Residual Characteristics Of HCHs In Soils Of A Former Lindane Production Enterprise And Research On Soil Remediation

With strong ahead of the pace of urbanization in China, much land-use nature has changeddramatically. Recently, a large number of pesticide manufacturers closed and soils of their former venueswere contaminated seriously, which have been "chemical time bombs" to the environment, arousing greatconcern from society. HCHs as refractory persistent organic pollutants, highly residue in soils. Because ofthe pre-mass production during the last centuries, soils polluted by organochlorine pesticides has been agreat soil pollution and caused widespread attractions. In this paper, we focus on a spot once being alindane production enterprise. Through the determination and analysis of the soil, we achieve thedistribution characteristics of HCHs in soils. Chemical oxidants were used to repair the polluted soil.(1)HCHs determination in soil samplesSoil cores were collected from different regions of a former a lindane production enterprise. Weuse Soxhlet extraction (SE)-Gas chromatography (GC)-electron capture detector (ECD) method to detectsoil residues of HCHs. The results showed that the extraction efficiency of the method is good andthe silica gel column chromatography is a complete purification way. When the concentration range is0.005-0.5mg/L, the method has a good linear relationship, correlation coefficient R2≥0.9989.(2)HCHs residue distribution in contaminated soils of a former lindane production enterpriseIn order to understand the organochlorine pesticide production manufacturing field soil pollution, soilsof a former lindane production enterprise were investigated. Results showed that in all sampling points, thedetection rate of four HCHs isomers were100%. In the0-20cm topsoil, concentrations of HCH residues(∑HCH) ranged from0.0343-19.5608mg/kg. In the layer of0-80cm soil around the hospital center,concentrations of HCH residues (∑HCH) varied from0.0313-0.2947mg/kg, lining with the trendof first increase and then decrease in general. Analysis of pollutants composition showed thatconcentrations of four isomers were in order with β-HCH﹥δ-HCH﹥γ-HCH﹥α-HCH.The average percentage of β-HCH isomer was about50%, far higher than others."Soil EnvironmentalQuality Standard (GB15618-1995) as the standard for risk assessment of contaminated sites, it indicatedthat western and eastern parts of backyard near the production plant are still seriously contaminated, causing great security risk to human and environment.(3)Research on degradation effect of different chemical oxidants to HCHs in soilsDifferent types of chemical oxidants were added to the soil samples, each oxidant with threeconcentration levels, reacting for one hour under the same vibration conditions and time. The resultsindicated when the chemical oxidants were potassium permanganate and activation of sodiumsulfate (FeSO4and citric acid activation), the optimal concentration of1mmol/g and2mmol/g. the totaldegradation rate of HCHs was highest. Activated sulfate has a removal rate to α-HCH,γ-HCH,δ-HCHisomers. After1h, average removal efficiency was more than45%, α-HCH isomer up to80%.However, β-HCH isomer removal rate is low.1mmol/g of potassium permanganate roling on α-HCH,γ-HCH,δ-HCH, the removal efficiency of the isomers are slightly lower than2mmol/g of theactivation sodium sulfate. But β-HCH isomer having a higher removal rate, remained at about50%.Sodium persulfate and potassium permanganate are environmentally friendly chemical oxidants, whosedegradation products do not cause secondary pollution to the environment. In situ soil remediation, theycan be combined with each other to achieve an efficient and harmless soil repair process.(4)The degradation effect of HCHs in water by Fe-C micro-electrolysisThe traditional Fe-C micro-electrolysis technology was used in the degradation of HCHs simulationwaste water.And liquid-liquid extraction (LLE)-Determination of gas chromatography (GC)–the electroncapture detector (ECD) analytical method was adopted to detect HCHs in water. The outcomes proved thatthe method is a satisfactory sample pre-treatment way and blank spike recoveries ranged from61-86%.The Fe-C micro-electrolysis method is an extremely powerful means of chemical degradation, which hashigh removal efficiency of HCH in water column.Degradation rate of all isomers and total∑HCH couldreach80-90%after3hours of reaction.Even the extremely stableβ-HCH isomer, the removal effiencyachieved more than80%. Laboratory studies laid steady theoretical foundations for its repair inthe degradation of organochlorine pesticides in actual water bodies.