【作者】 鞠晓东；

【导师】 金一和；

【作者基本信息】 大连理工大学 ， 环境科学， 2009， 博士

【摘要】 全氟有机化合物(PFCs)是一类新型的持久性有机污染物(POPs),具有环境持久性、长距离迁移能力、生物富集、食物链积累和生态毒性特征。经过五十多年大量生产和使用,这些物质已广泛存在于全球生态环境之中。由于具有较高的水溶解度和解离度,因而历史排放的绝大部分此类污染物质蓄积在环境水体之中。海洋是地球环境中的主要水体,在此类污染物质的环境行为过程中具有举足轻重的作用。由于全氟辛烷磺酸(PFOS)、全氟辛酸(PFOA)等PFCs具有表面活性易于在海洋表面吸附和富集,从而使海洋微表层在PFCs海洋环境行为方面具有特殊重要的作用。一方面富集在微表层中的PFCs有可能是环境中的一个潜在的再生污染来源。PFCs可能通过水气界面进入大气从而实现水气循环和大气迁移传播;另一方面,微表层又是鱼卵的孵化场所和其幼体的栖息地,对海洋生态系统的再生产过程具有深远的影响。研究海洋微表层中PFCs的分布问题不仅是了解其环境分布的重要内容,可以为研究其迁移机制和水气循环过程提供线索和依据,同时也是进一步开展PFCs海洋微表层污染暴露研究的基础。本文通过冬、夏两季海洋环境调查,观察了此类污染物在微表层中的富集状况、异构体及同系物的分布特征:通过实验室模拟,对微表层采样方法进行了优选、对调查结果进行了验证;采用表面张力测量方法和经典表面吸附热力学理论,研究了PFOA微表层富集状况和主要热力学影响因素。主要研究结果及结论如下:(1)环境调查表明大连沿岸海域普遍受到了PFCs的污染。PFOS和PFOA类表面活性污染物在沿岸表层水中的浓度为＜0.10～2.25ng/L和0.17～37.55ng/L。污染水平高于南中国海,与朝鲜沿岸相当,但低于日本沿岸和东京湾。(2)此类污染物在微表层中存在富集现象,尤其是在近岸点位PFOS的富集倍数高达23.5-108.6,体现出向海递减和沿海面分布不均匀的特性。PFOS和PFOA在沿岸表层水中的浓度也普遍高于次表层水中的浓度,表层水与次表层水浓度的比值的平均值分别为1.54和1.42。(3)对全氟表面活性剂(PFSs)异构体海洋微表层分布状况调查表明:PFOS直链和支链异构体在开阔海域微表层中普遍存在富集现象。在实际海洋环境中支链异构体比直链异构体具有更强的富集能力。其在次表层中的浓度比值为0.33～0.76,几何平均值为0.45;而微表层中监测到的比例为0.76～1.99,几何均值高达1.20。(4)次表层海水中PFNA与PFOA浓度的比值为0.07～0.26,几何平均值为0.10。相比较而言,微表层中PFNA与PFOA的比值范围为0.10～2.0,具有较高的几何平均值0.33。微表层中的PFOS异构体、PFOA和PFNA同系物的组成特征比例显著不同于体相海水和其产品中的组分比例。(5)实验室模拟发现玻璃板法和不锈钢栅网法都可观察到PFOA在微表层中的富集现象,而且都具有良好的线性。两种方法观察到的微表层采样厚度为50±10um和200um,富集倍数的几何均值分别为1.16(r~2=0.987)和5.25(r~2=0.994)。不锈钢栅网法具有较高的采样灵敏度和采样效率,是较玻璃板法更加适宜于PFSs微表层的采样方法。观察发现磺酸盐类表面活性剂的富集系数明显高于相同碳数的羧酸盐。随着碳数增加同系物的微表层富集系数体现出指数增长趋势。对PFCs异构体的模拟观察发现,PFOS支链和直链异构体在体相溶液中的比值为0.38时,微表层中的比值为1.04。模拟实验结果验证了PFOS支链异构体比其直链异构体具有更高的微表层富集能力这一环境调查结论。意味着PFCs支链异构体具有随气溶胶迁移优势。(6)表面张力测量方法和经典表面吸附热力学理论分析表明:在实际海洋环境浓度范围内,PFOA的表面吸附状态可采用Longmuir极稀溶液表面富集系数表征。溶液温度增加时将导致该富集系数随之降低;盐度增加导致该富集系数随之增加。而实际环境水平下的浓度和pH值的变化对其富集影响很小。海洋表层水温度和盐度是影响全氟表面活性剂微表层富集状态的主要热力学因素。更多还原

【Abstract】 Perfluorinated compounds（PFCs） is a new kind of persistent organic pollutants（POPs） that exhibits environmental persistence,long range transport ability,bio-concentration,food web accumulation and ecological toxicity.After more than fifty years of production and use, those chemicals have been found every where in the global ecosystem.Due to their higher solubility and liberation degree,the majority of this class of chemicals discharged historically accumulates in the environmental water bodies.That means the global ocean may play an important role in their environmental behaviors.Perfluorooctane sulfonate（PFOS） and perfluorooctanoate（PFOA） may be adsorbed on the sea surface attributed to their superior surface activity,implying that the sea surface microlayer（SML） may play a special role in oceanic environmental system.PFCs enriched in SML may be a potential regenerative source, by which PFCs may transfer into atmosphere from ocean water and undergo long-range atmospheric transport.Moreover,SML is the habitat for fish eggs and its emboys,which may find a profound influence on the reproduction of oceanic ecosystem.Studies on the PFCs’ distribution in SML not only favor to understand PFCs’ environmental distribution,but also favor to find clues for the studies of air/water cycling and transport of those chemicals.In the mean time,better understanding to PFCs’ distribution is the foundation for futher studies, such as SML-biota’s exposures.Through environmental investigation,laboratory simulation and laboratory surface tension measurements,the enrichment phenomena and isomeric and homologous distribution features of PFOS,PFOA and perfluorononanoate（PFNA） in SML were observed and discussed in the present work.The main experimental results and conclusions are as follow.（1） The investigation revealed that Dalian coastal sea is generally polluted by PFCs. Concentrations of PFOS and PFOA in surface water ranged＜0.10～2.25ng/L and 0.17～37.55ng/L.The pollution levels were higher than that in South China Sea,comparable to Korea coastal sea,but lower than those in Japanese coastal lines and Tokyo bay.（2） PFCs were found elevated in SML from corresponding subsurface water（SSW）.The enrichment factors（EFs） in SML collected with glass plate method for PFOS were as high as 23.5～108.6 at three near-shore sites.Concentrations in surface water（SW） was also generally higher than corresponding SSW samples,giving C_sw/C_ssw mean ratios of 1.5 and 1.4 for PFOS and PFOA in Dalian coastal sea,respectively. （3） Both PFOS branched and linear isomers were found generally elevated in SML from SSW.Especially,the concentration of the total branched monoperfluoromethyl substituted isomers（M-PFOS） was found higher than that of linear isomer（L-PFOS） in SML.The M-PFOS’ EFs in SML collected with stainless steel screen ranged from 4 to 127,with a higher geometric mean of 19.Comparatively,the L-PFOS’ EFs ranged from 3 to 57,with a lower geometric mean of 7.The branched M-PFOS to L-PFOS concentration ratios in SML ranged from 0.8 to 2.0 with a geometric mean of as high as 1.2,which was much higher than that in SSW and the estimated mean value of 0.43 in PFOS products as the original pollutants source.The findings of this work provided new clues that can be used in SML-mediated marine aerosol transport estimation and implied unique isomeric exposures to microlayer-biota.（4） PFOA and PFNA concentrations in SML collected with a stainless steel screen（with a depth of 200 um） ranged 1.92～17.66 ng/L（geomean 4.27 ng/L） and 0.40～9.30 ng/L （geomean 1.38ng/L）.The geomeans of EFs were 2.5（1.0～17） and 8.2（2.1～42）.PFNA to PFOA mean ratio was 0.33 that was significantly higher than the value of 0.10 in SSW.（5） Laboratory simulation revealed that both screen and glass plate methods can be used to measure the EFs for PFOA in SML with a good linearity.The EFs geomeans werel.16 （r²=0.987） for glass plate method and 5.25（r²=0.994） for screen method with a sampling depth of 50±10um and 200um,respectively.Due to the higher sampling efficiency and sensitivity,stainless screen method was quantified as more adaptive method for perfluorinated surfactants microlayer collection.Sulfonate surfactants show higher enrichment factors in SML than carbonate ones with the same carbon number.With chain length increase, homologues’ EFs increase in exponential trend.Branched to linear PFOS isomer ratio（1.04） was higher than that（0.38） in sea bulk water in the simulation.Experiment results confirmed branched PFOS isomers can exhibit higher enrichmental ability than linear ones,implying that branched PFCs isomers may show priority through marine aerosol transport.（6） Surface tension measurements and classical thermodynamic theory of surface adsorption indicate that the adsorption of PFOA on seawater/air interface can be characterized by Longmuir surface enrichment factors of extremely dilute solution.Temperature and salinity are the two major thermodynamic factors that affect their adsorptions in SML.When temperature rises,surface adsorptions decrease;while salinity increases,adsorptions increase. The variations of PFCs’ concentration and pH in actual environmental levels have less influence on PFSs’ EFs in SML.更多还原