Variation Characteristics And Controlling Factors Of Heavy Metals In The South Yellow Sea

The south Yellow Sea (SYS) is a semi-enclosed epicontinental sea of the northwestern Pacific. Since the 1960s, China and Korea have experienced rapid industrial developments. Marine environmental quality of the SYS has seen a major decline due to the increase of populations and pollutants. In the dissertation, on the basis of 33 stations of SYS heavy metal data for 8 continuous years, a series of results and viewpoints with regard to heavy metal distributions, controlling factors and variation of environment are presented.1. Geochemical characteristics of heavy metals and their main controlling factors were discussed in detailThe average concentrations of As, Cd, Cu, Hg Pb and Zn in surface seawater were 2.33, 0.078, 1.41, 0.0036, 0.37 and 6.21μg/L, respectively. The distribution patterns corresponded to the distance away from the coastline,that was, the content of heavy metals(except Pb) was low in central area while high inshore. According to the distribution patterns of heavy metals in the seawater, the SYS can be divided into"high Cd-Cu-Hg-Zn area","high Pb-Cu-Zn area"and"high Pb area".As for surface sediments, the metal content (except for As) was high in the central area where the fine grain size sediments were dominant, and low inshore area where more coarse sediments were present. This suggested that grain size was important in determining distributions of heavy metals. And the SYS can be divided into"high Cd-Cu-Pb-Zn area","high Hg, low As-Cu-Zn area", and"high As, low Cd-Hg-Zn area".The order of enrichment factors of heavy metals was Pb>As>Hg>Cd>Zn>Cr>Cu. And Pb and As was the most influenced metals by human activities, while Cr and Cu were nearly unpolluted compared with others.2. 10-year-scale and 100-year-scale heavy metal variation modes were studied for the first time.The average concentrations in seawater showed a relatively stable trend in 10 years, except Zn's distinct upward tendency, which was [Zn](μg/L)=0.9524Year+0.0034, (R=0.97). And the annual averages of metals showed a similar trend to that of seawater.Based on the systematical analysis of national environmental policy, economy development of China and Korea, and the Yellow and Yangtze rivers flood history, we depart the one hundred year period (1905~2006) into 3 subsections. They are before 1960s, from 1960s to 1990s and after 1990s. The first period is characteristic of receiving little impact from human activities. And the heavy metals changes were the response of fluvial input, so the annual changes showed no obvious rule. The second period was the time when firstly Korea and then China's GDP went into their blossom. During the time, the development was led by the economy-first policy and the SYS had been subjected to various pollutant sources, moreover, the peak years occurred at the early 1990s for some metals. The third period was the time when the environment has been partly improved due to the recognition and the financial investment to the environmental protection of the SYS by both countries.3. Ecological risk evaluation of the south Yellow Sea was initially elucidated.According to the marine sediment quality of China and 8-year-average of heavy metals, SYS was a first class sea area. Using potential ecological risk index (ERI) method to evaluate the integrated pollution effect of heavy metals, 38.7% of investigated area was moderate degree of contamination, while 77.8% was in moderate ecological risk. However, no distinct correlation was found between ERI and plankton biomass. In conclusion, the ecological risk of SYS was low and indicated that the sediment quality was relatively good in general.