靖海湾重金属污染及铅稳定同位素溯源研究

Study on Heavy Metal Contaminations and the Sources of Pb Pollution in Jinghai Bay Using the Stable Isotope Technique

对荣成市靖海湾表层沉积物和悬浮颗粒物中典型重金属(Cu、Hg、Pb、Zn、Mn、Cd、Cr、As)的含量进行了测定,并根据国家海洋沉积物质量标准和Hakanson沉积物重金属潜在生态危害系数与危害指数方法评价了该水域重金属污染程度及潜在生态危害.结果表明,该水域表层沉积物重金属含量较低和潜在生态危害较轻,S2采样点表层沉积物中Cu和Zn以及S3～S6采样点表层沉积物中Cd符合第二类沉积物质量标准,其余各采样点重金属含量则均符合第一类沉积物质量标准,处于较清洁水平.靖海湾表层沉积物中重金属的危害程度顺序为Zn<Cr<Pb<Cu<As<Hg<Cd.表层沉积物和悬浮颗粒物中重金属含量均以S2采样点最高,且随着与近海岸距离的增加重金属含量逐渐降低.表层沉积物烧失量和重金属含量的相关分析表明,烧失量与Cu、Cr、Pb、Zn、Mn、Hg和As均呈正相关关系.利用铅同位素技术对靖海湾表层沉积物和悬浮颗粒物进行铅污染源同位素示踪研究,结果表明,表层沉积物中208Pb/204Pb、207Pb/204Pb、206Pb/204Pb和206Pb/207Pb比值均大于悬浮颗粒物,表层沉积物和悬浮颗粒物的206Pb/207Pb比值均在S2最小,且与该采样点铅的浓度变化趋势相反,即随着铅的浓度增大206Pb/207Pb比值呈现降低的趋势.通过比较典型铅稳定同位素206Pb与207Pb天然本底比值与人类活动排放源比值,推测表层沉积物和悬浮颗粒物中铅污染主要来源于工业排放和含铅汽油燃烧等人类生产生活活动.

The concentrations of typical heavy metals including Cu,Hg,Pb,Zn,Mn,Cd,Cr and As in the surface sediment and suspended particulate matter（SPM） in Jinghai Bay,Rongcheng city were tested.The degree of heavy metal pollution in the surface sediment was assessed according to the national standard of marine sediment quality.The potential ecological risk（PER） of heavy metals to marine ecosystem in Jinghai Bay was assessed using PER coefficient and risk index.The results showed that the levels of heavy metals and PER in the surface sediments were low enough to meet the requirement of the first class of the sediment quality standards except the levels of Cu and Zn in the sampling site S2 and Cd in S3,S4,S5 and S6 which met the requirements of the second class of the sediment quality standards.The PER coefficients of heavy metals increased following the sequence of ZnCrPbCuAsHgCd.The levels of heavy metals in surface sediment and SPM were the highest at S2 and gradually declined with the increasing distance between the sampling sites and the shoreline.The correlation analysis of the loss on ignition（LOI） and the levels of heavy metals showed that LOI was positively correlated to the levels of Cu,Cr,Pb,Zn,Mn,Hg and As in surface sediment.Stable isotope technique was used to trace the dominant sources of Pb contamination in surface sediments and SPM.The results showed that the ratios of 208 Pb/204 Pb,207 Pb/204 Pb,206 Pb/204 Pb and 206 Pb/207 Pb in surface sediment were more closely related to that of SPM.The ratio of 206 Pb/207 Pb for both surface sediment and SPM was the lowest at the sampling site S2 and negatively correlated to the Pb concentration.The comparisons of Pb stable isotope ratio between the isotope ratios of natural and anthropogenic source showed that the Pb contamination was mainly derived from the human activities such as industrial discharges and leaded gasoline.