大沽河湿地表层沉积物重金属分布特征及污染评价

Distribution Characteristics and Pollution Assessment of Heavy Metals in Surface Sediments in Dagu River Wetland

胶州湾属半封闭海湾,水体交换能力较弱,受多条河流入海影响,污染日趋加重,通过大沽河的径流量、输沙量和溶解污染物占到胶州湾入海河流的首位。根据区域特征,于2009年2、5、8、11月对大沽河湿地48个采样点表层沉积物中的Cu、Zn、Pb、Cd、Hg、As、有机碳、粒度进行测定,探讨了重金属含量和污染特征与总有机碳、粒度的关系,利用污染评价法和潜在生态风险评价法进行污染和风险分析。结果表明:胶州湾大沽河湿地表层沉积物重金属含量较低,大部分测站符合海洋沉积物质量(GB18668—2002)Ⅰ类标准的要求。表层沉积物中Cu、Pb、Zn含量8月份最高、2月份次之、5月份最低。Pb、Hg、As3种重金属含量在2月份最高。Cu、Pb、Zn和Cd重金属之间存在显著正相关关系,Hg与As存在明显的相关关系;除Cd和As外的4种重金属与沉积物粘土、有机碳含量之间也存在显著正相关性。重金属单因子污染程度总体较轻,属于低污染水平,污染程度依次为Hg>Cd>Pb>Cu>As>Zn。大沽河河口区表层沉积物重金属潜在生态风险总体处于较低水平,风险程度依次为Hg>Cd>Pb>Cu>As>Zn。

Jiaozhou Bay is a semi-enclosed bay of weak water exchange capacity, the pollution is increasingly heavier for the rivers into the sea, the account of river runoff, sediment and dissolved pollutants into the sea through Dagu River are the first in all the rivers for Jiaozhou Bay. According to the characteristics of Dagu River, the contents of Cu, Pb, Zn, Cd, Hg, As, clay and organic carbon in the 48 surface sedi- ments samples in the wetland of Dagu River were measured, in February, May, August, November of 2009. Firstly, the content and distributed characteristics of these heavy metals, and the relevance with different particle size and organic carbon were discussed, and methods of pollu- tion assessment and the potential ecological risk assessment were used. The result indicated that the average contents of heavy metals were low, and most of them were lower than the first class of GB 18668--2002. Surface sediments of Cu, Pb, Zn had a similar seasonal variation, its highest level was in August, followed in February, the lowest levels in May. The highest concentrations in three heavy metals of Pb, Hg, As were in February. The Dagu River wetland surface sediment contents of Cu, Pb, Zn and Cd were controlled by clay and organic carbon . The single-factor of heavy metals in surface sediment indicated a lower pollution degree, and the descending order was Hg〉Cd〉Pb〉Cu〉As〉Zn. A low potential ecological risk assessment in wetland of Dagu River was showed, and the descending order was Hg〉Cd〉Pb〉Cu〉As〉Zn.