平原河网地区典型旱地面源污染排放系数时间变化特征及影响因素研究

Temporal variation in discharge coefficients of non-point source pollution and its determinants in river-network areas in a plain

【目的】探明平原河网地区典型旱地离田排放系数的变化特征,为农业面源污染监测管理提供参考。【方法】以上海市崇明岛某典型旱地为研究对象,通过构建水文-水质协同监测系统,对旱地面源污染排放系数进行测算,明确排放系数的时间变化特征,分析排放系数的影响因素。【结果】日尺度下,氮、磷的离田排放系数变化范围分别为2.2~9843.9、0.08~667.0 g/(hm^(2)·d);月尺度下,氮、磷离田排放系数变化范围分别为0.02~17.2、0.001~1.04kg/(hm^(2)·m)。在降水产流事件中,氮离田排放系数与降水历时呈极显著正相关,磷离田排放系数与产流事件的总降水量、平均降水强度、最大小时降水强度极显著正相关。施肥后,氮日排放系数迅速增大,磷日排放系数无明显变化。各时间尺度下,氮排放系数与地表径流不存在显著相关性,磷排放系数与地表径流极显著正相关。【结论】氮、磷离田排放系数的日、月际变化幅度较大,氮离田排放系数易受施肥措施影响,磷离田排放系数则更易受降水和地表径流的影响。

【Objective】Discharge coefficient is a coefficient describing the discharge of non-point source pollution to water bodies.It is affected by many biotic and abiotic factors.In this paper,we analyze its variation in typical drylands in river network areas in a plain.【Method】The studied area is located at the Chongming Island,Shanghai.A hydrology-water quality collaborative monitoring system was constructed in the island,which can accurately calculate the discharge coefficient of non-point source pollution,identify its temporal variation,and analyze the underlying influencing factors.【Result】①Daily discharge coefficient of total nitrogen(TN)and total phosphorus(TP)is 2.2-9843.9 and 0.08-667.0 g/(hm^(2)·d),respectively;monthly discharge coefficients of TN and TP is 0.02-17.2 and 0.001-1.04 kg/(hm^(2)·m)respectively.②The total nitrogen discharge coefficient during precipitation runoff period is significantly positively correlated with duration of the precipitation,while the TP discharge coefficient is significantly positively correlated with the total precipitation,average precipitation intensity,and maximum hourly precipitation intensity.③Following fertilization,the daily discharge coefficient of TN increases rapidly,while the daily discharge coefficient of TP remains almost unchanged.④At different time scales,there is no notable correlation between TN discharge coefficient and surface runoff,whereas the TP discharge coefficient exhibits a significant positive correlation with surface runoff.【Conclusion】The discharge coefficients of nitrogen and phosphorus vary with time scales,with significant differences observed between daily and monthly discharge coefficients.TN discharge coefficient is primarily influenced by fertilization,whereas TP discharge coefficient is more sensitive to precipitation and surface runoff.