【作者】 张倩；

【导师】 欧阳自远；

【作者基本信息】 华南理工大学 ， 环境科学， 2012， 博士

【摘要】 随着抗生素药物在人们日常生产和生活中的广泛使用，大量抗生素药物以母体或代谢物的形式进入环境中，给环境造成巨大的负荷，对生态环境带来潜在的威胁。尤其当环境中残留的抗生素通过雨水和渗滤作用从土壤迁移到江河湖泊，甚至是地下水时，其危害更加严重。因此，研究抗生素在土壤/水界面的吸附解吸过程及其作用原理，弄清土壤组分与抗生素的相互作用关系，在此基础上，进一步考察抗生素与其它污染物之间的相互作用，将有助于正确评价抗生素的环境风险，为控制污染物进入食物链及其循环、修复受污染的环境、指导农业尤其是养殖业的科学发展提供理论支持。本论文以常用的兽药抗生素泰乐菌素（TYL）为代表，系统研究了TYL在土壤/矿物-水界面的吸附行为及机理，初步探讨了复合污染条件下TYL对菲在矿物上吸附作用的影响及作用机理。论文取得了以下研究成果：1.以珠江三角洲地区典型农业土壤为吸附剂，研究了TYL在土壤上的吸附解吸行为。发现，TYL在各土壤上的吸附容量KD值在2.01-12.4L/kg之间，不同浓度下的Koc值在118-15850L/kg-OC之间。进一步分析发现：作为离子型化合物，泰乐菌素在土壤中的吸附与土壤的pH值呈负相关、与比表面积呈正相关。土壤中的粘土成份对吸附的影响是各种矿物综合作用的结果，而有机质与TYL在土壤中的吸附没有明显的相关性。由于泰乐菌素具有分子量大，可电离的特性，其在土壤中的吸附接近线性，解吸滞后不明显，吸附-解吸的主要作用力可能是离子交换和范德华力。泰乐菌素在土壤上具有中等的吸附能力，不容易迁移。同时，由于吸附可逆，泰乐菌素也有可能释放到水环境中造成污染。2.根据土壤中的矿物组成，考察了TYL在高岭石、蒙脱石、石英、针铁矿和铝土矿上的吸附情况。结果发现：几种矿物吸附TYL的大小顺序为：蒙脱石>针铁矿>高岭石>石英>铝土矿，且所有矿物对TYL的吸附均呈明显非线性（n=0.22-0.48）。TYL在矿物上的吸附与矿物的比表面积、等电点、溶液pH值密切相关。在酸性条件下，矿物带负电荷的表面对带正电荷的TYL具有较强的静电作用，而在中性和碱性条件下，矿物表面与不带电的TYL分子之间的分配作用是决定TYL在矿物上吸附的主要因素；几种矿物中，对TYL吸附起主要作用的是蒙脱石、高岭石和针铁矿。进一步对TYL在三种主要矿物上的吸附热力学进行分析发现，TYL在矿物上的吸附是一个放热反应，高温不利于泰乐菌素在矿物上的吸附。静电引力、范德华力及氢键作用可能是TYL在矿物上吸附的主要机理。TYL与矿物的亲和力随温度的减小而加强，吸附能随吸附量增加而减少，表明：TYL在吸附过程中可能首先占据低浓度条件下的高能量位点，然后再与低能量位点发生作用，而且低能吸附位置数较多，吸附位点的异质性明显。3.为深入探讨TYL在矿物上的吸附机理，对比研究了TYL在蒙脱石上和高岭石上的吸附，着重考察了pH值对吸附的影响。结果表明：TYL在矿物上的吸附能力随pH的增加而减小。从不同pH值条件下的吸附等温线、单点吸附实验结果分析，离子交换和表面吸附是TYL在矿物上吸附的主要机理，溶液中的阳离子可以与正价态的TYL竞争矿物表面带负电荷的吸附位。XRD分析结果发现，除去表面的作用，TYL可以进入蒙脱石层间形成单层吸附。进一步引入经验公式和双元吸附模型（DMM）分别评价了离子交换和表面吸附在整个吸附过程的贡献率，发现离子交换控制了整个吸附过程。同时，随着溶液中TYL浓度的增加，表面吸附的作用越来越强。被吸附的大分子的泰乐菌素之间可能存在疏水性作用。吸附的泰乐菌素可以作为矿物的有机质来影响其它有机污染物在矿物上的吸附。4.由于TYL在自然条件下所处的离子环境往往存在较大波动，本文还研究了离子强度及离子类型对TYL吸附的影响。发现，TYL在高岭石上的吸附随离子强度的增加而减少。而TYL在蒙脱石上的吸附与溶液中TYL浓度有关。高浓度时，吸附随离子强度的增加而减小。低浓度时，离子强度较低反而有利于TYL的吸附。原因是低浓度条件下，TYL首先占据高能吸附位，以表面吸附为主。此时离子强度增大一方面可能导致盐析作用使TYL在水溶液中的溶解度减小，从而增加TYL的吸附；另一方面，TYL可以与K+周围的水分子形成氢键而加强TYL在矿物表面的吸附。高浓度条件下，吸附主要发生在低能吸附位点，以离子交换为主，溶液中的阳离子与TYL的竞争作用导致了吸附随离子强度增加而减少。对矿物表面电荷的测定结果显示，表面负电荷随溶液离子强度的增加呈减小趋势，进一步验证了TYL在矿物表面的离子交换作用。TYL在不同盐溶液中的吸附结果显示：在一定的浓度范围内（低浓度），TYL在蒙脱石上的吸附随不同离子类型的背景溶液的变化趋势是，Mg²⁺≧Ca²⁺> K⁺> Na⁺。在溶液浓度较高的条件下，TYL在一价盐溶液中的吸附比二价盐溶液中的吸附要强，大小顺序为：K⁺> Na+> Ca²⁺≧Mg²⁺。TYL在高岭石上的吸附在整个浓度范围内均表现为K⁺> Na⁺> Ca²⁺≌Mg²⁺。低浓度条件下的表面吸附促使TYL与阳离子离子周围的水分发生氢键作用，导致了水化能大的阳离子溶液中TYL的吸附量变大。高浓度条件下，离子交换是主要的吸附机理。溶液中带正电荷离子与正价态的TYL竞争表面负电荷，因此高价态的阳离子溶液中，TYL吸附量较小。由于蒙脱石的层间作用，不同类型的蒙脱石表现出不同的吸附能力。TYL在K-蒙脱石上的吸附量小于Na-蒙脱石，其次小于Ca-蒙脱石。分析发现，蒙脱石层间域的水和状态是一个非常重要的影响因素。它不仅影响了层间离子的交换作用，而且其与有机化合物的氢键作用可能取代离子交换的主导地位。高价态的Ca2+因其较大的水化能，能与周围更对的水分子结合。水分子的-OH基团可以通过氢键与TYL相互作用，从而吸附更多的泰乐菌素。5.为了解TYL对其它有机污染物在矿物上吸附的影响，选择菲为代表，分别考察了菲在原粘土矿物和吸附泰乐菌素后的粘土矿物上的吸附行为。实验发现，蒙脱石和高岭石纯矿物对菲均有一定的吸附能力，吸附容量较小。菲在蒙脱石上的吸附比高岭石要大。用线性模型和Freundlich模型均能较好的拟合吸附数据，相关系数大于0.98。菲在蒙脱石和高岭石上的吸附容量KD值分别为0.012和0.0035L/g。菲在纯矿物上的吸附主要是在矿物表层水膜上的分配。矿物的比表面积尤其是内比表面极大的影响了菲的吸附。吸附泰乐菌素之后，菲在两种矿物上的吸附均明显提高。菲在矿物上的吸附容量随着泰乐菌素的初始浓度的增加而明显增大，非线性随着泰乐菌素的初始浓度的增加而明显减小。在蒙脱石上的吸附容量参数logKF值从初始浓度为0mg/L时的-4.047增加到初始浓度为100mg/L时的0.591，非线性因子n值从初始浓度为0mg/L时的1.692减小到初始浓度为100mg/L时的0.596。在高岭石上的吸附容量参数logKF值从初始浓度为0mg/L时的-3.621增加到初始浓度为100mg/L时的-0.711，非线性因子n值从初始浓度为0mg/L时的1.372减小到初始浓度为100mg/L时的0.658。粘土矿物吸附泰乐菌素后，泰乐菌素与粘土矿物构成一个有机粘土矿物复合体。泰乐菌素在矿物上以有机质的形式存在。随着泰乐菌素初始浓度的增加，矿物上有机碳含量也随之增加。菲在矿物上的吸附分配系数与矿物体系中有机碳含量呈正相关，n值与有机碳含量是显著性负相关，呈现很好的线性关系。疏水性分配是菲在有机矿物上吸附的主要作用方式。且随着矿物上有机碳含量的增加，吸附的非线性逐渐增加。说明，TYL可显著促进菲在矿物上的吸附作用。在同时存在抗生素和多环芳烃污染的环境中，抗生素的存在可促进多环芳烃在土壤上的吸附，从而减小多环芳烃的生物可利用性和迁移能力。更多还原

【Abstract】 Antibiotics are widely used in medicine, livestock industries and aquiculture industries.As the increasing demand for meat products, livestock industries and aquiculture industriesdevelop quickly, the farms begin to largely use antibiotic as a growth promoter to shortenanimal’s growth period for the maximum profit. Growth promoter is a major role ofantibiotics used in modern agriculture and livestock industries. High to30%-90%veterinaryantibiotics are excreted as the parent compounds through urine and feces and they are stillactivity. When the urine and feces are used as manure to applicate on soil, the antibioticsmetabolize or their paret compound could reach in environment to form hard controllablewildspreas pollution. It is believed that antibiotics in environment could induce resistance ofmicroorganism and lead to potential health problems for animals and even human beings.Antibiotic pollution in environment is a hot research in recent yeas, but it does not get enoughconcentration in Chian especially in Pearl River Delta. In this area, there are a lot of culturefarms. Developed livestock industries would be sure to cause antibiotics pollution in soiland water. In this paper, tylosin （TYL）, a widely used veterinary antibiotic was chose as thesorbate. Around the sorption characters of on soil, the paper discussed deeply the sorptionmechanism of TYL behaviour on the interface of soil-water. The main experiments andconclusions are as follows:1. Sorption of TYL was measured for four agricultural soils using a batch technique. Theexperimental data showed that the sorption could attain apparent equilibrium within24hrsand little or insignificantly desorption hysteresis was observed. The Freundlich isothermequation could fit data well, with the nonlinearity parameter n ranging from0.83to1.03.The single point distribution coefficients （KD） were in a narrow range from2.01to12.4L/kg.The Kocvalue at different concentration ranged from118to15850L/kg-OC. The KDvaluescorrelated well with soil pH and surface area, but poorly with the soil organic carbon content.The clay in the soil also influenced the sorption especially montmorillonite and kaolinite.Because of large molecular weight and ionization character of tylosin, the sorption of tylosinon soil was nearly linear. The little or no desorption hysteresis was observed. The majorinteraction of sorption-desorption may be ionic exchange and Van der Waals’force. Thestudy indicated that the mobility of tylosin is less than those of smaller and polar antibioticsand because of the reversible sorption on soils, the soil-bound TYL could transport readily togroundwater.2. From the previous experiments, minerals in soil were considered as the most important factor to influence the TYL sorption. Thereby, TYL sorptions on several pure minerals weremeasured. The minerals included kaolinite, montmorillonite, quartz, goethite and Al2O3.The completely mixed batch reactor （CMBR） systems were used in the experiment. Theresults showed that sorption of TYL on minerals decreased in the order of montmorillonite>goethite> kaolinite> quartz> Al2O3. All of the sorptions were abviously nonlinear with then value from0.22to0.48. TYL sorptions on minerals were correlation with surface area ofmineral, point of zera charge （pzc） and solution pH value. Under acid solution condition,strong electrostatic attraction between the negative charges of mineral surface and positivecharges of TYL determined the sorption of TYL on minerals. However, under netural andalkaline solution, distribution interaction of no charge tylosin on mineral surface dominated.Among the five representive minerals in soils, montmorillonite, kaolinite and goethite werethe most important minerals to affect TYL sorption. Further, analysis of the thermodynamicparameters for these three minerals shown that tylosin sorption on them were spontaneous,thermodynamically favorable, and exothermic. The site energy distribution indicated thatthe sorption sites with lower site energies were more heterogeneous. Temperature mayaffect the sorption site heterogeneity because of the different structure of minerals.3. Tylosin has an ionizable functional group. It is partly positive charge form atenvironmentally relevant pH values. So it complicates to predict its sorption, availabilityand transport. To futher discusse the sorption mechanism of tylosin on minerals, the study oftylosin sorption on montmorillonite and kaolinite were contrasted. The pH effect onsorption was first discussed. The results showed as followe: The sorption isotherms for twoclays were nonlinear and sorption capacity on motmorillonite was two orders of magnitudehigher than kaolinite at specific aqueous concentration. The sorption decreased as pH andthe overall uptake might be dominated by different sorption process in the varied pHcondition. The pH experiments indicated cation exchange and surface sorption were themain sorption mechanism of TYL on minerals. Further XRD analyses revealed thatinterlayer of montmorillonite could expand due to the uptake of tylaosin. The sorption oftylosin on montmorillonite was likely limited to monolayer coverage. A sorption model inwhich species-specific sorption coefficients were weighted by the pH dependent fraction ofeach species fit the data well. DMM sorption model was used to evaluate the contribution ofcation exchange and surface sorption for whole sorption process. The results showed thatcation exchange controlled the sorption. Meanwhile, surface sorption is more and moreimportant as the concentration of TYL increased. Hydrophobic interactions betweenadsorbed tylosin may exist. The tylosin adsorbed via ion exchange may act as an organic phase enhancing the hydrophobic interactions of pollutant with the mineral surfaces.4. In the natural environment, ionic condition of tylosin solution was always not stable. Sothe sorption of tylosin by pure clay minerals varying in ionic strength, ionic type in solutionand preliminarily studied interlayer interaction of tylosin on different type montmorilloniteswere investigated. The sorption capacity of tylosin at different ionic strengths decreasedwith the order of0.008M>0.051M>0.108M>0.508M. In different metal ions solution,the sorption of tylosin decreased in the following order: K⁺> Na⁺> Ca²⁺≧Mg²⁺.However, for montmorillonite the sorption displayed an opposite tendency at low initialconcentration of tylosin. While the initial solution was low, sorption capacities at the ionicstrength of0.051M and0.108M were nearly the same, however were larger than the sorptioncapacity at the ionic strength of0.008M. Sorption of tylosin at different ionic type solutionat pH6.5decreased in the order of Mg²⁺≧Ca²⁺> K⁺> Na⁺at low solution concentration.These results indicated that the sorption sites on minerals were heterogeneous. When theinitial concentration of tylosin was low, the molecular first occupied high affinity sites likehydrogen bond. Not only tylosin can interact with the mineral surface group, but alsointeract with the water molecular around metal ions in solution. Thereby, proper ionicstrength and high valence state metal ions in soultion could increase tylosin sorption. Whenthe tylosin concentration was high, the sorption was major on the low energy sorption site.Cation exchange was the major interaction. Competitive sorption between tylosin and cationin solution resulted in decrease sorption. The sorption of tylosin on differentmontmorillonites decreased in the order of Ca-montmorillonite> Na-montmorillonite>K-montmorillonite. It indicated that interlayer hydration influenced the sorption rather thaninterlayer cation exchange.5. To understand tylosin effect on the sorption of other organic pollution on minerals,phenanthrene was chosen as the typical pollution. Phenanthrene sorptions pure mineral andmineral with tylosin were investigetd. The results showed that montmorillonite andkaolinite with no tylosin can weakly sorb the phenanthrene and the sorption capacity onmontmorillonie was higher than that on kaolinite. Linear sorption model and Freundlichmodel can fit the sorption isotherms well. The R²values were more than0.98. Thesorption coefficients K_D on montmorillonite and kaolinite were0.012and0.0035L/g,respectively. However, after tylosin was sorbed on calys, the sorptions of phenanthrene onclays were increased obviously. The sorption capacities of phenanthrene on clays increasedwith the initial concentration of tylosin, while the nolinearity decreased with the initialconcentration of tylosin. On montmorillonite, the sorption capacity logKFincreased from -4.047to0.591, and the n values decreased from1.692to0.596, corresponding to initialconcentration of tylosin from0mg/L to100mg/L. After tylosin was sorbed on clays, thetylosin played as the role of organic matters of clays. The sorption coefficients ofphenanthrene on clays were positive relation with the content of organic matter (f_oc). The nvalues were negative relation with the f_oc. Hydrophobic distribution was the majorinteraction of phenanthrene sorption on organominerals. And as the f_oc of clay increased, thesorption nonlinearity of phenanthrene increased. This indicated tylosin could obviouslypromote phenanthrene sorption on minerals. As antibiotic and phenanthrene coexisted, thepresence of antibiotic could increase the mobility and bioavailability of phenanthrene in theenvironment.更多还原