河口沉积物-水界面物质交换过程与控制机制的研究，对于深入理解河口元素和重要生源要素的地球化学行为，以及沉积物的早期成岩作用，均有根本的重要性；囿于传统研究方法中固有的局限性，沉积物-水界面物质交换过程在河口元素与生源要素地球化学研究中通常是缺失的一环；本项研究拟择取珠江河口为研究区域，在这一区域里设定1条断面，之上沿盐度梯度布设8-9个站点，以DIC及营养盐为研究对象，通过春夏、冬2个航次，研究河-海水混合过程水柱中DIC及营养盐的地球化学行为。同时发展和完善申请人及合作者开拓的天然放射性同位素手段—224Ra/228Th不平衡法、并结合210Pb、7Be, 234Th, 研究这些站点上沉积物-水界面物质交换的关键过程和主控机制。计算沉积物-水界面DIC及营养盐的交换通量，进而结合地下水排放的研究，最后评判沉积物-水界面物质交换过程及地下水排放对河口元素和生源要素地球化学行为的相对重要性。

Transfer across the sediment-water interface is an important process that regulates the behaviors of many elements and constituents in the overlying water column during estuarine mixing. It is also key to understanding the early diagenesis that occurs in marine sediments. However, due to the inherent limitations associated with the traditional methods, this process was poorly constrained in previous studies. In this study, we propose to elaborate a newly developed approach – the 224Ra/228Th disequilibrium approach to investigate the processes that regulates solute transfer across the sediment-water interface in the Pearl River estuary. Sediment samples as well as water samples will be collected along a salinity transect at S=0, 2, 5, 10, 15, 20, 25, 30 in spring, summer, autumn, and winter. Dissolved inorganic carbon (DIC), and nutrients (NO3-, NO2-, NH4+, PO43-) will be analyzed in water samples and in pore-water samples. With the 224Ra/228Th disequilibrium approach, we are to examine the key processes operating at the sediment-water interface and to quantify the benthic fluxes of DIC and nutrients. Finally, we plan to assess the relative importance of pore water exchange and submarine groundwater discharge in the regulation of the geochemical behaviors of elements and constituents during estuarine mixing.