闽江下游河口区及其邻近海域表层沉积物的地球化学特征

GEOCHEMICAL CHARACTERISTICS OF THE SURFACE SEDIMENTS IN THE MINJIANG RIVER ESTUARY AND ITS ADJACENT SEA AREA

闽江是我国东南沿海地区最大的河流,年径流量位居全国第3位。对采自闽江下游及闽江口邻近海域的沉积物分析表明,沉积物以SiO2含量高、Al2O3等组分的含量较低为特点。样品中碎屑矿物主要是石英、斜长石、正长石、白云母和绿泥石。从SiO2看,闽江沉积物与石英砂岩的成分较接近,不同于浅海沉积物,与黄河、长江、珠江三大河流也有较大差异。地形地貌及水动力条件控制沉积物粒度的分布,粒度又控制沉积物的组分分布。总体表现为,由陆向海,呈SiO2逐渐降低、Al2O3等组分升高的趋势。人类活动对闽侯段及闽江北港到马江段河流沉积物的影响也不容忽视。闽江流域的源区特征、水动力条件和搬运距离以及物理化学条件与生物作用对沉积物的改造,使得沉积物组分间具有良好的相关性。

Minjiang River is the major river in the coast area of Southeast China and it is the third largest in terms of annual runoff over the country.According to XRF analysis of 25 sediment samples collected from the lower reaches of the Minjiang River and the adjacent waters of the Estuary,the sediments are characterized by a high SiO2,lower Al2O3 of components.The main detrital minerals of samples are quartz,plagioclase,orthoclase,muscovite and chlorite.Based on SiO2 content,the sediments composition of Minjiang River is closer to quartz sandstone,and different from the shallow sea sediments and distinct from the Yellow River,Yangtze River and Pearl River.From upper to sea,the SiO2 content is decreasing while Al2O3 increasing.It is reckoned that the topography and hydrodynamic conditions control the distribution of sediment granularity,which will further effects sediment component distribution.Moreover,human activities impact on the sediments of Minhou section and Peigang to Majiang section of the river cannot be neglected.The sediments of Minjiang River exhibit a reasonable correlation between different components which could be the combined effects of the source characteristics of the Minjiang River,the hydrodynamic conditions,the transport distance,as well as physical and chemical conditions and biological transformation of sediments.