郭庄泉岩溶水系统中多环芳烃的分布与归趋研究

发布时间：2018-06-28 19:48

本文选题：多环芳烃 + 岩溶水系统　；参考：《中国地质大学》2014年博士论文

【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。
[Abstract]:polycyclic aromatic hydrocarbons ( PAHs ) are typical persistent organic pollutants which are carcinogenic , mutagenic and difficult to degrade , and are mainly derived from incomplete combustion of fossil fuels and biomass .

Approximately 25 % of the population in the world uses karst water as the main source of drinking water . The distribution area of carbonate rocks in China accounts for 14 % of the country ' s land area . About a quarter of the groundwater resources are distributed in karst areas . In recent years , water pollution is increasing the water quality crisis in China .

In Shanxi Benxi Formation , the formation of Upper Ordovician , SILURIAN , Devonian and Lower Carboniferous strata is absent , and the Carboniferous strata are directly deposited on the Middle Ordovician strata . Only Benxi Formation is formed between the lower coal seam and the limestone aquifer . In the Benxi Formation in Shanxi , the formation distribution pattern of " water coal symbiosis " is presented . In this way , coal is mined in the formation spaced very close to the limestone aquifer , which will have an impact on the karst water environment .

In this paper , the source , composition , migration and transformation characteristics of persistent organic pollutants in karst groundwater system and the influence of human activities on karst groundwater pollution are very necessary . In this paper , the distribution , fate and influencing factors of polycyclic aromatic hydrocarbons ( PAHs ) in environmental media are studied , and scientific basis and technical support are provided for the protection of karst water resources .

The main contents of this paper can be divided into the following aspects : 1 . Distribution and source of polycyclic aromatic hydrocarbons

In this paper , the concentration of polycyclic aromatic hydrocarbons ( PAHs ) in surface soil , groundwater and suspended matter and the sources of pollution are studied . The concentration range of total PAHs in surface soil is 622 - 87882ng / g , the concentration range of suspended matter is 4739 - 59315 ng / g , the average concentration in the groundwater is 2137 - 9037ng / g , the average concentration in each environmental medium is 17174ng / g , 1992ng / g and 5020ng / L , respectively . According to the above data , the research area is considered to have been subjected to moderate or severe pollution . The polycyclic aromatic hydrocarbon in the recharge zone R1 is mainly derived from leaching and desorption of raw coal in coal - series formation ;
The polycyclic aromatic hydrocarbons in the Fenhe leakage section R2 are mainly derived from the migration of the recharge area and the emission of automobile exhaust gas ;
The polycyclic aromatic hydrocarbons of R3 are mainly derived from the emission of " three wastes " in coal industry .
The polycyclic aromatic hydrocarbons in the two zones of R3 and R4 are relatively high . In order to study the proportion of polycyclic aromatic hydrocarbons ( PAHs ) in the low - ring , middle - and high - ring polycyclic aromatic hydrocarbons ( PAHs ) in different media , 16 kinds of polycyclic aromatic hydrocarbons are divided into three types : 2 - ring and 3 - ring , 4 - ring , 5 - ring and 6 - ring .
The proportion of polycyclic aromatic hydrocarbons ( PAHs ) in the 4 - ring is higher than that of groundwater .
The high concentration of polycyclic aromatic hydrocarbons ( PAHs ) in groundwater and suspended matter indicates that the polycyclic aromatic hydrocarbons ( PAHs ) produced in the local area have already passed through the aquifer or contain polycyclic aromatic hydrocarbons ( PAHs ) . The ratio of anthracene / ( phenanthene ) to fluoranthene / ( fluoranthene + pyrene ) indicates that the polycyclic aromatic hydrocarbons in the study area are mainly derived from incomplete combustion of coal and wood , and the polycyclic aromatic hydrocarbons in a small amount of surface soil are derived from petroleum sources .

According to the possible sources of polycyclic aromatic hydrocarbons ( PAHs ) in the study area , five pollution factors such as petroleum source , combustion of coal , automobile exhaust gas , biomass combustion and coal coking are studied . The results show that the main source of polycyclic aromatic hydrocarbons in the study area is the combustion of coal or the discharge of coal industry " three wastes " , which accounts for 50 % of the total source of pollution .

2 . Photodegradation of polycyclic aromatic hydrocarbons ( PAHs )

The photodegradation of polycyclic aromatic hydrocarbons ( PAHs ) in surface water was studied by using self - made photodegradable devices . The results showed that the degradation rate was very fast under the action of light . The degradation rate constants were 0.031 , 0.045 and 0.017min - 1 , respectively , and the degradation kinetics of three polycyclic aromatic hydrocarbons ( fluorene : 4.17min , FI : 3.79min , pyrene : 4.77min ) .

The photodegradation of fluorene and pyrene was enhanced with the addition of NO 3 - , the photodegradation of fluorene and pyrene was enhanced .

When humic acid is added to the solution , the polycyclic aromatic hydrocarbons can adsorb on the humic acid to prevent the polycyclic aromatic hydrocarbons from being oxidized or photodegradable , and meanwhile , the humic acid can absorb part of the ultraviolet light correspondingly , and influence the absorption effect of polycyclic aromatic hydrocarbons to light .
FI ( 0.045 , 0.036 , 0.031min - 1 ) ;
The concentration of humic acid had the greatest influence on the photodegradation of pyrene .

3 . Adsorption process of polycyclic aromatic hydrocarbons ( PAHs )

The adsorption of polycyclic aromatic hydrocarbons on limestone can be described by pseudo first order kinetic equation . The isothermal line can be described by a linear adsorption model . The adsorption of phenanthropic can be divided into three stages : first stage , polycyclic aromatic hydrocarbon adsorbed on limestone surface from aqueous solution ;
In the second stage , polycyclic aromatic hydrocarbons migrate from the limestone surface to the inner particles of limestone ;
The diffusion of polycyclic aromatic hydrocarbons in the particles is the rate control process of the whole adsorption process . Based on the experimental results , it is concluded that the adsorption capacity is 12.31 渭g / g on limestone .

In order to study the influence of carbonate and organic carbon on the adsorption of phenoxide , we remove carbonate and organic carbon from limestone samples . The results show that the adsorption capacity of limestone decreases after removal of carbonate and organic carbon . Although carbonates account for a large proportion in limestone , the linear distribution coefficient decreases from 0.96 to 0.922 after removal of organic carbon . This is because the adsorption mechanism of phenoxide on inorganic component is spot adsorption , which is a physical adsorption process , which can be described by Freundlich model , and nonlinear adsorption .

The results of Fourier transform infrared spectrum analyzer ( FTIR ) show that the surface of limestone adsorbent contains a large amount of hydroxyl and carboxyl groups .
When the concentration of calcium chloride is increased from 0.005 to 0.1 M , the Gibbs free energy of the system can be reduced , indicating the increase of the adsorption capacity .

In order to investigate the effect of soluble organic matter ( DOM ) on the adsorption of fife , the interaction between humic acid ( HA ) and phenanthropic acid was studied : ( 1 ) The adsorption equilibrium of HA on limestone was studied . The results showed that the adsorption equilibrium of HA on limestone was stronger than that of fi and HA .

4 . Process for the biodegradation of polycyclic aromatic hydrocarbons

The biodegradation of polycyclic aromatic hydrocarbons is one of the most important factors affecting the migration , transformation and final fate of polycyclic aromatic hydrocarbons . In this paper , polycyclic aromatic hydrocarbons ( PAHs ) are screened from the polluted groundwater in the study area . The maximum adsorption capacity of polycyclic aromatic hydrocarbons ( PAHs ) was : fluorene ( 7.5 % ) , fife ( 8.5 % ) and pyrene ( 5 % ) .

With the addition of humic acid in solution , the degradation rate of polycyclic aromatic hydrocarbon is accelerated . The degradation rate of polycyclic aromatic hydrocarbon is increased from 50 % to 70 % .

In the karst water system of Guo Zhuang - quan , the waste water containing polycyclic aromatic hydrocarbons is firstly contacted with air in surface water to absorb enough dissolved oxygen and then enter into the aquifer . Therefore , the biodegradation of polycyclic aromatic hydrocarbons is firstly oxidized by monooxygenase or dioxygenase to convert into hydroxy aromatic and carboxyl aromatic intermediates . The final product is methane or alkane , carbon dioxide and water . It is worth noting that after 2 days of degradation , the intermediate product 2,5 - ( 1,1 - methylethylethyl ) - phenol is produced in the solution , and the substance cannot be degraded by the non - moving rod .

The main innovation points of this paper : ( 1 ) The source of PAHs in karst groundwater is revealed by PMF software analysis .
( 2 ) The high - efficiency degradation bacteria of polycyclic aromatic hydrocarbons ( PAHs ) are screened in the karst groundwater system in the influence area of coal industry , and the mechanism of biodegradation is discussed .
【学位授予单位】：中国地质大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：X523

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