珠江口沉积物与土壤的重金属特征及潜在生态危害评价

Heavy metal pollution features and potential ecological risk assessment in sediments and soils of the Pearl River Estuary

为了解珠江三角洲河口区重金属污染状况,采集了28个河口表层沉积物及57个河口西岸农田表土样本,分析了其中Cr、Co、Ni、Cu、Zn、Cd、Pb的质量比。以研究区内2个第四纪钻孔岩芯中沉积物的元素平均质量比为背景值,将测试结果与背景值及沉积物和农田土壤国家质量标准分别做比较。结果表明,1)研究区表层土壤与沉积物中的Co、Pb质量比相当,Cr、Ni、Cu、Zn、Cd则以河口表层沉积物中的质量比更高; 2) 85个样本中该7种重金属的平均质量比都高于背景值,其中Cu、Cd、Pb的平均质量比为背景值的2倍以上;3)表层土壤中全部样本的Cd和大部分样本的Cu质量比显著高于农用地土壤污染风险筛选值,但尚低于污染风险管制值;河口表层沉积物大多为二类,个别样点的Cd、Cu达到三类。最后,采用Hakanson法进行了重金属污染潜在生态危害性评价,结果表明研究区内Cd的潜在危害最大。

This paper is intended to make an investigation and identification of the heavy metal contamination seriousness level in the Pearl River Delta(short for PRD)area.As is known,PRD has now been an area with the most advanced industry and economy with the thickest population in the country.Nevertheless,extremely over-abundant human activities in the recent years have led to badly adverse impact on its ecological system.It is just to make clear the actual situation in this way,we have collected 28 surface sediment samples at the PRD estuary,57 agriculture land topsoil samples on the west bank of the estuary,and71 sediment ones from 2 boreholes obtained in the study area.In our investigation and examination practice,we have adopted the ICP-MS method to determine the mass ratios of such heavy metals as Cr,Co,Ni,Cu,Zn,Cd and Pb.Taking the mean mass ratios of the heavy metals in the borehole sediments as the background values,we have made a comparative analysis of the data of the surface samples with the background values,the marine sediment quality(GB 18668—2002)and the<Soil environmental quality Risk control standard for soil contamination of agriculture land>(GB 15618—2018)published by the corresponding state government departments,respectively.The results of our analysis demonstrate that:1)In terms of Co and Pb,the topsoil and surface sediment turn out to be in similar mass ratios,whereas in terms of Cr,Ni,Cu,Zn and Cd,the mass ratios in the surface sediment have been found higher than those in the topsoil;2)Of all the 85 surface samples,the mean mass ratios in all the 7 heavy metals turn out to be higher than the background values,especially for Cu,Cd and Pb,all of which tend to occupy twice as much high as the background values;3)As to the topsoil,the mass ratio for Cd in all the samples and the mass ratio for Cu in most samples prove to be much higher than the risk screening values for soil contamination of agricultural land,though still remaining in the limit of the risk intervention level.As to the regard of the marine sediment quality,most of the surface sediments in the PRD estuary can be said within the sediment of typeⅡ.Finally,we have also adopted Hakanson’method to evaluate the potential ecological risk of heavy metals contamination and confirmed that Cd is the most potentially harmful element in the research area due to its Eirhigher than 80 in 88.2%of samples.