南渡江塘柳塘底泥构建农田土壤的潜在生态风险与肥力潜力评价

目的]探明南渡江下游段河塘沉积物的肥力水平与重金属污染情况,为河塘清淤底泥资源化利用提供参考.方法]选取典型河段塘柳塘为研究对象,通过均匀布设断面与样品采集,测定底泥有机质、重金属含量,对河塘底泥的重金属污染水平、潜在生态风险以及底泥的肥力水平进行评价.结果]塘柳塘河塘底泥有机质丰富,肥力较高,平均有机质含量为29.80 g/kg,尤以中段（村庄段）河塘底泥有机质含量最高.全河段Cr、As、Cd、Pb和Hg含量分别为9.792～77.067、0.891～5.044、0.128～0.556、17.304～55.106和0.067～0.457mg/kg;Cr、As未超标,而Cd、Pb和Hg超标,Cd和Hg超标幅度分别为85.48％和82.95％.南渡江下游河塘底泥综合潜在生态危害指数处于低生态风险水平,但河塘中段Cd和Hg的单项污染生态风险均处于中等水平,在污染风险控制范围之外.结论]南渡江下游河塘底泥有机质丰富,肥力较高,适合构建农田耕作层;但需在重金属污染生态风险评价基础上,开展相应实验研究,确保底泥资源化利用过程中农业土壤不受污染与农产品安全.

Assessment on potential ecological risk and potential fertility of river sediments constructing cultivable layer in the lower Nandujiang River

Objective]Fertility level of organic matter and the contents of heavy metals were investigated in the river sediments of the lower Nandujiang River in order to provide references for river sediment reutilization.Method]The Tangliutang River,a typical river,was chosen as the target study area.The fertility level of organic matter and potential ecological risks of heavy metals were assessed by evenly collecting samples in the surface sediments of the river.Result]The average content of organic matter was 29.80 g/kg in the river sediment,which had rich organic matter and high fertility.The highest content of sediment organic matter appeared in middle reaches （i.e.village section）.The contents of the heavy metals in the sediments were in the range of 9.792-77.067,0.891-5.044,0.128-0.556,0.067-0.457,and 17.304-55.106 mg/kg for Cr,As,Cd,Hg and Pb,respectively.Cr and As did not exceed the standard,while Cd,Pb and Hg exceeded the standard.The contents of Cd and Hg were more than the standard of 85.48％ and 82.95％,respectively.The general potential ecological risk index was low in the lower reach of the Nandujiang River.Cd and Hg in the middle reaches of the Tangliutang River （i.e.village section）,at the risk of environmental contamination,had moderate individual ecological risks.Conclusion]Organic matter was abundant and fertility level was high in the river sediments,so they were suitable for constructing cultivable layer.To avoid soil contamination and ensure the safety of agricultural products,it is necessary to carry out ecological risk assessment of heavy metal and corresponding experimental research.