The contribution of Asian dust in the pedogenesis of ultisols in Southeastern China determined by soil grain size

Li, Jianwu; Song, Zhaoliang; Ruan, Li; Yang, Lihui; Zwieten, Lukas van; Hu, Zhongchen; He, Shengjia; Chenwu, Wentao; Wang, Hailong

The contribution of Asian dust in the pedogenesis of ultisols in Southeastern China determined by soil grain size

2019

PURPOSE: The present study was conducted to understand the pedogenesis of soils developed on basalts and reveal the impact of Asian dust on soils in subtropical China. MATERIALS AND METHODS: Soils developed on basalts in Xinchang-Shengzhou Basin are classified as ultisol and sampled by genetic horizon. For grain size analysis, organic matter was removed from soil samples, and then soil samples were dispersed overnight and followed by ultrasonic treatment. Grain size was measured by a Laser Grain size Analyzer. For isotopic analysis, soil samples were first dried at room temperature and then combusted at 700 °C, digested using an HNO₃ + HF mixture and dissolved in a 2 N HCl solution. Sr and Nd isotopes measured on a GV Isoprobe-T thermal ionization mass spectrometer (TIMS). RESULTS AND DISCUSSION: The grain size distribution with a significantly high content of the “basic dust fraction” (10–50 μm fraction) in the upper profiles (0–40 cm) indicates atmospheric deposition onto the surface layers of soils. The patterns of the grain size frequency curves in the upper layer imply that Asian dust has a great impact on soils. The grain size parameters also reflected the influence of Eolian deposits on soils. The ⁸⁷Sr/⁸⁶Sr and εNd values for soils show that the near-surface horizons are substantially impacted by dust. CONCLUSIONS: The grain size, its parameters, and Sr-Nd isotopes have been marked by Eolian characteristics for the upper layers of soil, while showing a dominant basaltic signature in the lower layers. Besides parent material, accumulation of Asian dust has played an important role in pedogenesis of soils in Southeast China.

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