The Combined Forms Of Trace Metal And Its Environmental Significance In Offshore Sediments Of Eastern Huanghua In Hebei Province

A study of four undisturbed sediment cores (W6, W7, W8 and W9) from the offshore of estuarine of Nanpaishui River in Eastern Huanghua, Hebei Province, has been undertaken. The acid volatile sulfide (AVS), simultaneous extracted metal (SEM), trace metal, grain-size, organic carbon has been analyzed. The contents of analyses metal including Fe, Mn, Cu, Pb, Zn, Cd, Cr, Mo, Co, Ni, Ba, Sr, As and Hg. The distribution regular pattern of metal has been performed using the vertical changing characteristic of trace metal, Fe and Mn with AVS and the vertical changing characteristic of reactive fraction and pyrite fraction. To forecast the environment danger, analyzing the trace metal and its bioavailability using AVS, SEM, degree of pyritization (DOP) and degree of trace metal pyritization (DTMP).Results of the AVS, SEM, grainsize and organic carbon indicate that the grain of the sediments in the study area, which is changing smaller from seacoast to father area, is homogeneous. The distribution of organic carbon is uniform, but it still changing regularly in different stations. Based on the understanding of the contents of SEM, AVS and their changes with depth, we can see that there are active layers of trace metal during the surface to 20cm depth in W7 and W8 area, where the trace metal can easily participate in the biogeochemical cycle of the aquatic ecosystem.The contents of most of the trace metals(Cu, Pb, Zn, Cd, Cr, Mo, Co, Ni) in the sediments, existed in reactive fraction and pyrite fraction, is more in W6 and W7 than in W8 and W9, where the distribution pattern is same to the clay. Then reducing environment is produced in farther area sediments from the estuarine, which include high contents of clay, organic carbon and reactive Fe. So its pyritization is much more obvious than offshore sediments. However, the DTMP and DOP of the trace metals in the four sediment cores almost present direct ratio except Pb. The behavior of trace metals indicate that they are pyritizing in the offshore sediments, which are deposited with pyrite. Of course, the pyritization is different because of vary chemical nature with various elements.