Аңдатпа
The world's highest grassland-dominated Qinghai-Tibetan Plateau (QTP) holds the largest yaks and Tibetan sheep population, which can alleviate the global organic meat demand; however, contamination of their farming systems is overlooked. Therefore, as an initiating pilot scale study, these livestock were engaged in grazing and stall-feeding (4/group) for heavy metals (HMs) and microplastics (MPs) detection and transferability assessment through the farming systems in winter. HMs' detection revealed higher concentration in food of the grazers (0.0001-2.5 mg/g) than in the stall-feeders (0.0001-0.08 mg/g), all within livestock permissible limits. Pasture grass had no MPs, but the feed of the stall-feeding group chiefly contained polyethylene (PE; 30-55%) and polypropylene (PP; 33-70%) polymers. Correlation analysis presented significant correlations of Cr, Cd, Cu, Co, and MPs concentration in grazing system with altitude, precipitation, and population density, but MPs were also significantly associated with wind speed and UV index ( p < 0.05). In livestock meat, HMs ranged from 0.0005 to 0.8 mg/g, below the permissible limits for humans, whereas, except for 1 transparent PE fiber in stall-fed sheep muscles, all other MPs (99%) accumulated in the digestive tracts. The total estimated HMs intake was within the standards, whereas MPs' ingestion was higher in stall-fed livestock, but neither of them showed unhealthy behavior. Transferability evaluation exhibited HMs bioconcentration mostly in grazing yaks and feeding sheep, while MPs bioaccumulated typically in feeding livestock (TTF/BCF>1). Non-carcinogenic risk was below the acceptable level (THQ<1) upon HMs/PE-contaminated meat consumption by humans. Overall, our study provides an important foundational dataset for highlands/QTP livestock-based food security.