太湖流域典型地区农村生活污水中污染物在表层土壤中的削减特征与测算

Characteristics and Estimation of Rural Sewage Pollutants Abatement by Surface Soil in Typical Rural Regions of Taihu Lake Basin

原位采集太湖流域典型平原河网地区农户化粪池排污口附近的表层土壤及化粪池出水,人工模拟研究区域典型降雨(夏季30 mm·次-1,冬季5 mm·次-1)、气温(夏季27℃,冬季5℃)条件以及排污负荷〔TN:(2.35±0.06)g·m-2·d-1,NH4+-N:(2.08±0.04)g·m-2·d-1,TP:(0.21±0.01)g·m-2·d-1,COD:(11.14±0.59)g·m-2·d-1〕,并进行室内模拟土柱试验,测算不同季节(夏季和冬季)、不同天气过程(雨前、雨天和雨后)排污口表层土壤对农村生活污水各类污染物的削减率并探讨其削减规律。结果表明:在季节差异上,雨前、雨天和雨后TN削减率均表现为夏季<冬季(P<0.05或P<0.001),NH4+-N削减率则均表现为夏季>冬季(P<0.01);雨前和雨后TP削减率表现为夏季>冬季(P<0.001),COD削减率无显著季节性差异;雨天TP和COD削减率则均表现为夏季<冬季(P<0.01或P<0.001)。在天气过程差异上,夏季土壤TN削减率表现为雨后>雨前>雨天(P<0.01),夏季TP和COD削减率表现为雨前≈雨后>雨天(P>0.05,P<0.01),而夏季NH4+-N,冬季TN、NH4+-N、TP和COD削减率在不同天气过程之间无显著差异(P>0.05)。据此划分,夏季雨前、雨天和雨后及冬季TN削减率分别为38.5%、-25.0%、46.0%和50.4%,夏季和冬季NH4+-N削减率分别为91.5%和85.5%,夏季雨天、夏季其余时间及冬季TP削减率分别为63.3%、93.1%和82.7%,夏季雨天及其余时间COD削减率分别为8.2%和66.2%。

Abstract： Samples of surface soils near the outlets of farmer household septic tanks and samples of the effluents from the tanks were collected in a plain river network region typical of the Taihu Lake Basin for use in an in-laboratory experiment with simulated rainfall （for summer,30 mm per event and for winter 5 mm per event,typical of the region） controlled temperature （27 ℃ for summer and 5 ℃ for winter,typical of the region） and simulated pollutant load [TN：（2.35 ± 0.06） g·m^-2 ·d^-1,NH4-N：（2.08±0.04） g·m^-2 ·d^-1,TP：（0.21±0.01） g·m^-2 ·d^-1,COD：（11.14±0.59）g ·m^-2 · d^-1] to estimate pollutants abatement rate in the polluted surface soils and to explore rules of the abatement as affected by seasons （summer and winter） and synoptic process （before the rain,during the rain,after the rain）.Results show that TN abatement rates,no matter whether before the rain,in the rain,or after the rain,all showed a tendency of summer 〈 winter （P〈0.05 or P〈0.001）,and on the contrary,NH4＋-N abatement rates all showed a reverse trend of summer 〉 winter （P〈0.01）.TP abatement rates showed a tendency of summer 〉 winter （P〈0.001） before the rain and after the rain,but COD abatement rates did not differ much between summer and winter.TP and COD abatement rates in the rain both showed a tendency of summer 〈 winter （P〈0.01 or P〈0.001）.As to difference between weather processes,TN abatement rates in summer showed a tendency of after the rain 〉 before the rain〉 in the rainy days （P〈0.01）,TP and COD abatement rates in summer showed a tendency of before the rain≈ after the rain〉 in the rainy days （P〉0.05,P〈0.01）,whereas,NH4 ＋-N abatement rates in summer did not differ much between synoptic processes and TN,NH4 ＋-N,TP and COD abatement rates in winter did not either （P〉0.05）.So,the TN abatement rate before the rain,in the rainy days,after the rain in summer and in winter was 38.5%,-25.0%,46.0% and 50.4%,respectively.The NH4＋-N abatement rate in summer and in winter averaged 91.5% and 85.5%,respectively.The TP abatement rate in the rainy days in summer,in the rest of summer and in winter averaged 63.3%,93.1% and 82.7%,respectively.The COD abatement rate in the rainy days in summer and in the rest of the year was 8.2% and 66.2%,respectively,on average.