Grain size distribution patterns and influencing factors of surface sediments in deserts and sandy lands in China

Drawing from the systematic collection and integration of grain size measurement data of surface sediments in Chinese deserts and sandy lands, their spatial patterns and distribution characteristics were clarified, and the influencing factors and formation mechanisms were thoroughly investigated. The results revealed that the differences in sediment grain size composition and distribution were more pronounced in western deserts compared to eastern sandy lands. Except for the Taklimakan Desert (TAD) in western China and Ulan Buh Desert (UBD) in central part of China, most deserts and sandy lands were dominated by fine (125–250 μm) and medium sand (250–500 μm). Sediment grain sizes varied among deserts, with the TAD having the smallest mean particle size (121.59 μm) and the Kumtagh Desert (KD) in western China the largest (248.50 μm). In contrast, sandy lands displayed relatively consistent grain sizes (193.21–237.06 μm). Sediment sorting in deserts was generally better, while in sandy lands were not well-sorted, with the Hulun Buir Sandy Land (HBSL) in eastern China showing the poorest sorting (1.06 Φ), and others displayed moderate sorting (0.80–0.99 Φ). Furthermore, the grain size distributions in both deserts and sandy lands were positively skewed or nearly symmetrical, with narrow to medium peak states. Western deserts were strongly influenced by natural conditions. Due to differences in local terrain and sand supply, their sediments did not exhibit the typical trend of becoming finer along the prevailing wind direction. In contrast, eastern sandy lands, along with the Gurbantunggut Desert (GD) which directly benefits from moisture supplied by westerlies, displayed better vegetation coverage and well-developed biological soil crusts. These factors redistributed surface sediments, preventing the downwind differentiation of grain size. The grain size composition and distribution of sediments in deserts and sandy lands are shaped by a complex interplay of factors. Therefore, these characteristics are unsuitable for use as proxy indicators when reconstructing the historical climate and environmental evolution of deserts and sandy lands.