辽河口盐沼湿地表层沉积物重金属污染评价

Assessing heavy metal pollution in surface sediments of saltmarshes in Liaohe Estuary

以辽河入海口典型盐沼湿地土壤为研究对象,采集6个区域内盐地碱蓬盐沼湿地和裸地中0~<10和10~20cm深度的土壤样品,测定土壤中As、Cd、Cr、Cu、Pb、Zn、Hg 7种重金属的质量分数,揭示其空间分布规律并对其污染风险进行评价.结果表明,6个区域重金属As、Cd、Cr、Cu、Pb和Zn的平均质量分数分别为12.23、0.33、62.25、24.29、23.75和74.12mg·kg^(-1),Hg未检出.在盐地碱蓬盐沼区域,表层土壤(0~<10cm深度)As、Cd、Cr、Cu、Pb和Zn质量分数的最高值都出现在远离河口一侧的样地D;10~20cm深度As、Cd、Cu、Pb和Zn质量分数的最高值都出现在远离河口一侧的样地E,而Cr质量分数的最高值出现在远离河口一侧的样地D.在裸地区域,表层土壤As、Cr、Cu、Pb和Zn质量分数的最高值都出现在远离河口一侧的样地F,而Cd质量分数的最高值出现在远离河口一侧的样地D.因此重金属质量分数在整个研究区域的空间上呈现由河流向海方向增长的趋势.运用地质累积指数法对7种重金属的污染进行评价,整个研究区内重金属为低污染水平,污染程度由大到小依次为Cd、As、Cu、Zn、Pb、Cr、Hg.

Soil samples at depths of 0-10cm and 10-20 cm were collected in Suaeda salsa marshes and bare areas from six saltmarsh sites in Liaohe Estuary.Contents of 7heavy metals（As,Cd,Cr,Cu,Pb,Zn and Hg）were determined to depict their soil-depth distribution.The average contents were（all in mg·kg^-1）：As 12.23,Cd 0.33,Cr 62.25,Cu 24.29,Pb 23.75,Zn 74.12,Hg 0.Suaeda salsa area maximal contents of As,Cd,Cr,Cu,Pb in top 10 cm soils appeared at Site D.Maximal As,Cd,Cu,Pb and Zn were observed in10-20 cm soil at Site E.Cr showed maximum content at Site D.Bare area maxima of As,Cr,Cu,Pb and Zn were observed in 0-20 cm soil at Site F,whereas Cd showed maximum at Site D.Heavy metal pollution in surface sediments was low.Geo-accumulation Index Assessment showed the following pollution classification：Cd〉As〉Cu〉Zn〉Pb〉Cr〉 Hg.Ecological risk of surface sediments was found to be mainly due to Cd pollution.