Physical weathering of Gobi Desert sediments under different temperature and humidity conditions

Abstract

Physical weathering of the Gobi Desert surface sediments involves complex processes. However, our understanding of its main driving factors is still limited, and experimental observations on the weathering intensity of Gobi Desert surface sediments under changing environmental conditions are still insufficient. Surface samples were collected from the Gobi Desert, divided into 0.063–0.125 mm, 0.125–0.25 mm, 0.25–0.5 mm, 0.5–1 mm and 1–2 mm groups, and washed with deionized water. Physical weathering and salt weathering experiments of these groups were conducted under temperature (T) of −40 °C–40 °C and relative humidity (RH) of 20 %–100 %. Salt and mineral analyses, grain size distribution, and morphology analysis of each fraction group before and after the experiments were conducted. The results showed that mean grain sizes for the 0.063–0.125 mm, 0.125–0.25 mm, 0.25–0.5 mm, 0.5–1 mm, and 1–2 mm groups decreased by 0.49 ± 1.09 %, −0.27 ± 2.14 %, 0.41 ± 3.14 %, 2.96 ± 3.14 %, and 0.19 ± 1.29 %, respectively. The mean size of each group decreased ∼ 0.76 ± 1.13 % /10 days, demonstrating a higher physical weathering intensity than the previous estimations. The d0.1 size (i.e., the grain diameter for which 0.1 % of each grain group is smaller) was more sensitive to physical weathering, and the skewness was a good indicator of physical weathering for groups obeying a normal distribution. Physical weathering was still affected by salt weathering, and there was no regular pattern for physical weathering under variations in salt and mineral contents. At present, there are still difficulties in developing an accurate physical weathering intensity model.