Abstract
Dissolved heavy metals (HMs), derived from natural and anthropogenic sources, are an important part of aquatic environment research and gain more international concern due to their acute toxicity. In this study, the geochemistry of dissolved HMs was analyzed in the upper Three Gorges Reservoir (TGR) of the Yangtze River (YZR) watershed to explore their distribution, status, and sources and further evaluate the water quality and HM-related risks. In total, 57 water samples were collected from the main channel and tributaries of the upper TGR. The concentrations of eight HMs, namely V, Ni, Cu, Zn, As, Mo, Cd, and Pb, were measured by ICP-MS. The mean concentrations (in μg/L) of eight HMs decreased in the order: As (1.46), V (1.44), Ni (1.40), Mo (0.94), Cu (0.86), Zn (0.63), Pb (0.03), and Cd (0.01). The concentrations of most HMs were 1.4~8.1 times higher than that in the source area of the YZR, indicating a potential anthropogenic intervention in the upper TGR. Spatially, the concentrations of V, Cu, As, and Pb along the main channel gradually decreased, while the others were relatively stable (except for Cd). The different degrees of variations in HM concentrations were also found in tributaries. According to the correlation analysis and principal component (PC) analysis, three PCs were identified and explained 75.1% of the total variances. combined with the concentrations of each metal, PC1 with high loadings of V, Ni, As, and Mo was considered as the main contribution of human inputs, PC2 (Cu and Pb) was primarily attributed to the contribution of mixed sources of human emissions and natural processes, and Zn and Cd in PC3 were controlled by natural sources. Water quality assessment suggested the good water quality (meeting the requirements for drinking purposes) with WQI values of 14.1 ± 3.4 and 11.6 ± 3.6 in the main channel and tributaries, respectively. Exposure risk assessment denoted that the health effects of selected HMs on the human body were limited (hazard index, HI < 1), but the potential risks of V and As with HI > 0.1 were non-negligible, especially for children. These findings provide scientific support for the environmental management of the upper TGR region and the metal cycle in aquatic systems.
Highlights
With the acceleration of economic globalization, it becomes more and more difficult to balance the excessive utilization of water resources and high-efficiency water environmental protection schemes [1,2]
This is supported by the similar mean values and median values of these heavy metals (HMs) (Table 2)
The mean concentrations of eight HMs in the upper Three Gorges Reservoir (TGR) area decreased in the order: As (1.46), V (1.44), Ni (1.40), Mo (0.94), Cu (0.86), Zn (0.63), Pb (0.03), and Cd (0.01)
Summary
With the acceleration of economic globalization, it becomes more and more difficult to balance the excessive utilization of water resources and high-efficiency water environmental protection schemes [1,2]. Given the current status of the global hydrosphere, it is of great significance to evaluate the contamination of river ecosystems (watershed scale), which is beneficial for the arrangement of water resources [3,4,5]. Characterized by bioaccumulation, non-biodegradability, and acute/chronic toxicity [8,9,10,11,12], HMs are harmful to the aquatic ecological environment and even threaten human health [13]. Both anthropogenic inputs (e.g., industrial/domestic wastes) and natural processes (e.g., rock weathering and soil erosion) can contribute to the riverine HMs [14,15]. The occurrences of HMs in water bodies include dissolved loads, riverbed sedimentary loads, and suspended loads [16]
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