College of Water Resources, North China University of Water Resources and Electric Power, Zhengzhou, 450046, China.
State Key Laboratory of Hydroscience and Engineering, Department of Hydraulic Engineering, Tsinghua University, Beijing, 100084, China.
Environ Sci Pollut Res Int. 2023 Nov;30(55):117250-117264. doi: 10.1007/s11356-023-30486-9. Epub 2023 Oct 21.
Drainage water quality is a crucial factor reflecting the regime of agricultural non-point source pollution in irrigation districts and is closely related to land use, soil texture, cropping pattern, fertilization, and irrigation and drainage conditions. However, the response of drainage water quality to various natural and anthropogenic factors needs further exploration in irrigation districts affected by shallow groundwater table. Spatiotemporal patterns of chemical oxygen demand (COD), total phosphorus (TP), total nitrogen (TN), and ammonium nitrogen (NH-N) were monitored and analyzed in ten agricultural drainage ditches in the arid region of China from 2011 to 2019. Spatially, water pollution in agricultural drainage ditches with small water quantity can be significantly exacerbated by urban sewage, whereas a large amount of agricultural drainage can effectively dilute the pollution of urban sewage. Severe soil salinization in the cropland increases the risk of water pollution due to easier losses of soil nutrient and organic matter. Soil salinization is a key factor in the crop distribution pattern based on the crop salt tolerance, and the maize/wheat field with a higher fertilizer application rate generally results in poorer drainage water quality. Temporally, for the agricultural drainage ditches, the monthly and annual COD, TP, TN, and NH-N concentrations fluctuate inversely with drainage water quantity and are positively correlated with fertilizer application, among which the monthly COD concentration in drainage water has larger variation in severe salinized areas. There exist critical annual and monthly drainage amounts, above which the probabilities of higher concentrations of COD, TP, TN, and NH-N reduce greatly.
排水水质是反映灌区农业面源污染状况的重要因素，与土地利用、土壤质地、种植方式、施肥和灌排条件密切相关。然而，在受浅层地下水位影响的灌区中，排水水质对各种自然和人为因素的响应仍需进一步探讨。本研究于 2011—2019 年对中国干旱区 10 条农业排水沟的化学需氧量（COD）、总磷（TP）、总氮（TN）和铵态氮（NH-N）进行了监测和分析。空间上，水量较小的农业排水沟受城市污水的影响，水污染可能会明显加剧，而大量的农业排水可以有效稀释城市污水的污染。农田严重盐渍化会增加因土壤养分和有机质更容易流失而导致的水污染风险。土壤盐渍化是基于作物耐盐性的作物分布格局的关键因素，施肥量较高的玉米/小麦田通常会导致较差的排水水质。时间上，对于农业排水沟，COD、TP、TN 和 NH-N 的月和年浓度与排水量呈反比，与施肥量呈正相关，其中排水水中 COD 浓度的月变化在严重盐渍化地区较大。存在临界年和月排水量，超过这些排水量后，COD、TP、TN 和 NH-N 浓度较高的概率会大大降低。
