Investigating the environmental capacity of soil heavy metals and its determinants in agro-pastoral regions of the qinghai-tibetan plateau.

Environmental capacity (EC) serves as the basis for environmental planning and management, as a key indicator for assessing environmental risk and quality, and as a foundation for achieving sustainable development. Studies on EC typically address agricultural or urban rather than pastoral areas, with few examining agro-pastoral areas. The EC of the Tibetan Plateau is particularly important, considering its importance as an agricultural area and ecological reserve. To address this gap, the Qingshizui area in Menyuan County, a typical agro-pastoral area on the Tibetan Plateau, was selected to quantify soil EC and its spatial distribution. In terms of the dynamic and static annual soil EC for this region, the heavy metals were ranked as follows, in ascending order: Cd, Hg, Co, As, Sb, Ni, Cu, Pb, Cr, and Zn. Most of the areas with high residual EC were in the west. For the 10 heavy metals, residual EC was significantly affected by geological background. For all the heavy metals except Zn and Hg, residual EC was significantly affected by soil type. The heavy metal elements in the agro-pastoral area's soil are mildly enriched, suggesting minimal human impact. The composite EC index of this soil is 0.98, indicating an intermediate EC and low health risk. This study underscores that integrating agriculture and pastoralism can optimize land use and mitigate ecological pressures associated with these practices when done separately. Our research provides valuable insights for resource optimization, environmental conservation, and enhancing the welfare of farmers and herders in the Qinghai-Tibet region.