Sources apportionment and ecological risk assessment of potentially toxic elements (PTEs) and polycyclic aromatic hydrocarbons (PAHs) in surface sediments of plateau Lakes of Qinghai Province, China

Qinghai Province, in northwest China's low-density population areas, is known for its high-altitude landscape and abundant surface water. This study investigates 48 sediment samples from 19 quintessential plateau lakes distributed in the Qilian Mountains, Qaidam Basin, Yellow River source regions, and Yangtze River source regions of Qinghai Province, focusing on 7 potentially toxic elements (PTEs ) and 16 priority polycyclic aromatic hydrocarbons (PAHs). Compared to other plateau lake sediments domestically and internationally, concentrations of PTEs ( Ni, Zn, Pb, Cu, Cr, Co, and As) and PAHs (Nap, Acy, Ace, Flu, Phe, Ant, Fla, Pyr, BaA, Chr, BbF, BkF, BaP, IcdP, DahA, and BghiP) in the studied sediment samples were relatively low. Spatial distribution characteristics of PTEs and PAHs contents show that the similar trend between the four regions was like that: Qaidam Basin> Yangtze River source>Yellow River source> Qilian Mountains. Additionally, positive matrix factorization (PMF) and species sensitivity distributions (SSD) are employed  to assess pollution source levels and ecological risks in the study lake regions,respectively.The study reveals that the total average concentrations of PTEs and PAHs in the sediments of the 19 Qinghai lakes were individually 132.93 mg/g and 27.64 ng/g,  which were quite low compared to lake sediments in other plateau regions both domestically and internationally. PMF analysis identified fisheries, animal husbandry, mining, rock weathering, and agriculture as PTE sources.While oil leakage, combustion, and auto emissions were identified as PAH sources. It is found that SSD-based health risk assessment shows the risks was far below the acceptable threshold (0.1). However, the highest risks were concentrated mainly in the downstream areas of the estuaries and near tourist and agricultural sites, such as the studied sites in Keluke Lake (Qaidam Basin), Eling Lake (Yellow River source region), and Tuosu Lake (Qaidam Basin). Notably, Cu, As, and Phe exhibited higher ecological risk indices. In general, despite the current research indicating low and negligible health risks posed by PTEs and PAHs in these plateau lakes, it is necessary to keep monitoring and controlling to prevent any escalation of ecological risks in the fragile lake environment.