胶州湾海水痕量金属?溶解有机质分配特征及其影响因素探讨

采集胶州湾表层和底层海水样品，分析了Cu、Cr、Cd、Pb、Ni、Co等痕量金属在海水中的空间分布特征及其在不同分子量溶解有机质中的分配特征，并探讨了痕量金属?溶解有机质分配机理及浮游生物活动与盐度等环境因素对该分配过程的影响。结果表明，胶州湾海水中痕量金属呈近岸浓度较高的分布特征，在湾东北部出现高值区，Cd和Pb还分别在湾口与湾中部出现高值区。胶州湾海水中痕量金属平均有70.1%分配于低分子量(<1 kDa)组分中，其中Cu和Cd低分子量组分所占平均比例分别达79.0%与77.6%，Cr、Ni和Co稍低，分别为71.5%、67.3%及66.9%，Pb则仅为58.2%。海水中的溶解有机碳也以低分子量组分为主，所占比例平均达73.1%，且光谱特征显示低分子量溶解有机质中类腐殖质含量更高，含有丰富的羧基和羟基，金属配合能力较高，导致痕量金属多分配于低分子量溶解有机质中。高分子量溶解有机质(>1 kDa)所占比例与叶绿素a浓度呈显著正相关，表明浮游植物初级生产通过释放高分子量溶解有机质影响海水痕量金属?溶解有机质的分配过程。胶州湾湾顶盐度较低海域痕量金属高分子量组分略高，可能是生物活动及陆源输入(产生更多高分子量溶解有机质)与盐度(低盐有利于高分子量有机质的稳定性)共同作用的结果。

Size distribution characteristics and influence factors of trace metals in seawater of the Jiaozhou Bay

The spatial distribution of Cu, Cr, Cd, Pb, Ni and Co in the Jiaozhou Bay seawater and their distribution among different size fractions were investigated. The distribution mechanism of trace metals and the influence of environmental factors such as plankton activity and salinity during the distribution process were also discussed. The results showed that the highest values for most trace metals were distributed along north and northeast coast, while Cd and Pb also presented high value areas in the mouth and middle of the bay respectively. The trace metals in the Jiaozhou Bay seawater were mostly partitioned in the <1 kDa fraction with an average value of 70.1%, of which the percentages of Cu and Cd were up to 79.0% and 77.6% respectively, while Pb was only 58.2%. Similarly, the bulk dissolved organic carbon was also mostly partitioned in the <1 kDa size fraction with an average value of 73.1%. Spectroscopic properties indicated that low molecular weight (LMW, <1 kDa) fractions which mainly composed of humic-like organic matters contained more effective functional groups like hydroxyl and carboxyl groups and had higher complexing capacities with trace metals. There were significant positive correlations between chlorophyll a concentrations and high molecular weight (HMW, >1 kDa) proportions, indicating that primary production by phytoplankton in the euphotic zone was the major source of HMW dissolved organic matters in seawater and influenced complexation between trace metals and dissolved organic matters. The top area of the Jiaozhou Bay with lower salinity was characterized with higher proportions of large size components, which may be resulted from the combined effects of biological activity, terrestrial input and salinity.