太湖湖心区的痕量金属历史沉积过程研究

以太湖湖心区的沉积物为研究对象,解析了湖心区痕量金属的沉积通量年变化,探明了湖心区痕量金属的历史沉积情况.结果表明:湖心区各样点沉积物的沉积速率从1950年以前的(0.032±0.023)g·cm-2·a-1缓慢递增到1980前后的(0.076±0.030)g·cm-2·a-1,1980年后突增明显,在2000年后达到(0.185±0.132)g·cm-2·a-1.湖心区沉积物中8种痕量金属(钒、铬、镍、铜、锌、砷、镉和铅)的含量年变化没有明显递增趋势,在20世纪80年代(对应沉积柱4~9 cm深度处)前后相差不大(变幅小于20%).但8种金属元素的沉积通量随时间推进而递增,与1980年前相比,金属沉积通量在1980年后突增倍数达到11倍以上.金属沉积通量与沉积物的沉积速率显著正相关,并与20世纪20年代以来太湖流域社会经济发展形势相一致.1980年后8种痕量金属沉积总量在湖心区西部最大,而沉积物沉积速率对湖心区南部的痕量金属沉积总量贡献最大.通过金属沉积通量可以更全面地研究太湖重金属的历史沉积过程和人为活动的干扰效应.

Study on the historical accumulation of trace metals in the central lake zone of Taihu Lake

The sediment cores in the central lake zone (CL) of Taihu Lake were collected and the yearly changes of the sedimentation fluxes of trace metals were analyzed to clarify the historical accumulation process of trace metals in CL of Taihu Lake. The results showed: the mass accumulation rates of sediment in CL increased slowly from (0.032±0.023) g · cm^-2 · a^-1 before 1950 to (0.076±0.030) g · cm^-2 · a^-1 around 1980 and surged to (0.185±0.132) g · cm^-2 · a^-1 after 2000. There were neither obvious yearly increases in the sedimental concentrations of the eight trace metal elements (vanadium, chromium, nickel, copper, zinc, arsenic, cadmium and lead), no significant changes (less than 20%) from pro-1980s to post-1980s (the 1980s corresponds to the sediment depth of 4~9 cm). However, the sedimentation fluxes of the 8 metal elements increased year by year, with large increases of over 11 folds after 1980. The sedimentation fluxes of the 8 trace metals had significantly positive correlation with the mass accumulation rates of sediment in the CL, in line with the development trend of society and economy in the Taihu Lake Basin since the 1920s. The total amount of the 8 elements in post-1980s sediment was largest in the north part of CL, and the mass accumulation rate of sediment contributed most to the total amounts of trace metals in the south part of CL. Studies on sedimentation fluxes of trace metals could help to comprehensively analyze the historical accumulation process and anthropogenic interference effect on trace metals in Taihu Lake.