This paper focuses on a collection of methods that can be used to analyze the water-energy-food (WEF) nexus. We classify these methods as qualitative or quantitative for interdisciplinary and transdisciplinary research approaches. The methods for interdisciplinary research approaches can be used to unify a collection of related variables, visualize the research problem, evaluate the issue, and simulate the system of interest. Qualitative methods are generally used to describe the nexus in the region of interest, and include primary research methods such as Questionnaire Surveys, as well as secondary research methods such as Ontology Engineering and Integrated Maps. Quantitative methods for examining the nexus include Physical Models, Benefit-Cost Analysis (BCA), Integrated Indices, and Optimization Management Models. The authors discuss each of these methods in the following sections, along with accompanying case studies from research sites in Japan and the Philippines. Although the case studies are specific to two regions, these methods could be applicable to other areas, with appropriate calibration.

Qualitative and quantitative analysis of organochlorine insecticide residues were conducted in water, sediment, aquatic plants and animals from 3 freshwater reservoirs. Ninety water samples, 90 sediment samples, 397 aquatic plants samples and 121 aquatic animals samples were collected during March-April and August-September 1989. There were about 14 kinds of aquatic plants, such as water hyacinth, water lettuce, algae and water lilly etc. Aquatic animals are fish, shrimps and snails, but most of them are fish. They are striped snake-head fish, carp and catfish etc. Total samples of 698 were analyzed by using gas chromatographic techniques at Agricultural Toxic Substances Division. The results indicated that 5 kinds of insecticides were found in most samples. They were lindane, heptachlor, aldrin, dieldrin, DDT and derivatives. Dieldrin was detected at higher concentration and found in all samples. The residue level of dieldrin ranged from 0.01-0.12 ppb in water, 0.005-0.036 ppm in sediment, 0.001-0.138 ppm in aquatic plants and 0.001-0.037 ppm in aquatic animals respectively. The accumulation of dieldrin residue in water and aquatic plant samples from all reservoirs are not different but the level of dieldrin residue in sediment samples from Bueng Boraphed is higher than the other 2 reservoris. However the levels of dieldrin residue in sediment, aquatic plant and aquatic animal samples higher than those in water samples respectively.

Food, energy and water are important basic resources that affect the sustainable development of a region. The influence of food–energy–water (FEW) nexus on sustainable development has quickly become a frontier topic since the Sustainable Development Goals (SDGs) were put forward. However, the overall context and core issues of the FEW nexus contributions to SDGs are still unclear. Using co-citation analysis, this paper aims to map the knowledge domains of FEW nexus research, disentangles its evolutionary context, and analyzes the core issues in its research, especially the progress of using quantitative simulation models to study the FEW nexus. We found that (1) studies within the FEW nexus focused on these following topics: correlation mechanisms, influencing factors, resource footprints, and sustainability management policies; (2) frontier of FEW studies have evolved from silo-oriented perspective on single resource system to nexus-oriented perspective on multiple systems; (3) quantitative research on the FEW nexus was primarily based on spatiotemporal evolution analysis, input–output analysis and scenario analysis; (4) the resource relationship among different sectors was synergies and tradeoffs within a region. In general, current research still focuses on empirical data, mostly qualitative and semiquantitative analyses, and there is a lack of research that can systematically reflect the temporal and spatial contribution of the FEW nexus to multiple SDGs. We believe that future research should focus more on how FEW nexus can provide mechanistic tools for achieving sustainable development.

Water, Energy and Food (WEF) are key elements of economic and social sustainable development, and present a complex nexus. Existed WEF nexus research is mainly confined to qualitative analyses, and it needs constant improvement and increases quantitative analyses. In China, water security is the most prominent problem in the WEF-nexus, which is manifested in the competitive relationship between food and energy production for water. Therefore, the matter of alleviating water resources stress has become a difficult and hot issue. After improving the existed water footprint accounting method for food and energy production, this study calculated the food water footprints (blue water footprint and green water footprint) in the 31 provinces of mainland China in 2015, as well as the blue water footprints of major energy systems (coal, oil, natural gas and thermal power generation). This study proposed water resources pressure index (IWS), water resources pressure contribution rate of food and energy (WCR), water consumption rate of food and energy (n) and competition composite index (CCI) of WEF, which were used to evaluate the consumption of water resources in food and energy production in different regions, and assess the intensity of competition for water resources in food and energy production. The results showed that the national food water footprint in 2015 was 690.8 Gm³, and the blue food water footprint was 287.8 Gm³. The main water-consuming blue energy water footprint was 18.5 Gm³, and coal production accounted for 9.9% and thermal power generation accounted for 87.6%. According to the competition indicators, the competition relationship among the administrative regions of the 31 provinces in mainland China was obtained. For example, 5 provinces had serious competition and 19 provinces had weak competition. The water consumption of the energy industry continues to grow rapidly by economic development. Corresponding measures should be taken according to the different competition levels for water resources.

Agriculture is the largest user of freshwater which is essential for food production. Water, energy and food are closely intertwined, as both water and energy are critical inputs for food production. Increasing pressure from shortages of resources and increasing demand for food reinforce the need for optimal management of the water, energy, and food nexus. Uncertainties caused by natural conditions and human activities complicate the optimal allocation. An integrated model, called AWEFSM, was developed for the sustainable management of limited water-energy-food resource in an agricultural system by incorporating multi-objective programming, nonlinear programming, and intuitionistic fuzzy numbers into a general framework. The AWEFSM model is capable of identifying the tradeoffs of water, energy and land resources among various subareas and crops, generating high-profile and environment-friendly strategies and policies, and addressing parameter uncertainties associated with the fluctuations of natural resources and variation of socioeconomic activities. The AWEFSM model was solved, considering nonlinear membership and non-membership functions with both optimistic and pessimistic views of decision makers, and was demonstrated for a real-world case study in northwest China. The interrelationships and trade-offs among system components, including water supply-demand, energy supply-demand, land demand, food production, as well as water and energy footprints, were quantitatively analyzed under different scenarios. The AWEFSM model is applicable for similar regions dominated by agriculture with limited resource supplies to determine water-energy-food strategies under uncertainty.

A rapid planar chromatographic method for identification and quantification of 25 water-soluble dyes in food was developed. In a horizontal developing chamber, the chromatographic separation on silica gel 60F(254) high-performance thin-layer chromatography plates took 12 min for 40 runs in parallel, using 8 mL ethyl acetate-methanol-water-acetic acid (65 + 23 + 11 + 1, v/v/v/v) mobile phase up to a migration distance of 50 mm. However, the total analysis time, inclusive of application and evaluation, took 60 min for 40 runs. Thus, the overall time/run can be calculated as 1.5 min with a solvent consumption of 200 μL. A sample throughput of 1000 runs/8 h day can be reached by switching between the working stations (application, development, and evaluation) in a 20 min interval, which triples the analysis throughput. Densitometry was performed by absorption measurement using the multiwavelength scan mode in the UV and visible ranges. Repeatabilities [relative standard deviation (RSD), 4 determinations] at the first or second calibration level showed precisions of mostly <or=2.7%, ranging between 0.2 and 5.2%. Correlation coefficient values (R >= 0.9987) and RSD values (<or=4.2%) of the calibration curves were highly satisfactory using classical quantification. However, digital evaluation of the plate image was also used for quantification, which resulted in RSD values of the calibration curves of mostly <or=3.0%, except for two <or=6.0%. The method was applied for the analysis of some energy drinks and bakery ink formulations, directly applied after dilution. By recording of absorbance spectra in the visible range, the identities of the dyes found in the samples were ascertained by comparison with the respective standard bands (correlation coefficients >or= 0.9996). If necessary for confirmation, online mass spectra were recorded within a minute.

In pursuit of continuous economic development, Bangladesh has undertaken long-term plans to boost its productivity in the agriculture, energy, and industrial sectors and to align with the United Nations Sustainable Development Goals (SDGs). Unless these strong interconnections and cross sectoral impacts are recognized, achievement of the future policy goals and national priorities of the concerned ministries regarding food self-sufficiency, cleaner energy sources, and water availability will be compromised. This study focuses on evaluating the impacts of cross-sectoral policy decisions on the interconnected resource systems at a national scale in Bangladesh. A quantitative analysis is performed to identify resource requirements, synergies, and trade-offs related to a set of future strategies. The analysis concludes by showing that land is the most limiting resource for future expansion and that fresh water will become a critical resource if alternative sources of water are not explored, and, that energy generation, if coal and other fossil fuels are favored over alternative energy sources, will significantly add to the total carbon emissions. Given the limitations of land available for agricultural expansion, of renewable water resources, and the challenges in meeting increasing water, energy, and food demands, the strong interdependencies among the interconnected resource systems must be accounted for. The SDG and national priority indicators are found to improve under scenarios for which resources are conserved via alternative sources.

As the basis of quantitative research over water-energy-food nexus (WEFN), qualitative analysis is indispensable for depicting the systems and providing effective measures and policies. Preceding qualitative WEFN studies largely neglected the role of local stakeholder participation, which could only reflect fragments of the systems. Causal loop diagrams (CLDs) have been proven to be effective for supporting stakeholder participation in many other areas. Nevertheless, there was a lack of impartial methods that could make CLD analysis tractable without significantly impairing the WEFN systems integrity. To fill such gaps, a novel method based on merging and reduction rules was proposed to reasonably merge and downscale WEFN CLDs built by stakeholders. Based on this improved method, a CLD-based methodology was developed as a prototype for characterizing WEFN systems, prescribing the WEFN problem, exploring its causes and consequences, and identifying effective measures and policies for alleviating conflicts. To validate the applicability of the developed methodology, it was applied to a real case. The results indicated that total water consumption, water allocation among varied sectors, available surface water, and available groundwater, as well as indirect factors such as volume of diverted water and agricultural water consumption, were the keys to alleviate water scarcity problem under WEFN in the study area. Measures and polices focusing on the interactions between surface water and groundwater could be viable for alleviating the problem. Directions to enhance tradeoffs and synergies within WEFN systems were also obtained.

Pesticide residues in human milk and environmental samples from Kafr El-Zayat Governorate in Egypt were analyzed. This governorate is located near one of the biggest pesticide factories in Egypt. Organochlorine and organophosphorus pesticides were monitored, including those that have been prohibited from use in Egypt. Human milk samples (31 samples) from Kafr El-Zayat were compared with 11 samples collected from Cairo. Data were compared with results from studies performed in 1987 and 1990. The present study showed that aldrin and dieldrin, heptachlor and heptachlor epoxide, and endrin residues have been eliminated from human milk. Estimated daily intakes (EDIs) of DDT complex and gamma-HCH by breast-fed infants in Kafr El-Zayat were 85.96 and 3.1% of respective acceptable daily intakes (ADIs). beta-HCH residues showed an increasing pattern, especially in human milk samples from Cairo. DDT complex and HCH isomers in orange, spinach, lettuce, potatoes, and clover samples ranged from undetectable to very low concentrations. Higher levels of DDT and HCH were detected, but aldrin, dieldrin endrin, and the heptachlors were not detected in food of animal origin. Residues in fish samples were below maximum residue limits established by some developed countries. Those in animal milk samples approached the extraneous residue limits of the Codex Committee on Pesticide Residues. HCH residues in soil were negligible, but DDT residues in soil were somewhat higher. Among water samples, groundwater samples had the highest residues of HCHs and DDTs, followed by Nile River water and then tap water. However, the organochlorine pesticide residues were found at concentrations below the maximum allowable limits set by the World Health Organization for drinking water. Among 12 organophosphorus pesticides monitored as parent compounds, dimethoate, malathion, methamidophos, and chlorpyrifos residues were detected in low concentrations in soil samples from a pesticide factory. No organophosphorus pesticide residues were found in plant samples, except for very low residues of dimethoate in an orange sample. Water samples were devoid of organophosphorus residues as parent compounds.

The nexus approach offers an important heuristic tool for the sustainable management of resources by considering the links among different sectors. The food-energy-water (FEW) nexus corresponds to links among the three of seventeen United Nations Sustainable Development Goals (SDGs), namely SDG2 (No Hungry), SDG6 (Clean Water and Sanitation), and SDG7 (Affordable and Clean Energy), and their interlinkages have a direct or indirect impact on other SDGs. However, there is still a lack of a systematic and quantitative analysis of how the nexus approach could promote achieving SDGs. Here, taking China as a case, we built an expanded FEW nexus framework from the lens of SDGs, which consists of six sectors, including food (SDG2), water (SDG6), energy (SDG7), economic (SDG8), consumption and production (SDG12), and forest (SDG15). We quantified the two-way interactions between the six sectors by the panel vector autoregressive (PVAR) model. Results indicate that sectors exhibit different response characteristics (positive or negative) in their interactions, and these responses could change over time. These results imply that changing the priorities of actions may be an effective measure to transform trade-offs into synergies. Moreover, the contribution of different sectors to each other varies considerably, with economic growth (SDG8) generally having a higher impact on changes in the FEW nexus than consumption and production patterns (SDG12). Our research suggests that strengthening the quantitative assessment of two-way interactions among the FEW nexus has crucial implications for leveraging nexus approaches effectively to achieve sustainable development for all.