Organochlorine Pesticides Distribution In Citrus Orchards And Soil Residues Phytoremediation

Researches were conducted to investigate organochloride pesticides(OCPs) residues in citrus orchard and to know about the pollution in citrus orchard by these pesticides.And high accumulation plants for OCPs phytoremediation were also selected in order to decrease the OCPs residues in citrus and improve the citrus quality.An analysis method was established to quickly determine multiresidues of several organochloride pesticides in citrus peel and pulp,soil and weeds of citrus orchard.The sample for analysis was extracted by acetone-petroleum ether(1:1,V/V).After then the extract was purified on columns,it was collected and evaporated to get dry.The samples were then determined by capillary gas chromatography with ECD.All tested organochloride pesticides in weeds roots,including HCH,aldrin,dieldrin,dicofol, chlordane,DDT,were well qualitative and quantitative determined.With the average recoveries of pesticides being 81.2-112.6%,the minimum detectable concentration would range from 0.01-0.05μg/L and the correlation coefficient(R~2) would not be less than 0.99. OCPs residues in soil,weeds and citrus fruits of citrus orchards were detected in six different locations of Fujian provinces.The average concentration of the detected 13 OCPs in soil was 3.929 mg/kg,which reflected the pollution in citrus orchard soil by OCPs.And aldrin,γ-BHC,dicofol,α-chlordane,p,p'-DDT,o,p'-DDT and p,p '-DDD were detected in every soil sample.Average concentration of 13 OCPs in citrus peel reached to 1.161 mg/kg, while all citrus pulps were not found OCPs residues except two samples,in which the OCPs concentrations were 0.088 and 0.068 mg/kg.In the collected the citrus orchard weeds,Ageratum conyzoides showed relative high accumulation ability to OCPs and the average concentrations of OCPs in roots and aerial tissues of A.conyzoides ranged from 4.214 to 13.660 mg/kgand from 6.946 to 20.969 mg/kg,respectively,which was considered as phytoremediation plant.Dicofol residues in soils,citrus fruits,Ageratum conyzoides of citrus orchards in 13 locations,Fujian province,were investigated.The dicofol was detected in all soil samples and in 61.538%citrus fruits samples.The concentrations of dicofol ranged from 0.0020 to 0.895 mg/kg and averaged 0.178 mg/kg.The average concentrations of dicofol in citrus fiuits' peel and pulp reached 0.191 and 0.0857 mg/kg,respectively,which were lower than the European Union limit.The concentration in aerial tissues or roots of Ageratum conyzoides was much higher than its in soil or fruits and the average concentrations in aerial tissues and roots of reached 2.415 and 1.530 mg/kg,respectively.The concentration of dicofol in aerial tissues of Ageratum conyzoides was higher than its in roots in 7 of ten locations.BCFs of Ageratum conyzoides and citrus orange were calculated based on dicofol concentration in soil and result showed that BCFs for aerial tissues and roots were much higher than its for citrus fruits.The averages of BCFs for aerial tissues and roots of Ageratum conyzoides were 191.931,106.567,respectively.Uptake and potential remediation of dicofol in soil by Ageratum conyzoides were studied.At the concentration of 250 mg/kg,the dicofol in aerial tissues of A.conyzoide showed decrease in both sterilization and free treatment.The dicofol in aerial tissues with sterilization treatment varied from 4334μg/kg in 10 d to 1556μg/kg in 30d.Contrasted with the variety of dicofol in aerial tissues in A.conyzoides,the roots growing in free soil contained much higher dicofol than these in sterilization soil.And the dicofol in roots reached 8039μg/kg in 30d increasing from 5442μg/kg in 10 d in free treatment.The concentrations of dicofol in the experience did not obviously affect its accumulation in aerial tissues of A.conyzoide,while its accumulation in roots showed some relationship with dicofol concentrations.With sterilization treatment,the half-lives of dicofol in soil planted A.conyzoides were 11.32,12.80,13.08 days,but without A.conyzoides the half-lives were 21.40,21.37,23.25 days when the concentrations used were 250,333,500 mg/kg.When the soil were treated without sterilization,the half-lives of dicofol in soil planted A.conyzoides were 10.72,11.71,12.07 days,but without A.conyzoides the half-lives were 16.89,17.33,16.17 days when the concentrations used were 250,333, 500mg/kg,respectively.In conclusion,the A.conyzoides can accumulate the dicofol from soil and showed the remediation potential for dicofol residues in soil.Meanwhile the microorganism in soil can affect the accumulation of dicofol by A.conyzoides.