【作者】 刘博；

【导师】 刘翔；

【作者基本信息】 清华大学 ， 环境科学与工程， 2016， 硕士

【摘要】 新兴污染物的污染风险是当前环境领域的热点问题之一,抗生素抗性基因的污染及其生态、健康安全问题更是关注的焦点,论文针对越来越受到人们重视的地下水抗生素抗性基因的来源和传播,结合北京再生水入渗现场四环素类抗生素抗性基因的分布特征,研究了游离态四环素类抗生素抗性基因在土壤中的吸附规律,主要取得了以下研究成果。以北京市潮白河再生水入渗场地作为典型研究区域,分析其地表水和土壤中tetB、tetM、tetO和tetW 4种四环素类ARGs的存在水平。结果表明,在地表水中tetB基因的检出率为83.3%,其余3种基因的检出率均为100%,四环素类ARGs的丰度大致符合沿程递减规律;在土壤中,4种基因的检出率均是100%,绝对量丰度高且变化幅度大,入渗场地内的底泥和包气带土样中4种基因的绝对量丰度均高于对照土。游离态四环素类ARGs质粒载体在研究区域的底泥和包气带介质中的吸附动力学符合双室一级动力学模型,吸附过程包含快速吸附和慢吸附两个过程。其吸附平衡符合Langmuir模型,拟合结果表明,底泥对其吸附量显著高于包气带介质,不同目的基因片段的导入对其在土壤中的吸附影响较小。使用qPCR方法,测定目标基因在吸附平衡前后的绝对拷贝数,以表征四环素类ARGs在土壤中的吸附特性。吸附达到平衡后,相比于加入量,四环素类ARGs的绝对量丰度降低1-2个数量级,吸附效果明显。四环素类ARGs在高拷贝数的初始量下,其吸附特性符合线性吸附。研究游离态四环素类ARGs在土柱模拟系统中的入渗迁移过程,“底泥-包气带”土柱I和“包气带”土柱II的表观渗透速率分别降低至0.046 m/d和0.17 m/d,达到稳定状态,对应的弥散度分别为3.2 cm和9.3 cm。高丰度配水回灌期内,相同时间点土柱II的出水基因丰度比土柱I的高一个数量级。游离态四环素类ARGs在底泥层和包气带层的滞留因子Rd分别为86.4和40.3。更多还原

【Abstract】 The risk of emerging contaminants has been obtained more attention in environmental area,especially the antibiotic resistance genes.In this study,tetracyclines antibiotic resistance genes using plasmids as carriers had been considered as the targeted pollutants,and their adsorption and transformation characteristics had been analyzed by batch and column experiments.Four tetracyclines ARGs(tet B、tet M、tet O and tet W)had been detected in the recharging area of Beijing Chaobai River.The frequency of tet B was 83.3%in reclaimed water,whilst the frequency of three other ARGs in reclaimed water and soil was 100%.The abundance of tetracyclines ARGs suffered from attenuation along the river,the absolute amount of tet O was generally higher than the other three tetracyclines resistance genes.In soil samples,the abundance of genes was of high level and showed a wide fluctuation range.Compared to the control soil,the absolute abundance of genes was greater in soil samples of sediment and vadose zone which had been collected from the above recharge site.The double-room first order kinetics could well simulate the adsorption process of plasmids,which included the process of rapid adsorption and slow adsorption.The adsorption isotherms of tetracyclines ARGs plasmids were perfectly fitted by Langmuir model.The results suggested that the adsorption of plasmid vectors was much stronger in the sediment samples than the vadose zone media.The different genes fragments introduced to the plasmids showed little impacts on the adsorption capacity.In order to demonstrate the adsorption characteristics of tetracyclines ARGs,this study quantitated the absolute copy numbers of targeted genes by the method of q PCR.After the adsorption reached equilibrium,the abundance of genes decreased 1-2 orders of magnitude as compared to the initial dosage,which showed obvious adsorption effect.Simulation between the soil adsorption amount and the equilibrium concentration was performed on log-normalizedcopy numbers.It fitted the linear model well that the r2 were all above 0.99,which indicated the adsorption characteristics of tetracyclines ARGs in soil were linear adsorption within high initial abundance.Two soil columns were designed to illustrate the different constructures of the recharge site.Column I was filled with sediment and vadose zone soil with a height ratio of 1:2,whilst column II was filled with vadose zone soil.Tetracyclines ARGs had been detected at the fifth day and the second day for column I and II,respectively.The abundance of genes in column II effluent was higher than the column I.更多还原