【作者】 吴亮；

【导师】 鲍恋君；

【作者基本信息】 暨南大学 ， 生态学， 2022， 博士

【摘要】 有机污染物种类和数量众多,其环境风险受到了广泛关注。水体中自由态有机污染物具有更高的生物可利用性及迁移性,与其构成的生态风险密切相关,需要特别予以重视。目前新兴有机污染物如多环麝香（polycyclic musks,PCMs）和有机紫外线吸收剂（organic ultraviolet absorbers,OUVAs）在水体中的自由态环境数据相对较少,尤其是大尺度的调查研究,难以进行科学管理。同时自由态持久性有机污染物在特定介质的迁移速率数据比较缺乏。因此,本研究采用两种以低密度聚乙烯（low-density polyethylene,LDPE）膜为吸附相的被动采样装置（水体被动采样装置和多段式沉积物孔隙水采样装置）对上述问题进行了探究,测定了我国淡水流域（包括东北松花江与辽河流域、长江流域、珠江流域、新疆及西藏的湖泊和大型水库）中自由溶解态PCMs和OUVAs的浓度水平,考察了不同社会经济因素对其分布的影响,并通过模拟装置原位测定了典型持久性有机物多氯联苯（polychlorinated biphenyles,PCBs）和多溴联苯醚（polybrominated diphenyl ethers,PBDEs）在沉积物中的迁移速率。结果显示PCMs广泛存在于中国的淡水环境中,检出率达到95%,其自由溶解态浓度范围为<RL-240 ng L^-1(4.1±7.2 ng L^-1),中值为0.99 ng L^-1。佳乐麝香和吐纳麝香是水体环境中PCMs的主要组成单体,这与它们当前在各类日化用品中被大量使用有关。水体中佳乐麝香、吐纳麝香以及萨利麝香的自由溶解态浓度之间均存在显著相关性,表明它们都具有相似的环境来源。同时,PCMs在大地理区域内的浓度分布深受人类活动影响,中东部和华南地区水体中的浓度要高于东北、西北和西藏地区,其自由溶解态浓度的平均值与相应采样区域的人口密度和单位面积GDP之间均存在显著相关性（r²>0.75,p<0.01）。因此水体中的PCMs浓度水平可以作为考察人类活动对水环境影响的参数之一。此外,水体中佳乐麝香和吐纳麝香的浓度比值为0.6-33（9±5）,其地区差异由各种环境因素共同作用导致,光降解是其中的主要敏感因素。该比值有助于解释PCMs在环境介质中的降解和传输。吸附动力学研究表明目标OUVAs化合物均可以被LDPE吸附,但其中部分化合物如EHMC和UV-531在水体中降解速率很快,未能确定其吸附动力学曲线。野外采样结果显示全国78%的采样水体中至少检出了一种OUVAs,其中检出率较高的为EHMC（56%）和UV-326（55%）,较低的为UV-350和UV-PS（<7%）,UV-234和UV-531则均未检出。水体中典型OUVAs的自由溶解态浓度为<RL-24 ng L^-1(1.6±4.1 ng L^-1),中值为0.23 ng L^-1。区域上,中东部和华南地区水体中OUVAs的自由溶解态浓度高于东北、西北和西藏地区。季节上太湖水体中的结果显示夏季浓度显著高于冬季,其中EHMC是造成季节差异的最主要贡献者,这与其在当前防晒产品中的大量使用有关。主成分分析显示典型城市湖泊水体中UV-326、UV-328和PCMs同属一个主成分,对应潜在来源为污水厂出水排放,反映了典型OUVAs进入水体的间接途径;EHMC、UV-327和UV-329同属另一主成分,潜在来源为工业制品/防晒产品中添加剂排放并通过气体吸收及降水径流进入水体,体现了OUVAs进入水体的直接途径。另一方面,在分子扩散机制下被动采样测定PCBs和PBDEs在沉积物中的向上迁移速率为0.02-0.03 cm d^-1(7.7-10.6 cm y^-1),而传统采样方法则未能在沉积物相中监测到相应化合物的迁移。目标化合物的孔隙水无量纲浓度分布显示,疏水性强的化合物在迁移过程中浓度递减幅度更大,表明其在迁移过程中受到的迟滞作用更为明显。但值得注意的是,不同疏水性化合物在单位时间内的最终迁移距离未展现出差异,即它们有着相同的迁移速率。此外,大型钻蚀生活型底栖生物的活动会在沉积物表层产生大量孔穴,从而形成孔隙水与水体两种介质并存的扩散体系,显著促进化合物的向上迁移。在底栖生物的扰动作用下,目标化合物的平均沉积物-水界面扩散通量增加了约24倍。因此,底栖生物扰动会使得先前被掩埋的污染物再活化,由此增加上覆水中生物体的潜在暴露风险。本研究验证了被动采样技术对水体中PCMs和OUVAs的监测有较好适用性,且首次对中国淡水环境中的PCMs和OUVAs进行了大尺度调查研究,并获得了它们的自由溶解态浓度分布,为评估此类污染物在大地理区域内的环境风险提供了重要基础数据。同时,测定的PCBs和PBDEs在沉积物中的迁移速率对了解典型疏水性有机物的区域地球化学过程和生态风险也具有重要意义。更多还原

【Abstract】 A number of typical persistent organic pollutants have received extensive attention due to their outstanding environmental risks.Freely dissolved organic contaminants in aquatic environment could be bioavailable and migrate in sediment or water,which may give rise to ecological risk.As a result,the fate of freely dissolved organic cotamiannts should be addressed.However,the occurrence of emerging organic pollutants,such as polycyclic musks（PCMs）and organic ultraviolet absorbers（OUVAs）in water,are relatively scarce,especially in large-scale investigations.Meantime,the migration rates of polychlorinated biphenyls（PCBs）and polybrominated diphenyl ethers（PBDEs）in sediments have not been determined.To fill the above-mentioned knowledage gap,two passive sampling devices（a passive water sampler and a multi-section passive porewater sampler）with low-density polyethylene（LDPE）film as the adsorption phase were used to explore the above issues.The present study was intended to determine the freely dissolved concentrations of PCMs and OUVAs in freshwater of China,examine the influence of different socio-economic factors on their spatial distribution,and in situ measure the migration rate of PCBs and PBDEs in sediments in a microcosm.The results showed that the dection frequency of PCMs in freshwater of China was up to 95%.Their freely dissolved concentrations were in the range of<RL to 240ng L^-1,with a median value of 0.99 ng L^-1.Galaxolide and tonalide were predominant components of PCMs in freshwater,which was related to their extensive use in various household products.The freely dissolved concentrations of galaxolide,tonalide,and celestolide in freshwater were significant correlated with each other,indicating that they had similar environmental sources.Spatially,the concentrations of PCMs in the Middle and East China were significantly higher than that in the West China and Northeast China.Moreover,the levels of PCMs were correlated well with the corresponding regional population density and GDP per area unit（r ²>0.75,p<0.01）.Therefore,the occurrence of PCMs could be a parameter for examining the effects of anthropogenic activities on aquatic environment.In addition,the ratios of galaxolide and tonalide were0.6–33（9±5）nationwide.Photodegradation may be the main contributor to the regional difference in the ratio of galaxolide and tonalide.Therefore,this ratio is helpful to explain the degradation and long-term transport of PCMs in water and air.All target OUVAs could be adsorbed by LDPE,but some of them,such as EHMC and UV-531,were rapidly degraded in water,their adsorption kinetics could not be determined.At least one OUVA was detected in 78%of the sampling sites in freshwater of China.2-ethylhexyl,4-methoxycinnamate had the highest detection frequency（56%）,followed by UV-326（55%）.UV-234 and UV-531 were not detected in all sampling site.The freely dissolved concentrations of OUVAs in freshwater of China were in the range of<RL to 24 ng L^-1(1.6±4.1 ng L^-1),with a median value of 0.23 ng L^-1.Regionally,the concentrations of OUVAs in water of the Central and East China were significantly higher than that in the West China and Northeast China.Seasonally,their concentrations were significantly higher in summer than in winter in Taihu Lake（p<0.01）.Principal component analysis showed that effluent from wastewater treatment plant was the primary sources of UV-326,UV-328,and PCMs in water,whereas EHMC,UV-327,and UV-329 may enter into water through gas absorption and wet deposition.The upward migration rate of PCBs and PBDEs in sediment was 0.02-0.03 cm d^-1(7.7-11 cm y^-1)measured by passive sampling under the molecular diffusion mechanism.The dimensionless concentration profiles of PCBs and PBDEs in porewater showed that the compound with stronger hydrophobicity suffered more hysteresis in migration.Nevertheless,the observed migration rates of PCBs and PBDEs in sediment were comparable,suggesting that ultrafine particle may carry PCBs and PBDEs and move to water due to sediment deposition.In addition,the burrowing activity of macrobenthos produced a large number of holes in the surface sediments,thus forming a diffusion system with coexistence of porewater and water phase,which significantly promoted the upward migration of compounds.Under the bioturbation of boring macrobenthos,the average diffusion flux of target compounds at the sediment-water interface increased by about 24 times.As expected,bioturbation can significantly remobilize previously buried contaminants,which may increase the exposure of aquatic organisms in the overlying water.The present study verified the applicability of passive sampling techniques for monitoring PCMs and OUVAs in water,and conducted a large-scale investigation on PCMs and OUVAs in China’s freshwater for the first time.The results provided important basic data for assessing the environmental risks of these pollutants in a large geographical area.In addition,the measured migration rate of PCBs and PBDEs in sediments is important for understanding the geochemical processes and ecological risks of typical hydrophobic organic compounds in aquatic environment.更多还原