【作者】 欧冬妮；

【导师】 刘敏； 许世远；

【作者基本信息】 华东师范大学 ， 自然地理学， 2007， 博士

【摘要】 多环芳烃（PAHs）是一类含量很低、具有明显毒性（致癌和致突变性）、难降解性及颗粒活性的典型持久性有机污染物（POPs），可通过各种环境介质（大气、水、生物等）长距离迁移并普遍存在于河口及其滨岸生态环境。河口滨岸是陆海交互作用的典型地带，具有水动力作用强烈、泥沙输移和物质交换频繁、多物质多界面相互作用复杂、理化要素梯度变化大、生物多样性丰富等特点，且受人类高强度活动的干扰和改造，是全球变化区域响应最为敏感的地带。本文以长江口滨岸为典型研究区，分析了PAHs的多相分布规律，探讨了它们在滨岸颗粒物-水相间的分配机制，阐明了PAHs的主要来源及其迁移输入途径，对其进行了生态风险评价。通过研究长江口滨岸水-颗粒物-沉积物体系间PAHs的时空分布规律，发现温度和水体再悬浮作用是影响PAH化合物分布特征的主要因素，受河口区复杂水动力条件以及滨岸污染物排放等人类活动的影响，水体盐度、沉积物颗粒对PAHs的控制并不显著，揭示了沿岸污染物排放、船舶运输及捕鱼等人类活动对PAHs多介质分布的重要作用。生态风险评价揭示该区PAHs污染物已存在潜在的不利生物影响效应。通过研究PAHs在长江口滨岸颗粒物-水相间的分配，获得了表征有机碳归一化分配系数K_oc与辛醇-水分配系数K_ow之间关系的线性自由能方程，发现了研究区颗粒态有机碳（POC）的弱亲脂性，揭示了PAHs在颗粒物-水相间的分配过程主要受非均一混合物碳黑（PSC）的控制。含PSC相的颗粒物-水分配模型较为准确地模拟了PAHs野外原位（in situ）分配过程，揭示了高强度人类活动作用下的长江口滨岸PAHs的多介质分配过程受多重因素影响，因此，在研究滨岸环境PAHs分配行为时应重点考虑整个区域PAHs的来源及颗粒物特性等。环境中的SC具有强烈结合PAHs的能力，可能使现有的PAHs吸附-解析、毒性测试等室内模拟实验无法反映原位PAHs参与这些过程的实际有效性。为了能够更好地定义含有PSC相的憎水化合物分配模型，应对不同条件下的K_sc值进行估算。通过此次原位PAHs与PSC相相互关系的定量化研究，加深了我们对两者关系的认识，有助于进一步深化河口滨岸PAHs生物地球化学循环过程研究。高强度人类作用下的城市化河口滨岸环境中PAHs具有多重潜在来源，多参数指标的应用有助于较为准确地辨析污染物的特殊来源，降低了单一指标源解析的不确定性。一般判源指标（LMW／HMW、同分异构体比值）初步确认长江口滨岸PAHs污染物主要来源于各种油类（柴油、汽油）、煤炭和木材低至中温的不完全燃烧，此外还有部分柴油和原油的输入；排污口、滨岸河流、城市中心城区是河口区PAHs的潜在输入源。特殊判源指标（有机单体化合物稳定碳同位素，Compound-specific stable carbon isotope）进一步确定了与各类SC颗粒结合的PAHs是滨岸多介质环境中污染物的主要来源，它们包括木材不完全燃烧产生的SC颗粒物、煤炭来源的SC颗粒、汽车来源（包括轮胎摩擦产生）的SC颗粒、家用来源的SC颗粒。另外，表层沉积物中还存在木材的不完全燃烧来源。利用BaA／Chry迁移指标推断出滨岸沉积相PAHs的长距离迁移模式，即通过大气传输、水-气界面交换，被分配与悬浮颗粒物结合，最终沉降进入沉积物。通过BaA／Chry指标和CSIA指标，结合潜在输入区域PAHs源信息，推断出沉积物中木材不完全燃烧来源的PAHs主要从滨岸河流及排污口直接进入河口；与木材和煤燃烧形成的SC颗粒结合的PAHs，除了从滨岸河流及排污口直接进入河口外，还有部分为城市街道灰尘被暴雨冲刷后，随地表径流最终汇入河口；与汽车来源SC颗粒结合的PAHs，主要富集在城市交通区、商业区和文教区的街道灰尘中，主要通过大气迁移（枯季）和暴雨径流冲刷（洪季）进入河口。主成分分析结果反映了多介质环境中PAHs不完全燃烧来源的相对贡献率。其中，溶解态PAHs中煤炭、汽油和柴油的不完全燃烧贡献率为74.3％；焦炭来源的贡献率为9.5％；颗粒态PAHs主要为煤炭、油类物质和焦炭的燃烧排放，贡献率为77.1％，汽油不完全燃烧的贡献率仅为为10.5％；沉积物相PAHs中，煤炭和油类燃烧排放的贡献率为67.1％，汽油和柴油的不完全燃烧贡献率为11.0％，焦炭来源的贡献率为8.6％。含碳化合物OC、SC对了解不完全燃烧来源PAHs在河口滨岸环境中的迁移转化过程非常重要，而SC的分离和定量又是了解这一过程的关键环节。含碳化合物的定量结果显示，长江口滨岸颗粒态和沉积相OC与SC具有燃烧源排放特征，发现POC主要来源于河口滨岸环境中的生物过程／早期成岩作用，或滨岸河流及排污口污染物的直接输入，对PAHs的控制弱于不完全燃烧来源的PSC；而沉积物中的OC_s、SC_s主要以燃烧排放为主，对PAHs的亲和力要强于POC和PSC，且不完全燃烧产生的SC_s要多于OC_s，这可能与迁移过程中雨水对OC_s的冲刷有关，另一方面还与SC_s不易溶于水，经大气迁移进入水体后被分配直接沉降进入沉积物有关，这一模式与滨岸沉积物PAHs的长距离迁移模式相似。更多还原

【Abstract】 Polycyclic aromatic hydrocarbons （PAHs） are carcinogenic to humans, and a number ofPAH compounds have been identified as either carcinogenic or mutagenic to both terrestrial and aquatic organisms. PAHs accumulated in different environemtal media, such as air, waters and organisms, are introduced into the coastal environment by long distance transportation. The estuarine and coastal area, as a typocal transitional zone between land and ocean, is a multifunctional and complex ecosystem with special ecological values and potential resources. Due to the interaction of land and ocean, the estuarine and coastal area is characterized by intense hydrodynamic conditions, frequent sediment transport and material exchange, steep physiochemical gradients and high biodiversity. In addition, the estuarine and coastal area is one of highly human activities zone where response to global changes sensitively. So taking the Yangtze estuarine and coastal ecosystem as a research object, multi-media distribution of PAHs, PAH transport and partition mechanisms near the interface between particle and water, sources identification and its input pathways, ecological risk assessment have been discussed in this work. The main findings are as following:Based on analyzing the temporal and spatial distribution of PAHs in overlying waters, suspended particles and sediments respectively, the present work revealed temperature and resuspension condition of estuarine system were the main factors influenced the variation of PAH compounds in the study area. Because of the complex hydrodynamic condition of the Yangtze Estuary and coastal pollution discharge, the effect of water salinity and sediment grain size on PAHs distribution was not significant. In addition, human activities, such as the sewage discharge, commercial shipping and fishing, also play an important role on PAH multi-media distribution. Ecological risk assessment showed that some PAH compounds had the primary potential impacts on the Yangtze tidal flat ecosystem.Through the discussion of PAH transport and partition process near the interface between particle and water, the results demonstrated that organic carbon in the suspended particles had weakly lipophilic characteristic, and the partition process of PAHs was controlled by a heterogeneous mixtures of soot carbon. The exsisting equilibrium partitioning model that incorporated soot carbon phase could well predict the partition of PAHs in situ. Thus, the sources of PAHs and particle properties should be involved when studying the partition behavior of PAHs in the estuarine coastal area. One further implication of the environemntal soot-associated PAHs is that current laboratory-based practices in sorption-desorption and toxicity testing may not realistically reflect the actual availability of in situ PAHs to participate in such process. To further constrain the proposed extension of the hydrophobic partitioning model to include soot-phase partitioning, K_sc should be evaluated under controlled conditions. This direct investigation on the quantitative relationship between in situ PAH distribution and the presence of soot phases indicates that understanding this link may prove crucial to elucidating the biogeochemical cycling og such combustion-derived compounds.Given the large number of potential sources of PAHs to the multi-media of this highly intense human activities urban estuary, multiple techniques are helpful to identify specific sources of this contminants. By applying the general techniques （e.g., LMW/HMW, isomer ratios）, PAHs in the Yangtze estuarine and coastal area were indicative of incompleted combustion at low to moderate temperatures as well as some uncombusted petroleum products. The primary potential inputing sources, such as sewage discharge, coastal rivers draining and road dusts in urban central area, were also proposed by general techniques. By applying the sources specific techniques （CSIA）, identification of dominant PAH sources is PAHs that associated with different types of soot carbon, including wood combustion soot, coal soot, car soot, tyre soot and domestic soot. In addition, PAHs derived from wood incompleted combustion was also contributed PAHs to surface sediments.BaA/Chry index inferred that most volatile PAH compounds could enter the water body via air-water exchange, partition into suspended particles, and deposit onto the sediments. Compared with that original source information in potential regions, both BaA/Chry index and isotopic values indicated that PAHs derived from wood incompleted combustion could reach the coastal sediments from rivers and pollution discharge. Those PAHs associated with wood and coal soot which enriched in road dusts could enter coastal area via surface runoff after being washed out by rainstorm. In addition, PAHs associated with car soot in road dusts from urban traffic district, commercial district and culture and education district, were imported mainly via atmospheric transport in dry season and rainstorm wash out in flood season.Sources apportionment by principal component analysis reflected PAHs derived from incompleted combustion. As for dissolved PAHs, coal, petroleum and diesel oil combustion accounted for 74.3%, coke source accounted for 9.5%. As for PAHs in suspended partcles, coal and oil combustion accounted for 77.1%, petroleum combustion accounted for 10.5%. And PAHs in sediments had 67.1% coal and oil combustion, 11.0% petroleum and diesel oil combustion, and 8.6% coke combustion.Separation and quantification of organic carbon and soot carbon is the key to estimate the environmental behavior and effects of combustion-derived PAHs in estuarine and coastal area. Particel and sedimentary organic carbon and soot carbon presented in the Yangtze estuarine and coastal area were the characteristic of combustion origin. Sources identification revealed that particle organic carbon mainly came from organism processes or diagenesis, and imput directly from coastal river and discharge, and had poor affinity to PAHs compared with soot carbon which generated from incompleted combustion. Combustion was the main source for sedimentary organic carbon and soot carbon whose affinity were stronger than particle organic carbon and soot carbon. Sedimentary organic carbon should be washed out by rainwater during transportation and soot carbon could not soluble in water which resulted in sedimentary soot carbon was more abundant than organic carbon.更多还原