长江口南槽底沙再悬浮对重金属吸附的影响

对长江口南槽底部水样中的含沙量、悬沙粒径以及水相和悬浮相重金属含量进行测试分析，探讨重金属的吸附规律及底沙再悬浮对水体自净能力的影响。依据长江口南槽底层悬浮相8种重金属元素的相关显性分析，将重金属元素分为3类，分析表明，重金属元素在该水域进行的是选择性置换吸附。同时，主成分分析表明，第一主成分与第二主成分的累积贡献率达到89．3％，两主成分已能较好地反映该水域重金属元素的变化，其中第一主成分的贡献率为70．4％，主要反映第一类元素Cu、Zn、As、Cd，说明这4种元素对长江口南槽重金属污染的影响最大。含沙量与元素吸附量的相关分析表明，随着泥沙含量的增加，单位质量悬浮泥沙吸附重金属元素的能力下降，总吸附量上升，但南槽底沙较强的再悬浮作用影响了相关显性。水相中重金属浓度与底沙再悬浮作用强度有关，依据浓度剖面ACP图像，涨、落急阶段再悬浮作用强，泥沙含量高，重金属浓度一般较转流阶段低。

EFFECT OF BED-SEDIMENT RE-SUSPENSION ON ABSORPTION OF HEAVY METALS IN THE SOUTH PASSAGE, YANGTZE ESTUARY,CHINA

Based on the measurement of the suspended sediment concentration, grain size, heavy metal concentration in water phase and the suspension phase in the bottom in the South Passage, Yangtze Estuary, this paper is mainly concerned with the effect of the bed sediment re suspension on the absorption of heavy metals and the water's self purification. According to the correlative analysis of absorption amount of heavy metals in suspension phase in the South Passage, the heavy metals ( Zn, Cu, As, Cd, V, Cr, Ni and Pb ) latent in the sediment in the area can be divided into three classes: (1) Zn, Cu, As and Cd; (2) V, Cr and Ni; (3) Pb. It is also known that heavy metals are exchanged selectively under certain conditions in the area. At the same time, the chief component analysis (PCA) shows that the accumulative percent of the first two factors of PCA is up to 89.3%. Therefore, they can basically represent the heavy metals in the zone. And the accumulative percent of the first factor is 70.4%, which represents the first class (Zn, Cu, As, Cd). Hence it can be assumed that they are the chief components to contaminate the water in the South Passage. The correlative analysis also indicates that there exists a certain positive correlation between sediment concentration and gross absorption amount of heavy metals. At the same time, there exists some negative correlation between sediment concentration and the unit absorption of heavy metals. Nevertheless, the correlation coefficient is still far from being strong enough to result in sedimentation or diffusion of the suspended particulate matters so as to form intense bed sediment re suspension in the zone in the bottom before absorbed equilibrium of heavy metals. Since bed sediment re suspension contributes to the decrease of heavy metal concentration in water phase, the quality of the water during the flux rapids or ebb rapids is much better than that during the turn fluxion because of more intense re suspension.