太湖典型河网区地表水与沉积物氮、磷和重金属含量空间分异

将无锡城乡交错区河网分为城镇生活区水巷、工业区主河道、农业区主河道、农业区支流和鱼塘5种类型区.通过秋季(旱季)和夏季(雨季)2次采样,研究氮、磷和Cu、Zn、Pb、Cr、Cd在地表水和沉积物中的含量及其空间变化.结果表明:(1)城乡交错区地表水氮、磷来源于生活污染和工业污染的比例大于农田,同时具有来源分散、污染面广的特征.(2)由于城镇地表径流和工业活动影响,各类型区地表水重金属含量均有不同程度提高.但地表水重金属主要沿主河道迁移,旱季和雨季主河道重金属含量均大于农业区支流,而且随着与城镇距离增加,主河道沉积物重金属含量迅速降低,重金属污染影响范围较小.(3)与重金属相比,地表水氮、磷污染仍是太湖水网区主要的环境问题.但城镇及其周围河流沉积物中富集的重金属含量很高,其潜在环境风险不容忽视.

Spatial Variations of Nitrogen, Phosphorus and Heavy Metals in Surface Water and Sediment of a Typical River Network Zone in Taihu Lake Region

In the peri-urban river network area of Wuxi,which could be classified into 5 parts,i.e.watercourses in the residential area,main river course in the industry area,main river course in the farming area,ditches of the farming area and fishpond area.Sampling was carried out in both autumn(dry) and summer(rainy) seasons.Concentrations of nitrogen,phosphorus and Cu,Zn,Pb,Cr,Cd in samples of surface water and sediment were determined and their spatial variations were studied.Results show that 1) industrial wastewater and domestic sewage were the main contributors of nitrogen and phosphorus pollution in the surface water,rather than agriculture fields.And they were scattered in distribution and extensive in impact.2) Concentrations of heavy metals in the water and sediment were elevated to varying extents in the above-listed 5 types of water zones.Heavy metal pollution was induced mainly by industrial activities and urban surface runoff.However,heavy metals in the surface water were transported mainly along the main river courses.In both dry season and rainy season,heavy metal concentrations in the main river course were higher than that in ditches of the farming area and heavy metal concentrations in the sediments of the main river courses decreased sharply with increasing distance away from the town,which indicates that the range of river water affected by heavy metal pollution was small.3) The prominent problem of the water environment in the Taihu Lake region was still nitrogen and phosphorus pollution,rather than heavy metal pollution.However,the potential risk of heavy metal pollution in the water should not be overlooked considering the high concentrations of heavy metals in the river sediments in and around towns.