Study On The Organic Pollution Status Of PCBs In Water And Sediment Of HongFeng Lake

The paper has made a brief introduction to Persistent Organic Pollutants(POPs),and elaborated on the characteristcis,toxicity of polychlorinated byphenyls(PCBs) and their transport and toxicological characterics in ambient mediums.The internal and abroad research working present situation has also been expounded in details.This paper takes Hongfeng Lake as its study object and 7 kinds of indicative PCBs internationally accepted as target substances.This study determined the species and content of PCBs in water and sediment of HongFeng Lake.Solid phase extraction(SPE) and soxhlet extraction(SE) were utilized to pretreat samples,followed by detection method of high sensitive GC-ECD(Gas Chromatography-electron Capture Detector).According to the results,we analysed the source of PCBs and made a preliminary evaluation about the pollution level of PCBs in Hongfeng Lake.In the work of pretreatment for water,we discusseed the influence of injection volume on the recovery and detection results during SPE.The results indicated that when the injection volume was 400mL,the recovery of PCBs ranged between 81.80%and 94.35%and the detection result was non-detectable. The recovery of PCBs' ranged between 61.46%and 79.36%and the detection result was one kind of PCBs could be detectable when the injection volume was 1L.Comprehensive consideration about recovery and detedction results,PCBs in 1L water sample should be enriched.Regarding the study on extraction method of sediment,the samples were pretreated with SE technique.In order to obtain the best experimental condition of SE,we designed orthogonal experiment method,and discussed the influence of extraction agent species and dose,time of extracting on the extraction results.The results showed that the experimental conditions comprised by n-hexane/acetone(1:1 in volume),24h of extracting time and 120ml of extraction dose permitted the most ideal spiked recovery,which range between 63.48%and 86.30%.We have done certain amount of investigation about purifying method of sediment and compared 3 purification efficiency brought about by Al₂O₃ chromatography column,Al₂O₃ and silica gel chromatography column and multilevel complex chromatography column.Our results revealed that the third purification was superior to the former two.Our detection results for the water and sediment of Hongfeng Lake showed that the total content of PCBs in the water was 1.390ng/L,average content was 0.174ng/L.Four kinds of PCBs were detected,the detectable ratio of PCB₂₈ was 100%.The total content of PCBs in the sediment was 13.764ng/g,average content was 1.721ng/g.Seven kinds of PCBs were all detected, the detectable ratio of PCB₂₈ was 100%,PCB₂₈ and PCB₅₂ had higher contents.The detection results suggested that the content of PCBs in sediment was much higher than in water,the former was four orders of magnitude in the total content than the latter. It can be seen that the PCBs which existed mainly in sediment of lake bottom were a type of hydrophobic substance from the further confirmation by detection results.In addition,we inferred the pollution history of PCBs in Hongfeng Lake by analysed clomnar section of sediment.The results showed that the pollution of PCBs became more serious in Hongfeng Lake and relevant department should pay corresponding attention.Our analytic data fill the vacancy of PCBs pollution for water quality monitor data in Hongfeng Lake.The results have provided some certain scientific bases for government departments and related environment authorities.