太湖北部沉积物金属和营养元素的垂向变化及其影响因素

Vertical Variations of Metals and Nutrients in Sediments from northern Taihu Lake and the Influencing Factors

通过对太湖北部2个柱状沉积物进行了210Pb、粒度、金属元素、有机碳、总氮、总磷及磷的形态分析,探讨了其垂向分布特征及其影响因素. 粒度分析表明,沉积物呈现随深度变浅而变细的总体趋势. 210Pb分析显示该区域表层沉积物扰动较为强烈,并存在侵蚀现象. Cu、Zn、Ni、Li、V、Fe、Al垂向上的变化主要与粘土含量呈正相关,其含量表明金属污染不显著. 沉积物C/N比值显示有机质主要为陆源性质,磷以无机磷占绝对组分,有机磷含量向表层明显升高,反映了表层沉积物有机磷的输入较多或更好的保存条件.

Concentrations of metals, organic carbon (OC), total nitrogen (N), total phosphorus(P) and forms of phosphorus as well as activities of 210Pb and particle size were determined on two cores from northern Taihu Lake, China. The sediments are dominated by silts and clayey silts, which become finer upward. Results of 210Pb analysis indicate strong disturbance and erosion at the sampling sites. Concentrations of metals are: Cu,15.8-35.6 mg/kg;Zn,61.0-136.4 mg/kg;Ni,26.6-46.2 mg/kg;Li,36.7-69.0 mg/kg;V,88.3-142.0 mg/kg;Ti,3929.2-5508.9 mg/kg;Mn,840.9-2369.8 mg/kg;Fe,2.88-6.24 %;Al,5.17-10.13 %. Levels of Cu, Zn, Ni, Li, V, Fe and Al show significant positive relationships with the fraction of clay and their down-core variations are therefore caused mainly by particle size. When compared to the mean contents of shale, these metals show no significant anthropogenic pollution. The ratio of OC to N (C/N) range from 9 to 20, suggesting a dominance of detrital input of organic matter. The dominant pool of phosphorus is the detrital form. In both cores, organic phosphorus increases toward the surface layer, implying either higher organic phosphorus input in recent years or its better preservation.