Material composition of city surface soil in Harbin in relation to sand-dust weather

Abstract：Different kinds of surface sediments are distributed in main roads of each urban area of Harbin, which include road bare soils, river alluvial deposits, soils, building soils and so on. These surface sediments were sampled on the basis of an analysis of their grain sizes and chemical composition. The results show that there exist plenty of coarse-grained components (>63μm) in riverbed alluvial deposits but less fine-grained components of silt and clay, and hence the latter have exerted relatively insignificant influence on the sand-dust weather of Harbin. Although there exist certain amounts of fine-grained materials in soils, they fail to participate in the sand-dust weather under the action of wind power because of the vegetation cover and the cohesion between soil particles. The road bare soils and building soils with large amounts of fine-grained materials that are liable to be transported for a long distance have similar chemical composition and chemical weathering features to sand-dust deposits in Harbin. Characteristics of grain sizes and chemical composition indicate that road naked soil and building soil constitute important material sources for sand-dust weather in Harbin in that they can supply sand-dust weather with a large amount of silt-dust materials. It is considered that it is the city building soil and road naked soil with large amounts of fine particles that exert a remarkable influence on the dust-sand weather in Harbin, and that the control of the loose earth surface naked soil is the key to the prevention of the dust-sand weather in Harbin.