| In this paper, aiming at the blurry grasp about contaminated status of heavy metals as a whole in the East China Sea, the heavy metals fluxes into sea and their concentrations since1980 are collected, their temporal and spatial changing trend are analyzed, the in situ mensuration for heavy metal NDEC with phytoplankton as experimenting object is established, and applied to perfect assessment method for environmentally ecological effect with phytoplankton growth inhibition rate as target parameter. Then environmentally ecological effect of heavy metal in the East China Sea is assessed. Based on box model and combination with calculating method of spatial gridding average concentration, minimum environmental capacity in the East China Sea is estimated. Main achievements are described as follows:1. Since the begining of 1980s, contamination Cu, Pb, Zn and Cd into East China Sea largely come from land source especially discharge by river, the changing trend of total fluxes basically took on the pattern of asymmetric inverse'U', which increased firstly, then kept up and decreased finally.(1) For the main source of Cu, Pb, Zn and Cd into East China Sea, the flux discharged by rivers is overwhelmingly dominant, being up to 88.0% on average; the sewage takes second place, being 7.5% approximately; sedimentation from atmosphere is smallest, being 5.5% on average. The heavy metals into East China Sea mostly come from the land-based discharge, especially from rivers. The flux of Cu, Zn and Cd from Changjiang drainage area are the highest, that from Qiantangjiang the second and that from Minjiang the lowest. The flux of Pb from Changjiang drainage area are the highest, that from Minjiang the second and that from Qiantangjiang the lowest.(2) The total flux of Cu, Pb, Zn and Cd into East China Sea were about 1.68×103, 1.69×103, 4.26×103, 0.073×103 t/a respectively at the end of 1970s, however, the values began to increase from the middle end of 1980s; in the 1990s, they increased to the max of 13.58×103, 5.34×103, 295.73×103, 0.41×103 t/a respectively, and presently decreased to 3.47×103, 1.84×103, 5.66×103, 0.081×103 t/a respectively, which still higher than those at the beginning of 1980s.2. Since 1980, the horizontal concentration distribution of Cu, Pb, Zn and Cd in the East China Sea don't basically take on the obvious pattern of decrease from inshore to offshore area, the seasonal changing of spatial average concentrations of them in this sea area isn't large basically, the chronical changing trend of annual average concentrations of them in this sea area basically take on the pattern of asymmetric inverse'U'.(1) Since 1980, the concentration changes of Cu, Pb, Zn and Cd are not big in the East China Sea, and their horizontal concentration distributions do not basically take on the clear pattern of decrease from inshore to offshore area. The relatively high concentrations often locate in the Changjiang River estuary, inshore part of Hangzhou Bay and Zhoushan fishery.(2) The difference of spatial average concentration of Cu, Pb, Zn and Cd in the East China Sea is not big seasonally, the seasonal changing is not clear.(3) From the beginning to the middle of 1980s, the annual average concentrations of Cu, Pb, Zn and Cd in the East China Sea are lower than the grade-one sea water quality standard of China. From the end of 1980s to the end of 1990s, the annual average concentrations of them are the highest, with the Cu and Pb levels higher than the grade-two sea water quality standard of China and Zn and Cd concentrations higher than the grade-one sea water quality standard of China. In the beginning of 21st century, , the annual average concentrations of Cu, Pb, Zn and Cd decrease gradually, and are lower than the grade-one sea water quality standard of China at present.3. From the begining to the middle of 1980s, the annual concentration of heavy metal in the East China Sea do not inhibit the water ecosystem, but inhibition exist obviously from the middle end of 1980s to the end of1990s. At the beginning of 21st century, inhibition don't exist basically. (1) Heavy metal NDECs to typical phytoplankton in the East China Sea are 4.1, 45.2, 131.7, 138.9μg/L respectively, and those to water ecosystem are 4, 0.8, 20, 0.2μg/L respectively.(2) From the begining to the middle of 1980s, annual average concentrations of Cu is usually lower than its NDEC to typical phytoplankton, the inhibition don't exist. However, in 1990s, inhibition happenes every now and then, the biomass inhabitation rates is estimated to be up to 80% with maximum annual average concentrations and up to 90% with maximum concentrations in partial sea area. At the beginning of 21st century, inhibition don't exist basically with annual average concentrations but up to 30% with maximum concentrations in partial sea area. NDECs of Cu, Pb, Zn and Cd to typical phytoplankton are higher than maximum annual average concentrations and maximum concentrations in partial sea area since 1980, inhibition don't exist basically.(3) From the begining to the middle of 1980s, annual average concentrations of Cu, Pb, Zn and Cd are usually lower than their NDECs to seawater ecosystem, the biomass inhibition don't exist, it is the same with the maximum concentrations in partial sea area. From the middle end of 1980s to the end of 1990s, it happenes every now and then that annual average concentrations of Cu, Pb, Zn and Cd are higher than their NDECs to seawater ecosystem, the biomass inhabitation exist obviously, and the biomass inhabitation rates are estimated to be 85%, 10%, 30%, 20% respectively with maximum annual average concentrations and up to 95%, 30%, 60%, 50% respectively with maximum concentrations in partial sea area. At the beginning of 21st century, annual average concentrations of Cu, Pb, Zn and Cd are usually lower than their NDECs to seawater ecosystem, inhibition don't exist basically. With maximum concentrations in partial sea area, the biomass inhabitation rate of Pb, Zn and Cd are 0, but that of Cu is up to 30%.4. Minimum oceanic environmental capacities of Cu, Pb, Zn and Cd in the East China Sea are computed to be approximately 1.70×104, 0.47×104, 11.31×104, 0.071×104 t/a, and minimum surplus environmental capacities of them are about -0.004×104, 0.02×104, 4.5×104, 0.003×104 t/a with present gross discharge fluxes, indicating that maximum concentrations of Pb, Zn and Cd in the East China Sea can still comply with their no detected toxic concentrations to seawater ecological system, but 8% of present gross discharge fluxes of Cu must be reduced for satisfying this criterion. |
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