电子供体基质和电子穿梭体对电子转移过程有重要影响，进而可能影响厌氧反应体系中2，2-双（4-氯苯基）-1，1，1-三氯乙烷（DDT）还原脱氯降解。为了阐明电子供体基质正丁酸与电子穿梭体蒽醌-2，6-二磺酸盐（AQDS）对红壤性水稻土中DDT还原脱氯效果的影响，本研究采用厌氧土壤培养试验并设定以下5个处理：①灭菌对照，②对照，③正丁酸，④AQDS，⑤正丁酸+AQDS。结果表明，厌氧培养20 d后，土壤中DDT可提取态残留量减少了85.2%～96.3%。DDT厌氧脱氯降解的主要产物为2，2-双（4-氯苯基）-1，1-二氯乙烷DDD。添加正丁酸在培养前8d显著提高产CH4速率，而对DDT脱氯降解无显著促进作用，第8天之后，随着产CH4速率降低，添加正丁酸处理的DDT脱氯速率逐渐升高。添加AQDS显著增强土壤还原性并加速三价铁氧化物还原生成电子供体二价铁，进而显著促进DDT还原脱氯降解。同时添加正丁酸和AQDS对促进DDT还原脱氯的效果最佳，但是正丁酸和AQDS对加速DDT还原脱氯无显著交互作用。本研究结果对于制定DDT污染土壤的高效原位修复技术方案具有指导意义。%1,1,1-Trichoro-2,2-bis(p-chlorophenyl)ethane(DDT)is one of the most extensively used organochlorine pesticides worldwide. As a result,DDT can be detected in various environmental compartments in recent years,and its concentration is much higher in the soil than in the air and water. Therefore,it is of great significance to develop an efficient technology to remedy DDT contaminated soils. Reductive dechlorination seems to be a crucial pathway for DDT degradation under anaerobic conditions, because the five electrophonic chlorine substitients in a DDT molecule make aerobic oxidative degradation difficult. However,reductive dechlorination requires the addition of two electrons for each chlorine removed. Therefore,the existence of electron donor substance and electron shuttle is vital to electron transfer,and hence may affect the reductive dechlorination of DDT in anaerobic reaction systems. In order to investigate reductive dechlorination rate of DDT in Hydragric Acrisols which is widely distributed in tropical and subtropical regions and contains abundant iron oxides;to examine single and interactive effects of n-butyric acid as electron donor substance and AQDS as electron shuttle on soil microorganisms degrading DDT;and to elucidate relationship between DDT dechlorination and methane generation rate,a batch anaerobic incubation experiment of Hydragric Acrisols was conducted. The experiment was designed to have five treatments, i.e.(1)Sterile control,(2)Control,(3)n-Butyric acid,(4)AQDS,and(5)n-Butyric acid +AQDS,and three replicates for each treatment. The treated samples in sealed culture flasks were incubated at 25 ℃ in darkness for 20 days. During the incubation,gases in the flasks were sampled once every four days for analysis of CH4 concentration,and soil samples,too,for determination of Fe(Ⅱ)contents, DDT and its degradation products,and oxidation-reduction potential(Eh)of the reaction systems were measured simultaneously. Results show that after 20 days of incubation,DDT residue in treatment 1,2, 3,4 and 5 decreased by 44.5%,85.2%,90.2%,93.2% and 96.3%,respectively,as compared with the initial value. In terms of first-order kinetic constants(k)of DDT transformation,the five treatments displayed an order of Treatment 5 > Treatment 4 > Treatment 3 > Treatment 2 > Treatment 1. DDD(1, 1-dichloro-2,2-bis(4-chlorophenyl)-ethane)was found to be the dominant degradation product of reductive dechlorination of DDT in the current assay. DDE(1,1-dichloro-2,2-bis(4-chlorophenyl) ethylene)and DDMU(1-chloro-2,2-bis(p-chlorophenyl)ethylene)were also detected as the secondary dechlorinated products of DDT,though not much,and the former was higher than the latter. Some non-extractable DDT and its degradation products were detected to be bonded by soil organic matter and clay particles,and hence retained in the soil as residues,mainly in the first 4 days of incubation. During the first 8 days of incubation,Treatment 3 significantly increased CH4 generation rate,but did not do much DDT dechlorination. However,in the days later,with declining CH4 generation rate and rising Fe(Ⅱ)content, DDT dechlorination rate gradually increased in the treatment. The findings indicate that the amendment of n-butyric acid leads to completition for electrons between methanogenesis and reductive dechloriantion of DDT during the early incubation period,which is not conducive to reductive dechloriantion of DDT. The amendment of AQDS significantly increased soil Eh values and accelerated reduction of Fe(Ⅲ)oxides into electron-donor Fe(Ⅱ),thus promoting markedly reductive dechlorination of DDT,which indicate that the quinone moieties in AQDS molecules act as redox modulator promoting DDT dechlorination under anaerobic conditions. Treatment 5,the addition of nvbutyric acid + AQDS,was the most efficient in accelerating reductive dechlorination of DDT,but in this effect,no significant interactive effect between the two was observed. The present study has demonstrated that the application of both electron donor substance and electron shuttle is an ideal approach to acceleration of DDT dechlorination in the soil,and the findings may have some important meanings for developing efficient in situ remediation technology for DDT contaminated soils.
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