丰乐河污染输出特征研究

Characteristics of pollutant export from Fengle River

为动态跟踪丰乐河水质和营养性污染物氮、磷输出通量的变化,自1995至2005年在其中下游桃溪断面进行每月一次的水质监测和取样分析,在同一站点进行连续的流量测定。结果表明,丰乐河桃溪断面水质总体在Ⅱ～Ⅳ类水之间,硝酸盐氮浓度普遍高于氨氮浓度;污染物浓度年内变化不同指标呈现不同的季节性变化特征,氮、磷输出负荷在短历时的洪水期较高,其中总磷负荷随流量增加较显著;氮、磷输出通量和浓度年际差别较大,但没有明显的趋势变化,总体来说丰水年溶解性无机氮和总磷的输出通量与浓度均较枯水年大,变幅也相对较大。这主要是由于桃溪断面控制的流域主要是农业用地和林地,污染源以非点源为主,河水水质及其变化受污染来源及复杂输送过程的影响。

Water at Taoxi section of Fengle River was sampled and monitored monthly from 1995 to 2005 in order to understand pollutant export evolution and temporal variation. Continuous daily water flow data were also available at the same site. The results showed that the water quality of Fengle River varied between level Ⅱ and level Ⅳ according to the surface water quality standard, and nitrate and nitrite levels were higher than ammonia levels. Different pollutants showed different seasonal variations. Nitrogen and phosphorus loads were much higher during the short period of high water flow, with the load of total phosphorus （TP） increasing sharply when the discharge was greater than 50 m3 · s^ - 1 （ percent of time discharge exceeded was 11% ）. Pollutant loads and concentration varied from year to year without any obvious trend. The interannual variation was connected with catchment rainfall-runoff condition, demonstrating higher levels and greater variation of nitrogen and phosphorus export in terms of both concentration and total loads in wet years than that in dry years. The studied catchment was characterized of agriculture and forest in terms of land use. So nonpoint sources contributed most of the pollutant export which was under the great influence of rain fall-runoff conditions.