鄱阳湖沙地沉积物粒度特征及其影响因素北大核心CSCD

鄱阳湖沙地是亚热带湿润区典型风沙化土地,土地沙化问题严峻。鄱阳湖沙地研究多在小范围开展,研究意义有限,应在多处进行沙地粒度比对研究。选取庐山市、都昌县、永修县和南昌市新建区等沙地样品57个,分析其粒度特征。结果表明:(1)鄱阳湖沙地主要由中沙、细沙和粗沙组成,三者总含量超90%;Mz均值为1.79Φ,分选较差,呈正偏和尖锐分布;(2)鄱阳湖沙地不同土地类型沉积物表层(0-5 cm)与20-40 cm深度粒度特征存在一定差异,固定沙丘、半固定沙丘、流动沙丘和河滩表层比20-40 cm深度粒径大,但流动沙丘和湿地草滩表层分选优于20-40 cm深度;湿地草滩和河滩优势粒级含量和粒度参数有别于沙丘;(3)鄱阳湖沙地固定沙丘、半固定沙丘和流动沙丘为风成沉积;河滩以河流作用为主,风蚀为辅;湿地草滩是在风力和水动力共同作用下形成的。鄱阳湖沙地沿盛行风向从南到北S、SK、K依次减小,风沙运动多以两跳一悬式为主,以就地起沙为主,河滩湖滩作为补充。

Grain size characteristics of sediments in sandy land around the Poyang Lake and its influencing factors

The sandy land around the Poyang Lake is a typical sandy land in subtropical humid region. The problem of land desertification is serious， and has always been a research hotspot. However， there is little significance for the study of sandy land around the Poyang Lake because it is concentrated in a small area. Hence， it is extremely important to study the grain size comparison based onf a lot of sampling points around the Poyang Lake. In this paper， 57 sand samples were selected from Lushan City， Duchang County， Yongxiu County and Xinjian District， etc， and their grain size characteristics were analyzed. The results showed that： （1） The sandy land around the Poyang Lake is mainly composed of medium sand， fine sand and coarse sand， and the content of the three sand is more than 90%.The mean value of M_z is 1.79 Φ， and the sorting is poor with positive deviation and sharp distribution. （2） The grain size characteristics of sediment surface layer and 20-40cm depth were different in different sandy land types around the Poyang Lake. The surface layer of fixed dune， semifixed dune， active sand dune， wetland grass beach and benchland were coarser grain size than those of 20-40 cm depth， but the surface layers of active sand dune and wetland grass beach were better sorting than those of 20-40 cm depth. The dominant grain size content and grain size parameters of wetland grass beach and benchland are different from those of dune. （3） The fixed dune， semifixed dune and active sand dune are eolian deposits around the Poyang Lake. The benchland is dominated by fluvial action and supplemented by wind erosion.The wetland grass beach is formed under the combined wind force and hydrodynamic force. The S_d， SK and K_g of sandy land decreased from south to north along the prevailing wind direction. The aeolian sand movement of the Poyang Lake is mainly two jumps and one suspension style， and the main source of aeolian sand is on the spot， supplemented by river beach and lake beach.