The evaluation and prediction of agriculture-related nitrate contamination in groundwater in Chengdu Plain, southwestern China

Zhang, Han; Yang, Ruxing; Wang, Yu; Ye, Rongzhong

The evaluation and prediction of agriculture-related nitrate contamination in groundwater in Chengdu Plain, southwestern China | Evaluation et prévision de la contamination par les nitrates d’origine agricole des eaux souterraines de la Plaine de Chengdu, dans le sud-ouest de la Chine La evaluación y predicción de la contaminación por nitratos en el agua subterránea relacionada con la agricultura en la llanura de Chengdu, en el suroeste de China 中国西南部成都平原地下水中农业有关的硝酸盐污染的评估和预测 Avaliação e previsão de contaminação por nitrato em águas subterrâneas relacionada à agricultura na planície de Chengdu, sudoeste da China

2019

Zhang, Han | Yang, Ruxing | Wang, Yu | Ye, Rongzhong

The aquifer beneath Chengdu Plain is a main water resource for drinking and industry, which has severe groundwater nitrate contamination due to the shallow water table and intensive agricultural activities. The aim of this study is to estimate nitrogen loading to the aquifer and to predict nitrate concentration in groundwater in response to changes in land-use and agricultural practices, i.e. nitrogen fertilizer application, in ‘Jingyang region’ of the Chengdu Plain, one of the most developed agriculture areas in southwestern China. The framework utilized a geographic information system to account for the spatial and temporal distribution of on-ground nitrogen sources and corresponding loadings, and employed an export coefficient model to estimate the corresponding nitrogen loss. The simulation of nitrate fate and transport in the aquifer was conducted by developing a groundwater mass transport model using MODFLOW and MT3DMS. A number of predictive simulations for year 2026 were carried out to evaluate the impact of land-use and proposed future management options on controlling groundwater nitrate contamination. The results show that a nitrate plume would extend over most of the study area with some local areas having concentrations exceeding 20 mg L⁻¹ under the current setting and the scenario of increasing agricultural land use. Reduction in fertilizer application rates did mitigate nitrate contamination; however, this effect diminished with the expansion of agricultural land use. Land-use planning should consider the significant effects of agriculture to improve the quality of groundwater in the Chengdu Plain.

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