College of Environmental Science and Engineering, Ocean University of China, Qingdao, 266100, China; Key Laboratory of Marine Environment and Ecological Education, Ocean University of China, Qingdao, 266100, China.
College of Environmental Science and Engineering, Ocean University of China, Qingdao, 266100, China; Key Laboratory of Marine Environment and Ecological Education, Ocean University of China, Qingdao, 266100, China.
Chemosphere. 2024 Oct;366:143449. doi: 10.1016/j.chemosphere.2024.143449. Epub 2024 Oct 2.
Leaching of dissolved organic nitrogen (DON) is a significant pathway for nitrogen (N) loss in agricultural ecosystems. The excessive application of N for enhanceing agricultural productivity often results in the leaching of N into groundwater. Yet not well understood, the extent of retention in the vadose zone has critical implications for risk management and remediation strategies. This study aims to advance simulation techniques for modelling the transport process of reactive DON within a heterogeneous vadose zone. Through a combination of laboratory experiments and numerical simulations, the study firstly examines the extent of DON retention in the vadose zone and quantitatively analyse groundwater contamination risk from this kind of accumulation. Our findings indicate that heavy N fertilizer application and high-intensity rainfall events led to elevated contents of DON in the vadose zone and increased DON leaching fluxes into groundwater. Besides, intensifier rainfall reduced the N storage more quickly in scenarios devoid of DON application with higher mineralization rate, while DON slowly mineralized to other forms, largely accumulated in the top layer and migrated deeper with intensifier rainfall after input of urea. In our scenarios, DON accounted for a substantial portion (33-68%) of the total dissolved nitrogen (TDN) leaching fluxes, with exogenous DON content contributing significantly (25-85%) to the overall DON leaching into the aquifer. These results underscore the need for effective strategies to mitigate groundwater contamination risks associated with agricultural N use.
溶解有机氮（DON）的淋失是农业生态系统中氮（N）损失的一个重要途径。为了提高农业生产力而过量施用氮肥，往往会导致氮淋溶到地下水中。然而，人们对其在包气带中的截留程度还了解甚少，这对风险管理和修复策略具有重要意义。本研究旨在推进模拟技术，以模拟反应性 DON 在非均质地层中的运移过程。本研究通过实验室实验和数值模拟相结合，首先考察了 DON 在包气带中的截留程度，并定量分析了这种积累对地下水污染风险的影响。研究结果表明，大量施氮肥和强降雨事件会导致包气带中 DON 含量升高，增加 DON 淋溶通量进入地下水。此外，在没有 DON 应用的情况下，强降雨会使氮储存更快地减少，而 DON 则会以较高的矿化率缓慢转化为其他形式，大部分在表层积累，并在输入尿素后随着强降雨的增强而向深层迁移。在我们的场景中，DON 占总溶解氮（TDN）淋溶通量的很大一部分（33-68%），外源 DON 含量对 DON 整体淋溶到含水层中的贡献很大（25-85%）。这些结果强调了需要采取有效策略来减轻与农业 N 利用相关的地下水污染风险。
