A comparative analysis between local soils and dust deposition on snow in Shenyang, China and implications on loess-paleosols evolution

Abstract

Loess deposition from wind is one of the major sources of soil development in many regions including northeastern China. The dust deposition on snow from 6 sites in Shenyang, northeastern China was collected and characterized physically and chemically to determine its origin (modern vs. re-deposited loess). The origin and characteristics of the dust deposition were evaluated through comparisons with possible sources of sand desert areas based on elemental compositions, such as the A-CN-K (Al2O3-CaO + Na2O-K2O) ternary plot and ratios of Al2O3/TiO2, Fe2O3/TiO2, and Fe2O3/Al2O3. The texture and composition results showed that the dust deposition was most recent and not re-deposited loess. The dust deposition was predominantly silt-sized grains (2–50 μm) and had greater amounts of Na2O (1.7% vs. 1.5% average), MgO (2.1% vs. 1.2%), and CaO (3.2% vs. 1.2%) when compared to the local soil. Its mineral composition was mainly quartz, feldspar, and mica. The magnetic susceptibility of the dust deposition was 30.9 × 10−8 m3/kg and lower than the local soil which was 40.4 × 10−8 m3/kg. Based on the A-CN-K ternary plot, the dust had a weaker weathering intensity than the local soil, loess-paleosol sequences, and red clay. This indicated that the dust was not a re-deposited loess. Furthermore, according to the discriminating analysis using ratios of Al2O3/TiO2, Fe2O3/TiO2, and Fe2O3/Al2O3, the source for the dust was traced from the deserts of south Mongolia, Tengger, Gulban Tungut, and Taklimakan.The two primary factors transporting the dust were the Mongolia Cyclone and westerlies. The dust was blown into the atmosphere, and transported by the atmospheric circulation from west to east and/or from northwest to southeast, which was accompanied also by a cold front cyclone moving southeast towards the study area. The origin, transportation, and deposition process of the dust deposition in this study provides further evidence about the origin of the loess and its likely role in soil development in Shenyang, northeastern China.