The Phase Exchange Of Persistent Organic Pollutants In The Lower Reaches Of Yangtze River In Anhui Province

Persistent organic pollutants(POPs)has the characteristics of stability,semivolatility,toxicity,and can accumulate in the organism,which has attracted public’s attention.This kind of chemicals can migrate to remote area via atmosphere and damage to the ecological system and human health.Organochlorine pesticides(OCPs),polychlorinated biphenyls(PCBs)and polycyclic aromatic hydrocarbons(PAHs)were studied to investigate their behaviors and fates in environment.The exchange of pollutants between atmosphere and soil phase were also calculated.Tree bark as a passive air sampler was studied to summarize its features.A related tree bark model was verified with field data and some advice were gave.The average concentration of OCPs,PCBs and PAHs in the atmosphere of the lower reaches of Yangtze River in Anhui province(LYA)was 660,590 and 16000 pg/m3 respectively.Endosulfans had the highest average concentration(310 pg/m3)which contributed 47% of total OCPs.An extremely high concentration of Endosulfans(1600 pg/m3)was measured in one agricultural site,indicating a new source of it.Endosulfans have be prohibited from producing and using in China since 2014,while the illegal using of remaining endosulfans leaded to a high level of it in studied area.The concentrations of 23 PCBs of LYA were higher than adjacent regions.An urban-rural gradient descending effect was observed,because PCBs was mainly used in urban.The concentrations of high chlorinated PCBs were high,such as CB167 and CB180,suggesting that local sources should be responsible for the high level of PCBs in air.Phe and Fla made up 68% of PAHs.The concentration of individual compound had a good linearity with total concentration,indicating a same source of PAHs.The source analysis showed that biomass burning was the main source of PAHs in the atmosphere.Back trajectory model illustrated that air mass from northwest affected local atmosphere,what’s more agricultural zone was in this direction,and endosulfans in these sites had high concentrations.We could conduct that endosulfans in the air transported from neighbor districts to studied area.The average concentration of OCPs,PCBs and PAHs in the soil was 15,1.3 and 1100 ng/g respectively.DDT contributed 95% of total OCPs.A high level of DDTs was detected near an industrial park and the ratio of DDT/(DDE+DDD)was higher than 0.5,indicating a new input recently.An agricultural sample site had the highest concentration of DDTs(62 ng/g),p,p’-DDT(10 ng/g)and p,p’-DDE(47 ng/g)were the dominated congeners in this site.This field sample didn’t show new sources of DDTs,but the historical usage was numerous.4-Cl and 5-Cl PCBs were the highest congeners in soil and the high chlorinated individual compounds had higher concentrations,such as CB101 and CB187.This constitution was consistent with those in air.Pry and Fla were the most abundant compounds which contributed 43% of total PAHs.Individual concentration of PAHs had a strong linearity with total concentration,and from the ratio of Fla/(Fla+Pyr)and Phe/(Phe+Ant)we speculated that the source of PAHs in soil came from biomass burning.The relationships between TOC and the concentrations of OCPs and PCBs didn’t show a significant regression,while TOC had a good response with PAHs.Organic matter could promote the absorption of pollutants from new contamination source,while organic matter could enhance microbial degradation after pollutants being trapped in soil for a long time.The fugacity of soil-air exchange showed that soil was a source to release pollutants for α & γ-HCHs,p,p’-DDE,1-3 Cl polychlorinated biphenyls and 2 to 4 rings PAHs.The mean concentration of OCPs,PCBs and PAHs in tree bark was 13,6.0 and 66 ng/g dry weight.The concentrations of endosulfans contributed 58% of total OCPs.High chlorinated PCBs were dominated in tree barks.Phe and Fla taken up 47% of total PAHs.Those constitutions of pollutants in tree barks were similar to the results from passive air sampler,suggesting tree bark could be regard as a good passive air sampler.The estimated air concentrations of OCPs and PCBs by tree bark model were comparable with measured values,however the calculated PAHs concentrations were much lower then the data from passive air sampler.The concentrations of PAHs in air and barks didn’t reach equilibrium could be responsible for this results.It was invalid to estimate the concentrations of pollutants in air with tree bark model when the exchange of POPs in two phases in an unequal states.Tree barks need much more time to reach adsorption equilibrium with air than polyurethane foam passive air samplers.For tree barks,it is hard to reflect the event of accidental pollutants input.Therefore tree barks are tend to represent the average concentrations of stable chemicals in a long time scale.