Assessment Of The Concentration,Distribution And Health Impacts Of Persistent Organic Pollutants In Agricultural Soils From Huangpi Wuhan,Central China

Persistent organic pollutants(POPs)are heterogeneous groups of industrial compounds like organochlorine pesticides(OCPs),polychlorinated biphenyls(PCBs)and polybrominated diphenyl ethers(PBDEs)or by-products of industrial and natural process often dominated by polycyclic aromatic hydrocarbons(PAHs).Most of POPs in the environment are byproducts from manufacturing industries,urban wastes and combustion processes.Due to their potential for long-range transport,persistence in the environment,ability to bio-magnify and bio-accumulate in ecosystems,as well as their significant negative effects on human health and the environment they are considered as chemicals of global concern.Human exposure to POPs can occur in different scenarios mainly through the food we eat,air,water and workplace.Because of their low environmental concentration,POPs can induce less acute toxic effect,however;they are known for their sublethal effects such as impairing reproductive potential of living organisms,immunological disturbances,cancer and endocrine system disruptions.This study was aimed at determining the concentration,distribution,potential sources,ecological and human health impacts of four groups of POPs in Huangpi district,Wuhan.Soil samples in 18 sites were collected from two depths(0-10 and 10-20 cm)and four land-use types barren,farmland,plastic greenhouse and paddy field.The differences in the mean concentration of POPs with soil depth,land-use types and sampling places were analyzed using a one-way analysis of variance(ANOVA)at a significance level of a<0.05.A modified matrix solid-phase dispersion extraction method was applied to extract analytes from the soil samples.Polycyclic aromatic hydrocarbons are large groups of ubiquitous environmental pollutants composed of two or more fused aromatic rings.The sum mean concentrations of the polycyclic aromatic hydrocarbons were 138.93 and 154.99 ?g kg-1 dw in the 0-10 cm and 10-20 cm soil depths,respectively.Benzo[a]pyrene and fluorene were the most abundant compounds in the 0-10 cm and 10-20 cm soil depths,respectively.The sum average concentration of PAHs from both soil layers in the four land-use type was higher in barren lands(68.64 ?g kg-1 dw),followed by plastic greenhouse(64.17 ?g kg-1 dw),paddy field(61.54 ?g kg-1 dw)and farmlands(45.18?g kg-1 dw).The quantitative values of the pyrogenic index,total index and diagnostic ratio used in this study showed that the polycyclic aromatic hydrocarbons are originated from a pyrogenic,partial combination of petrogenic and pyrogenic agents.The negligible and maximum permissible concentrations values for naphthalene,acenaphthylene,acenaphthene,phenanthrene,anthracene,pyrene,benz[a]anthracene and benzo[a]pyrene indicated a moderate ecological risk.Concerning the human health impacts,the incremental lifetime cancer risk values for adults and children showed a low and moderate cancer risk,respectively.Regarding organochlorine pesticides,they are groups of chemicals applied to prevent pest and insect infestation.The total mean concentration of OCPs tanged from 0.00-32.7 ng-1 dw in the surface and 0.01-100.45 ng g-1 dw in the subsurface soil layer.Beta hexachlorocyclohexanes(?-HCH)with 2.20 and 7.71 ng g-1 dw in the surface and subsurface soil layers,respectively was the dominant compound.The mean concentrations of OCPs in all samples were less than the threshold values for hexachlorocyclohexanes(HCHs)and dichlorodiphenyltrichloroethane(DDTs)in China soil.The concentrations of OCPs in the four land-use types were in decreasing order of:paddy field>barren land>farmland>plastic greenhouse.Results of composition analysis revealed recent applieation of lindane as a major and historical application of technical HCHs as a minor source of HCHs.On the other hand,the application of new technical p,p'-DDT is the main source of DDTs in the study area.The estimated lifetime average daily dose,incremental lifetime cancer risks and hazard quotient values revealed that there is less likelihood of carcinogenic and negligible non-carcinogenic health risks of OCPs on the local residents.Polychlorinated biphenyls(PCBs)and polybrominated diphenyl ethers(PBDEs)are the other ubiquitous and environmentally persistent organic pollutants.The obtained concentration for PCBs was ranged from ND to 54.12 ng g-1dw(dry weight)(mean=7.08 ng g-1 dw)in the 0-10 cm and ND to 35.35 ng g-1(mean=7.03 ng g-1dw)in the 10-20 cm.PCB-28 and PCB-52 were the frequently detected PCBs congeners.Regarding PBDEs,the overall concentration of PBDEs in this study was varied from ND-34.88 ng g-1 dw(mean=4.57 ng g-1 dw)and ND-32.43 ng g-1dw(mean=5.02 ng g-1 dw)in the 0-10 cm and 10-20 cm,respectively.PBDEs(BDE-47 and-28)were the frequently detected congeners.Samples collected from places close to big infrastructures and residents showed relatively higher concentrations of PCBs and PBDEs.However,the concentration of PCBs in all samples was below the ceiling ecological impacts quality guideline limits.The Pearson's correlation analysis results showed a weak correlation of PCBs and PBDEs congeners with the total organic carbon,soil moisture content and soil pH.The estimated lifetime carcinogenic and non-carcinogenic health impact values revealed exposure to both PCBs and PBDEs can currently pose negligible health impacts.