Determination of background concentrations and risk-screening values for elements in oasis soils in the arid zone of the Tibetan Plateau using multifractal models.

Oases on the Tibetan Plateau serve as vital buffers in the arid alpine zone, sustaining ecological security under high-altitude conditions; however, their soil quality remains underexplored. This study addresses the limitations of traditional soil assessment methods-which lack defined thresholds and are poorly adapted to spatial heterogeneity-by applying multifractal analyses to determine risk-screening values and background concentrations for 20 soil elements in the Delingha-Ulan Oasis, northeastern Tibetan Plateau, using 1517 samples. The model was validated by comparing the screening values of six regulated elements (e.g., Cd, Hg, As, Pb, Cu, Zn) with the corresponding national standards, enabling robust evaluation of unregulated elements (e.g., B, Ge, Se). Results reveal multifractal patterns, with nine elements (e.g., Cd, I) showing heavy-tailed distribution indicative of localized contamination risks, and Hg, N, and P reflecting subtle anthropogenic impacts from wolfberry farming and pastoral activities. Notably, iodine exhibits extreme enrichment, posing significant ecological threats. This framework fills a critical gap in alpine oasis soil benchmarks, enhancing pollution identification and ecological management in fragile plateau ecosystems. These findings offer a scalable tool for sustainable soil protection in arid, high-altitude regions.