太湖梅梁湾沉积物中重金属的赋存相态及其对污染历史的示踪

本文以梅梁湾沉积物中的重金属元素为研究对象,利用五步连续提取的方法将梅梁湾沉积物中的重金属元素分水溶态、可交换态、碳酸盐结合态、铁锰氧化物结合态、有机物结合态和残留态六种相态.应用210Pb、137Cs定年法相结合,通过对百年沉积物的连续提取及元素富集系数的分析,得到重金属元素在不同相态中的含量随时间的变化.与历史时期人类活动相比较,重建了自19世纪末期到2000年的人类活动影响流域环境的历史,证实了重金属元素含量变化主要受人类活动的强度和方式制约.具明显影响的人类活动分三个时段,其中最为严重的时段是自1977年至今.与无锡历年工业产值变化的对比分析表明,各相态中重金属含量的相似变化记录了梅梁湾受湖湾沿岸居民的经济生产活动影响,污染程度日益加剧,且工业废污水中重金属主要以铁锰氧化物结合态进入太湖生态系统中.

Chemical fractions of heavy metals of sediments in Meiliang Bay, Lake Taihu and tracing for its pollution history

The concentrations of heavy metals in different Chemical fractious of sediments collected from the Meil- iang Bay, Lake Taihu, were measured. Sequential extraction method was used to gain the concentrations of sediment-bound heavy metals in six fractions, i.e. , soluble, exchangeable, bound to carbonates, bound to Fe-Mn ox- ides, bound to organic matter, and residual. By use of ^210pb and ^137Cs activities to obtain age of sediments, temporal variations of heavy metals in different fractions and their enrichment factors were shown. Among them, variations of heavy metal concentration in Fe-Mn oxides fraction of the sediments can be used to reflect contaminant input by human activities. On the basis of our data, the history of catchment human activities was divided into three periods, among which the most heavily affected by human activity was from 1977 A.D. to present. By comparing the concentrations of heavy metals in Fe-Mn oxides fraction with historical industrial product values of Wuxi City, their similar trends suggest that the increasingly environmental pollution is due to a fast development of industries a- round northern Taihu region, further indicating that heavy metals was mainly as a form of bound to Fe-Mn oxides into the Lake Taihu ecosystem.