巢湖典型农村流域面源氮磷污染模拟及来源解析

Simulation and source analysis of nonpoint source nitrogen and phosphorus pollution export in a typical agricultural catchment draining to Chaohu Lake,China

为探究巢湖典型农村流域面源氮磷污染特征及来源,以巢湖北岸烔炀河流域为对象,基于2018—2020年监测数据和流域污染源调查数据,采用改进的输出系数法,模拟了该典型流域氮磷污染输出时空变化。结果表明:2018—2020年烔炀河流域面源污染氮、磷输出平均值分别为(261.33±173.87)t·a^(-1)和(11.03±9.98)t·a^(-1),水雨情条件大幅改变造成污染输出的年际差异显著。源头子流域为流域面源污染总量的首要贡献者,炀河源头子流域的总氮年均输出[(32.76±21.80)t·a^(-1)]和烔河源头子流域总磷年均输出[(1.81±1.64)t·a^(-1)]最高;生活污水和土地利用的氮磷输出在炀河源头子流域最高,畜禽养殖的最高氮磷输出位于烔河源头子流域。农田对全流域面源总氮和总磷污染输出的贡献分别高达81%和52%,化肥施用强度高依然是农村流域面源污染的核心问题。流域污染组成结构的高度异质性表明农村流域面源污染防控应抓住重点,且分区、分类施策。

To investigate the characteristics and sources of nonpoint source(NPS)nitrogen and phosphorus pollution in a typical agricultural catchment draining to Chaohu Lake,the spatial and temporal variations in nitrogen and phosphorus pollution export from the Tongyang River catchment were simulated using an improved export coefficient model based on monitoring data and survey data from 2018to 2020.Results showed that the average exports of NPS nitrogen and phosphorus pollution in this catchment were(261.33±173.87)t·a^(-1)and(11.03±9.98)t·a^(-1)during 2018—2020.The significant inter-annual variation was attributed to radical fluctuations in the hydrologic condition.The headwater sub-catchments were the main contributors to the total NPS nitrogen and phosphorus pollution in the Tongyang River catchment.The annual average export of total nitrogen(TN)was(32.76±21.80)t·a^(-1)in the Yang River headwater sub-catchment.The average annual export of total phosphorus(TP)in the Tong River headwater sub-catchment was(1.81±1.64)t·a^(-1),both of which were the highest of all the sub-catchments.The highest exports of TN and TP from domestic sewage and land use were from the Yang River headwater sub-catchment,whereas the highest exports of TN and TP from livestock and poultry breeding were from the Tong River headwater sub-catchment.Croplands contributed 81%and 52%of the NPS nitrogen and phosphorus pollution,respectively.Highintensity fertilizer application was the key issue of NPS pollution in this typical agricultural catchment.The high heterogeneity of the NPS pollution composition indicates the need to focus on critical areas and implement classified measures for controlling NPS pollution in agricultural catchments.