Grain size and fractal characteristics of surface sediments of nebkhas in the lower reaches of Hetian River,Xinjiang,China
The study of nebkha is of great significance to regional ecological environment protection,desertifi-cation control and environmental evolution analysis.The grain size and fractal characteristics of surface sedi-ments of Populus euphratica nabkha and Tamarix nabkha in different geomorphologic parts of Hetian River Ba-sin were analyzed,and the differences were analyzed.The results show that:(1)The surface sediment content of different nebkhas is different.The surface sediment of Populus euphratica nabkha and Tamarix nabkha is main-ly composed of extremely fine sand,fine sand and coarse silt,and the total percentage content is 93.67％and 90.17％respectively.(2)Sediment grain size of each geomorphologic part of different types of nebkhas has a cer-tain rule of change.The average grain size of Populus euphratica nabkha and Tamarix nabkha is gradually thinner from the foot of the windward slope to the top of the sand pile,and gradually coarser from the top of the sand pile to the foot of the lee slope.The grain size frequency distribution curves of Populus euphratica nabkha and Tamarix nabkha are bimodal,in which the grain size frequency distribution curve of Populus euphratica nabkha is higher and narrower,and the particle size is more concentrated.(3)In the surface sediment probability cumu-lative curve,the saltation component slope of Populus euphratica nabkha along the main wind direction is larg-er,the sorting ability is better,and the saltation component content is 7.25％higher than that of Tamarix nabkha.The suspended component content of Tamarisk nabkha is 5.84％higher than that of Populus euphratica nabkha.(4)There is a significant negative correlation between the fractal dimension of surface sand and the average parti-cle size(P＜0.05).The sorting coefficient,skewness and peak state are significantly positively correlated(P＜0.05).There is a significant positive correlation between the fractal dimension and the content of clay,very fine silt,fine silt,medium fine silt and coarse silt(P＜0.01),and the positive correlation between the fractal dimen-sion and clay content is the highest.There is a significant negative correlation with fine sand(P＜0.01).Regional wind dynamic conditions,plant morphologic characteristic,vegetation coverage and the source of sand material are the main reasons for the difference in grain size and fractal characteristics of surface sediments of different types of sand piles in Hetian River Basin.
particle size characteristicsfractal dimensionsedimentary environmentlower reaches of Hetian River
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NSTL
万方数据
