长江口及邻近海域表层沉积物中重金属元素含量分布及其影响因素

根据2003和2006年长江口及邻近海域表层沉积物样品的粒度组成和元素铬、铜、镍、铅、锌、铝、钙和锶的含量,分析了重金属元素含量的分布特征,探讨了含量的变化趋势及其对人类活动的响应。自2003年三峡工程一期蓄水完成到2006年6月,长江输沙量逐年减少,长江口海域沉积物中黏土的百分含量明显增加,但是沉积物分布的总体格局并没有发生明显的变化。重金属元素大多在泥质区沉积物中富集,高值区沿岸线呈带状分布,在最大浑浊带和口外羽状锋处达到峰值。在长江大量物质输入的背景下,研究区沉积物中重金属元素含量相对其他类似河口较低。河流的陆源颗粒输入、水动力条件、细颗粒物质的吸附以及絮凝作用是控制沉积物中重金属元素含量分布的主要因素,氧化还原条件也对重金属元素含量变化有一定的影响。人类活动(重大工程的建设和人为污染)对长江口外泥质区中重金属元素含量有重要影响,尤其对铅和锌的含量及其分布的影响显著。自2003年三峡工程一期蓄水以来,长江口海域表层沉积物中重金属元素沉积机制未有明显的变化,但是重金属元素含量有逐渐降低的趋势。

The distribution of heavy metal contents in surface sediments of the Changjiang Estuary in China and surrounding coastal areas

In order to discuss the response of heavy metals to human activities, two cruises'data in 2003and 2006 and surface sediments were collected in the Changjiang Estuary and its surrounding coastal areas. Contents of some elements (chromium, copper, nickel, lead, zinc, calcium and strontium) and grainsize composition were analyzed. The result showed that there were no significant changes in the pattern of sediment distribution, although the percentages of clay component increased significantly. The low content and zone-type distribution of heavy metals were observed and heavy metals were enriched in an mud area. And the two areas of heavy metal high contents were located in the turbidity maximum zone and the west of plume front which was caused by the mixing between diluted water and seawater. Terrigenous discharge, hydrographic dynamics, adsorption and flocculation played important role in the distribution of heavy metals. In addition, the redox condition and the human activity which was more important for lead and zinc, were also two important factors. The Phase-Ⅰ engineering of Sanxia Reservoir stored water since 2003, there had been not obvious change in the heavy metal deposition mechanism of surface sediments in the Changjiang Estuary, but the contents of heavy metals had a gradually decreasing trend.