Grain-size characteristics of the inter-tidal flat sediments of Shanghai non-resident islands

30 surface sediment samples were collected from the islands of Shanghai.All of the samples were analyzed by using LS13320 laser particle size analyzer.There are five sediment types in the study area of six non-resident islands,among all types of sediments,the silt sediment is the most abundant.The sediment parameters of all samples are generally bad sorting,positively skewed,leptokurtic.The study area is located in the Yangtze River Estuary.The open mouth provides a broad space for the development of the tidal flat and the influence of the strong river runoff,tidal flow and waves provide dynamical factors to form the tidal flat.By drawing Pejurp triangle pattern,it displays that all the samples are in Ⅲand Ⅳdynamic sections which means the hydrodynamic condition is strong generally.Besides Guyuan Sha,accompanied by the declining hydrodynamic conditions,from ocean to shore,the grain size decreases and the sand content decreases,clay and silt increases.