渤海湾表层沉积物重金属污染状况及年际变化分析

根据2014~2018年渤海湾海洋生态环境沉积物质量业务化监测数据,对沉积物中Hg、Cu、Pb、Cd、Cr、Zn和As等7种重金属元素的含量及年际变化趋势进行了分析.通过单因子污染指数法、地累积指数法和潜在生态风险指数法,评价了研究区近岸海域沉积物重金属污染状况和潜在生态风险程度.结果显示,符合一类标准的站位达92%以上,主要超标因子为Cd和Hg,这两种重金属含量的高值区一般分布在渤海湾南北两侧近岸地区,包括北侧天津港、黄骅港附近,南侧滨州、东营近岸.Hg、Cu、Pb、Cd、Cr、Zn和As等单个重金属含量年际变化有所不同,年平均单因子污染指数均不大于1,年平均地累积指数均小于0,表明研究海域沉积物质量状况良好,其中Cu单因子污染指数较大,近5年的平均值达到0.653;Cd地累积指数相对较大,对其监测工作值得重点关注.2014~2018年研究区域沉积物重金属的总潜在生态危害程度为轻微等级,仅Hg和Cd部分站位出现强和中等的生态危害程度,各类重金属元素对渤海湾海域生态构成潜在危害风险顺序为Cd>Hg>As>Pb>Cu>Cr>Zn;RI基本表现为先升高后降低、然后略微上升的年际变化趋势,生态风险较高的区域主要位于渤海湾中部天津港附近和东北部曹妃甸附近海域.

Pollution status and annual variations of heavy metals in the surface sediments of Bohai Bay

The pollution concentration of sediment heavy metals Hg, Cu, Pb, Cd, Cr, Zn and As and their annual variations in Bohai Bay were analysized basing on the monitoring data of the surface sediment samples collected from Bohai Bay during the period from 2014 to 2018. The pollution status and potential ecoloical risk of sediment heavy metals in Bohai Bay was evaluated by the methods of single factor standard index(PI_i), geoaccumulation index(I_geo) and potential ecological risk index(RI). The results show that above 92% of the sampling sites measure up to the first standard of the national marine sedimentary evaluation criterion. The main exceeded standard heavy metals were Cd and Hg, and the distribution area of their higher concentration were in the north and south ends in the bay, especially including Tianjin Port coastal areas, Huanghua Port coastal areas, Binzhou coastal areas and Dongying coastal areas. The sediment quality status of Bohai Bay was well, and the single factor standard index(PI_i) and geoaccumulation index(I_geo) of all heavy metals annual average were less than 1 and 0, respectively. The annual variations of the seven heavy metals were different from each other, Cu the standard index (PI_i) value was higher than the others, the recent five years average standard index(PI_i) of which reached 0.653. Cd the geoaccumulation index(I_geo) was higher than the others, which should be worthy of attention. The potential ecological risk assessment of sediment heavy metals was generally slight in the period from 2014 to 2018. Metals Hg and Cd showed strong and medium ecological risk in the small proportion of stations. The potential ecological risk(RI) order of heavy metals for Bohai Bay was Cd>Hg>As>Pb>Cu>Cr>Zn. An increase-decrease-slightly increase type of RI annual variation was found. The areas of higher ecological risk(RI) were mainly near the coastal areas of Tianjin Port which was in the central part of Bohai Bay, and the Caofeidian coastal areas which was in the northeast of Bohai Bay.