塔克拉玛干沙漠北缘沙尘暴源区地表沉积物粒度特征

Study on Grain Size Characteristics of Surface Sediment in Sandstorm Source Regions in the Northern Marginal Zone of the Taklimakan Desert

研究表明,在肖塘地区,地表沙主要以细砂（0.125~0.25 mm）为主,占48.35%,极细砂（0.0625~0.125mm）占30.05%,中砂（0.25~0.5 mm）占14.34%,粉砂（0.003 9~0.062 5 mm）占6.09%,同时丘间沙有黏土（0.00002~0.0039 mm）存在,含量在0.5%~0.8%;以细砂为主是造成肖塘地区沙尘暴结束后,很少出现浮尘天气的主要原因,也是造成该地沙尘暴主要以就地起沙为主,只有少数几次较强的天气系统形成远源沙尘暴;沙丘砂样分选良好,标准偏差（σ1）为0.61,其次是胡杨林带和生态防护林带,分别为0.65,0.69,古河床的砂样分选最差为1.31,河床沉积土为1.64;沙尘暴输沙贡献以沙为主,河床裸露面积小,表土胶结紧实,对沙尘暴沙源贡献不大。

In this paper, the grain size characteristics of surface sediment in sandstorm source regions in the northern marginal zone of the Taklimakan Desert are researched. The results show that the surface sand samples in the Xiaotang region are dominated by fine sand （0. 125 -0.25 mm） and very fine sand （0. 062 5 -0. 125 mm） , their proportions are 48.35% and 30.05%, and the proportions of medium sand （0.25 - 0.5 ram） and silt （0. 003 9 -0. 062 5 mm） are 14.34% and 6.09%, respectively. Clay （0. 000 02 -0.003 9 ram） is distributed in inter-dune lowlands, and its content varies in a range of 0.5% - 0.8%. The granular characteristics dominated by fine sand are the main causes why floating dust weather occurs seldom after a sandstorm in the Xiaotang region and why sandstorm is mainly caused by local sand sediment, and a few of strong weather systems can cause distant sand-source sandstorm only. Sorting of the sand samples collected from sand dunes is fine, and then that collected from the Populus euphratica forest belts and the ecological conservation forest belts, and their standard deviations （ σ1 ） are 0.61, 0.65 and 0.69 respectively ; the sorting of sand samples collected from fossil riverbed is the poo- rest, its standard deviation is 1.31 only, and that of riverbed sediment samples is 1.64. The highest contribution to the transported sand of sandstorm comes mainly from sandy surface. The vegetation-uncovered area of riverbed is small, the topsoil is tightly cemented, and its contribution to sandstorm is not so high.