Poyang Lake is the biggest freshwater lake in China as well as one of the most important international wetlands that provides ideal habitats for many overwintering birds. In recent years, heavy metal pollution in Poyang Lake has increased both in scope and intensity with the nearby growth of human population, industrialization, and intensive agricultural activities. There are many studies on heavy metals in the sediments of Poyang Lake, but there has been little focus on the spatial distributions of dissolved heavy metals in the water of Poyang Lake.
In this study, dissolved trace metal (As, Cd, Cr, Cu, Pb, and Zn) concentrations were measured in the water of Poyang Lake using inductively coupled plasma-mass spectroscopy (ICP-MS) in order to evaluate their spatial variations and health risks. The concentrations of dissolved trace metals in Poyang Lange ranged as follows: As: 0.84-3.24 μg/L (average 1.43 μg/L); Cd: 0.027-0.091 μg/L (average 0.052 μg/L); Cr: 1.76-4.74 μg/L (average 2.21 μg/L); Cu: 1.15-5.05 μg/L (average 2.67 μg/L); Pb: 0.20-2.37 μg/L (average 0.81 μg/L); and Zn: 7.99-77.99 μg/L (average 28.82 μg/L). These values met the national first-level or second-level criterion for drinking water quality of China. The concentrations of As and Cr were higher in the northern part than those in the southern part of the lake, and the Cu content in the northern and southern parts were higher than that in the middle part. The concentrations of Pb and Zn in the northern part were lower than those in the southern part. No obvious spatial distribution pattern of Cd was observed in Poyang Lake. Significant correlations were found between Cu and the other five metals (As, Cd, Cr, Pb, and Zn), indicating that Cu has similar sources or/and identical geochemical behaviors with other metals. This can be attributed to the diversified sources of Cu in the lake. There was a significant association between heavy metals Cr, Cu, and Cd, and there were significant relationships between Pb and Cu, Cd, and Zn. The values of personal annual risk caused by the heavy metals had the following ranges: As: 0.66 ×10^-5-2.54×10^-5 a^-1 (average 1.12×10^-5 a^-1); Cd: 0.86 ×10^-7- 2.91×10^-7 a^-1 (average 1.66×10^-7 a^-1); Cu: 1.41 ×10^-10-6.17×10^-10 a^-1 (average 3.26×10^-10 a^-1); Pb: 0.87 ×10^-10 a^-1 -10.35×10^-10 a^-1 (average 3.54×10^-10 a^-1); Zn: 1.63 ×10^-11-15.85×10^-11 a^-1 (average 5.87×10^-11 a^-1); and Cr: 3.77 ×10^-5-10.14×10^-5 a^-1 (average 4.74×10^-5 a^-1). The values of personal annual risk caused by As, Cd, Cu, Pb, and Zn were lower than the maximum acceptable value (5×10^-5 a^-1) for drinking water recommended by the International Commission on Radiation Protection (ICRP), but the personal annual risk caused by Cr (4.74×10^-5 a^-1) was close to the acceptable level, and the total health risks (5.88×10^-5 a^-1) caused by these six metals were beyond the acceptable level. The sum of the personal annual risk caused by Cr and As was 99.72% of the total risk, suggesting that As and Cr were the major health risk pollutants, and Risk Decision-making Departments should focus on these two metals.