长江口和东海海域沉积物粒径对有机质分布的影响

摘要

Surface sediment samples were collected from 78 stations in East China Sea continental shelf in November 2007 and suspended matter samples were collected from Changjiang River Estuary and Zhejiang coastal mud area. The grain size, organic carbon and total nitrogen of surface sediment samples as well as some suspended samples from Changjiang River Estuary and East China Sea were analyzed, and the impact of sediment grain size on the process of transport and deposition of organic matter were explored. The results showed that the average grain size of suspended matter decreased from Changjiang River Estuary southward to the Zhejiang coastal area, and had a better correlation with the contents of suspended matter and particulate organic carbon, indicating that the grain size of suspended matter was an important factor to influence the transport of organic matter. In addition, the distribution of surface sediment grain size appeared to have an obvious area variation characteristic, and the organic carbon and total nitrogen were closely related to the distribution of surface sediment grain size. The smaller the surface sediment grain size was, the higher contents of organic carbon and total nitrogen appeared. The sand contents of surface sediments from Changjiang River Estuary and Zhejiang coastal mud area was low, while those from middle and out of the shelf were high. The sand contents gradually increased seaward. With the increase of sand contents and sediment grain size, organic matter contents gradually reduced. There was strong correlation between TOC contents and mud proportions, suggesting muddy sediments were the primary control to the organic matter distribution. Fine grained sediments were the main carrier of organic matter transport, at the same time, they controlled the distribution of organic matter.%利用2007年11月采集于长江口和东海陆架区域的78个站位的表层沉积物样品,以及2007年11月、2008年4月采集于长江口东南和浙江近岸泥质区的悬浮物样品,对长江口和东海海域表层沉积物以及部分站位的悬浮物进行了粒度、有机碳和总氮的分析和研究,探讨了沉积物粒径对有机质运移和沉积过程的影响.结果表明:(1)水体中悬浮物的平均粒径从长江口沿浙江近岸向南逐渐减小,与悬浮物含量和颗粒有机碳含量都有较好的相关性,表明悬浮物粒径是影响有机质运移的重要因素.(2)表层沉积物粒径分布呈现出明显的区域性变化特征,有机碳、总氮的分布趋势与表层沉积物的粒径分布密切相关,表层沉积物的粒径越小,有机碳和总氮的含量则越高；长江口和浙江沿岸泥质区表层沉积物中含砂量低,而中外陆架和长江口水下三角洲东北隅表层沉积物中的含砂量较高,含砂量呈现出由近岸向外海逐渐增加的趋势.由此可见,随着含砂量的增加、沉积物粒径的增大,有机质含量由陆向海方向逐渐降低,而有机质含量与粘土粉砂含量有着明显的正相关性,细粒沉积物是有机质运移的主要载体,同时也控制着沉积物中有机质的分布.