Research On The Migration Law Of Typical Toxic Organic Pollutants In Crops

Due to the high toxicity,difficult degradation of organic toxic pollutants(OTPs),with accumulation and amplification in animals and human body in food chain,which have been widely concerned for long time.In recent years,with the efforts of all the countries in the world,the pollution situation of OTPs in the world has been somewhat improved.However,the global pollution situation is still not optimistic due to OTPs has the characteristics of POPs and remain in the environment for a very long time,causing harm to the environment,animals,plants and human body.Meanwhile,some of them,such as PAHs,are still discharged in large quantities all over the world,causing serious pollution problems because of the development of economic globalization and the acceleration of industrial process.Therefore,the challenge of constainly detecting and control of OTPs in the environment is still serious and necessary.Electronic waste(e-waste)is a source of environmental contaminants that has been receiving much attention from scientists and the general public.E-waste contains harmful substances such as polychlorinated biphenyls,polybrominated diphenyl ethers,and heavy metals that can be released to the environment when the e-waste is disposed of or dismantled.Toxic chemicals such as PAHs and polychlorinated dibenzo-p-dioxins and dibenzofurans can also be produced and released into the environment during e-waste dismantling processes such as incineration,roasting,and acid washing performed under inappropriate conditions.However,PAHs have been found to be emitted from e-waste dismantling sites in a few studies.Meanwhile,E-waste dismantling sites are usually in agricultural areas,toxic chemical such as OCPs can also be pollutant in environment and few researches were found.Hence,the concentration and distribution characteristics of PAHs and OCPs in the air,soil and crops of farmland near two typical e-waste dismantling areas in Taizhou City,Zhejiang Province were studied in this research.The characteristics of PAHs and OCPs in the environment absorbed and translocation by crops were also discussed.The result showed that the concentration of ?15PAHs and ?19OCPs in air samples were 13.1?22.5 ng·m-3 and 0.38?1.49 ng·m-3,respectively.The concentration of DDTs and HCHs in air samples were 0.04?0.48 ng·m-3 and 0.03?0.0 7 ng·m-3.OCPs such as HCB,heptachlor and chlordane et al were found lower concentration with high detection,deserving attention constantly.No significant difference in concentrations of PAHs and OCPs in air between Fengjiang(FJ)and Binhai(BH)was found from Taizhou.PAHs in the air samples were mainly three-and four-ring PAHs and a various in distribution of DDTs and HCHs in air was found between FJ and BH.p,p'-DDD+o,p'-DDT and ?-HCH were no detected in air samples in BH and detected in FJ.The concentration of ?15PAHs and ?19OCPs in surface soil and rhizosphere soil samples were 155?7.21×103 ng·g-1 and 65.9?9.11×103 ng·g-1,34.8?56.2 ng·g-1 and 4.22?1.06×103 ng·g-1,respectively.The concentration of DDTs and HCHs in surface soil and rhizosphere soil samples were 18.0?21.9 ng·g-1 and 0.81?3.80 ng·g-1,2.88?353 ng·g-1 and 0.38?435 ng·g-1,respectively.HCB,heptachlor and chlordane et al were also detected in soil samples.No significant difference in concentrations of PAHs and OCPs in soil between FJ and BH was found and the concentrations of PAHs and OCPs in the rhizosphere soil samples were lower than the surface soil samples.The dominant PAHs in the surface and rhizosphere soil samples were four-ring PAHs and distribution between in surface soil and rhizosphere soil from reeds and solanum were significantly different(solanum p<0.01;reed p<0.05).Interestingly,PAHs distribution in surface soil and rhizosphere soil around taro were not significantly different(p=0.2).No significant difference in DDTs distribution in surface soil and rhizosphere soil was found,whereas a significant difference was found in HCHs.?-HCH and ?-HCH were detected in surface soil but not in rhizosphere soil samples.It may caused by different physical and chemical properties of HCHs and the various of organic matter content and water content in soil.The PCA result showed that distribution of PAHs was significantly different between air and soil.The distribution of DDTs and HCHs were significantly correlated in the atmosphere and soil as well as the sources analysis showed that the input of DDTs and lindane still exists in this area,indicated that long-term input of OCPs from foreign sources could be found in China.The concentration of ?15PAHs and ?19OCPs in crops were 29.7?1.95×103 ng·g-1 and 38.2?1.85×103 ng·g-1,respectively.The PAHs concentration gradients from the tops to the bottoms of the crops showed that higher concentration were found in leaves and root meanwhile lower concentration were found in stems.However,the lowest PAH concentration were found in peeled taproot for crops.The concentration of DDTs and HCHs in crops were N.D.?566 ng·g-1 and N.D.?197 ng·g-1,respectively.Lowest DDTs and HCHs were found in peeled taproot for crops like PAHs.The DDTs and HCHs concentration gradients from the tops to the bottoms of the crops were different between FJ and BH and it may be affected by long-distance transfers.The 3-4 ring PAHs and HCHs were absorbed more easily than the larger PAHs and DDTs by crops root.High-molecular weight and higher LogKow value pollutants such as 5-6 ring PAHs and DDTs were prevented from entering crops via roots,particularly into peeled taproot(edible)by root exudates and peel.Most of crops leaf absorbed HMW PAHs easier than other tissues from ambient air.OCPs in atmosphere have little influence on the aerial parts of crops and it may because of lower concentration from long-distance transfers.The distribution of PAHs and OCPs in fruits of crops were showed different from other aerial parts,indicating that fruit can selectivity uptake pollutants.3-4 ring PAHs were more easily transfer than other pollutants in crops and it may be due to the lower molecular weight than others.HCHs would transform isomers due to the influence of physical and chemical properties in the process of translocation.The significant correlation negatively were found between the ratio of PAHs and OCPs in the roots and leaves and the add of the ratio in the stem,indicating that the transport of pollutants in crops were main affected by the concentration in the root and leaf.Furthermore,different from lipid contents in crops tissues were also can be influence of translocation by enriched and fixed.