Spatial variability of the physicochemical characteristics of surface sediments in the "Three Rivers and One Dune" Region in the Kuye River Basin, Mu Us Sandy Land, China

Eolian-fluvial interactions are a common geomorphic phenomenon and Earth surface process in arid regions. We selected the "Three Rivers and One Dune" region, in the Kuye River Basin, in the northeastern Mu Us Sandy Land in Northern China, for a study of eolian-fluvial interactions, based on a geomorphological survey and analysis of the grain size and chemical element contents of surface sediments. The results showed that the interactions of wind and water flow enhanced have caused the mixing of the surface sediments, which is reflected by the spatial heterogeneity of their physicochemical properties, which are different from those of the local parent rock and local sandy environments. In detail, the variations of the chemical weathering-related indicators, including the CIA, CIW, CPA, Na/K and Rb/Sr, along four transects all indicated that the degree of chemical weathering was generally low in the region (CIA < 50), implying that the materials are unweathered or in an incipient chemical weathering state. Combined with the grain size results, in the upper reaches (transect KYH-1) the mean grain size was coarser, the degree of sorting was lower, and there was a lower degree of chemical weathering. Transect KYH-4, located in the most southeasterly part of the study area, has the lowest mean grain size and is relatively well sorted; hence, it has undergone a greater degree of chemical weathering. Transects KYH-2, KYH-3 and KYH4 span the "Three Rivers", and their sediments are relatively well mixed and heavily influenced by locallyderived materials. The differences in physicochemical properties between the transects can be attributed to the diversity of slope directions and of the angles between the wind direction and the river flow. Overall, our results, combined with regional comparisons, indicate that the sand sources of the dunes in the study area are mainly locally derived.