Distribution And Ecological Risk Assessment Of PAHs And PCBs In The Surface Sediments Of Dishui Lake Watershed

Trace organic matters including polycyclic aromatic hydrocarbons(PAHs) and polychlorinated biphenyls, have the characteristics ofpersistence, toxicity, mutagenicity, and carcinogenicity, and are harmful tohuman health. Dishui Lake is the largest artificial lake in China. PAHs andPCBs were measured bimonthly in sediments from Dishui Lake watershedin2012. Meanwhile, distribution and ecological risk assessment of themwere analysized in this study.Ultrasonic extraction-C18solid phase extraction (SPE)-highperformance liquid chromatography (HPLC) analysis method was used forthe determination of PAHs and PCBs residues. The method detection limits(MDL) of PAHs and PCBs were0.07~2.40ng/g and0.30~0.35ng/g,respectively. Recovery ranges of blank spike were62%~129%(PAHs) and82%~96%(PCBs), sample added recoveries were64%~116%(PAHs) and81%~126%(PCBs). Due to the low MDL values and high recoveries, theanalysis method was considered to be suitable for determining PAHs andPCBs of the surface sediment samples in the lake watershed.The total concentrations of16PAHs were ranged from74.03to579.20ng/g, with the mean value of272.55ng/g. Total PAHs in riversediment outside the diversion sluice [(407.64±6.90) ng/g] were similar tosediment inside the diversion sluice [(427.99±213.84) ng/g], while bothwere greater than those in Dishui Lake [(156.33±62.00) ng/g]. Total organic carbon (TOC) contents were positive correlation with total PAHsconcentrations, with the determination coefficient (R2) value was0.197. Asthe value of Ant/(Ant+Phe) in each site of study area was higher than0.1,petroleum combustion was considered to be the main sources of PAHs. Theresult of ecological risk assessment indicated that serious ecological riskdidn’t exist, but the flowing rivers maybe had a weak potential risk, whileDishui Lake was considered risk-free.The total concentrations of7PCBs were ranged from no detected to2254.50ng/g with the mean value of347.92ng/g. Residual PCBs increasedgradually in the flowing river, while fluctuated slightly inside the lake. Thespatial distribution showed that PCBs outside the diversion sluice[(844.74±687.62) ng/g] was higher than that inside the diversion sluice[(516.83±645.45) ng/g], and both were much higher than that in DishuiLake [(81.63±72.18) ng/g]. TOC contents were positive correlated withtotal PCBs concentrations, with the R2value of0.241. Judged by principalcomponent analysis method, the possible sources included import capacitormigration (43%), paint additive pollution (33%) and domestic capacitorand transformer pollution (11%). The ecological risk assessment indicatedthat biological toxicity effect of PCBs was serious in the flowing river,whereas Dishui Lake had potential hazards. Compared with other studies,PCBs contaminated sediments in the flowing rivers were at a seriouspollution level, while Dishui Lake was considered at a medium pollutionlevel.