Accumulation pattern and risk assessment of metal elements in permafrost-affected soils on the Qinghai-Tibet Plateau

Abstract

Permafrost-affected soils can serve as a major reservoir of metal elements (MEs) from anthropogenic sources by atmospheric transport. Understandings of the contents, sources, and ecological risks of MEs in high-altitudinal permafrost regions are helpful to mitigate environmental and human health hazards under climate change. Thus, we investigated the concentrations of 21 MEs of topsoil (0–50 cm) and evaluated the environmental quality using the ecological risk assessment methods in permafrost regions on the central Qinghai-Tibet Plateau (QTP). The results showed that (1) Ca, Al, Fe, K, Mg, Ti, and Mn (max values in mg/kg d.w.: 7.61 × 104, 5.93 × 104, 3.12 × 104, 2.33 × 104, 1.49 × 104, 0.52 × 104, and 0.06 × 104, respectively) were abundant in all sampling sites. (2) The concentrations of most MEs in the alpine wet meadow were the highest, followed by the alpine meadow and alpine desert steppe. (3) Land cover types and soil properties (soil organic carbon, pH, and soil texture) were associated with MEs. (4) Ca, Al, Fe, K, Mg, Mn, Rb, Sr, Th, Zn, V, Ni, As, Pb, Cu, and Co likely originated from geogenic/pedogenic processes, and Ti, Cr, Cd, and Hg were enriched by both natural and anthropogenic sources. (5) The modified contamination degree indicated that sampling sites in permafrost regions of the QTP were in a low pollution state, while the geoaccumulation index and enrichment factor have revealed that 37.14 % of soils showed moderate pollution of Hg, and 84.44 % of soils had moderate to high enrichment levels for Cd. This study reveals accumulation patterns of MEs in permafrost regions and provides a scientific basis for the research on the ecological security of MEs in permafrost regions influenced by climate change.