Residue And Pollution Evaluation Of Polychlorinated Biphenyls In The Pearl River Delta

Polychlorinated biphenyls （PCBs） is a kind of persistent organic pollutants （POPs）,and they have very strong ecological toxicity. Although PCBs have been banned fromproduction long ago, they exist in the environment, causing serious environmentalproblems. PCBs have stability chemically stable, low conductivity, good resistance tothermal and flame retardant, so they have been widely used in industrial production innineteen seventies. They are toxic and biorefractory, long-term accumulation in theenvironment and the human body. PCBs can be through volatilization, diffusion,convective heat transfer to the atmosphere, surface water and underground water,sediments are considered to be one of the main destinations of polychlorinated biphenyls（PCBs） in the aquatic environment. PCBs have serious toxic effects to aquatic organisms,studies have shown that PCBs have bad effects on aquatic organism growth,development and reproduction, immune system of aquatic organisms.In order to assess the pollution level of PCBs in the aquatic environment of thePearl River Delta and their impact on the ecological environment, we collected andanalyzed residual PCBs in surface water and sediments from19sampling stations in thePearl River Delta in dry and wet seasons2012. Aquatic animals were also detected inNovember2012. Through survey of PCB residues, analysis of PCB composition anddistribution characteristics, and pollution risk assessment, we aimed to provide basicinformation for assessment of the potential environmental hazards caused by PCBs inthis area. The concentration of seven PCB residues was determined using a gaschromatography-electron capture detector. Seven polychlorinated biphenyl congeners （including PCB28, PCB52, PCB101, PCB118, PCB153, PCB138, and PCB180） weredetected.Seven polychlorinated biphenyl congeners were detected in water of the PearlRiver Delta. The total concentration of the seven PCBs in water of Pearl River Deltaranged from5.38to22.11ng·L^-1, with an average value of10.25ng·L^-1. The detectionrate of PCB52and PCB180were the highest, and the highest concentration was PCB52,it was the main pollutants, accounting for about40%of the total.There wrere8sampling stations higher than the United States EnvironmentalProtection Agency which made continuous benchmark concentration14ng·L^-1in thewet season, accounting for the total sample of42.1%, including4sampling stationsbeyond "environmental quality standard for surface water" of China; there was1sampling points in the PCBs concentration was higher than14ng·L^-1in the dry season,accounting for the total sample of5.3%sampling points, all PCBs content were in linewith the "environmental quality standard for surface water".Seven indicative PCB congeners were detected in the surface sediments, amongwhich the detection rate and mass concentrations of PCB52were the highest. Theconcentrations of low-chlorine PCBs were higher than those of high-chlorine PCBs.Tetra-PCBs accounted for the largest proportion of the total amount of sediment PCBs.Further, the total concentration of the seven PCBs ranged from19.75to110.78μg·kg-1,with an average of48.22μg·kg-1.We evaluated the concentration, the composition and the spatial distributions ofPCBs and the potential influence of sediment properties in the surface sediments of thePearl River Delta. In conclusion, the∑PCB concentrations in the sediments of theinvestigated area were in the mid-range compared with those elsewhere in China andother countries. In terms of the distribution of different chlorinated PCBs, tetra-PCBs（PCB52） were dominant. Regarding the spatial distribution, the∑PCB concentrationsfor the sites that were located in the city region of the Pearl River Delta weresignificantly higher than the∑PCB concentrations for the eight outlets of the Pearl RiverDelta （P <0.05）. Considering the temporal variation of PCBs, the∑PCB concentrations in the dry season were higher than those in the wet season. In addition, no apparentco-relationships between PCB concentrations and sediment properties were obtained.The ERL and the ERM indicate that PCBs in the sediments of the investigated area mayoccasionally lead to adverse effects, especially in the dry season. Therefore, it isimportant to control PCB contamination in sediments in the Pearl River Delta.The total concentration of the seven PCBs in the Pearl River Delta fish body rangedfrom3.92to9.59μg·kg-1, with an average of5.95μg·kg-1. The total concentration of theseven PCBs in shellfish ranged from3.62to14.61μg·kg-1, with an average of8.67μg·kg-1. The total concentration of the seven PCBs in shrimp ranged from7.05to9.80μg·kg-1, with an average of8.37μg·kg-1.