| The modified methods for the determination of total dissolved inorganic arsenic (As(III+V)) and As(III) by hydride generation-atomic fluorescence spectrometry (HG-AFS) are presented in this dissertation. And study the biogeochemical behavior of dissolved arsenic in Jiaozhou Bay, Yellow Sea and East China Sea, which will give some contributions to the knowledge of oceanal biogeochemical cycle of arsenic.Under the condition of our experiments, the detection limit (LOD) of arsenate is 0.11nM, with the relative standard deviation ( R. S.D.) of 1.4%, 6.8% and 0.4% for the arsenate levels of 11.35nM, 1.60nM and 22.96nM, respectively. The recovery of the method is 98.0-104.0%. The liner limit is between 0.11nM and 267.0nM. We use hydrogen generator to supply H2 for determination of As (III) .The detection limit of arsenite is 0.02nM, which is ten times lower than before. R. S. D. of the method are 1.1%, 13.1% and 0.7% for As (III) levels of 6.67nM, 1.33nM and 13.35nM, respectively. The recovery of the determination for As (III) is 99.3-105.6%%. The liner limit is between 0.02nM and 66.7nM.Band on the result of the Jiaozhou Bay (2001.8-2001.10), concentrations of As (III+V ) and As(III) are ranged from 7.71nM to 25.31nM and from0.77 to 12.59nM, with the average of 16.51nM and 2.70nM, respectively. The distribution of As (III+ V ) and As(III) is significant influenced by the terrestrial input, especially from the large runoff of Daguhe and Yanghe. The concentration of As(III) is not only transformed by biologic activity, but related to the reduction by microorganisms and organic matters diffused from sediments through the stirring of seawater. In the year of 2001-2002, the concentrations of arsenic in the rivers around Jiaozhou Bay is higher in summer than those in spring. The concentration of As(III) in the sewage rivers such as Moshui- he is significantly high, which may relate to the anoxicenvironment of sediments.In October 2000, May 2001 and September 2002, three cruises were performed in Yellow Sea and East China Sea. Concentrations of As (III+V ) and As(III) for each cruise are given in the thesis. The concentrations of As (III+V ) and As(III) are seasonally fluctuated, which shows about 2nM higher in spring than that in autumn. And the ratio of As(III) to As (III+V ) is even higher in spring , it is nearly ten times higher than autumn. The concentration of As (III+ V ) some relationships with chlorophyll a. And the different species of arsenic may be produced by phytoplankton and bacteria, and this is why As is seen as a member of the nutrient-type elements in sea water. The distributions of As (III+V ) and As(III) are influenced by currents and runoffs in the Yellow Sea and East China Sea, especially by Kuroshio Current, Taiwan Current, Yellow Sea Coastal Current, East China Sea Coastal Current and the Changjiang runoff etc. Especially in spring, concentrations of As (III+V) in the coastal water are larger than open seawater, and the concentrations of surface water are larger than that of bottom, since the runoff of terrestrial input. According to our calculation, the net import flux of As(III+ V) in the PN section is estimated to be 0.50mol/s , and the annual import flux is 1.6 l07mol/yr. In September 2002, the ratio of As to P is 1.41 10-2, which is higher than Norway offshore (2.08-2.54 10-3), and lower than North Atlantic Ocean (0.25 0.04). The difference in the As to P ratios could be induced by different biological factors, such as plankton species and amounts differences. The seasonal variation in the lower reaches of Changjiang (Nantong) shows that the concentration of As(III+ V) is mainly controlled by season and river discharge. The concentration of As(III+V) is not decreased in recent years, and the annual flux is estimated about 1.66 l08mol/yr .In order to understand the relationships between harmful algal blooms and arsenic, two cruises were performed in the coastal areas near the estuary of Changjiang in August and November 2002, The concentration of As(III+V), salinity and SPM in a... |
