These prior studies demonstrate the importance of rainfall to chemical dilution of wastewater in the land treatment reservoirs and receiving waters relative to upstream watershed sources of unplanned water reuse such as septic systems, livestock waste management, and agriculture. The extended exposure of chemicals to sunlight, biological degradation, and mixing for 10–14 days in reservoirs merits notation when comparing chemical number and abundance of wastewater from this land treatment system to conventional wastewater treatment. Studies have linked unplanned water reuse in watersheds to anthropogenic COC presence in food crops, particularly corn, wheat, and soybean . Compagni et al. coupled two distinct models, a water quality and plant uptake model, to estimate concentrations of 13 pharmaceuticals in edible plant tissues from repeated simulated crop irrigation of surface water downstream of permitted municipal wastewater discharge to evaluate COC risk to food crops from unplanned water reuse. Model estimations of COCs in plants agreed with literature data of COC transfer to leaves more so than roots or fruits; overall, human health risks from dietary intake were negligible based on toxicological thresholds of concern or hazard quotients except for sulfamethoxazole and 17a-etyinylestradiol . Montemurro et al. reported that earthworms did contain COCs from soils amended with spiked COCs in tapwater, but only bisphenol A was detected in earthworms collected and analyzed from actual municipal wastewater irrigated soils.
The literature and our observations emphasize the pervasive presence of anthropogenic COCs in watersheds and the need to evaluate comparative risk of COC uptake in wastewater-irrigated plants to other watershed irrigation sources for drinking water sources . Since 2015, about 20 published studies per year address COC uptake by plants for pharmaceuticals, ebb and flow bench personal care products, and PFAS . A majority of these studies utilize hydroponics or greenhouse soil studies with spiked COC solutions to understand COC translocation to roots, shoots, and fruits. Field studies of COC uptake to plants from wastewater are poorly represented but warranted to understand realistic COC uptake and dietary risk from repeated irrigation applications to food crops . Physio-chemical properties of COCs greatly influence COC transport in plants from irrigation water and irrigated soils to food crops. COCs with moderate log Kow of 1–5 transport to plant leaves and stalks via transpiration streams and will leach from irrigated soil to groundwater . Our recent review of hydroponic COC studies comprising 7 leafy vegetables and 39 COCs shows that polar, smaller COCs translocate more to shoots and leaves and that COCs with higher log Kow values cannot be ignored in food crop leaves and fruits. Collectively, the targeted literature and our non-targeted analyses show a similar range of log Kow values for COC detection in leafy tissues and fruits for food plants irrigated with wastewater. For past targeted studies, translocation factors were less than 0.04 for ToxCast chemicals with log Kow values less than 5 and between 0.1 and 0.4 forToxCast chemicals with log Kow values between 2 and 4 . In our nontargeted study, the majority of TICs and ToxCast chemicals extracted from soybean leaves, beans, and roots had log Kow values between 2 and 4.
A recent Monte Carlo simulation of perfluoroalkyl acids to edible plants and a proposed tiered framework of PPCP risk via edible plant ingestion prioritized PFAs and PPCPs with moderate log Kow values and estimated translocation factors greater than 0.1. The latter review recommends more nontargeted studies to assess the accumulation and transformation of PPCPs in edible plant tissues and better represent chemical mixtures present in wastewater. In our non-targeted study, hundreds of TICs and more than a hundred distinct ToxCast chemicals were detected in plant tissues. Both TICs and ToxCast chemicals represented a diversity of log Kow values and chemical use categories from tap water, wastewater, groundwater, and surface waters.Passive samplers have provided integrated COC assessments in aquatic system and often detect more chemicals at lower concentrations with less analytical clean-up prior to instrument analysis than conventional liquid-liquid or solid phase extraction of water samples . Passive samplers not only improve COC detection and representation over time in a given water source, but samplers can estimate COC concentrations in target organisms such as mussels, fish, worms, and plants . Previous studies found strong correlations of chemical uptake between samplers and soil organisms but variable correlations of chemical uptake between samplers and plants . In this study, the majority of ToxCast chemicals detected in CIPS had log Kow values between 2 and 4. Combining passive sampling with suspect screening HRMS allows for more representative COC exposure analysis to humans and organisms . HRMS analysis of silicone wristbands is promising for human exposomics to workplace exposure . Coupled passive sampling with SS-HRMS and targeted HRMS evaluated pesticides in agricultural watersheds during drought , COCs in sediment pore water , COCs in surface-, ground-, and waste waters , and COCs in marine waters . SS-HRMS analyses of POCIS samplers yielded 65 tentatively-identified chemicals compared to 35 TICs from grab samples .
When specific sorptive dynamics are measured for a specific COC, time-weighted concentrations in water can be determined from the sampler . Alygizakis et al. contends that wastewater irrigation of crops should use passive samplers coupled to HRMS to assess COC risk to food crops. This study demonstrates the integration of passive sampling with HRMS and hydroponic assays to improve our knowledge of COC uptake to edible plant tissues and to expand our knowledge of COC dynamics in agro-food systems . A variety of passive samplers exist, such as Chemcatcher™, polyethylene strips , polyoxymethylene, polydimethylsiloxane, polar organic chemical integrated sampler and composite integrated passive sampler , and can improve assessment of COC translocation to plant tissues from conventional and novel irrigation sources.The rapid growth in population and subsequent increase in water and energy consumption to meet the demand for products and services have resulted in resource depletion and environmental deterioration. Consequently, the study of what is known as the energy, water and food nexus has gained significant interest over the last few years as a potentially effective approach for the management of resources considering the inherent interlink ages that exist between them. As such, the integrated analysis will enable the identification of key synergies and trade-offs that may exist in the design and operation of EWF resource systems . In addition, the EWF nexus approach is holistic, such that it aids decision-makers in pre-empting unintended, and possibly damaging, consequences resulting from the interventions made in any part of the nexus system. Thus, there is a need for implementing efficient and resilient resource management systems based on an optimization framework that considers environmental, economic and societal aspects of sustainable development in achieving the EWF resource security .
EWF Nexus and decision-making tools, such as optimization,agent-based modeling and game theory are important for effective integrated resource management . This is especially significant for the State of Qatar, with it its highly arid climate and inconsistent distribution of resources; whilst it is rich in energy resources, it suffers from water scarcity, environmental and food security challenges. Moreover, Qatar is now looking at extensively developing its agricultural capacity despite the risk of climate and resource stress impacts . This study proposes a geospatial nexus approach to support decision-making for resource management in risky environments and demonstrates its application in a case study for Qatar. Within this methodology, a novel concept is developed, referred to as the “EWF nexus node”. Each node represents a food system, which is a function affected by exogenous risks, such as climate, water and land factors. Based on the food production sector, the data related to spatial risk factors are collected from different data sources that are either in the form of maps from hard copy books or electronic formats, such as reports and peer-reviewed journal publications. The data is then digitized and integrated into a unified geo-processing platform, enabling both visualization and further processing of the risk factors. Other data types used include, districts and roads, industries, water resources and weather station locations. The assignment of weights that represent the importance of various risk factors is conducted using a multi-criteria decision-making method, known as the Analytical Hierarchy Process , in order to generate the composite geospatial risk indicators. The variabilities in risk maps are also captured for various seasons. Finally, the node assessments are conducted using these maps to assess the risk levels, productivity and the consumption of water and energy for various food production scenarios. Thus, the overall quality of the node is assessed based on the developed composite indicators, assessments, and the ability of the nodes to optimize for risk mitigation and adaptation. It is envisaged that the proposed EWF Nexus node approach will identify specified locations that perform better than others under risks. This paves the way for further optimization and decision-making to reduce the impact of endogenous and exogenous risk factors, thereby enhancing the resilience of EWF systems on a national level.
There exists a growing concern about the limited availability and access to energy, water and food resources, and the inequalities in their distribution as outcomes of poor management and inappropriate governance structures . Thus, an evidence was provided that the nexus approach helps improve energy, water and food security, through integrated management and governance across various scales and sectors. In addition, the nexus approach can also support the transition to a green economy, through the reduction in negative environmental,4x8ft rolling benches social and economic externalities, hence, overall leading to efficient utilization of resources and better policy coherence . The EWF nexus assessment is used to assess and evaluate the nexus interlinkages and highlights synergies between sector interferences at any scale. Existing indicators are usually used to measure and quantify these linkages. However, in case indicators for the desired level or scale are not available, then new and specific indicators will be developed . According to the Organisation for Economic Cooperation and Development , any variable that is observable and measurable can be later transformed into an indicator, which is a value with specific purposes that represent the variables themselves . Studies showed that indicators are the alternative to a direct impact measurement , where they have the ability to perform various functions. Within sustainable development, indicators are important to provide perspectives on environmental, economic and social performance . In fact, there are many dedicated models that assess the status of sustainable development, for instance, the Index of Sustainable Economic Welfare which were used to analyse the impact of used resource or to study the sustainability of specific sectors or sub-sectors such as organic food consumption . In terms of assessing the sustainability of agricultural systems and environmental impacts of agricultural activities, several indicator-based methods have been developed, such as water pollution by nitrates and pesticides; in order to address the risk of pesticide . Furthermore, indicators can be used within geographic information systems in order to determine spatial extension and geographic distribution of areas and to relate anthropogenic activities to environmental impacts .
The performance of energy, water and food sectors within national boundaries has been traditionally analysed separately, where indicators focus on a specific resource type such as energy , or water . For instance, the United Nations and World Bank provide number of indicators, although providing a partial view of the sector’s resources and do not fully consider the interrelationship between the sectors. However, in order to understand the state of sustainable development for a region or country, it is vital to quantitatively combine information pertaining to energy, water and food sectors . In order to achieve a rapid nexus appraisal and measure the performance of a system in terms of efficient resource use, then indicators for each type of intervention can be quantified using specific tools, such as input-output, modeling and information resources tools . In this regard, several indices provide information on the status of EWF nexus within the analysis of resources security, such as the WEC Energy Trilemma Index , the Water Exploitation Index Plus and the FAO Food Price Index .