Soil enrichment of potentially toxic elements in relation to land‐use types in an alpine meadow of the Qinghai–Tibet Plateau

Abstract

The Qinghai–Tibet Plateau, a fragile ecosystem with unique biodiversity, is particularly susceptible to soil contamination from increasing anthropogenic activities like grazing and farming. However, research exploring the relationship between these factors remains limited. Our study examines soil changes and potentially toxic elements (PTEs) after converting alpine meadows, providing insight into the impact of land‐use in this area. We found significant differences in the concentrations of PTEs (Cd, Cr, Hg, and Pb) among the three land‐use types. Soil from Oat Field (OF) had lower levels of Cd, Cr, Hg, and Pb compared with Fence Enclosure (FE) and Winter Grazing (WG), indicating a potential uptake/phytoextraction of these elements by oats. Different profiles of soil physiochemical properties were also detected, particularly in the OF soil, which showed significantly lower available potassium, microbial carbon, and microbial nitrogen but higher soil bulk density and total and available phosphorus. Additionally, significant stratification was observed in soil concentrations of most studied PTEs and nutrients in FE and WG, but not in OF. Specifically, lower levels of As, Cr, and most nutrients were found in the top layer (0–10 cm) compared with the bottom layer (20–30 cm). By comparison, Cd and Hg showed higher concentrations in the top layer in FE. These contrasting trends suggest potential differences in the mobility or bioavailability of these elements in the soil of the alpine meadow. Furthermore, significantly negative correlations were found between most soil nutrients, and the concentrations of As, Cr, and Pb, whereas significantly positive associations were observed for soil nutrients with Cd and Hg. However, such relationships predominantly existed in soils of WG and FE, but not OF. Collectively, our results suggest the potentially disrupted PTE accumulation and nutrient distribution by anthropogenic activities, particularly agricultural practices within the studied land‐use types, and warrant further evaluation of the associated ecotoxicological risks.