Reducing impacts of rice fields nitrate contamination on the river ecosystem by a coupled SWAT reservoir operation optimization model

The present study proposes a multipurpose reservoir operation optimization for mitigating impact of rice fields’ contamination on the downstream river ecosystem. The developed model was applied in the Tajan River basin in Mazandaran Province, Iran, in which the rice is the main crop. We used soil and water assessment tool (SWAT) to simulate inflow of the reservoir and nitrate load at downstream river reach. Nash–Sutcliffe model efficiency coefficient was used to measure the robustness of SWAT. NSE indicated that SWAT is acceptable to simulate nitrate load of the rice fields. The results of SWAT was applied in the structure of a multipurpose reservoir operation optimization in which three metaheuristic algorithms including differential evolution algorithm, particle swarm optimization and biogeography-based algorithm were utilized in the optimization process. Reliability index, mean absolute error and failure index were used to measure the robustness of the optimization algorithms. Fuzzy Technique for Order of Preference by Similarity to Ideal Solution was utilized to select the best algorithm. Based on results, particle swarm optimization is the best method to optimize reservoir operation in the case study. The reliability index and mean absolute error for water supply are 0.6 and 5 million cubic meters, respectively. Furthermore, the failure index of contamination is 0.027. Hence, it could be concluded that the proposed optimization system is reliable and robust to mitigate losses and nitrate contamination simultaneously. However, its performance is not perfect for minimizing impact of contamination in all the simulated months.

Rural population health risks caused by nitrate contamination of locally grown vegetables

Objectives to assess the levels of health risks in the rural population associated with the consumption of local vegetables contaminated with nitrates. Material and methods. We established the concentration of nitrates in local vegetables, grown on farms and private subsidiary plots of agricultural areas of the region using a retrospective analysis of the statistics from the Office of Federal Service for Surveillance on Consumer Rights Protection and Human Well-being (Rospotrebnadzor) in the Saratov region and our own research results. The health risks in the rural population from exposure to nitrates in local vegetables were assessed according to the Risk Assessment Guidelines (R 2.1.10. 1920-04). Results. It was revealed that local vegetable products are widely used in the diet of the rural population of the agricultural areas of the Saratov region, amounting to 203.422.5 kg/year per adult resident. Significant differences were revealed in the nitrate contamination of vegetables grown by farmers and on private subsidiary plots of agricultural areas of the Saratov region. Discussion. The high nitrate load detected in vegetable products of farms was determined by a significant amount of fertilizers applied to the soil in the form of ammonium nitrate. On the contrary, the use of special biomass from plants of the legume family by workers of personal subsidiary farms for feeding the growing vegetables, made it possible to obtain vegetable products with a significantly lower quantitative content of nitrates. Conclusion. The assessment of the hazard coefficients of nitrates in vegetable products of the studied areas testified to the possible effect of the nitrate component on the health of the local population. The individual carcinogenic risk caused by nitrate contamination of local vegetables was assessed as low; the population carcinogenic risk value associated with the presence of nitrates in vegetables had the possibility to contribute from 0.01 to 1.3 additional cases of malignant neoplasms to the general level of oncological morbidity in the population of the surveyed territories.

Challenges of groundwater pollution and management in transboundary basins at the African scale

We address the significant knowledge gap for groundwater pollution in Africa methods by assessing groundwater pollution risk at the African scale. To do so, we compiled the most recent continental-scale information on soil, land use, geology, hydrogeology, and topography in a Geographical Information System at the resolution of 15 × 15 km and the 1:60 000 000 scale. We produced a vulnerability map by using the generic DRASTIC vulnerability indicator. This map revealed that groundwater is highly vulnerable in Central and West Africa groundwater basins, where the water table is shallow. In addition, very low vulnerability classes are found in the large sedimentary basins of Africa deserts where groundwater is situated in very deep aquifers. The generic groundwater pollution risk map is obtained by overlaying the DRASTIC vulnerability indicator with current land use. The northern, central, and western parts of the African continent are dominated by high vulnerability classes and very strongly related to water table depths and the development of agricultural activities. Given the availability of data, we concentrate first on nitrate vulnerability mapping. To this end, groundwater nitrate contamination data are compiled in literature using meta-analysis technic and used to calibrate as well linear and nonlinear statistical models; the latter performing much better as compared to simple linear statistical models. This study will help to raise awareness of the manager's International Basin Authorities or Transboundary Basin Organizations in Africa and in particular on transboundary groundwater pollution issues.

Nitrate contamination level in groundwater of the randublatung basin and its surroundings

The community of Randublatung basin and its surroundings (Grobogan, Blora, and Bojonegoro Regencies) using groundwater for agricultural, farming, and daily needs. However, these activities can contaminate the groundwater through nitrate and chloride in fertilizers, pesticides, animal waste, and household waste. Therefore, it is crucial to know the amount of nitrate and chloride content in the groundwater of The Randublatung basin and its surroundings. This research aims to analyze nitrate and chloride content and the ratio between ions in the groundwater of The Randublatung basin and its surroundings to find contaminant resources. The method to analyze the nitrate and chloride content is using Ion Chromatography. The analysis result from 35 samples of groundwater shows that the average nitrate content in dug wells samples is 10.06 mg/L, while the average from pump wells is 6.31 mg/L. The average chloride in dug wells samples is 43.65 mg/L, and the average from pump wells is 54.57 mg/L. These nitrate and chloride level are still in safe category based on Health Ministry Indonesia and WHO. The nitrate: chloride ratio in dug wells is 1:5, 1:9 from pump wells. The ratios indicate that the nitrate’s resource is associated with the on-site sanitation and will increase if there is no mitigation action to the contaminant resource.

The effect of coal stockpile on shallow groundwater aquifer: Study case Tarahan

This paper aims to determine the existence of groundwater contamination due to coal stockpile activity in shallow groundwater. The research area is located in a stockpile that has been operating since 1986. We conducted chemical content analysis at several points around the coal stockpile and outside the stockpile area to see the impact of pollution on the surrounding residents’ areas. This study also uses geoelectric methods and direct observations to identify shallow groundwater levels (water table). The research area has a groundwater depth of about 2 m from the surface, and groundwater flows from northeast to southwest (sea). The chemical content analysis results show that each sample taken around the stockpile is below the water quality standard threshold, so it can be concluded that coal stockpile activity does not contaminate the shallow groundwater. However, there is nitrate contamination from shallow groundwater located outside the stockpile area taken from dug wells and drilling wells with a depth of 8 m shows a value of 14.08-23.67 ppm (>10 ppm threshold). We suspect that this pollution is caused by the large number of mining activities carried out in the north of the study area.