Study On Distribution Of Polycyclic Aromatic Hydrocarbons And Heavy Metal In The Water Of Surface Microlayer And Subsurface Microlayer From Guangzhou Section Of Pearl River

Polycyclic aromatic hydrocarbons (PAHs) and heavy metals have been of great concern due to their persistence in the environment, their bioaccumulation potential in the tissues of animals and humans through the food chain, and their toxic properties for human and wildlife. The distribution and composition of The dissolved and particulate PAHs and distribution of heavy metals in the water of surface microlayer and subsurface microlayer from Guangzhou section of Pearl River from February 2009 to January 2010 were studied on this paper.The PAHs in the water of Guangzhou section of Pearl River has obvious seasonal and spatial distribution characteristics, which effected by precipitation, temperature and human activities. The dissolved concentrations of 16 PAHs ranged from 773.0 to 2966.6 ng·L-1, there is a positive correlation between the concentrations and DOC. The particulate concentrations of PAHs ranged from 114.7 to 879.3 ng·L-1, which show approximately linear behavior with the particle concentration. Most PAHs consisted of 2 to 3 aromatic rings, they accounted for 86.8 to 88.2% of the total PAHs in the dissolved phase, which was well above the particulate phase (75.7 to 76.0%). The octanol-water partitioning coefficients and physicochemical property of the PAHs contributed to their differences. Microlayer has definite enrichment on PAHs, EF (enrichment factor) ranges from 0.7 to 2.3 (1.0 to 1.4 for dissolved and 0.7 to 2.3 for particulate).the water in Guangzhou section of Pearl River was polluted by 6 kinds of heavy metals in different degrees, the concentration of heavy metals obvious seasonal changes which has high concentration in the spring and winter low in the summer. Heavy metal concentrations of spatial variation are obvious too. Among the health risks caused by the heavy metals by drinking water pathway, the average total health risk caused by the carcinogens of microlayer was 3.7×10-4·a-1 which was 1.5 times of subsurface microlayer (2.5×10-4·a-1) and 7.4 times of the maximum allowance levels recommended by ICRP(5×10-5·a-1). The health risk caused by the carcinogens (As, Cd and Cr) accounted for about 99.8% of the total risk which was high above the noncarcinogens (Cu,Zn and Pb) (0.2%), it is an effective way to reduce the discharge of Cr and As into the Guangzhou section of Pearl River to decrease the environmental health risk.