The Sedimentary Environment Changes Of Jiaozhou Bay In Recent Hundred Years And The Information Indicators Extraction Of Human Activities Impacts

Jiaozhou Bay is a typical bay under the influence of human activities, in the dissertation, on the basis of precise 210Pb chronology of typical core sediments, the sedimentary environment changes of Jiaozhou Bay in the past hundred years are presented. Through the general analysis of nitrogen, phosphorus, heavy metals in sediments and ecology environment, the information indicators of human impacts are extracted and a series of results and viewpoints are presented.Firstly, the sedimentation rates of Jiaozhou Bay in the recent hundred years are characterized of distinguished spatial and temporal changes. Generally, the sedimentation rates of inner Bay are relatively high, and the sedimentation rates of mouth Bay change greatly. Moreover, the sedimentation rates of outer Bay are lower than that of inner Bay and mouth Bay. On the whole, the sedimentation rates of Jiaozhou Bay have the trend of increase, especially in the recent years. Take B3 station as a example, the sedimentation rates at 1984 or so was up to 1.17 cm/a, however, the sedimentation rates was only 0.30 cm/a before this time, which may be due to the rapid development of agro-industry around Jiaozhou Bay and the population increase of Qingdao City in the recent years. But the coastal environment management and reinforcement of pollution control, the situation has been improved since 2000 and the sedimentation rates decreased slightly.Secondly, the biogeochemical characteristics and ecology environmental significance of nitrogen and phosphorus in Jiaozhou Bay sediments are presented. The Ex-P (exchangeable phosphorus), Al-P (aluminum-bound phosphorus), Fe-P (iron-bound phosphorus) and OP (organic phosphorus) are the main parts of bioavailabile phosphorus in sediments. Al-P, Fe-P and Oc-P can be used to indicate the degree of pollution. The organic nitrogen (SOEF-N) in Jiaozhou Bay sediments are the primary forms and it can take part in the nitrogen cycle of overlying water potentially. And the parts of participating in nitrogen have close relationship with particle size of sediments. Moreover, the nitrogen in sediments can be used to evaluate roughly the biomass of overlying water.The results showed that inorganic phosphorus is the main forms in Jiaozhou Bay sediments. And the percentage were 44.57% ~ 94.41 %( B3), 44.83 % ~ 95.54 % (D4) and 55.09% ~ 95.20 % (D7). Al-P, Fe-P and Oc-P have close relationships with pollution degree and can be used to indicate the sedimentary environment degree. Ex-P, Al-P, Fe-P and OP had positive relation with the phytoplankton abundance and phosphate of overlying water and they are constitution of bioavailabile phosphorus in Jiaozhou Bay. The strong oxidant extractable form (SOEF-N) was primary form of transferable nitrogen in sediments, the contents were 0.070 mg/g(B3), 0.069 mg/g(D4)and 0.049 mg/g (D7). Moreover, the contents of nitrogen were higher if the grain sizes were smaller. Nitrogen in different grain size sediments had also positive correlations with phytoplankton abundance, chlorophyll-a and NO3- concentrations of overlying water and can be used to evaluate roughly the biomass of overlying water.Thirdly, through the research of the biogeochemical characteristics of heavy metals in Jiaozhou Bay sediments systematically, the human impacts on sedimentary environment are interpreted. The results of enrichment factors and geoaccumulation index showed that Cd, Pb and Cu in Jiaozhou Bay sediments were the impacted heavily by human activities. The distribution characteristics of heavy metals in sediment layers showed that the heavy metals contamination became serious since 1970s and 1980s. However, at the beginning of this century, the condition has been improved. On the whole, the heavy metals pollution in Jiaozhou Bay is not serious. Except some estuaries and coastal areas, the water and sedimentary environment quality are relatively superior. Combined with the results of biogeochemical elements, the viewpoints"Three Stages"of Jiazhou Bay sedimentary environment are put forward, which can define three periods, before 1980s, from 1980s to 2000 and after 2000. The first period is characteristic of relatively low sedimentation rate, weak heavy metal pollution and the eutrophication was not serious. The second period was the time when Qindgao City developed quickly, during the time, Jiaozhou Bay had been subjected to various pollutant sources and led to the serious heavy metal pollution and hypernutriention; moreover, the peak years occurred at the 1990s. Correspondingly, the sedimentation rate has accelerated and the land-derived inputs have become the main source of sediment. The third period was the time when the sedimentary environment has been improved due to the measurements supported by the financial investment to mange the Jiaozhou Bay.