长江粘土矿物示踪标记稳定性的初步研究

选择物质来源相对单一、区域较广的浙江沿岸东海内陆架区，以4种主要粘土矿物(伊利石、蒙皂石、高岭石、绿泥石)为研究对象，以探讨长江粘土矿物作为示踪标记的稳定性问题。研究区5组沉积物样品中粘土矿物的X射线衍射实验及含量分析结果表明，伊利石、蒙皂石和高岭石的相对含量较稳定，具有作为长江物源示踪标记的价值．而各区域的绿泥石含量之间不具有显著的统计相似性。现有资料还不能完全解释长江口及邻近东海内陆架区内粘土矿物组合的相对稳定状态，今后应对絮凝作用、沉积分异作用、海底生物地球化学作用等因素的效府做进一步的研究。

PRELIMINARY EVALUATION OF THE STABILITY OF CHANGJIANG CLAY MINERALS AS FINGERPRINTS FOR MATERIAL SOURCE TRACING

Mixing models, as a quantitative tool to trace sediment sources, require a certain number of tracing fingerprints that are stable in terms of their physical and chemical properties, or the changes in the properties during transport and accumulation can be defined quantitatively. Clay minerals are often used as tracing fingerprints and there have been some studies on modifications of clay minerals during transport and temporary storage from estuary to continental shelf. However, disagreements exist with regard to clay mineral behaviour in marine environments, implying uncertainties in applying the mixing model, e.g., to the estimation of the relative importance of the Changjiang and Yellow River sediment inputs on the East China Sea continental shelf. In this paper, the main types of clay minerals (i.e. illite, montmorillonite, kaolinite and chlorite) are examined, to evaluate their stability as Changjiang River fingerprints, using the seabed sediment samples from an extensive region of the inner continental shelf of the East China Sea where the sediment source is relatively simple (i.e. dominated by the Changjang materials). On the basis of X ray diffraction analysis of five groups of samples, the contents of illite, montmorillonite and kaolinite are shown to be stable along the inner shelf waters from Hangzhou Bay to the southern Zhejiang coast; therefore, these contents can be used directly as tracing fingerprints of Changjiang sediment. Statistical analysis shows that the content of chlorite does not have a sufficiently high stability and, as a result, its use as a Changjiang sediment fingerprint may depend upon a definition of its changes along the transport pathways. The existing data are insufficient to explain the spatial distribution of the clay mineral and further studies on material sorting and biogeochemical alterations are required, taking into account the factors of flocculation of cohesive sediments, differential settling of clay particles and biogeochemical processes at the water sediment interface.