【作者】 王丽丽；

【导师】 刘敏； 许世远；

【作者基本信息】 华东师范大学 ， 环境科学， 2010， 硕士

【摘要】 河口地区作为海陆作用的重要地带、一个复杂的生态系统,具有其独特的生态价值。同时,受海陆交汇作用影响,各种环境因素变化剧烈,使河口环境又具有脆弱和敏感的特点。经济的快速发展,使大量的污染物输入到河口地区,对河口滨岸的环境产生了不同程度的影响。其中,多环芳烃(Polycyclic Aromatic Hydrocarbons, PAHs)由于其致畸、致癌、致突变等特性,得到了国内外学者的广泛关注。而多环芳烃在环境介质中的迁移、转化、生物有效性等,则是学者们所关注的焦点。因此,本研究选择具有典型海陆作用的长江口滨岸地区作为研究对象,通过对典型3环多环芳烃—菲在沉积物-水间的分配及其影响机制进行研究,结合实测数据建立菲在长江口环境系统中的多介质归趋模型,不仅对多环芳烃的环境地球化学循环研究具有重要意义,也为多环芳烃污染治理提供了理论依据。PAHs在长江口滨岸沉积物中的分布特征表明,沉积物中PAHs的总量为246.5～1493.5ng／g,平均值为661.2ng／g。从空间分布看,SDK样点PAHs累积量最高,其次为WSK,从SDK沿岸线PAHs含量依次降低,金山PAHs含量较高。长江口滨岸沉积物中PAHs以3-4环为主,而PAHs单体中,占总量比例最高为菲(23.2%),其次为萘(16.5%)。与同类文献比较,长江口沉积物PAHs远低于国外一些污染严重的河口,而高于国内多数研究区,且长江口潮滩沉积物PAHs含量有下降的趋势。长江口滨岸沉积物中多环芳烃LMV/HMV结果显示,LHK、SDK、WSK样点LMV/HMV值小于1,显示出较强的高温燃烧来源,BLG、LG、FX、JS、CM的LMV/HMV值均大于1,表现为中低温燃烧和石油产品来源。尤其是CM,低分子量PAHs含量远高于高分子量组分,可见该点PAHs几乎全部来源于中低温燃烧和石油产品。对长江口滨岸带沉积物中PAHs特征比值判源结果显示,多种特征比值显示结果一致。沉积物中PAHs主要来源表现为矿物燃料不完全燃烧和石油产品输入两种途径。应用Freundlich模型、线性模型、Langmuir模型、二元模型对所得吸附试验数据进行拟合,研究长江口滨岸沉积物对菲的吸附特征,结果表明：Freundlich模型对数据拟合效果最好,除SDK和WSK表现出较高的线性和较高的吸附能力外,其他样点均呈较高的非线性和较低的吸附能力；线性模型对SDK和WSK的拟合效果较好,而其他样点线性较差；吸附等温线也符合Langmuir模型,其Qmax最高值也出现在SDK和WSK；二元模型模拟结果显示,线性部分吸附能力大于非线性部分,因此推断非线性部分对菲吸附起作用的不是炭黑,而是矿物质。对于SDK, WSK样点来说,Freundlich模型、线性模型和Freundlich型二元模型拟合结果均表明,在研究区当foc>0.01时,吸附过程以分配作用为主。线性模型计算logKoc值高于二元模型拟合Kp值,且该两点计算Koc。大于其他样点,表明该两点有机碳吸附力大于其他foc<0.01的点。LHK、LG、JS、CM沉积物中foc含量为0.001～0.01,只有当OC含量相对较高时,吸附过程才以分配为主,而矿物的吸附作用在水溶液浓度较低,特别是当Cw/Sw在0.0001-0.001时尤为明显,而该浓度则与自然界水体中浓度接近。对沉积物吸附PAHs影响因素的研究结果表明,环境因素中的盐度和温度对吸附的作用不显著,营养盐对吸附的影响不明显。在WSK和JS样点,随着盐度的增加,沉积物的吸附能力和等温线的非线性有增强的趋势,而在有机碳含量较低的CM,没有发现盐度对吸附的影响。随着温度的升高,WSK和JS的logKFr值均有不同程度的降低,吸附是放热的过程表明,温度升高不利于沉积物吸附菲。NH4-N浓度对吸附的影响不明显,随着NH4-N的增加,logKFr和n值均没有显著变化,表明氨氮不是影响沉积物吸附菲的主要影响因素。沉积物组成是影响沉积物吸附的主要因素。沉积物中有机碳部分是吸附菲的主要成分,用H2O2去除的有机碳组分的在实验浓度范围内的Freundlich常数表明,其n值均约为1,与有机碳吸附特征相吻合。因此计算出的WSK和LG有机碳分配值koc分别为4.07和3.87,与经验公式预测值3.98接近。通过应用Ⅲ级稳态假设模拟菲在长江口各环境介质中的归趋,得到菲的浓度以及在各介质间的迁移转化通量。通过将模拟值与实测值对比,证实该模型对长江口环境模拟具有效性,直观的表达了PAHs在长江河口环境中的环境行为。模型模拟结果显示,PAHs主要富集于植物和沉积物中；平流是PAHs输入输出该环境的主要方式；PAHs在植物中的降解速率最快,沉积物中最慢；迁移通量中大气向植物和水体的迁移最为显著。更多还原

【Abstract】 As an important area between land and ocean, the estuarine and coastal area is a complex ecosystem with special ecological value. Due to the interaction of land and ocean, the environmental factors change dramatically, making the estuarine and coastal area sensitive and fragile. With the development of economy, a large number of pollutants were brought to these areas and caused different extent of pollution. PAHs (Polycyclic Aromatic Hydrocarbons) had been frequently detected in estuarine and coastal area and caused great concern because of their carcinogenic and mutagenic features. In the present study, we take the Yangtze River estuarine and coastal area as the researching object, Phenanthrene sorption to surface sediment and the mechanism had been discussed, a multimedia model was established to simulate the fate of PAHs. The main conclusions are as follows:The concentrations of PAHs in surface sediments were in the range of 246.5～1493.5 ng/g (average value:661.2 ng/g). PAHs concentration is highest in SDK, and decreased from SDK to CM, JS has a relative higher concentration of PAHs among them. The 3～4 ring of PAHs are the dominated monomers in sediments of researching area. The highest proportion of the PAHs is Phenanthrene (23.2%), followed by Naphthalene (16.5%). The comparison with similar literatures showed that the contamination of PAHs in Yangtze River estuary and coastal area is much lower than foreign severely polluted estuaries and higher than most reported data of China. The LMV/HMV ratio indicated that PAHs of LHK, SDK, WSK are from the pyrogenic source while BLG, LG, FX, JS, CM are from the petrogenic source. Source apportionment by principal component analysis reflected PAHs derived from incompleted combustion and petroleum.In general, the Freundlich isotherms fit the best to the experimental sorption data for all the samples. Excluded BLG, FX and CM samples, the dual model comprising either Freundlich isotherm or Langmuir equation yield satisfied fitting, indicating two sorption domains in the samples studied. OC is one of the dominant sorbents in samples studied. TOC content showed significantly positive correlation with logKFr (R2=0.83,p<0.005) and n values in the Freundlich model,logQmax (R2=0.868, p<0.001) in the Langmuir model and logKFr,x (R2 =0.974, p<0.0005) and logQmax,x (R2=0.911, p<0.005) in the dual models, respectively. At SDK and WSK sites, Freundlich, linear and Freundlish inclusive dual model suggested the partitioning dominant sorption where foc>0.01. Using linear partitioning model, we get logKoc values higher than the predicted Kp values in dual models. Moreover the estimated Koc values at these two sites were higher than others, indicating the higher affinity of organic carbon than those in other samples where foc<0.01. The significance of BC was not concluded in this study. For other samples with foc<0.01, sorption coefficients higher than predicted Kp values suggested the occurrence of other sorbents besides OC. In spite of BC, the significance of minerals in the samples was concluded in this study. Previous studies has concluded that for sediments contained only small amount of OC (foc<0.001), mineral phase contributes significantly to sorption other than OC. In the present study, for LHK, LG, JS and CM sediment samples with foc in the range of 0.001 to 0.01, partitioning dominated sorption contributed by OC only at relatively high water concentration. Mineral phase adsorption dominated sorption at lower water concentration especially when Cw/Sw in the range of 0.0001 to 0.001 in the natural aqueous system.Sediment composition in the main factor control sorption. The result of sequential extraction experiments removing the inorganic and organic carbon showed that the sorption capacity decreased dramatically when organic carbon was removed, indicating that the organic carbon played an important role in sorption. The Freundlich parameter of H2O2 removed component showed that the n value is approximate to 1, in accordance with the characteristic of OC.Temperature is an environmental factor affecting the sorption of PAHs. The increase of temperature was not favorable to sorption, logKFr decreased along with the increasing temperature from 25℃to 55℃. The sorption results from the salinity effect showed that both logKFr and n value decreased with the increase of salinity in SDK and WSK, indicating that higher salinity will lead to higher sorption capacity and strengthen the non-liner trend. But this trend is not significant especially at CM, where mineral is one of the domain controlling sorption. The sorption results from NH4-N concentration effect showed the difference is not significant indicating NH4-N is not the main environmental factor affect PAHs sorption at Yangtze River estuarine and coastal area.A levelⅢmultimedia fate simulation model was established to simulate the transformation of PAHs in the Yangtze River estuarine and coastal area. The model was proved to be valid by comparing the simulated and measured data, and it can be used to study the environmental behavior of PAHs in the Yangtze River estuarine and coastal area.The simulating results showed that PAHs mainly enriched in vegetation and sediment phase; PAHs are transported to the study area by advection; the degradation rate of PAHs is fastest in the vegetation and slowest in sediment; the most predominant transportation fluxes are air-water and air-vegetation flux.更多还原