南京东郊蔬菜种植基地地表水氮、磷、重金属含量及影响因素

南京东郊典型蔬菜基地地表水环境质量的调查分析表明:(1)在当前的生产和生活条件下,地表水尚未受Pb、Cu、Zn、Cd和Cr污染,但有不同程度的氮、磷污染。(2)河流氮、磷污染比池塘严重。河流水中氨氮和水溶性磷的比例相对较高,而池塘水中硝态氮、有机氮和有机磷的比例相对较高,这种差别有助于识别地表水中氮、磷的来源。河流底泥中总氮、总磷和重金属含量(Cr除外)比塘泥高,表明河水氮、磷及重金属污染风险比池塘水高。(3)南京东郊蔬菜基地地表水中氮、磷及重金属主要来自城市生活污水的排放,其次来自蔬菜栽培中有机肥过量投入造成的流失。因此,保护城郊地表水应从城市生活污水净化和蔬菜栽培中有机肥的合理施用入手。

Concentrations of nitrogen,phosphorus,heavy metals and their affecting factors in the surface water of peri-urban vegetable bases of Nanjing City

An investigation on the environmental quality of the surface water in peri-urban vegetable bases of Nanjing was conducted.The results indicate: i)the surface water has been polluted to a varying extent by nitrogen and phosphorus,rather than by Pb,Cu,Zn,Cd and Cr; ii)the nitrogen and phosphorus pollution of river water was severer than that of pond water.In terms of forms of nitrogen and phosphorus,the proportions of ammonium nitrogen and water soluble phosphorus were higher in river water than in pond water,while the proportions of nitrate nitrogen,organic nitrogen and organic phosphorus were higher in pond water than in river water,which is helpful in identifying sources of nitrogen and phosphorus in the surface water.The concentrations of total nitrogen,total phosphorus and Pb,Cu,Zn and Cd were higher in river mud than in pond sludge,which implies the risk of nitrogen,phosphorus and heavy metals pollution was higher in river water than in pond water; iii)the nitrogen,phosphorus and heavy metals in the surface water of peri-urban vegetable bases came mainly from the discharge of domestic sewage and the overdosed application of manure in the vegetable fields.So,it is necessary to protect the surface water from contamination first by purifying the domestic sewage before being discharged into rivers and rationalizing manure application in vegetable production.