长江口及其邻近海域孔隙水地球化学特征

对长江口沉积物有机碳、总氮、总磷、Fe、Mn、AI及孔隙水和上覆水体中营养盐、Fe、Mn的含量进行了测试，结合早期成岩模型及地球化学热力学分析，探讨了在河口环境中影响孔隙水营养盐和Fe、Mn分布的主要因素，并对沉积物-水界面营养盐扩散通量进行了估算。结果表明，孔隙水中NH4^＋、NO3^-、PO3^4、H4SiO4和Fe、Mn的含量显著高于上覆水体。早期成岩过程是控制长江口沉积物孔隙水营养盐和Fe、Mn分布的主要因素。NH^4＋剖面暗示长江口近岸和远岸海域存在两类不同的生物地球化学过程。孔隙水Fe、Mn剖面暗示在河口环境中其是有机质降解的重要电子受体。在近岸海域MnO2可能是底部NH4^＋ -N移除的重要机制。长江口孔隙水中低磷酸盐与铁及沉积物中磷的形态有关。通量计算结果显示NH4^＋、NO3^-、PO4^3-、地SiO4、Fe和Mn向上覆水体扩散的通量分别为356—3074μmol／（m2·d）、-45．3～62．6μmol／（m2·d）、-0．3～1．7μmol／（m^2·d）、323—3172μmol／（m^2·d）、3．0～10．5μmol／（m^2·d）和35．7～439．5μmol／（m^2·d）。N、P、Si界面通量对上覆水体浮游生物所需营养盐的贡献分别为0．19％～1．65％、0．13％～0．14％和1．2％～12．2％，因此在考虑长江口区域浮游生物所需营养的来源时，沉积物-水界面营养盐扩散通量可以忽略。

Geochemical characteristics of pore water in the Yangtze Estuary and adjacent areas

The major factors that govern the vertical distributions of nutrients and Fe^2＋, Mn^2 ＋ in pore water were studied by analyzing the concentrations of nutrients and Fe, Mn in pore water and overlying water and total organic carbon, total nitrogen, phosphorus, iron, manganese, aluminum in sediments in the Yangtze Estuary, combined those in overlying water. The interstitial nutrients, iron and manganese are mainly controlled by early diagenetic processes in Yangtze Estuary sediments. Interstitial ammonium profiles indicate that there are two different kinds of biogeochemical processes in near and off shore areas. Interstitial iron and manganese profiles indicate that they are important electron acceptor for organic carbon degradation in the Yangtze Estuary. Manganese peroxide plays an important role in the removal of ammonium in the lower part in the near shore area. The lower concentrations of phosphate in pore water are related to iron and phosphorus forms in sediments. The diffusive fluxes toward the overlying water of NH4^＋, NO3^-, PO4^3-, H4SiO4, Fe and Mn range between 356 and 3074 μmol/（m^2·d）, -45.3 and 62.6μmol/（m^2·d）, -0.3 and 1.7 μmol/（m^2·d）, 323 and 3172 μmol/（m^2·d）, 3.0 and 10.5 μmol/（m^2·d） and 35.7 and 439. 5 μmol/（m^2·d）, respectively. The contributions of diffusive fluxes of nitrogen, phosphorus, silicate for the nutrients required by the plankton in the surface water range between 0. 19% and 1.65%, 0. 13% and 0. 14%, 1.2% and 12.2%, respectively. The diffusive fluxes can be neglected when we consider the source of nutrients required by plankton in the Yangtze Estuary.