College of Agricultural Science and Engineering, Hohai University, Nanjing, 210098, China; Jiangsu Province Engineering Research Center for Agricultural Soil‒Water Efficient Utilization, Carbon Sequestration and Emission Reduction, Nanjing, 210098, China.
College of Agricultural Science and Engineering, Hohai University, Nanjing, 210098, China; College of Soil and Water Conservation, Hohai University, Changzhou, 213200, China.
Environ Res. 2024 Jun 1;250:118484. doi: 10.1016/j.envres.2024.118484. Epub 2024 Feb 18.
The Ningxia Yellow River irrigation area, characterized by an arid climate and high leaching of NO-N, exhibits complex and unique groundwater nitrate (NO-N) pollution, with denitrification serving as the principal mechanism for NO-N removal. The characteristics of N leaching from paddy fields and NO-N removal by groundwater denitrification were investigated through a two-year field observation. The leaching losses of total nitrogen (TN) and NO-N accounted for 10.81-27.34% and 7.59-12.74%, respectively, of the N input. The linear relationship between NO-N leaching and N input indicated that the fertilizer-induced emission factor (EF) of NO-N leaching in direct dry seeding and seedling-raising and transplanting paddy fields was 8.2% (2021, R = 0.992) and 6.7% (2022, R = 0.994), respectively. The study highlighted that the quadratic relationship between the NO-N leaching loss and N input (R = 0.999) significantly outperformed the linear relationship. Groundwater denitrification capacity was characterized by monitoring the concentrations of dinitrogen (N) and nitrous oxide (NO). The results revealed substantial seasonal fluctuations in excess N and NO concentrations in groundwater, particularly following fertilization and irrigation events. The removal efficiency of NO-N via groundwater denitrification ranged from 42.70% to 74.38%, varying with depth. Groundwater denitrification capacity appeared to be linked to dissolved organic carbon (DOC) concentration, redox conditions, fertilization, irrigation, and soil texture. The anthropogenic-alluvial soil with limited water retention accelerated the leaching of NO-N into groundwater during irrigation. This process enhances the groundwater recharge capacity and alters the redox conditions of groundwater, consequently impacting groundwater denitrification activity. The DOC concentration emerged as the primary constraint on the groundwater denitrification capacity in this region. Hence, increasing carbon source concentration and enhancing soil water retention capacity are vital for improving the groundwater denitrification capacity and NO-N removal efficiency. This study provides practical insights for managing groundwater NO-N pollution in agricultural areas, optimizing fertilization strategies and improving groundwater quality.
宁夏引黄灌区气候干旱，硝态氮淋失量大，地下水硝酸盐（NO-N）污染具有复杂而独特的特征，反硝化作用是 NO-N 去除的主要机制。通过两年的田间观测，研究了稻田氮素淋失和地下水反硝化去除 NO-N 的特征。总氮（TN）和 NO-N 的淋失损失分别占氮素投入的 10.81%-27.34%和 7.59%-12.74%。NO-N 淋失与氮素投入呈线性关系，表明直播和育秧移栽稻田肥料诱导的 NO-N 淋失排放因子（EF）分别为 8.2%（2021 年，R=0.992）和 6.7%（2022 年，R=0.994）。研究表明，NO-N 淋失损失与氮素投入的二次关系（R=0.999）显著优于线性关系。地下水反硝化能力通过监测二氮（N）和一氧化二氮（NO）的浓度来表征。结果表明，地下水过量 N 和 NO 浓度具有明显的季节性波动，特别是在施肥和灌溉后。地下水反硝化去除 NO-N 的效率范围为 42.70%-74.38%，随深度而变化。地下水反硝化能力似乎与溶解有机碳（DOC）浓度、氧化还原条件、施肥、灌溉和土壤质地有关。保水能力有限的人为冲积土壤在灌溉过程中加速了 NO-N 向地下水的淋失。这一过程增强了地下水的补给能力，改变了地下水的氧化还原条件，从而影响了地下水反硝化活性。DOC 浓度是该地区地下水反硝化能力的主要限制因素。因此，增加碳源浓度和增强土壤保水能力对于提高地下水反硝化能力和 NO-N 去除效率至关重要。本研究为农业区地下水 NO-N 污染管理、优化施肥策略和改善地下水质量提供了实践见解。
