【作者】 蓝家程；

【导师】 袁道先；

【作者基本信息】 西南大学 ， 自然地理学， 2014， 博士

【摘要】 岩溶地下水资源对我国西南岩溶区的重要性不言而喻,然而随着社会经济快速发展和城市化进程的加快,我国西南岩溶区水环境问题日益突出。这不仅与人类活动有关,同时也与岩溶环境本身的脆弱性密切相关。多环芳烃(PAHs)是一类持久性有机污染物(POPs),普遍存在于环境介质中,其主要来自能源的燃烧。由于其具有毒性、能致癌、致突变而受到广泛关注。一旦进入岩溶环境有可能成为其最终归宿,危害岩溶生态系统和人类健康。为此,弄清岩溶地下河系统多环芳烃的来源、组成特征、环境行为、迁移和分配过程及生态风险,有助于提高对多环芳烃在岩溶地下河系统的污染机理的认识,具有重要意义。本论文以重庆市南山老龙洞地下河系统为例,通过野外岩溶水文地质和污染源地面调查,野外定位观测、降雨期间采样监测,利用气相色谱—质谱联用仪为主要分析测试手段,以地下河及其地表污染来源为主线,研究多环芳烃在土壤、地表水、悬浮颗粒物、地下水、沉积物中的分布和污染特征及来源,分析多环芳烃在地下河中多相分配及影响因素,探讨多环芳烃在岩溶地下河系统中的迁移传输过程。结果分析表明：1、地下河流域环境介质中PAHs含量、组成及污染水平。老龙洞流域表层土壤PAHs总量变化范围为277～3301ng/g,平均值为752.6±635.5ng/g,其组成以2-3环为主。其中7种致癌性PAHs总量平均占到∑PAHs的36.17%。土壤有机质(SOM)可能是影响PAHs含量的主要因素。受污水、季节的影响及不同PAH化合物的性质差异,水中]PAHs含量和组成呈现不同的变化特征。与溶解态PAHs相比,地下河颗粒态PAHs含量较低,表现为雨季水中赋存于颗粒物上的PAHs含量高于旱季,主要与颗粒物的来源和性质有关。流域内水中PAHs以及悬浮颗粒物结合的PAHs组成均以低环为主,而高环PAHs几乎未检测到,这与低环溶解性相对较高有关。相对于溶解态PAHs,沉积物中,高环PAHs的比重相对富集,表明随着分子量的增大,PAHs化合物倾向于吸附在颗粒物上根据Mali szewska-Kordybach制定的土壤PAHs污染标准,研究区表层土壤PAHs污染水平分别达到轻、中等和重污染水平,其中大部分为中等污染水平；根据Baumard等的划分标准,老龙洞地下河沉积物PAHs污染处于中等到高污染水平。按照荷兰地下水水质标准和加拿大水质标准,老龙洞流域水中PAHs以低环污染为特征；而以PAHs总量来看,地下河流域水中PAHs污染只有少数月份超出中国饮用水标准。与其他地区河流相比地下河PAHs污染水平居中,但岩溶区特殊的形态和环境有利于富集PAHs等持久性有机污染物,应该引起足够的重视。根据地下河潜在来源水中PAHs分子量特征及PAHs同分异构体比值解析表明,流域内水中PAHs主要来自于石油源；综合运用PAHs分子量特征比值、同分异构体比值和主成分/多元线性回归分析表明,流域内土壤PAHs污染主要来自交通排放与煤炭、石油及生物质的燃烧源和石油产品泄漏的混合源,其中来自于燃烧源占56.4%,而石油源占到43.6%。2、岩溶地下河PAHs多相分配及影响因素。研究表明有机质是控制老龙洞地下河水相、沉积物、颗粒物中PAHs的行为和归宿的重要的因素。其中溶解性有机碳(DOC)、有机碳(TOC)与PAHs的关系相对明确,而与颗粒物有机碳(POC)的关系比较复杂。溶解性有机质(DOM)能够促进和积累低环的溶解态PAHs,是影响溶解态PAHs含量的主要因素,同时是高环PAHs重要的贮存库。悬浮颗粒物(SPM)是影响溶解态PAHs含量的因素之一。与溶解相PAHs有所不同,颗粒物有机质(POM)对PAHs的影响不显著,主要是因为存在DOM等胶体物质的影响。老龙洞地下河沉积物TOC与总PAHs含量成显著正相关,表明了沉积物有机质是影响沉积物PAHs含量的主要因素,但InP、DaA和BgP与TOC并不显著相关。说明除了有机质外,还有另外的因素在影响沉积物PAHs的含量,需要更为详细的分析。通过研究表明颗粒相—水相PAHs分配系数与POC无关系,而悬浮颗粒物对分配系数有显著影响,原因是悬浮颗粒物浓度能够带来更多的DOC,导致DOM与POM相互竞争吸附PAHs。通过研究PAHs在沉积物—水相间的分配,获得了表征有机碳归一化的分配系数Koc与辛醇-水分配系数Kow之间的线性自由能方程。发现地下河沉积物对PAHs化合物的亲脂性较差。3、岩溶地下河系统PAHs迁移传输过程。老龙洞地下河水与流域内其它水中PAHs相似的组成特征,示踪试验和不同水之间PAHs含量关系表明了岩溶形态对地下河系统PAHs的迁移有重要的作用。通过地下河上游与下游PAHs含量及组成比较发现2-3环PAHs表现为远距离迁移,而4-6环PAHs亲颗粒性高,溶解性低,容易被沉积物或者碳酸盐岩吸附,迁移能力不足。多环芳烃在地表土壤和地下河沉积物间的交换模式表明,地下河出口沉积物主要来源于上游水体传输及地表土壤的输入。降雨监测表明,降雨期间落水洞的水输入和地表水渗入是控制PAHs迁移过程的主要因素,不同结合态的PAHs受控于水动力条件。降雨能够促进地下河系统PAHs由地表向地下迁移,而且流量越大,迁移量越大,一旦有足够的雨强,不仅带来更多的悬浮颗粒物,而且使高环PAHs更容易迁移,同时迁移过程中受DOC、POC、悬浮颗粒物浓度及颗粒物本身的种类和性质的影响,使得PAHs在各相中的分配产生差异。4、岩溶地下河流域PAHs的生态风险评价。运用风险商值(RQ)法对水中PAHs生态风险进行评价,结果发现在检测到的PAH化合物的生态风险水平处于中等污染和重污染风险。以总PAHs来看,桂花湾泉和老龙洞地下河出口达到高风险等级,已严重污染；赵家院子泉和地表水处于中等风险2级别。老龙洞沉积物PAHs处于低风险水平,很少产生负面生态效应,而仙女洞PAHs污染存在较高的生态风险,这与ERL/ERM和TEL/PEL法,平均效应区间中值商法(M-ERM-Q)评价结果基本一致。土壤PAHs污染为中等风险。老龙洞流域水中3环PAHs对生态压力贡献较大,而土壤和沉积物中2环和3环贡献较大,因此需要采取有效措施减少2-3环PAHs的污染。表层岩溶系统由于土层薄,岩溶裂隙发育,利于PAHs进入表层泉,导致桂花湾泉和赵家院子泉PAHs污染仍存在较高的生态风险。黄桷垭污水切断前后,老龙洞水PAHs污染分别处于高风险和中等风险状态。地下河的补给来源的介质中PAHs污染的生态风险越高,地下河中PAHs污染的生态风险也越高。不同分子量PAHs迁移行为的差异,导致老龙洞地下河上游和下游生态风险水平在水中和沉积物中有所差异,高环PAHs富集在地下河管道,其在逐渐往下游迁移过程中,将对下游的生态构成威胁。更多还原

【Abstract】 It is well known that karst groundwater is very important in southwest China. However, with the rapid economic development and urbanization, karst groundwater pollution has become a predominant problem. This is not only related to human activities, but also closely related to the vulnerability of karst environment. Polycyclic aromatic hydrocarbons (PAHs), one of a group of persistent organic pollutants (POPs), are ubiquitous in various environmental systems, and have attracted much concern due to their toxicity, carcinogenicity and mutagenicity. The primary environmental source of PAHs is energy combustion. Once they enter into karst environment, it may become their final destination, which will be harmful to karst ecosystem and public health. For these reasons, it is very important to understand the composition, behavior, transport, partitioning of PAHs and their environmental risk to ecosystems, especially in karst underground river systems, which can help recognizing the pollution mechanisms of PAHs in karst underground river systems.In this thesis, the Laolongdong Underground River System (LURS) in Nanshan of Chongqing City has been chosen for studying the distribution, contamination characteristics and sources of PAHs in different medium such as soil, water, particle and sediment, partitioning of PAHs in the underground river, as well as the transporting process of PAHs in the system, based on hydrogeological and pollution source investigation, sampling and monitoring monthly and during rainfall, and measuring by GC/MC or GC/MS. It is found that:(1) Concentrations, composition and pollution levels in environment medium in LURS. In the surface soil of LURS, the total concentrations of PAHs range from277.4～3301ng/g, with a mean value of752.6±635.5ng/g, dominated by2～3ring PAHs, seven carcinogenic compounds of which account for36.17%of the total PAHs with an average. Soil organic matter (SOM) may be the primary factor controlling the concentrations of PAHs. There are differences among monthly variations of PAHs contents in the waters, due to waste water, season and different characteristics of PAH compounds. The concentrations of particle associated PAHs are lower than those of dissolved PAHs, and higher in rainy season than that in dry season, which may be related with the sources and quality of the particles. The PAHs compositions are dominated by low ring compounds in all waters and particles, and high rings PAHs are almost not detected due to relative high solubility of low PAHs. However, high rings PAHs are enrich in the sediments because of their tendency to be adsorbed on the particles with the increase of molecular weight..According to PAHs pollution standard made by Maliszewska-Kordybach, the soil samples of the LURS are slightly, moderately and heavily polluted by PAHs respectively, and most of them are moderately polluted. According to the criteria for classification of Baumard, PAHs pollution level in the sediments is moderate or slight. Based on underground water quality of Netherlands and the water quality standard of Canada, PAHs pollution of LURS are featured by low-ring PAHs. For the monthly total concentrations of PAHs, only several exceeded the limit of drinking water quality standard of China. Compare with other areas, pollution level here is moderate. However, karst features and environments are in favor of enriching PAHs and other POPs, which should attain enough attention. Isomer ratios and molecular weight characteristics show that PAHs in the waters mainly come from petroleum. Isomer pair ratios, molecular weight characteristics and principal component analysis (PCA) suggest that vehicles, coal, petroleum and biomass combustion are the main sources of PAHs, another major source being petroleum. Combustion accounts for56.4%while petroleum accounts for43.6%.(2) Multi-media distribution of PAHs and impact factors. The results show that organic matter is the most important factor governing the behavior and fate of PAHs in the water, particles and sediments of the underground river. The relationships among PAHs and DOC or TOC are unambiguous, while the relationship between PAHs and POC is more complicated. DOM is not only a facilitator for the accumulation of freely dissolved PAHs, but also an important pool for dissolved heavy PAHs in the underground river. Suspend particle matter (SPM) is one of the factors influencing on dissolved PAHs. In contrast with the dissolved PAHs, particle organic matter do not significantly affect PAHs, because of the existing other influencing factors such as DOM. Positive correlation has been found between TOC and PAHs in sediments, except InP, DaA and BgP, which indicates that sediment contaminations are primary controlled by organic matter, and might have some other influencing factors.Studies have shown that particle phase-water phase partition coefficient of PAHs have no relationship with POC, while significantly affected by SPM, because more SPM contents will bring more DOC contents, leading to competitive adsorption PAHs between POM and DOM. Through the research of PAHs partition between sediments and water, the linear free-energy equation between organic carbon normalized partition coefficient (K∝) and octanol-water partition coefficient (Kow) has been built. It is found that sediments have poorly lipophilic for PAHs compounds.(3) PAHs migration and transfer process in LURS. The similar composition of PAHs between the underground river and other waters, tracer tests and the relationship among different waters show that karst landforms play an important role in the migration of PAHs in the system. Different combination patterns of PAHs are controlled by hydrodynamic conditions. It is found through comparing the composition of PAHs between upstream and downstream that2-3rings PAHs have higher transport capability with farther migration distance, while lower transport capability and shorter migration distance for4-6rings PAHs, because4-6rings PAHs are affinity particle with low solubility and can be easily absorbed by sediments or carbonate rocks. The exchange mode of surface soil and underground river sediments indicates that the sediments in the outlet of the underground river mainly come from the transportation of the upstream water and surface soil.It is implied by the rainfall monitoring that sinkhole input and surface water infiltration are two major factors controlling the transport process of PAHs during rain events. Rainfall can promote the migration of PAHs from surface to underground. The more the discharge is, the stronger the migration will be. Once there is enough rainfall intensity, it will not only bring more suspended particles, but also make high ring PAHs easier to migrate. The PAHs distribution among different phases are controlled and influenced by the concentrations of DOC, POC, SPM and characteristics and species of the particles, leading to the different partitioning of PAHs in different phases.(4) Ecological risk assessment of PAHs in LURS. Based on risk quotient (RQ) method for ecological risk assessment of PAHs, it is found that all detected PAHs are in moderate or heavy ecosystem risk. The total PAHs show that the Guihuawan Spring and the outlet of Laolongdong Underground River are severely polluted, reaching high risk, while the Zhaojiayuanzi Spring and the surface water are in level2risk. The ecological risk level of the sediments of Laolongdong is low, leading to little negative ecological impact. However, the ecological risk level of the sediments of Xiannvdong is high. The coincident results are shown according to the methods including ERL/ERM, TEL/PEL and mean ERM quotient. The Ecological risk level of the surface soil is moderate. Low and moderate molecular PAHs presented much more ecosystem risk than high molecular PAHs in the Laolongdong underground river system. The3-ring PAHs have higher contribution to the ecological pressure of the water system of Laolongdong, while2-ring and3-ring PAHs contribute more to the soil and sediments. Therefore, some measurements should be taken to control2-3rings PAHs.Due to thin soil and karst fissure of epikarst system, PAHs can easily enter into karst springs, resulting in high ecological risk in Guihuawan Spring and Zhaojiayuanzi Spring. Affected and unaffected by the sewage of Huangjueya Town, the ecological risk of Laolongdong water is in high risk and moderate risk respectively. The higher the ecological risk of recharge of the underground river in different media is, the higher that in Laolongdong Underground River will be. Difference of migration behavior of different molecular weight PAHs lead to the difference of ecological risk levels in water or sediment between upstream and downstream in Laolongdong Underground River. The high molecular PAHs are enrichment in the sediments of the underground river conduit. Once migrating from upstream to downstream, it will produce ecological threat for the downstream.更多还原