarity of the xenobiotic. Phase III is typified by sequestration, resulting in the formation of bound residues . As shown for many xenobiotics in mammals and plants metabolites from phases I and II often retain biological activity , and therefore should not be discounted. In this study, sulfamethoxazole was selected as the compound of interest because of its prevalence in WWTP effluents and increasing concerns over the propagation of antibiotic resistance . Since its introduction in 1961 sulfamethoxazole has been widely prescribed due to its potency against both gram-positive and gram-negative bacteria . Currently, sulfamethoxazole has been detected from ng L-1 to µg L-1 in surface and effluent waters and µg kg-1 to mg kg-1 in soils and manure .Recent long-term studies of waste-water application under realistic field conditions have highlighted the potential for sulfamethoxazole to be taken up and translocated in crop plants, including to the fruit . The structures of sulfamethoxazole metabolites, including conjugates from Phase II metabolism, were identified using high-performance liquid chromatography coupled with time-of-flight high-resolution mass spectrometry and further quantified using ultra-high performance liquid chromatography in tandem with a triple quadrupole mass spectrometry . Furthermore, Phase III terminal products in the form of bound residues were quantified using 14C labeling. Arabidopsis thaliana cells were selected as the experimental organism due to their extensive use in the literature, commercial availability, and their membership in the commonly consumed Brassica family . Further, Arabidopsis thaliana plants are found worldwide under several common names and are consumed by a wide variety of animals as well as humans . Cucumber was selected in the hydroponic experiment due to the fact that it is often consumed raw, rapid growth, and amiability to soilless culture .Non-labeled sulfamethoxazole was purchased from MP Biomedicals . Sulfamethoxazole-d4 was purchased from C/D/N Isotopes and 14C-labeled sulfamethoxazole was obtained from American Radiolabeled Chemicals . Stock solutions of 14C-sulfamethoxazole and non-labeled sulfamethoxazole were prepared in methanol to reach a specific radioactivity of 1.2 × 103 dpm µL-1 and a chemical concentration of 1.0 mg mL-1 , respectively. HPLC grade acetonitrile and methanol were used for extraction along with ultra pure water. Mobile phases were prepared using Optima™ LC/MS grade methanol and deionized water. Standards were prepared in HPLC grade methanol and stored in the dark at -20 °C. All solvents used in this study were purchased from Fisher .PSB-D A. thaliana cell line was purchased from the Arabidopsis Biological Resource Center at the Ohio State University . The cells were maintained in liquid suspension culture at 25 °C and rotated at 130 rpm in the dark according to the ARBC protocol . To explore metabolism of sulfamethoxazole in A. thaliana cells, 7 mL of cell culture was inoculated in 43 mL fresh culture and cultivated for 96 h at 25 °C and 130 rpm in the dark to produce the seed culture. A 30 µL aliquot of the non-labeled stock solution and 10 µL aliquot of 14C-sulfamethoxazole were spiked into 30 mL of A. thaliana cell culture, resulting in a nominal initial concentration of sulfamethoxazole of 1 µg mL-1 and a specific radioactivity of 1.2 × 103 dpm mL-1 . Simultaneously, control treatments were prepared by autoclaving cell suspensions before chemical spiking , flasks containing sulfamethoxazole without cells , and flasks containing live cells but no sulfamethoxazole . These control treatments were used to determine adsorption, abiotic degradation, and potential toxicity to cells.

Maximizing Yields, Minimizing Footprint: The Hydroponic Advantage

The observations suggest that OsZHD2 increases the amount of local auxin occurring in the dividing zone of the roots. We propose that OsZHD2 induces auxin biosynthesis in the RAM by increasing ethylene levels. However, we do not rule out the possibility that OsZHD2 directly increases auxin levelsby controlling other genes that we did not investigate in the present study . OsZHD2 induces root development by increasing ethylene biosynthesis and sequentially auxin biosynthesis. It determines meristem-specific homeobox protein functions as an activator for meristem activity by regulating the ethylene–auxin interaction. In the RAM region, ethylene–auxin crosstalk plays important roles .Root system architecture is a critical agronomic trait that influences crop productivity by altering soil mineral absorption and lodging . Deep rooting is a key trait that facilitates drought stress tolerance, since plants can absorb water from deeper soil layers . In addition, the introgression of the DEEPER ROOTING 1 allele from a deep-rooting rice cultivar into a shallow-rooting rice cultivar increases yield under drought conditions , while root-specific over expression of OsNAC5 enhances root diameter, resulting in greater drought tolerance and higher grain yield . Here, we demonstrated that the over expression of OsZHD2 increases the volume of the root system and overall yield, particularly under a poor nutritional status .

Therefore, our results suggest that OsZHD2 is a key trait that could be applied in the improvement of grain yield.We observed that the increased expression of OsZHD2 stimulated root growth. The effect was more significant for lateral roots. Although the total number of lateral roots increased due to the over expression of the gene,plastic pots plants their density did not change . Therefore, the function of OsZHD2 seems to be associated primarily with root growth rather than root initiation. In situ RNA hybridization analyses revealed the preferential and uniform expression of OsZHD2 in the lateral root meristem region, supporting the root growth function . The number of dividing cells in the RAM region was significantly higher in the OsZHD2-OX plants, further indicating that the gene stimulates root growth . The process of initiating lateral roots has been elucidated extensively using numerous mutants defective in that step. However, the molecular mechanisms of lateral root emergence and growth remain poorly understood . Mutations of orc3 in rice interrupt the cell cycle process and block lateral root emergence . The ORC is a critical element in DNA replication, cell cycle checkpoint regulation, heterochromatin assembly, and chromosome assembly. The expression levels of the genes of the D-type cyclin family are down-regulated significantly in orc3 mutants . In the present study, the expression levels of CYCD4;1 increased in OsZHD2-D, suggesting that OsZHD2 promotes cell cycle progression during lateral root growth .

Plants rely on an array of phytohormones to coordinate and finely regulate response networks to biotic and abiotic stresses . Studies of phytohormone regulation of defense responses in plant–microbe interactions generally have focused on salicylic acid , jasmonic acid , and ethylene . In Arabidopsis, SA-mediated defenses are considered deterrents to biotrophic pathogens, whereas JA/ET-mediated defenses deter necrotrophic pathogens . However, this dichotomy with respect to parasitic strategy may be less clear in other host species . While studies of SA and JA/ET signaling have shaped our current understanding of induced resistance mechanisms, consideration of other phytohormones is gaining traction in terms of how multiple stress response pathways overlap as non-linear networks to coordinate plant responses to diverse biotic challengers . These interactions can be synergistic or antagonistic, or phenotypically neutral if the disease assays cannot discern subtle differences. For example, SA and JA can be antagonistic in certain contexts leading to trade-offs in defense against different attackers . Similarly, there is substantial evidence that elevated levels of the phytohormone, abscisic acid , can diminish host resistance . Nonetheless, ABA enhances resistance in some biotrophic and other interactions . This parasitic context dependency of ABA action illustrates the challenge in identifying a unifying mechanism to explain ABA’s effects in plant–microbe interactions.

Various root stresses reduce plant water potential and induce ABA accumulation to trigger adaptive biochemical and physiological changes that enable plants to maintain water balance . However, episodic root stresses, even those from which plants fully recover, occur routinely in agricultural and natural systems, transiently elevating cellular ABA concentrations to levels that predispose plants to inoculum densities they would normally resist . Disease predisposition from abiotic stress has long been recognized in the plant pathology literature , and is particularly well-documented in classic studies of root and crown diseases caused by Phytophthora spp., where episodes of water logging, soil salinity, and drought are important factors in disease development . Although a role for ABA in conditioning the increased susceptibility during and following stress episodes is recognized, the underlying mechanisms and impacts on host defenses are unresolved . Furthermore, relatively little attention has been directed at defense-related phytohormone signaling in root–pathogen interactions where the predisposing stresses of water deficit, hypoxia and soil salinity are encountered most directly . Salicylic acid is involved in multiple physiological processes , but is perhaps most studied for its role in systemic acquired resistance and as a strong inducer of pathogenesis-related proteins . SA biosynthesis in plants occurs by two pathways, one via isochorismate synthase , and the other via phenylalanine ammonia lyase . Knockout mutants in the ICS pathway and transgenic plants carrying nahG encoding a bacterial salicylate hydroxylase have reduced SA levels, are highly susceptible to pathogens, have severely reduced levels of PRproteins, and fail to develop local and systemic resistance . ABA appears to antagonize SA action in defense . Jasmonic acid is an oxylipin involved in defense responses against necrotrophic pathogens and insect herbivores, and has been found to have positive or negative interactions with SA depending on the specific host-parasite/pest context . JA also acts synergistically with the phytohormone ET, and either synergistically or antagonistically with ABA . In soybean leaves, JA levels increase with ABA during dehydration, and a few studies have shown ABA signaling necessary for JA biosynthesis and elaboration of defense responses . In Arabidopsis, application of ABA suppresses some JA/ET activated genes such as PDF1.2, while JA/ET responsive genes are up-regulated in ABA-deficient mutants such as aba1 and aba2 . Several JA synthesis mutants are available in tomato, including defenseless-1 , blocked in the conversion of 13-hydroperoxylinoleic acid to 12-oxophytodienoic acid, and acx1, a mutant defective in acyl-CoA oxidase . These mutations result in reduced JA accumulation and pathogen-related transcripts . Phytophthora capsici is a broad host-range pathogen that can cause significant economic losses in vegetable crops in the Cucurbitaceae, Solanaceae, and Leguminosae families . Similar to other soilborne Phytophthora species, P. capsici causes extensive root and crown rots that are exacerbated by predisposing stresses such as water logging and salinity. In a previous study, we imposed acute levels of salt stress on hydroponically grown tomato seedlings prior to inoculation with P. capsici to show that predisposition in roots and stems occurred in an ABA-dependent and ET-independent manner . In a related study ,plastic nursery pots we showed that plant activators that engage SA-mediated defenses in tomato induce resistance to the bacterial speck pathogen, Pseudomonas syringae pv. tomato , both in non-stressed and salt-stressed plants, but not in the case of P. capsici where plants exposed to these same treatment regimes displayed similar severity of root and crown rot.

The objective of this study was to further assess the impact of salt stress on the infection and colonization of tomato roots by P. capsici and to determine if there is discernible interaction between ABA and SA or JA during salinity-induced predisposition. We examined the impact of salt stress on P. capsici zoospore attraction and early infection and colonization in tomato roots in wild-type and ABAdeficient mutants. Since ABA can alter the action of SA and JA , we evaluated SA- and JAdeficient tomato plants for altered predisposition phenotypes. In addition, we profiled the expression of hallmark genes for stress adaptation and defense during predisposition onset and recovery and P. capsici infection. Tomato plants of cultivars ‘New Yorker,’ ‘Rheinlands Ruhm,’ or ‘Castlemart’ and mutant or transgenic lines within these backgrounds were used in experiments. ‘New Yorker’ and ‘Rheinlands Ruhm’ are determinate and indeterminate cultivars, respectively, used primarily for fresh market consumption, and ‘Castlemart’ is a determinate, processing cultivar that was bred for the arid growing conditions of California and other regions. In our experimental format, all three cultivars are susceptible to P. capsici. ‘New Yorker’ seeds were obtained from a commercial source . The homozygous ABA-deficient mutants sitiens and flacca were compared with their isogenic, wild-type background, ‘Rheinlands Ruhm,’ and seeds for these were obtained from the C. M. Rick Tomato Genetics Resource Center, University of California, Davis. ‘Rheinlands Ruhm,’ sitiens, and flacca plants were grown for seed production in the greenhouse. NahG transgenic plants were generated in the ‘New Yorker’ background, similar to the method used by Gaffney et al. . The nahG construct containing the transgene salicylate hydroxylase under control of the CaMV 35S promoter in the binary vector pCIB200 was a gift of Syngenta Crop Protection, Inc. SA deficiency of our transgenic line was confirmed previously . The acx1 and def1 mutants in the cv. ‘Castlemart’ background were a gift of Gregg Howe, Michigan State University. Seeds of ‘Castlemart’ were obtained from the C. M. Rick Tomato Genetics Resource Center. Four-week-old plants with two or three true leaves were grown hydroponically as described previously . Experiments were conducted in a growth chamber . A pepper isolate of P. capsiciwas used for most experiments. A P. capsici isolate transformed with the green fluorescent protein was a gift of Christine Smart and William Fry, Cornell University . Wildtype and transformant P. capsici strains were maintained on V8 juice agar plates or V8 juice amended with 100 mg/L geneticin , respectively. Zoospore inoculum was prepared using methods described previously .The salt stress regime selected for these experiments was based on prior studies of root stress predisposition . The impact of salinity stress differs from other osmotic dehydration stresses primarily in that salt-stressed plants are additionally exposed to abnormally high extracellular concentration of ions such as sodium and chloride . The inclusion of calcium helps to mitigate the confounding toxicity caused by sodium and emphasizes the osmotic facet of salinity stress, which is likely applicable to other dehydration stresses . Plants were subjected to salt stress by replacing the 0.5X Hoagland’s solution with 0.2 M NaCl and 0.02 M CaCl2 for 18 h. Plants were returned to 0.5X Hoagland’s solution, allowed to regain turgor and recover for 2 h, and then inoculated with zoospores of P. capsici . To determine whether there was an effect on zoospore motility and chemotaxis, a microcapillary swim-in assay similar to that described by Morris and Ward was used with exudates collected from tomato roots. Following 18 h salt stress, tomato roots of uniform volume were rinsed in deionized H2O and transferred to tubes containing 2 ml of deionized water. Exudates were allowed to accumulate for 2 h, tomatoes were then removed, and the exudates were vortexed and immediately loaded into 1 µl microcapillary tubes . Exudate-loaded microcapillaries were placed into 15 cm petri dishes with one end submerged in a 500 µl droplet of 5 × 105 zoospores ml−1 . Microcapillaries were photographed under a dissecting microscope 15 min after being placed into the zoospore suspension. Zoospore attraction was determined as the proportion of the microcapillary’s inside diameter blocked by encysted zoospores and scored on a 0–5 rating scale .The P. capsici-GFP transformant was visualized 24 and 48 hours post inoculation in tomato roots using a Leica TCS SPE confocal system . Following infection and just prior to microscopy, roots were dipped into a 10 µg/ml solution of propidium iodide for 30 s and rinsed in sterile water before mounting on microscope slides . GFP was excited at 488 nm and emission was collected between 510 and 550 nm. PI was excited at 534 nm and emission was collected between 600 and 650 nm. Laser power was set to 50% with a gain of 800–900 for both the 488 nm and 534 nm channels. Final images were composites of five Z steps through root tissues approximately 40 µm in depth.To estimate the progression of P. capsici colonization in tomato seedlings by qPCR, nahG, def1, and acx1 plants and wild-type plants of their corresponding backgrounds were frozen in liquid N2 at 48 hpi, and stored at −80◦C until extraction and analysis.

Beyond Soil: Exploring the Wonders of Hydroponic Agriculture

Five replicate columns were prepared and analyzed for each treatment. Metal concentrations for all three ENMs are reported as ionic, although neither CeO2 nor TiO2 were expected to dissolve to a significant degree under the conditions used in this experiment. TiO2 is known to be highly insoluble in water and CeO2 is similarly insoluble at pHs similar to those found in the soils used here. However, Cu2 has been shown to undergo partial dissolution under acidic to neutral conditions, although at acidic pHs less dissolution occurs in media with high concentrations of dissolved organic matter.Based on this, dissolution of Cu2 is not expected to occur to a significant degree under the conditions and time scales used in this experiment. To measure size distribution of particles throughout the column, air-dried samples of contaminated soils were collected from the top and bottom 3 cm of columns and analyzed using environmental scanning electron microscopy with back scattering electron detection and energy-dispersive X-ray spectroscopy to confirm identification of CeO2, Cu2, or TiO2 ENMs. Beam voltage was set at 12 kV, spot size at 6.0, water vapor pressure was kept at 2.7 Torr,square plastic pot and working distance averaged around 10.5 cm. These settings were chosen in order to minimize X-ray subsurface penetration for EDS analysis. Elemental hypermap data was collected over a period of 6 min per image.

ImageJ image analysis software was used to determine particle or aggregate size. Soil solution extracts of potting, grassland, and farm soils were prepared following Rhoades, although no Na3PO4 was added in order to avoid influencing ENM physicochemical behavior. Soil solution extracts were stored at 4°C until use.Gravity-driven vertical transport of ENMs through unsaturated soil was found in general to follow the hypothesis that the majority of ENMs would be retained in the upper portion of the column, but as predicted was found to be highly dependent on soil type with increased retention occurring in the denser, less porous natural soils . However, ENMs coated with natural organic matter did not have increased vertical transport, and in fact were retained more in potting soil. TiO2 and CeO2 aggregate sizes were seen to decrease with column depth, suggesting physical straining to be the primary impediment to transport. Aggregate hydrodynamic diameters tended to be larger in soil solution extracts than Nanopure H2O and were also generally larger with NOM-coated particles, with several exceptions .All three ENMs largely passed through the entire length of potting soil columns, being present in lower concentrations than the hypothetical homogeneous concentrations at all points, although there was some retention in the upper 0-6 cm that was increased with NOM-coated particles . These trends can likely be explained by the primarily organic composition of the potting soil, which gave it very low density, high porosity, and high reactivity . The low density and high porosity prevented aggregates from being physically strained, which is shown for TiO2 and CeO2 by the similar aggregate sizes in the tops and bottoms of columns for both uncoated and NOM-coated particles .

If physical straining was strongly influencing particle transport in potting soil it is unlikely similar aggregate sizes would be observed throughout the length of the column, but rather would result in smaller aggregates or particles penetrating through the column while larger aggregates would be retained at the surface – as was seen in the two natural soils. All three ENMs had similar hydrodynamic diameters in potting soil solution , although NOM-coated aggregates were significantly smaller than uncoated aggregates . ζ-potentials for all three ENMs in soil solutions from all three soils were also similar , although again the presence of NOM coatings, as well as the ENM and soil types, had significant impacts on ζ-potentials . Coating particles with NOM appears to increase their affinity for the organic components of the potting soil. This resulted in the increased overall retention of NOM-coated CeO2 as well as the decreased vertical transport of NOM-coated TiO2 and Cu2 . Evidence for this can be found in Figures 2.3A-B, which show that both NOM-coated and uncoated aggregates have nearly identical hydrodynamic diameters in potting soil solution extract, so the additional retention of NOM-coated aggregates is unlikely to be due to increased physical straining. This was visually confirmed in micrographs of NOM-coated TiO2 in potting soil including Figure 2.4D, which revealed the formation of TiO2 encrustations occurring primarily on the organic components of potting soil over the Al/Si/Na/K perlite minerals. These encrustations may have been caused in part or whole to interactions between the NOM coating and the organic matter in the potting soil.

This finding is counter to several previous transport studies using TiO2, CeO2, and ZnO25 in quartz sand that found organic coatings decreased ENM retention by increasing electrostatic repulsion between coated aggregates and the sand grains, which further suggests interactions between the organic coating and organic soil components. In the grassland and agricultural soils CeO2 and Cu2 shared similar transport profiles , forming large aggregates in the soil solutions that were retained almost entirely in the upper 0-3 cm of the soil columns. However, the widely variable background concentrations of Ti in these natural soils prevented precise measurement of TiO2 ENM distribution throughout the soil columns by ICP-AES , the majority of TiO2 aggregates were confirmed to be retained immediately at the surface through both visual identification of white buildup on the column surfaces and through BSE/EDS analysis. As shown in Figure 2.4, both uncoated and NOM-coated TiO2 ENMs formed large encrustations on the surfaces of all three soils with the exception of uncoated TiO2 in potting soil. Despite having nearly identical surface charges in soil solution extracts , CeO2 formed large porous sponge-like aggregates instead of the more solid encrustations seen with TiO2. These differences in aggregate morphology may be due to differences between the primary particle shapes of these two ENMs, with TiO2 being nanospheres and CeO2 being nanorods. Afrooz, et al. found that spherical Au ENMs had higher attachment efficiencies and deposition rates than rod-like Au ENMs identical in composition, which they attributed to differences in electrosteric and physical packing characteristics. Similarly, Zhou, et al. found the critical coagulation concentration of TiO2 nanospheres was directly related to particle diameter while the CCC of TiO2 nanrods was better explained by particle surface area, which they postulated was a consequence of differences in exposed crystal faces. It has alsobeen shown that metal oxide nanospheres and nanorods interact differently with NOM,square plant pot which may also be a factor in explaining the differences in aggregate morphology seen here.Little research has been done on the effects of ENM exposure on soil properties. In one of the only available studies available on this subject, Ben-Moshe, et al. 1 observed that CuO and Fe3O4 ENMs did not change the total organic content or macroscopic properties of two types of soil but altered the humic substances in the soils. The authors also observed an effect on the soil microbial community, which has been reported in other studies , but did not attempt to link changes in important soil properties with these effects. VandeVoort, et al. found that silver ENMs could limit denitrification processes in soil, but that the effects were dependent on ENM concentration and coating. While previous studies in this area suggest that the effects of ENMs on soil properties are somewhat limited, there may be additional impacts not considered in these studies. For example, metal oxide surfaces are amphoteric, capable of producing both protons and hydroxide ions , but tend to be predominantly acidic in nature.

Due to this metal oxide ENMs may be able to alter the pH of soil pore water and consequently the overall pH of the soil. pH has been called one of the “master variables” for soil systems7 because it controls a number of critical physical and chemical properties, and if ENMs are able to alter soil pH when present above certain concentrations they may pose a hazard to organisms that rely on the soil for habitat or sustenance. However, soils are typically well-buffered, and may be able to withstand ENM accumulation without changing pH. Additionally, ENMs will likely aggregate as a result of the high ion content of soil solutions, thus decreasing total surface area and, potentially, proton/hydroxide production. Additionally, metal oxide ENMs bear many similarities to naturally occurring nano-scale poorly crystalline metal oxide minerals known as short-range order minerals. SRO minerals have been shown to influence nutrient availability in natural soils via sorptive processes, and metal oxide ENMs may also demonstrate this effect. In particular, metal oxides are well known for their ability to covalently adsorb phosphate ions and, depending on the strength of this interaction, may prevent organisms from accessing this important nutrient. Two hypotheses were addressed in these series of experiments. First, I hypothesized that none of the soils would experience a significant change in pH after spiking with ENMs due to the presence of buffering compounds in the soils. Second, I hypothesized that these ENMs would sorb soil nutrients, including phosphate, and reduce their mobility in the soil.The effect of ENM contamination on soil pH were tested over a range of ENM concentrations by adding potting, grass, or farm soil with 0, 0.1, 1, 10, and 100 µg g-1 TiO2, CeO2, or Cu2 ENMs with and without the addition of 10% NOM. Soil aliquots were then air dried and mixed with Nanopure water to make a 20% soil paste from which the pH was measured. All treatments were performed in triplicate. Changes in soil ion release due to the presence of ENMs was tested by mixing aliquots of potting, grass, or farm soil with 100 µg g-1 TiO2, CeO2, or Cu2 ENMs as suspensions, centrifuging at 8000 x g for 10 min, and analyzing the supernatant for ion concentrations. NO3 – was measured via colorimetric methods and Al, Ca, Fe, K, Mg, Na, P, and S were measured via ICP-AES after acidification to 10% HNO3. The influence of the three ENMs on the bio-availability and mobility of P was investigated further by contaminating agricultural, grassland, or potting soil samples with 100 µg g-1 ENMs and testing P content in three fractions: water extractable P, bio-available P, and immobile P. Soil aliquots were first mixed with water for 1 min, centrifuged at 8000 x g for 10 min, then the supernatant was removed and acidified to 10% HNO3. The same soil aliquots were then mixed with Bray extract11 for 1 min, centrifuged at 8000 x g for 10 min, then the supernatant was removed and acidified to 10% HNO3. The soil aliquots were then acid digested in 1:3 HNO3:HCl at 200°C for 1.5 hours in a microwave digestion system, and all samples were analyzed for P content via ICP-AES. Soil solution extracts of potting, grassland, and farm soils were prepared following Rhoades, although no Na3PO4 was added in order to avoid influencing ENM physicochemical behavior. Soil solution extracts were stored at 4°C until use. Despite varying ENM concentrations over four orders of magnitude, changes in soil pH due to ENM contamination were largely independent of both ENM type and concentration . Contrary to the first hypothesis, changes in soil pH due to ENM contamination did occur, but they were found to be highly dependent on soil type. All three ENMs increased grass soil pH , decreased farm soil pH , and had no effect on potting soil pH . Additionally, the presence of NOM had no effect on the influence of ENMs on soil pH except in the case of farm soil, where a slight buffering effect was seen . As nearly all changes in soil pH were independent of ENM concentration it is unlikely these ENMs directly influenced soil pH through the production of H+ /OH-due to their amphoteric properties. One possible alternate explanation is that the ENMs increased the release of ions that act as buffering or pH-altering agents, such as Al3+ , Ca2+, H+ , K+ , Mg2+, Na+ , and OH- , by replacing them on the mineral surfaces of the soil matrix. Since there is a limited pool of ions available for desorption in a unit of soil, changes in ion release due to ENM sorption would be relatively independent of ENM concentration beyond the point at which total sorption/desorption occurs.