【作者】 高波；

【导师】 贾凌云；

【作者基本信息】 大连理工大学 ， 生物化工， 2011， 博士

【摘要】 有机氯农药(Organochlorine Pesticides, OCPs)是一类典型的持久性有机氯代污染物,具有高毒性、高生物富集性和难以生物降解等特点。OCPs污染点处理技术的研究一直是环境科学技术领域的热点。微生物修复技术和活性炭固定技术被认为是有很好应用前景的处理技术。本论文首先考察了实验室前期筛选的polychlorinated biphenyls (PCBs)高效降解菌株Enterobacter sp. LY402对十四种OCPs的降解能力,包括α-六六六(α-HCH)、β-六六六(β-HCH)、γ-六六六(γ-HCH)、δ-六六六(δ-HCH)、六氯苯(HCB)、p,p’-滴滴伊(p,p’-DDE)、o,p’-滴滴涕(o,p’-DDT)、p,p’-滴滴滴(p,p’-DDD)、p,p’-滴滴涕(p,p’-DDT)、艾氏剂(Aldrin)、七氯(Heptachlor)、狄氏剂(Dieldrin)、α-氯丹(α-Chlordane)和β-氯丹(β-Chlordane),评价了该菌株对水体中持久性有机氯代污染物的降解普适性；详细研究了LY402对环戊二烯结构的Dieldrin和氯代苯结构的滴滴涕类农药(DDTs)的降解特性。进一步以Dieldrin和DDTs为研究对象,尝试利用可回收的高性能吸附剂活性炭纤维毡(ACFF)提取模拟污染水体沉积物中的Dieldrin和DDTs,耦合化学方法降解ACFF吸附的OCPs,探讨了该方法的可行性,并系统研究了相关影响因素,研究结果如下：(1)研究了Enterobacter sp. LY402休眠细胞体系对十四种OCPs的好氧降解能力。结果表明LY402在30℃对浓度为2.8 m/L的OCPs的7 d总降解率达到了72.2%,该菌株对除β-HCH和δ-HCH外的十二种OCPs均表现出较强的降解能力。在OCPs混合物中,氯代环戊二烯类OCPs的降解先后顺序如下:Heptachlor>Aldrin>β-Chlordane>α-Chlo-rdane>Dieldrin;氯代苯及其衍生物类OCPs的降解先后顺序如下：p,p’-DDD>p,p’-DDE> HCB>p,p’-DDT>α-HCH>γ-HCH>o,p’-DDT。与氯代环己烷结构的HCH类农药相比,环戊二烯和苯环结构的OCPs更容易被LY402降解,这可能与OCPs的结构和毒性抑制作用有关。考察了LY402对不同浓度的OCPs的降解能力。发现4.2 mg/L、7 mg/L和14 mg/LOCPs的8 d总降解率分别达到了72%、61.3%和46.7%,说明该菌株对较高浓度的OCPs仍具有较好的降解效果。(2)Enterobacter sp. LY402对Dieldrin和DDTs的好氧降解特性研究表明,Dieldrin和p,p’-DDT的生物降解的最佳条件是30℃-40℃,pH值为7左右的中性条件。考察了农药的表观浓度对其生物降解的影响,发现LY402对0.5 mg/L、2 mg/L、5 mg/L和10mg/L的Dieldrin的7 d降解率分别达到94.8%、83%、40.4%和34.5%,对0.5 mg/L、2 mg/L、5 mg/L和8 mg/L的p,p’-DDT的5 d降解率分别达到95.1%、64.5%、57.7%和55.5%。此外,LY402对1 mg/L、5 mg/L、15 mg/L和30 mg/L的DDTs的10 d总降解率分别为88%、57.3%、39%和13.3%,高浓度的DDTs对生物降解表现出抑制作用。考察了外源营养物质的添加对农药生物降解的影响,结果表明酵母提取物和蛋白胨均能够明显促进Dieldrin和DDTs的生物降解。LY402降解Dieldrin的过程中出现明显的脱氯现象。p,p’-DDT的降解过程中GC-ECD检测到未知代谢产物的累积,其生成量过低无法被GC-MS鉴定。(3)研究了ACFF对液相体系中Dieldrin的吸附规律。结果表明ACFF能够有效吸附去除水体中的Dieldrin。pH值为6左右的条件有利于Dieldrin的吸附；ACFF对Dieldrin的动态吸附过程符合二级吸附动力学模型；Dieldrin的吸附行为符合Freundlich吸附等温线。(4)研究了ACFF对模拟污染沉积物中DDTs的动态吸附规律,证明ACFF对取自不同河流的三种沉积物中的DDTs均有一定的吸附提取效果。ACFF介导的DDTs解吸附过程可以分为快速和慢速两个阶段,0.02 g(2%,W/W) ACFF对老化7 d的HR、LR和QR沉积物中8mg/kg∑DDT的332 h去除率分别达到41%、28.9%和6.7%。考察了ACFF吸附提取沉积物中DDTs的影响因素,发现污染沉积物老化时间的延长、污染物疏水性的增强、沉积物的有机碳含量的提高、污染物初始浓度的减小都会使DDTs的去除率有所降低。通过增大ACFF的加入量或间断更换ACFF的方式能够明显提高DDTs的去除率。(5)研究了ACFF吸附的OCPs的Fenton氧化处理法,发现Fenton反应仅进行1.5h时,吸附态的Dieldrin、p,p’-DDE、o,p’-DDT、p,p’-DDD和p,p’-DDT均有明显降解,其总降解率达到60.6%,有望实现对ACFF的再生利用。以上研究结果表明,PCBs高效降解菌株Enterobacter sp. LY402对多种OCPs具有较强的生物降解能力。ACFF是一种理想的吸附材料,可以有效提取污染水体和沉积物中的Dieldrin和DDTs, Fenton氧化法能够快速有效降解吸附在ACFF表面的DDTs和Dieldrin,这种耦合方法在修复OCPs污染水体沉积物方面具有良好的应用潜力。更多还原

【Abstract】 Organochlorine Pesticides (OCPs) are typical persistent chlorinated pollutants, which are recalcitrant to degradation and highly toxic to living organisms, particularly when accumulated through food chains. Thus, developing novel techniques to remediate the sites contaminated with OCPs has been a continuous effort in environmental science and technology. Microbial remediation and activated carbon stabilization are the promising treatment techniques for OCPs pollution control.In this research, an Enterobacter sp. strain LY402, which was isolated previously to degrade polychlorinated biphenyls (PCBs), was explored to degrade 14 OCPs, includingα-HCH,β-HCH,γ-HCH,δ-HCH, HCB, p,p’-DDE, o,p’-DDT, p,p’-DDD, p,p’-DDT, aldrin, heptachlor, dieldrin,α-chlordane andβ-chlordane. Cyclodiene pesticide (dieldrin) and chlorinated benzene pesticide (DDTs) were chosen to evaluate the degrading versatility of the strain LY402. Moreover, retrievable activated carbon fiber felt (ACFF) was applied to extract dieldrin and DDTs from the simulated aqueous solutions and sediments, and then treated by the chemical method. The results are as below:(1) The aerobic degradation of the OCPs mixture in solutions by the resting LY402 cells was studied, which degraded 72.2% of the total OCPs at the initial concentration of 2.8 mg/L at 30℃within 7 d. The strain has strong degradation capacity for 12 OCPs, while not forβ-HCH andδ-HCH. The sequence of two kinds of OCPs degradation is heptachlor> aldrin>β-chlordane>α-chlordane>dieldrin for the hexachlorocyclopentadiene pesticides and p,p’-DDD >p,p’-DDE>HCB>p,p’-DDT>α-HCH>γ-HCH>o,p’-DDT for the chlorinated benzene and derivative pesticides. It was found that the pesticides consist of cyclodiene or benzene structures are more likely to be degraded than the ones consist of cyclohexane structures, which might be related with the structure of OCPs and toxic inhibition. Moreover, about 72, 61.3 and 46.7% of the total OCPs at the initial concentrations of 4.2, 7 and 14 mg/L were degraded within 8 d, respectively.(2) Aerobic degradation of dieldrin and DDTs by the strain LY402 was systematically studied. The best environmental factors for the biodegradation were 30℃-40℃and pH7. The effects of the concentrations of the pesticides on their biodegradation were investigated. About 94.8,83,40.4 and 34.5% of dieldrin were consumed within 7 d for the initial concentrations of 0.5,2,5 and 10 mg/L, respectively, and about 95.1,64.5,57.7 and 55.5% of p,p’-DDT were consumed within 5 d for 0.5,2,5 and 8 mg/L, respectively. Moreover,88, 57.3,39 and 13.3% of∑DDT were degraded within 10 d for 1,5,15 and 30 mg/L, respectively. High concentrations of DDTs pose negative effect on their biodegradation. The effects of additional nutrients on the biodegradation of dieldrin and DDTs were also studied. It was found that yeast extract and peptone could improve the biodegradation of these pesticides. Significant release of inorganic chloride was observed during the degradation of dieldrin. An unknown metabolite was detected by GC-ECD in the degradation of p,p’-DDT, but the metabolite could not be identified by GC-MS because of its low accumulation level.(3) ACFF effectively removed dieldrin from the aqueous phase. The optimal pH of the solution for dieldrin adsorption was determined to be around 6. The adsorption process obeyed the second-order kinetic model. Freundlich isotherm was better in describing the behavior of dieldrin adsorption onto ACFF.(4) ACFF also removed DDTs from three laboratory-spiked sediments. The ACFF-mediated desorption process of DDTs from the sediments included rapid and slow phases. At the end of 332 h of adsorption, the removal of∑DDT from 7-d aging HR, LR, QR sediments spiked with 8 mg/kg∑DDT were 41,28.9 and 6.7%, respectively. Lower removal of DDTs by ACFF occurred with longer aging time of the spiked sediments, higher hydrophobicity of contaminants, higher organic carbon contents in the sediments, and lower initial spiking concentrations. Moreover, the adsorption ability was enhanced by increasing the amount of ACFF, as well as by its sequential replacement.(5) The OCPs adsorbed onto ACFF were degraded by Fenton’s reagent. After 1.5 h of the Fenton’s reaction, the adsorbed dieldrin, p,p’-DDE, o,p’-DDT, p,p’-DDD and p,p’-DDT were significantly degraded, and the degradation percentages of the total OCPs was 60.6%. These results suggested that the Fenton method was expected to regenerate the ACFF.In conclusion, Enterobacter sp. LY402 has strong degradation capacity for OCPs. ACFF is the optimal adsorbent for extracting dieldrin and DDTs from the contaminated water and sediments, and the Fenton oxidation could effectively degrade the same OCPs adsorbed onto the ACFF, suggesting that the coupling method could potentially be applied for the remediation of OCPs-contaminated water and sediments.更多还原