模拟降水条件下农田径流面源污染形成机制与协同防控策略研究

Study on formation mechanisms and synergistic control strategies of agricultural runoff non-point source pollution under simulated rainfall conditions

摘要

【目的】为防控面源污染对水环境的不良影响，精准解析降水-土壤-作物系统中面源污染动态形成机制与协同防控策略具有重要作用。【方法】设计多维度动态对比模拟降水试验，通过控制作物类型(小麦和玉米)、生育期(生长期和成熟期)及管理措施(施肥和未施肥)三个关键变量，结合高频径流监测与土壤理化分析量化不同情景径流污染特征差异。【结果】径流在降水2 h后形成且污染物浓度随历时衰减；85 cm株高玉米田径流、铵氮、总氮、硝态氮和总磷浓度较小麦田分别高210.3%、38.0%、188.5%、275.4%和128.1%;株高200 cm玉米田径流铵氮、总氮、硝态氮和总磷流失通量较80 cm株高分别下降68.8%、79.3%、88.5%和62.5%。小麦生长期施肥使径流COD、总氮、硝态氮和总磷浓度较未施肥分别增加43.9%、15.9%、57.5%、56.1%,玉米生长期施肥使径流COD、铵氮、总氮和硝态氮浓度较未施肥分别下降18.2%、68.2%、25.6%和60.7%。【结论】径流污染触发需满足临界降雨强度且污染物通量随降雨历时显著衰减，表层土壤存在“冲刷极限”效应。玉米成熟期强化冠层截留与根系吸收使氮磷流失通量较80 cm株高时下降。

Abstract

[Objective] To mitigate the adverse impacts of non-point source pollution on the aquatic environment, it is crucial to accurately elucidate the dynamic formation mechanisms of such pollution and the synergistic control strategies within the precipitation-soil-crop system. [Methods] A multi-dimensional dynamic comparative precipitation simulation experiment was designed by controlling three key variables: crop type(wheat and maize), growth stage(growing and mature), and management practice(fertilized and unfertilized). Differences in runoff pollution characteristics under different scenarios were quantified through high-frequency runoff monitoring and soil physicochemical analysis. [Results] Runoff formed 2 hours after precipitation, and pollutant concentrations decreased over time. In maize fields with a plant height of 85 cm, runoff concentrations of chemical oxygen demand(COD), ammonium nitrogen(NH₄~+-N), total nitrogen(TN), nitrate nitrogen(NO₃~--N), and total phosphorus(TP) were 210.3%, 38.0%, 188.5%, 275.4%, and 128.1% higher, respectively, than those in wheat fields. For maize at 200 cm plant height, runoff fluxes of NH₄~+-N, TN, NO₃~--N, and TP decreased by 68.8%, 79.3%, 88.5%, and 62.5%, respectively, compared to those at 80 cm plant height. Fertilization during the wheat growing stage increased runoff concentrations of COD, TN, NO₃~--N, and TP by 43.9%, 15.9%, 57.5%, and 56.1%, respectively, compared to unfertilized plots. In contrast, fertilization during the maize growing stage reduced runoff concentrations of COD, NH₄~+-N, TN, and NO₃~--N by 18.2%, 68.2%, 25.6%, and 60.7%, respectively, compared with unfertilized plots. [Conclusion] Runoff pollution is triggered only when rainfall intensity exceeds a critical threshold, and pollutant fluxes show a pronounced decay over the rainfall duration, reflecting a “scouring threshold” effect in the surface soil. Compared to the 80 cm plant height stage, enhanced canopy interception and root uptake significantly reduced nitrogen and phosphorus loss fluxes during the mature maize stage.

关键词

面源污染 / 农田径流 / 降水 / 冲刷极限 / 施肥 / 水环境 / 总氮 / 冠层结构

Key words

non-point source pollution / agricultural runoff / precipitation / scouring threshold / fertilization / water environment / total nitrogen / canopy structure

基金资助

国家自然科学基金项目(42277394)

河南省重点研发与推广专项(科技攻关)(232102320104)