黄海和东海海域溶解铋地球化学分布特征

Geochemical Distribution of Dissolved Bismuth in the Yellow Sea and East China Sea

结合大面调查，典型断面剖析及关键站位连续观测结果，研究了黄海和东海海域溶解铋的含量水平，时空分布特征及与生态环境的耦合关系，探讨其主要来源和影响因素．结果表明，表层海水溶解铋含量在0～0．029μg·L^-1之间，平均值为0．008μg·L^-1；底层海水浓度稍高，介于0．001～0．189μg·L^-1。之间，平均值为0．016μg·L^-1．水平方向上，溶解铋低值分布与盐度所示长江冲淡水双支扩散特征吻合，表明其可示踪长江冲淡水路径；高值出现在黄海暖流和苏北沿岸流途经之处及长江冲淡水与沿浙闽沿岸水交汇之处，表明其分布受控于海流系统循环．垂直方向上，水体对流和涡动混合使近岸海水均匀混合，陆架区强潮混合锋面将近岸垂向混合区和离岸层化海水区分隔，阻挡了溶解铋向外输运，使锋区内溶解铋含量明显高于外海．周日内，溶解铋变化主要与潮汐、再悬浮作用和温盐跃层等海域特定水动力条件密切相关，与温度，盐度等环境因素波动尚未呈现明显关系．溶解铋与悬浮颗粒物显著正相关，表明其易从固相释放至水体，并确定由颗粒态转化为溶解态的最佳温度（22～27℃）、盐度（28～31）和pH（7．9～8．1）．

Occurrence level, geochemical distribution of dissolved bismuth and its coupling relationship to eco-environment were investigated in the Yellow Sea and East China Sea to explore the source and influencing factors. The results showed that the concentration of dissolved bismuth was within the range of 0-0. 029 μg·L^-1at the surface and 0. 001-0. 189μg·L^-1 at the bottom, with the averages of 0. 008 and 0. 016 μg·L^-1, respectively. Horizontally, low value of dissolved bismuth exhibited the bidirectional extension feature, indicating that it could trace the path of Changjiang Diluted Water. High value of dissolved bismuth was observed where the Subei Costal Current and Yellow Sea Warm Current flowed and the Changjiang Diluted Water and Zhejiang-Fujian Coastal Current met, suggesting that it was controlled by the cycle of current system. Vertically, the coastal water was fully mixed by water convection and eddy mixing, and was divided from the stratified water by strong tidal front, which blocked the transport of dissolved bismuth to the open sea. Thus, the concentration in front area was significantly higher than that in the open sea. Diurnal variation of dissolved bismuth was related to the hydrodynamic conditions （tide, suspension and thermocline） instead of the environmental factors （temperature and salinity）. Positive relationship to SPM （suspended particulate matter） clarified that bismuth was prone to release from solid phase to liquid phase. Furthermore, conditions with temperature ranging 22-27℃ , salinity ranging 28-31 and pH ranging 7.9-8. 1 were shown to be optimal for the release process. Key words ：dissolved bismuth; distribution; source; influencing factor; Yellow Sea and East China Sea