【作者】 邵一先；

【导师】 王焰新；

【作者基本信息】 中国地质大学 ， 环境科学与工程， 2014， 博士

【摘要】 多环芳烃(PAHs)是一类具有致癌性、致突变性、难降解的典型持久性有机污染物,由两个或两个以上的苯环结构组成,主要来源于化石燃料和生物质的不完全燃烧。多环芳烃对人体的中枢神经和血液的破坏作用很强,尤其是带烷基侧链的PAHs,对人体粘膜的刺激性及麻醉性极强。多环芳烃可以通过各种环境介质(大气、土壤、悬浮颗粒、水体、生物体等)长距离迁移,并能长期存在于生态环境中,对生态环境、动植物和人体健康造成严重的危害。世界上约有25%的人口以岩溶水作为主要的饮用水源。我国碳酸岩分布面积约占全国陆地面积的14%,全国约有四分之一的地下水资源分布在岩溶地区。近年来,水体污染正加剧我国的地下水水质危机。山西省郭庄泉域缺失了上奥陶统、志留系、泥盆系和下石炭统的地层,石炭系地层就直接沉积在中奥陶统地层之上,下部煤层和灰岩含水层间仅只有本溪组地层。在山西本溪组地层厚度一般为30多米,南部地区较薄,一般为20米左右,呈现出一种“水煤共生”的地层分布格局。这样在与灰岩含水层相隔很近的地层中开采煤炭,势必会对岩溶水环境产生影响。岩溶水易受人类活动的影响。深入研究岩溶地下水系统中持久性有机污染物的来源、组成、迁移转化特征,以及人类活动对岩溶地下水污染的影响都是非常必要的。本文以山西省郭庄泉岩溶地下水系统为例,对地表水渗漏过程中多环芳烃的光降解、含水层介质的吸附、地下水环境中微生物的降解作用进行研究,阐明多环芳烃在环境介质中的分布、归趋及影响因素,为岩溶水资源的保护提供科学依据和技术支撑。论文的主要研究内容可以分为以下几个方面：1.多环芳烃的分布与来源本文研究了郭庄泉岩溶水系统中多环芳烃在表层土、地下水、悬浮物中的浓度、空间分布规律和污染来源。总多环芳烃在表层土中的浓度范围为622-87882ng/g,悬浮物中的浓度范围为4739-59315ng/g,地下水中的浓度范围为2137-9037ng/L,各环境介质中的平均浓度分别为17174ng/g,11992ng/g及5020ng/L。根据以上数据,研究区被认定为已经遭受中度甚至重度污染。补给区R1的多环芳烃主要来源于煤系地层中原煤的淋滤与解吸；汾河渗漏段R2的多环芳烃主要来源于补给区的迁移和汽车尾气的排放；双池河区R3的多环芳烃主要来源于煤工业“三废”的排放；排泄区R4的多环芳烃主要来源于以上三个区的迁移。R3和R4两个区的多环芳烃浓度相对较高。为研究低环、中环、高环多环芳烃在不同介质中占总多环芳烃的比例,我们将16种多环芳烃分为三类：2环和3环,4环,5环和6环。从三线图中,我们可以看出地下水中主要以低环多环芳烃为主,高环多环芳烃未检出；地下水悬浮物中主要以中低环多环芳烃为主,与地下水相比,4环的多环芳烃比例开始升高；而高环的多环芳烃主要集中在表层土中。中低环多环芳烃在地下水、悬浮物中的高浓度检出表明了当地所产生的多环芳烃已经通过含水层的渗漏或是含多环芳烃沉淀物的渗透进入到了地下水中,对地下水造成污染。蒽/(菲+蒽)与荧蒽／(荧蒽+芘)的比值表明研究区的多环芳烃主要来源于煤和木材的不完全燃烧,少量表层土中的多环芳烃来源于石油源。尽管多环芳烃同分异构体间的比例可以指示其污染来源,但却不能计算各种污染来源占多环芳烃总浓度的比重。本文根据研究区多环芳烃的可能来源,主要研究了石油源、煤的燃烧、汽车尾气、生物质燃烧、煤焦化等五个污染因素。这五个污染因素在总多环芳烃中的贡献分别为2%,32%,22%,27%,18%。结果表明研究区多环芳烃的主要来源为煤的燃烧或是煤工业“三废”的排放,占总污染来源的50%。和中国北方的许多其他城市一样,大量煤炭能源的开采和利用,使煤成为了郭庄泉岩溶环境中多环芳烃的主要贡献者。2.多环芳烃的光降解过程采用自制的光降解装置对地表水中多环芳烃的光降解进行模拟研究。研究表明,所选的三种多环芳烃在光的作用下,降解速度非常快,降解速率常数分别为0.031,0.045,0.017min-1,且符合一级降解动力学。三种多环芳烃的光降解半衰期都只需要几分钟(芴：4.17min,菲：3.79min,芘：4.77min)。由于三种多环芳烃在紫外光下不同的吸收峰数量和吸收强度(其中芘的吸收峰最少且较弱,而菲在紫外光下具有很好的吸收峰),所以三种多环芳烃的光降解速率快慢顺序依次为菲>芴>芘。文中探讨了岩溶水中的主要阴离子(SO42-, HCO3-,NO3-)对多环芳烃光降解的影响。三种阴离子的加入都不同程度地促进了菲的光降解,表明菲在光降解过程中没有自由基的参与。随着HC03-的加入,芴和芘的光降解过程得到了抑制,而且当HCO3-的浓度从200增加到400mg/L时,芴和芘的光降解抑制作用增强,说明羟基自由基的氧化是芴和芘的主要光降解过程。NO3-是水体中-OH的主要来源之一,随着NO3-的加入,芴和芘的光降解作用得到了加强,但当N03-浓度大于20mg/L时,光降解速率却有减少,主要是因为硝酸盐对紫外光有过滤作用,导致紫外光不能很好的进入到溶液中。S042-既能产生-OH,同时又能消耗-OH。研究指出,随着S042-的加入,水体中自由基消耗反应占主导作用,抑制了多环芳烃的光降解。当溶液中加入腐殖酸时,多环芳烃会在腐殖酸上产生吸附作用,阻止了多环芳烃被氧化或是光降解。同时,腐殖酸也会相应地吸收部分紫外光,影响多环芳烃对光的吸收效果。在实验过程中,腐殖酸浓度为0,10mg/L,20mg/L时,多环芳烃的光降解速率常数分别为：芴(0.032,0.0290.026min-1)；菲(0.045,0.036,0.031min-1)；芘(0.016,0.0081,0.0042min-1)。腐殖酸的浓度对芘的光降解作用影响最大。3.多环芳烃的吸附过程多环芳烃菲在灰岩上的吸附可以用伪一阶动力学方程来描述,等温线可以用线性吸附模型来描述。菲的吸附主要可以分为三个阶段：第一阶段,多环芳烃从水溶液中吸附于灰岩表面；第二阶段,多环芳烃从灰岩表面迁移扩散到灰岩的内部颗粒上；第三阶段,12h后,吸附达到平衡。多环芳烃在粒子内的扩散是整个吸附过程的速率控制过程。根据实验结果计算得出：菲在灰岩上的吸附量为12.31μg/g。为了研究碳酸盐和有机碳对菲吸附的影响,实验中,我们去除了灰岩样品中的碳酸盐和有机碳。结果表明,去除碳酸盐和有机碳后,灰岩的吸附能力下降,在去除有机碳后,吸附能力下降的尤为明显。虽然碳酸盐在灰岩中占很大的比例,但是在菲的吸附过程中起的作用较小。同时,去除碳酸盐和有机碳后,线性分配系数从0.96下降到0.922,这是因为菲在无机成分上的吸附机理为点位吸附,是一个物理吸附过程,可以用Freundlich模型来描述,而非线性吸附。菲的吸附量在酸性和碱性条件下都逐渐降低。傅氏转换红外线光谱分析仪(FTIR)检测结果证实灰岩吸附剂的表面含有大量的羟基和羧基。酸性条件时,羟基会被质子化成OH2+基团,而且碳酸盐会发生溶解,导致吸附点位减少,菲的吸附量降低；碱性条件时,有机官能团CH2会从灰岩表面解析,而且羧基官能团开始减少,不利于菲的吸附。溶液中的离子强度较低时,钙离子会占据部分的吸附点位,导致菲的吸附量降低,相反,当氯化钙的浓度从0.005增加到0.1M时,系统的吉布斯自由能降低,表明了菲吸附量的增加。为了探讨溶解性有机物质(DOM)对菲吸附的影响,腐殖酸(HA)与菲的相互作用,设计了三种情形进行研究：(1)HA在灰岩上吸附平衡后加入菲进行吸附。结果表明,加入的菲很快的被灰岩吸附,而且吸附量增大。这种现象表明灰岩吸附HA后,仍有吸附孔位来吸附菲,而且HA和灰岩间的亲和力要比菲与灰岩间的亲和力强,所以菲几乎不能解析出HA。(2)菲在灰岩上吸附平衡后,加入HA进行吸附。结果表明,已经吸附的菲被后加入的HA置换,菲被释放到溶液中,HA吸附在灰岩上。这种置换现象表明,HA对灰岩上吸附位点的竞争力比菲强。(3)菲及HA在灰岩上同时吸附。在这种情况下,溶液中共同存在的菲和HA在灰岩上会产生竞争吸附。HA对灰岩上吸附点位的竞争能力比菲大,亲和力更强,HA会优先吸附在灰岩表面。这一结果表面,在含有可溶性有机物的污染地下水中,DOM有助于灰岩对多环芳烃的吸附。4.多环芳烃的生物降解过程多环芳烃在含水层中的迁移、转化及最终归宿的重要影响因素之一就是其生物降解过程。本文从研究区受污染的地下水中筛选出了多环芳烃降解菌,经DNA测序,鉴定其为不动杆菌属。不动杆菌属可以利用多环芳烃作为唯一的碳源,对其进行高效的降解。经过6天的培养,低环多环芳烃如萘、蒽基本被降解完全,而高环的多环芳烃也被降解了65%。在降解过程中,我们发现加入接种液后,微生物作用有近12小时的滞后期,说明不动杆菌属对环境有个适应期(对酶、化学物质毒性的适应)。多环芳烃会在生物体表面产生吸附,整个实验过程中,多环芳烃的最大吸附量分别为：芴(7.5%),菲(8.5%),芘(5%)。不动杆菌属可以同时利用多环芳烃、葡萄糖和HCO3-作为其碳源,结果表明外加的碳源对多环芳烃的生物降解有促进作用。葡萄糖类有机碳源对多环芳烃的生物降解促进作用更强。随着溶液中腐殖酸的加入,多环芳烃的降解速率加快,高环多环芳烃芘的降解率从50%增大到70%。这是因为腐殖酸中含有羟基官能团,在微生物作用下,能够转化成相应的极性基团,从而影响酶的活性。同时腐殖酸可以为微生物提供相应的营养元素,促进微生物的生长。在郭庄泉岩溶水系统中,含多环芳烃的废水首先在地表水中与空气接触,吸收足够的溶解氧,然后进入到含水层中。所以,多环芳烃的生物降解途径首先是通过单加氧酶或双加氧酶对苯环进行氧化,转化成羟基芳香族和羧基芳香族中间体。最后的产物为甲烷或烷烃、二氧化碳和水。值得注意的是,降解2天后,溶液中产生了中间产物2,5-(1,1-甲基乙基)-苯酚,而且该物质不能被不动杆菌属所降解。论文的主要创新点：(1)借助PMF软件分析揭示岩溶地下水中PAHs的来源；(2)在煤工业影响区岩溶地下水系统中筛选出多环芳烃的高效降解菌并探讨其生物降解机理。更多还原

【Abstract】 Polycyclic aromatic hydrocarbons (PAHs) are a group of persistent organic pollutants (POPs) that are carcinogenic, mutagenic and resistant to be degraded. They mainly derive from the incomplete combustion of fossil fuels and biomass. The destructiveness of PAHs to the central nerve and blood system of human beings is very strong. Especially for PAHs with alkyl chain, they cause extremely strong irritability and anesthesia to the mucous membrane. PAHs are widely distributed and persistent in the ecological environment due to their long-distance migration through environmental media (air, soil, suspended solids, water, biological), causing serious harm to the ecological environment, animals, plants and human health.Karst aquifers provide abundant high-quality groundwater resources for drinking water supply of the human society and more than25%of the world’s population lives in karst areas. The distribution area of carbonate rocks in China accounts for about14%of the whole land area. And about1/4groundwater resources across the country are located in karst area. However, the groundwater quality has been under threat of contamination.At Guozhuang karst system, the carboniferous are deposited directly on the middle Ordovician strata due to the missing of Ordovician, Silurian system, Devonian system and Lower Carboniferous strata. There are only layers of the Benxi formation between coal-bearing strata and the carbonate aquifers, showing a pattern of co-existence of "water with coal". The thickness of the Benxi formation is commonly more than30meters in Shanxi, but only20meters in the southern part of the province. It is bound to have an impact on the groundwater environment due to the coal mining activities that are so close to the limestone aquifers.Karst water is particularly vulnerable to the impact of anthropogenic activities. It is necessary to study the source, composition, migration features of POPs, and the influence of human activities in karst water system. In this paper, taking Guozhuang karst water system in Shanxi province as an example, the photodegradation, adsorption and biodegradation of PAHs in the process of surface water leakage were investigated. The concentration, distribution, formation mechanism and controlling factors of the transport of PAHs were also evaluated to provide scientific evidence and technical support for the protection of karst water resources. The research contents of this thesis are summarized as follows:1. The source and occurrence of PAHsThe concentration, spatial distribution and source of polycyclic aromatic hydrocarbons (PAHs) in topsoil, groundwater and groundwater suspended solids (SS) at Guozhuang karst water system of northern China were investigated. The total concentration of PAHs ranged from622to87882ng/g dry weight in topsoil, from4739to59315ng/g dry weight in SS, and from2137to9037ng/L in groundwater, with mean values of17174ng/g,11992ng/g and5020ng/L, respectively. The study area could be considered moderate to highly polluted with PAHs. The PAHs in groundwater samples from R1may originate from the desorption of raw coal. The PAHs in groundwater of R2may mainly originate from the recharge area and automobile exhaust emission. PAHs in R3could be related to the discharge of coking wastewater into the river water which may later leak into the subsurface. PAHs of discharge area R4mainly came from the migration from above three areas. The contents of PAHs in samples from R3and R4were higher than those from R1and R2.In order to distinguish the proportions of low molecular, medium molecular and high molecular (LM, MM and HM) PAHs in different environment media,16PAHs compounds were divided into three groups:2+3rings,4-rings and5+6rings. The composition of PAHs indicated that LM PAHs were predominant in groundwater samples, and HM PAHs such as6-ring PAHs were not detected. The contents of MM PAHs were elevated in SS samples, and carcinogenic HM PAHs were frequently detected in topsoil. The high contents of low-medium molecular weight PAHs in groundwater and SS suggested a relatively recent local source of PAHs that were transported into the aquifer via leakage of contaminated river and/or infiltration of PAHs-containing precipitation. ANT/ANT+PHE versus Fla/Fla+PYR was plotted, which illustrated that PAHs in groundwater, SS and topsoil mainly originated from wood and coal combustion, and PAHs in very few topsoil samples originated from petroleum combustion.Although the composition and ratio of selected PAHs compounds could be taken as indirect indicators of their sources of PAHs, the relationship among different factors and their percentage of contribution to total contamination was not clear. So five factors (oil, coal combustion, vehicle, biomass combustion, coal tar) were selected to analysis the sources of PAHs using PMF model. The relative contributions for the1-5factors were2%,32%,22%,27%,18%, respectively. The major sources of PAHs in groundwater were categorized in this study as pyrogenic origin, especially coal combustion, accounting for50%. And like many other areas in northern China, large amounts of consumption in both industrial and domestic sectors may have made coal the primary contributor to PAHs in Guozhuang karst water system. 2. Photodegradation of PAHsThe photodegradation of PAHs in surface water was studied using self-designed cylindrical photodegradation reactor. The photolysis rates of the selected three PAHs in water were quite fast and the photolysis half-lives of PAHs only need several minutes (fluorine (FLU),4.17min; phenanthrene (PHE),3.79min; pyrene (PYR)4.77min). The photodegradation data fitted first-order kinetics well. The absorption spectrum and peak values were different (PYR absorption spectrum was the least, and the peak value was the smallest, when PHE absorption spectrum included lots of different intensity of wavebands). So the photolysis rates of PAHs, followed the decreasing order: PHE> FLU> PYR.The influence of main anions (SO42-, HCO3-and NO3-) of karst water to the PAHs photodegradation was investigated. The addition of bicarbonate radical led to different degrees of increase in the removal rates and efficiency of PHE, which indicated that there was no free radicals reaction involving in the PHE degradation. However, in the presence of HCO3-, the photodegradation of FLU and PYR was significantly inhibited. And further increasing of the HCO3-concentration from200to400mg/L resulted in additional decrease in the degradation of FLU and PYR, indicating that oxidation by hydroxyl radicals was the main degradation pathway of FLU and PYR. NO3-is a main source of OH in natural water, which can improve the efficiency of the PAHs photodegradation. However, at higher concentration (20mg/L) of NO3-, a slight decrease in photodegradation of the PAHs was observed. There was a strong adsorption of NO3-as an inner inert filter in the ultraviolet region, preventing light through the solution. There were both "·OH" generation and capture reaction in sulfate reaction in water. The photolysis rates of FLU and PYR decreased with the addition of SO42-, which indicated that the "·OH" capture reaction was dominated in the experiment process.In the presence of HA, it was more likely to protect it from oxygen and photodegradation due to the adsorption of PAHs within the complex HA structure. And the photolysis rates decreased due to the light absorption by HA. In our experiments, When HA concentrations were0,20and40mg/L, the photolysis rates k were0.032,0.029and0.026for FLU;0.045,0.036and0.031for PHE;0.016,0.0081and0.0042for PYR, respectively. Photodegradation of PYR was restricted most significantly.3. Adsorption of PAHs The kinetics of PHE was well fitted with the pseudo-first order model, and isotherms could be described with the liner isotherms. The sorption of PHE could be divided into three stages: the first stage, PHE was adsorbed by the exterior surface of limestone; the second stage, the molecular PHE might enter intraparticle pores of the limestone and adsorbed by the interior surface of the particle; the third stage only occurred after12h. The adsorption of PHE on limestone was controlled by particle diffusion. The adsorption capacity of limestone to PHE was calculated to be12.31μg/g.In order to reveal the effect of carbonate and organic carbon (OC) on PHE sorption, limestone sample was treated sequentially to remove carbonate and OC. The Kd value decreased after carbonate remove, especially after OC remove, which indicated that carbonate played a minor role in the sorption, in spite of its dominant content in limestone. The R2of linear isotherm decreased from0.960to0.922after removal of carbonate and OC. Because the sorption of PAHs by inorganic fraction (i.e. carbonate, residue) represented by Freundlich isotherm, was primarily a physical process and the contaminants were adsorbed on many sorption sites.It can be seen that the sorption significantly decreased under both acidic and alkaline conditions. The FTIR spectra results showed that the existence of hydroxyl and carboxyl groups on the surface of limestone samples. Under acidic conditions, the hydroxyl groups were becoming protonated to OH2+groups, resulting in the decrease of the sorption of PHE. And acidic condition was thought to lead the dissolution of carbonate, which reduced the sorption sites for PHE; CH2groups indicated organic carbon desorbed from the surface at alkaline condition. Also the decrease of PHE sorption could be attributed to the change of the carboxy groups on the surface of limestone. In the presence of low ionic strength, calcium ions would occupy part of adsorption sites, which led to the decrease in PHE adsorption. Standard free energy (ΔG0) became larger negative when the concentration of CaCl2increased from0.005M to0.1M, which was consistent with the increase of adsorption amount.To investigate the effects of dissolved organic matter (DOM) on PHE adsorption by limestone, three conditions were designed to investigate by considering interaction of humic acid (HA) with PHE.(1) After pre-equilibrium of HA adsorbed on limestone, and subsequent sorption of PHE. It was observed that the HA concentration in solution did not obviously increase but the PHE concentration sharply decreased. This phenomenon indicated that there were still some pores for PHE after the HA adsorption equilibrium. And there was a competition adsorption between PHE and HA, the affinity of HA and limestone was stronger than that of PHE. So PHE can only replace a small amount of HA.(2) After pre-equilibrium of PHE adsorbed on limestone, and subsequent sorption of HA. The results showed that the added HA replaced PHE which was released into the solution, and HA was then adsorbed on limestone. This replacement phenomenon implied that competitiveness of HA on sorption sites of limestone was stronger than PHE.(3) In simultaneous sorption of PHE and HA on limestone, competition of HA on sorption sites of limestone was much stronger than PHE. This finding implied that even in contaminated groundwater containing DOM, limestone was effective for PAHs adsorption.4. Biodegradation of PAHsMicrobial degradation is the major degradation process in the transport and transformation of pollutants. A bacterial strain Acinetobacter sp. WSD with PAHs-degrading ability was identified based on biochemical tests and16S rDNA gene sequence analysis, which was isolated from PAHs-contaminated groundwater. Acinetobacter sp. WSD could utilize PAHs as its sole carbon source and degrade them with high efficiency. Low molecular weight PAHs such as naphthalene and anthracene were completely degraded after6d. And for high molecular weight PAHs, the degradation percentage could reach65%. Approximately12h lag phase of biodegradation and subsequent high biodegradation rate were observed for each compound. This result indicated that an acclimatization process, such as induction or de-repression of enzymes or adaptation to the toxic chemical, occurred and allowed the bacteria to cope with the toxicity of PAHs before further degradation. The results of adsorption experiments showed that a maximum of7.5%of FLO,8.5%of PHE,5%of PYR were adsorbed on the biomass.Acinetobacter sp. WSD could use PAHs, glucose and HCO3-as its carbon source at the same time. And the additional carbon source in the form of glucose or HCO3-may have increased the metabolism of PAHs in our experiments. And Acinetobacter sp. WSD more inclined to use organic carbon than inorganic carbon. The degradation rates of PAHs were stimulated in the presence of HA. And the amount of PYR degradation was increased from50%to70%with the addition of HA. HA contains hydroxyl groups, which can be converted to the corresponding polarity matrix and affect enzyme activity. And HA can provide nutrition elements to promote the growth of microorganisms.At Guozhuang karst water system, before their transport into karst aquifer, the PAHs-containing wastewater or gas emissions were first discharged or deposited in the river water containing free oxygen. Leaking river water then transported PAHs into the karst aquifer. Thus the initial step may include the oxidation of the benzene ring by mono or dioxygenase enzymes, converting the aromatic compounds to hydroxy aromatic intermediates which are further dehydrogenated to form carbonyl compounds. The final products were alkanes, carbon dioxide and water. It was important to note that after2d biodegradation phenol,2,5-bis(1,1-dimethylethyl) was formed. And it could not be degraded or utilized by Acinetobacter sp. WSD. There are two major novel points in this thesis:(1) to reveal the proportion of each pollution source using PMF software;(2) to isolate high efficient degradation bacteria of PAHs from karst groundwater in a coal-mining area and explore their biodegradation mechanism.更多还原