沉水植物对养殖池塘底泥中重金属的生物有效性

Bioavailability of heavy metals in aquaculture pond sediments with submerged plants

为探究苦草、黑藻、菹草等沉水植物修复对养殖池塘底泥中重金属的去除效果及其生物有效性,对沉水植物修复前后底泥中重金属Cu、Zn、Pb、Cd、Hg、As、Cr的总量和赋存形态进行测定。结果表明,沉水植物修复可以有效去除底泥中重金属污染并降低生态风险,其中对底泥中Cu、Pb、Cd、Hg的去除率较高,但对Cr的去除率较低。不同季节生长的沉水植物对不同重金属的修复效果不同。聚类分析显示,苦草、黑藻等春夏季生长沉水植物对Cd、As、Cu、Zn、Pb的去除效果较好,而菹草等越冬沉水植物对Cr的去除作用较好。形态分析显示,底泥中生物有效态含量和迁移率(MF)较高的Cu和Cd在沉水植物修复后底泥中生物有效态含量和迁移率相比其他元素显著增加。此外,相关性分析显示,底泥中重金属的去除率与其生物有效态含量和迁移率均呈现极显著正相关(P<0.01)。因此,底泥中重金属的生物有效态含量和迁移率可以有效表征沉水植物对底泥中复合重金属污染的去除效果。

This paper is aimed at restoration of aquaculture pond sediments with submerged plants.We chose plastic boxes to make a terrarium and selected three kinds of submerged plants,namely Vallisneria,Potamogeton crispus and Hydrilla verticillata to plant on sediments.Then we investigated the total contents and occurrence characteristic of heavy metals(Cu,Zn,Pb,Cd,Hg,As,Cr)in sediments and analyzed their bioavailabilities.Results showed that the contents of heavy metals in aquaculture pond sediments were rather high,which may lead to high ecological risk.After planting submerged plants,we found that the contents of heavy metals in sediments were lower and their ecological risks were reduced.Compared with all heavy metal elements,we discovered that submerged plant restoration showed a good removal effect on Cu,Pb,Cd and Hg,while it appeared poor to Cr in sediments.There are different restoration effects between submerged plants which lived in different seasons.Cluster Analysis showed that submerged plants that grew in spring and summer can obtain a better restoration effect to Cd,As,Cu,Zn,Pb,while overwintering plant can reduce the content of Cr more efficiently.Speciation analysis on heavy metal in sediment reflected that bioavailability fraction contents of Cu,Cd and their mobility factor(MF)were higher before planting submerged plants.After restoration,the bioavailability fraction contents and MF of Cu,Cd increased significantly compared with the others.Besides,it showed extremely significant correlation(P<0.01)between the bioavailability fraction contents of heavy metals and their MF to the removal rate of heavy metal.In conclusion,the bioavailability and MF of heavy metals in sediment can effectively characterize the removal effect of heavy metal restoration with submerged plants.