| During July 2010, totally 38 surface sediment samples and 30 core sediment samples were collected from inshore areas around Leizhou Peninsula,China. The analysis of distribution characteristic, accumulation and migration rule of heavy metals in inshore ecosystem was studied under the comprehensive function of nature and human activities. The possible input pathway of heavy metals within marine sediments was also discussed in this work. Environmental quality and ecological risk assessment on heavy metals along the coastal areas of Leizhou Peninsula were also conducted. Six heavy metal elements: copper(Cu), lead(Pb), arsenic(As), cadmium(Cd), zinc(Zn) and chromium(Cr) were chosen as the research objects, while three relatively independent areas was divided into: East zone, South Zone(Qiongzhou Strait) and West Zone, according to actual geographical conditions. The main conclusions drawn in this work were as follow:(1) The mean values of six heavy metal elements in surface sediments were: As-6.40±3.40μg/g, Pb-21.2±12.7μg/g, Cr-45.0±22.4μg/g, Cu-12.0±9.44μg/g, Zn-44.6±31.2μg/g, and Cd-0.082±0.061μg/g, respectively. Besides, the average of Pb, Cr, Cu, Zn and Cd was obeyed the decreasing changed as follows: East zone> West Zone >South Zone. For As, the changing sequence was West Zone >East zone >South Zone. The similar peak value for As, Cr, Pb, Cd was found near WuChuan city and Zhanjiang harbour, which displaying the close relationship with Jianjiang river near by WuChuan city. And the relatively lower concentration level of heavy metals in South Zone was associated strongly with seawater dynamic existing in Qiongzhou Strait.(2) The mean values of six heavy metal elements in core sediments were: As-10.4±4.67μg/g, Pb-28.7±11.4μg/g, Cr-57.0±36.1μg/g, Cu-18.5±13.6μg/g, Zn-63.1±44.0μg/g, and Cd-0.134±0.212μg/g, respectively. By comparison of vertical distribution data from bottom to top, the results showed that no obvious ascendant trend was found in Cd. The obvious ascendant trend of As was found nearby Naozhou Island in East zone, and Jiepao Town in West Zone. Cu had obvious ascendant trend nearby Qiangshan Town in East zone, and also Beihe Town in West Zone. Zn had stronger ascendant trend nearby Naozhou Island than Qiangshan Town in East zone and Qishui Town in West zone. Pb had stronger ascendant trend nearby Beihe Town in West Zone than Naozhou Island in East zone, and Jiepao Town in West Zone. Cr had more obvious ascendant trend nearby Qiangshan Town in East zone than Naozhou Island in East zone, and Beihe Town in West Zone. So the vertical distribution characteristic of heavy metals was mainly associated with human activities, marine geographic conditions and migrating ability themselves.(3) With BCR sequential extraction method, the results of chemical forms of heavy metals in surface sediments showed that As, Cr, Cu, Zn and Cd was mainly bounded to residual state, and reached the proportion of 94.1% ,91.3%, 77.1%, 68.4% and 72.4% , respectively. While the main forms of Pb were iron manganese oxide and residual state, accounting for 41% and 44% respectively. Taking the high proportion of unsteady state, actual concentration and toxic response coefficient into consideration, the conclusion was that the most likely element causing indirect harm to human beings would be Pb.(4) According to the Quality Criteria of Marine Sediment (GB18668-2002), all the mean concentration of heavy metal elements within surface sediments was below the limited value of Category I, which meant the surface sediment was maintaining safe statue. According to the assessment of the potential ecological harm index, marine sediments around Leizhou Peninsula were under the minor ecological harm statue. It also showed in certain marine areas, the gradual accumulations of As, Pb and Cr were observed, which there had a great possibility to overpass the alarm line. And Cr was the most likely one because of its mean concentration was the closest to Category II. |
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