【作者】 何真；

【导师】 杨桂朋；

【作者基本信息】 中国海洋大学 ， 海洋化学， 2013， 博士

【摘要】 挥发性卤代烃（VHCs, Volatile halocarbons）是大气中一类重要的痕量温室气体，在全球气候变化和大气环境方面起着重要作用。大气中VHCs既有人为来源，也有天然来源。海洋在挥发性卤代烃的生物地球化学循环中起着重要作用，海-气界面层是VHCs交换的重要场所之一，因此，海洋是大气中挥发性卤代烃的主要的源汇区。而近岸海域海洋环境比较复杂，可能是大气中VHCs的源区。研究这些海洋环境中VHCs的生物地球化学循环过程，对在全球尺度上准确估算海洋对大气中VHCs的贡献和对未来气候的影响具有重要意义。本文以中国陆架海—东海、黄海和渤海为研究目标，从海水和大气两方面入手，对海水中VHCs的浓度分布特征、时空变化、影响因素、海-气交换通量进行了较为系统的研究，同时对近海大气中VHCs的浓度水平进行了研究。主要研究结果如下：1.参考国内外文献，基于大气采样罐和三级预浓缩仪-气相色谱-质谱分析系统在实验室改进了海洋大气中VHCs的分析方法，其方法检出限为0.5-4.2pptv，精密度为1-6%，准确度为4-10%。该方法与国外同类方法相当，为中国近海海洋大气中VHCs的分析测定工作打下了坚实的基础。2.于2011年3月至4月（春季）、7月（夏季）、10月至11月（秋季）和2011年12月至2012年1月（冬季）对东海、南黄海海域5种VHCs浓度分布和海-气通量的时空变化进行了研究。结果表明：春季东海、南黄海表层海水中CHCl3、C2HCl3、C2Cl₄、CHBr2Cl和CHBr₃浓度平均值及范围分别为62.45（24.6-361.2）、29.67（5.22-72.04）、14.55（1.71-38.90）、44.29（1.44-242.81）和134.62（57.46-512.37）pmol L^-1；夏季浓度平均值及范围分别为51.96（15.85-129.04）、10.85（1.70-78.30）、9.47（3.15-29.45）、27.11（6.94-90.20）和57.63（28.46-90.41）pmol L^-1；秋季浓度平均值及范围分别为63.91（24.63-361.23）、28.46（1.82-85.77）、21.04（9.85-89.3）、20.92（7.98-59.89）和75.91（0.04-537.04）pmol L^-1；冬季浓度平均值及范围分别为33.50（6.77-275.58）、35.06（5.30-83.15）、9.86（0.96-40.06）、16.10（10.18-65.22）和19.84（2.99-80.61）pmol L^-1。由此看出，东海、南黄海5种VHCs浓度呈现明显的季节变化，除C2HCl3外，其他4种VHCs浓度春秋高、冬季最低。这与长江径流的输入、海洋浮游植物的季节性消长以及东海、南黄海海域复杂的水团变化有关。东海、南黄海5种VHCs的空间分布明显受到沿岸径流（如长江冲淡水）和高温高盐黑潮水系及其分支的影响，各季节5种VHCs的浓度水平分布特征大致相似，即东海、南黄海5种VHCs的浓度分布总体表现出近岸高、外海低的趋势，但是每一个季节每一种VHCs又呈现出各自一定的特征。春秋季节垂直断面的分布研究表明，不同VHCs浓度垂直分布不同，同种VHCs在不同季节其垂直分布不同，总体上最大浓度均出现在上层混合层。另外，春季和秋季东海海水中5种VHCs的浓度均表现出明显的周日变化，呈现双峰特征。5种VHCs浓度最髙值出现在中午前后，可能与生物生产和光化学来源有关，而在夜间的较髙值可能是呼吸作用、浮游动物摄食及潮汐作用共同作用的结果。根据现场的风速和表层海水的VHCs浓度，利用Liss&Merlivat公式（LM86）和Wanninkhof公式（W92）分别计算了5种VHCs的海-气通量。受到地理位置、气象条件（如风速）的影响，东海、南黄海5种VHCs海-气通量表现出明显的季节差异，春季较高的VHCs浓度和冬季较大的风速对VHCs海-气通量贡献较大。海-气的计算结果表明：春夏秋冬季节调查期间东海、南黄海是大气中CHCl₃、C₂HCl₃、C₂Cl₄、CHBr₂Cl和CHBr₃的源。3.于2009年12月23日-2010年1月5日对中国东海表层海水和PN断面不同深度海水中4种VHCs进行了测定，并对其来源进行了分析。结果表明，表层海水中CHCl₃、C₂HCl₃、C₂Cl₄和CHBr₃浓度平均值及范围分别为23.04（6.04-107.81）、18.18（10.67-32.35）、3.72（0.39-9.77）和24.33（13.44-33.01）pmol L^-1。4种VHCs浓度水平分布总体呈现近岸高、外海低的趋势；PN断面4种VHCs的浓度最大值出现在上混合层（50m以浅）。4种VHCs浓度的分布总体上受到长江冲淡水、黑潮水及生物活动的共同影响。相关性分析结果表明：C₂HCl₃与C₂Cl₄浓度呈现显著正相关，推测二者存在相似的来源；CHBr₃浓度与叶绿素a浓度呈现一定的正相关性，推测CHBr₃分布受到浮游植物生物量的影响，在调查区内CHBr₃可能主要来源于浮游植物。海-气通量估算表明冬季调查海域是大气中CHCl₃、C₂HCl₃和CHBr₃的源。4.于2010年11月27日-12月10日对中国东海表层海水和PN断面不同深度海水中6种VHCs浓度分布、来源和海-气通量进行了研究。研究结果表明，表层海水中CHCl₃、C₂HCl₃、C₂Cl₄、CCl₄、CH3CCl₃和CHBr₃浓度平均值及范围分别为16.90（0.40-62.92）、16.27（2.78-83.33）、2.40（0.39-9.33）、32.29（19.72-57.68）、1.70（0.39-8.73）和17.11（4.33-34.46）pmol L^-1。除C₂HCl₃外，其他5种VHCs浓度分布大致呈现出近岸高、外海低的趋势。研究发现CCl₄和CH₃CCl₃主要受陆源输入的影响，而CHCl₃、C₂HCl₃、C₂Cl₄和CHBr₃主要受陆源输入和生物释放的共同作用。6种VHCs浓度垂直分布比较复杂，最大值均出现在0-100m水体。调查期间CHCl₃、C₂HCl₃、C₂Cl₄和CHBr₃海-气通量分别为21.08、29.94、2.05和35.50nmolm-2d-1，表明东海是大气中CHCl₃、C₂HCl₃、C₂Cl₄和CHBr₃的源。5.于2012年5月对南黄海大气中8种VHCs的浓度分布进行了调查。结果表明，南黄海大气中CH₃Cl、CH₃Br、C₂HCl₃、C₂Cl₄、CH₃CCl₃、CCl₃F （CFC-11）、CCl2FCClF2（CFC-113）和CCl2FCF3（CFC-114）的大气浓度平均值及范围分别为606.1（412.0-870.6）pptv、16.0（9.9-22.1）pptv、27.3（9.5-52.6）pptv、29.5（10.7-49.0）pptv、9.1（5.8-14.3）pptv、225.1（213.5-233.7）pptv、77.1（69.0-87.9）pptv和18.8（16.7-24.2）pptv。近岸陆源污染物的扩散和输送是南黄海大气中VHCs的重要来源。我们的结果表明CH₃Cl、CH₃Br和CFCs在山东半岛海域存在较强的来源。CH₃CCl₃、CFC-11和CFC-113浓度显著低于全球大气浓度平均值，表明目前三种化合物的利用逐渐被废除；而C₂HCl₃和C₂Cl₄浓度显著高于全球大气浓度平均值，表明二者仍被大量使用。6.于2012年5月和11月对北黄海、渤海表层海水中5种VHCs浓度分布和季节变化特征进行了研究。研究表明：春季北黄海、渤海表层海水中CHCl₃、C₂HCl₃、C₂Cl₄、CHBr₂Cl和CHBr₃浓度平均值及范围分别为402.62（63.06-926.72）、18.99（3.65-34.21）、12.61（0.84-28.29）、4.00（0.96-11.28）和20.62（3.29-79.87）pmolL^-1；秋季浓度平均值及范围分别为189.13（11.31-310.99）、55.69（17.46-136.54）、41.11（2.67-78.00）、20.35（5.12-53.65）和46.18（15.86-94.54）pmol L^-1。由此可见，北黄海、渤海表层海水中5种VHCs的浓度呈现明显的季节变化，CHCl₃浓度春季高于秋季，C₂HCl₃、C₂Cl₄、CHBr₂Cl和CHBr₃浓度则是秋季高于春季，VHCs的季节性变化主要与陆源径流和浮游植物释放的相对贡献有关。研究表明，春季CHCl₃的来源主要为陆地径流输入；而秋季C₂HCl₃、C₂Cl₄、CHBr₂Cl和CHBr₃的来源主要为陆地径流输入和生物释放的共同作用。春秋季节北黄海、渤海表层海水5种VHCs浓度空间分布呈现出不同的分布特征。由于调查海域为封闭和半封闭海域，受人类活动的影响严重，加上不同VHCs来源强度不同，因此没有表现出一致的分布特征。如春秋季，5种VHCs浓度髙值区出现在辽东半岛西南侧海域、黄河口海域和山东半岛西北部及东部海域等。原因可能是近岸地区经济和工业发达，人口密集，海上交通及人类活动频繁。相关性研究表明，秋季CHBr₂Cl与叶绿素a有显著的相关关系，其他VHCs与叶绿素a不存在相关关系，说明春秋季节浮游植物生物量不是控制北黄海、渤海VHCs浓度的主要因素。春季CHBr₂Cl与温度的相关关系表明其分布与温度有关。C₂HCl₃和C₂Cl₄以及CHBr₂Cl和CHBr₃之间的显著相关关系表明它们分别存在相似的来源或者去除途径。根据现场的风速和表层海水VHCs浓度，利用Liss&Merlivat公式（LM86）和Wanninkhof公式（W92）分别计算了海水5种VHCs海-气通量。结果表明：春秋季节北黄海、渤海是大气中CHCl₃、C₂HCl₃、C₂Cl₄、CHBr₂Cl和CHBr₃的源。5种VHCs海-气通量受到表层海水VHCs浓度以及风速的影响。7.东海、黄海和渤海海区所处的地理位置和环境不同，特别在初级生产力、水团变化、陆源影响等方面存在明显差异。渤海、北黄海CHCl₃、C₂HCl₃和C₂Cl₄的年平均浓度高于东海、南黄海的年平均值；而CHBr₂Cl和CHBr₃的年平均浓度低于东海、南黄海的年平均值。VHCs海-气通量的计算结果表明，东海、南黄海、北黄海及渤海海域VHCs的海-气通量变化较大，存在明显的空间和季节性差异。根据VHCs年平均通量和东海、南黄海的海域面积，初步估算出东海、南黄海CHCl₃、C₂HCl₃、C₂Cl₄、CHBr₂Cl和CHBr₃释放量分别为0.45Gg Cl yr^-1，0.17Gg Cl yr^-1，0.12Gg Cl yr^-1，0.23Gg Br yr^-1和0.71Gg Br yr^-1。虽然东海、南黄海只占到全球海洋面积的0.27%，而其向大气中释放的CHCl₃、C₂HCl₃、C₂Cl₄、CHBr₂Cl和CHBr₃却分别占全球海洋CHCl₃、C₂HCl₃、C₂Cl₄、CHBr₂Cl和CHBr₃年释放总量的1.4%，8.5%，6%，5%和0.8%。当然由于各种不确定因素的存在，该释放量与实际释放量之间可能存在较大的误差。由于东海和黄海是全球最有代表性的陆架区之一，此研究结果表明陆架、近岸海域虽然只占到全球海洋面积的一小部分，但对全球海洋释放的Cl和Br贡献很大。更多还原

【Abstract】 Volatile halocarbons （VHCs） with both natural and anthropogenic sources areimportant atmospheric trace gases, which play significant role in the global warmingand atmospheric chemistry. The ocean plays important and complex roles in theglobal biogeochemical cycles of these VHCs, and the marine boundary layer is one ofthe most important places for gas exchange between water/atmosphere. Therefore,Oceans may act as a sink or source of these compounds. Coastal and shelf regions,with the complex marine environment, may be the sources of the VHCs. Anunderstanding of the biogeochemistry of the VHCs in the shelf seas is important inorder to estimate the contribution of oceanic emission to the atmospheric VHCs on theglobal scale, and to predict the influence of oceanic emission to the global climate.The research presented in this dissertation focused on the spatial and temporalvariations of distributions, sources and sea-to-air fluxes of the VHCs in the Chinashelf seas—the East China Sea, the Yellow Sea and Bohai Sea. The main conclusionsare drawn as follows:1. An analytical method for measurement of marine atmospheric volatile halocarbonshas been developed based on canister sampling and an automated preconcentrationgas chromatography-mass spectrometer system. The method detection limit of thegases of interest was in the range of0.5-4.2pptv. The accuracy of the method was inthe range of4-10%with the precision of1-6%.2. The distributions and sea-to-air fluxes of five kinds of VHCs in the East China Seaand the South Yellow Sea during spring, summer, autumn and winter2011areinvestigated. The results showed that the mean （range） concentrations of CHCl₃,C₂HCl₃, C₂Cl₄, CHBr₂Cl and CHBr₃were62.45（10.33-250.50）,29.67（5.22-72.04）,14.55（1.71-38.90）,44.29（1.44-242.81） and134.62（57.36-512.37） pmol L^-1in spring,respectively. Summer concentrations are51.96（15.85-129.04）,10.85（1.70-78.30）,9.47（3.15-29.45）,27.11（6.94-90.20） and57.63（28.46-90.41） pmol L^-1, respectively.Autumn concentrations are63.91（24.63-361.23）,28.46（1.82-85.77）,21.04（9.85-89.3）,20.92（7.98-59.89） and75.91（0.04-537.04） pmol L^-1, respectively, and winter concentration are33.50（6.77-275.58）,35.06（5.30-83.15）,9.86（0.96-40.06）,16.10（10.18-65.22） and19.84（2.99-80.61） pmol L^-1, respectively. In general, withthe exceptions of C₂HCl₃, the mean concentrations of other four kinds of VHCs in thesurface water of the East China Sea and the South Yellow Sea showed a notableseasonal variation with high values in spring and autumn and lowest ones in winter.The spatial distributions of VHCs in the East China Sea and the South Yellow Sea areobvious influenced by the Yangtze River effluent and the oligotrophic Kuroshiowaters as well as the biogenic release. When the distribution patterns are comparedwith each other in different seasons, they are nearly synoptic and generally exhibited adecreasing trend with distant from the coast, with being strongly biased by temporalchange. The vertical distributions of five kinds of VHCs during the spring and antumnare studied. The results showed that the vertical profiles of the five VHCs differamong stations, and the vertical distributions of VHCs were different from each otherduring different seasons, with maxima generally appearing in the mixed layer. Inaddition, the VHCs concentrations exhibited obvious diurnal variation in the surfaceseawater. The highest concentrations of VHCs appearing around noon time may beassociated with biogenic production and photosynthesis of the algae, while therelatively high concentration in the night may be attributed to algal respiration andtidal frequency. Liss and Merlivat relationship （LM86） and Wanninkhof relationship（W92） are employed to calculate the sea-to-air fluxes of VHCs based on the in-situwind speeds and the measured VHCs concentrations in the surface waters. Thesea-to-air fluxes of VHCs showed obvious seasonal variations duo to the influence ofwind speeds and concentrations of the VHCs. For example, the higher VHCsconcentrations in spring and large wind speeds in winter contribute to the large fluxesof VHCs. Sea-to-air fluxes indicated that the East China Sea and the South YellowSea was a source for the fiver VHCs in the atmosphere during the study periods.3. The concentrations of four kinds of VHCs including CHCl₃, C₂HCl₃, C₂Cl₄andCHBr₃in seawater were determined in the East China Sea during23December2009-5January2010, and the sources of the VHCs were studied. The result showedthat the means （ranges） of the concentrations of CHCl₃, C₂HCl₃, C₂Cl₄and CHBr₃inthe surface waters were23.04（6.04-107.81）,18.81（10.67-32.35）,3.72（0.39-9.77）and24.33（13.44-33.01） pmol L^-1, respectively. The concentrations of VHCs nearshore were higher than those in the open sea. In the PN section the verticaldistribution of VHCs had a common feature with the maxima in the upper mixed layer. The distributions of four kinds of VHCs were clearly influenced by the Yangtze Rivereffluent, the Kuroshio water and biological activity. A marked correlation between theC₂HCl₃and C₂Cl₄concentrations was observed in the surface waters, suggesting thatthey might have some common sources. Besides, a positive correlation was foundbetween chlorophyll a and CHBr₃concentrations in the surface seawater, indicatingthat phytoplankton biomass might play an important role in determining thedistribution of CHBr₃in the study area. Our data indicated that the entire East ChinaSea shelf acted as a source for atmospheric CHCl₃, C₂HCl₃and CHBr₃during thestudy period.4. The concentrations of six VHCs in the East China Sea were measured in Novemberand December2010. Mean （range） concentrations of CHCl₃, C₂HCl₃, C₂Cl₄, CH₃CCl₃,CCl₄and CHBr₃in the surface water were16.90（0.40-62.92）,16.27（2.78-83.33）,2.40（0.39-9.33）,32.29（19.72-57.68）,1.70（0.39-8.73） and17.11（4.33-34.46） pmolL^-1, respectively. With the exception of C₂HCl₃, the concentrations of other five kindsof VHCs generally exhibited a decreasing trend with distance from the coast, with thelow values found in the open sea. The anthropogenic sources contributed to theelevated levels of CCl₄and CH₃CCl₃, whereas a combination of the anthropogenicand biogenic sources might be responsible for the elevated levels of CHCl₃, C₂HCl₃,C₂Cl₄and CHBr₃. In the depth profiles, vertical distributions of the six VHCs in thewater column were complicated, with the maxima occurring at0-100m depths. Themean sea-to-air fluxes of CHCl₃, C₂HCl₃, C₂Cl₄and CHBr₃were estimated to be21.08,29.94,2.05and35.50nmol m-2d-1, respectively, indicating that the East ChinaSea was a source for the four VHCs in the atmosphere.5. The concentrations of8VHCs, including methyl chloride （CH₃Cl）, methyl bromide（CH₃Br）, trichloroethene （C₂HCl₃）, tetrachloroethene （C₂Cl₄）, methyl chloroform（CH₃CCl₃） and three chlorofluorocarbibons （CCl₃F （CFC-11）, CCl2FCClF2（CFC-113）and CCl2FCF3（CFC-114））, were measured using canister sampling technique and anautomated preconcentration gas chromatography-mass spectrometer system in themarine atmosphere of the South Yellow Sea in May2012. The mean （range） marineatmospheric mixing ratios for CH₃Cl, CH₃Br, C₂HCl₃, C₂Cl₄, CH₃CCl₃, CFC-11,CFC-113and CFC-114were606.1（412.0-870.6） pptv,16.0（9.9-22.1） pptv,27.3（9.5-52.6） pptv,29.5（10.7-49.0） pptv,9.1（5.8-14.3） pptv,225.1（213.5-233.7） pptv,77.1（69.0-87.9） pptv and18.8（16.7-24.2） pptv, respectively. The diffusion andtransportation of terrestrial pollutants from the coastal area play an important role in the source of selected halocarbons over the South Yellow Sea. Our data indicated thatCH₃Cl, CH₃Br and CFCs had strong local sources from the Shandong Peninsula. Thebackward trajectory analysis suggested that enrichment of CH₃CCl₃in the south of thestudy area might be caused by the long-range transportation of air-masses from theChina mainland. Our results implied the signs of successful phase-out of CFCs andCH₃CCl₃, but substantial releases of C₂HCl₃and C₂Cl₄. The sea-to-air fluxes ofCH₃Cl, CH₃Br and C₂HCl₃were estimated based upon the simultaneous measurementof atmospheric and seawater concentrations of these three gases and the resultsconfirmed that coastal and shelf waters constitute important sources of atmosphericCH₃Cl, CH₃Br and C₂HCl₃.6. The distributions and sea-to-air fluxes of the five kinds VHCs are investigated inthe North Yellow Sea and Bohai Sea in May and Nov.2012. The mean （range）concentrations in the surface water of CHCl₃, C₂HCl₃, C₂Cl₄, CHBr₂Cl and CHBr₃inspring are402.62（63.06-926.72）,18.99（3.65-34.21）,12.61（0.84-28.29）,4.00（0.96-11.28） and20.62（3.29-79.87） pmol L^-1, respectively, whereas those in theautumn are189.13（11.31-310.99）,55.69（17.46-136.54）,41.11（2.67-78.00）,20.35（5.12-53.65） and46.18（15.86-94.54） pmol L^-1, respectively. The results show the fiveVHCs concentrations show obvious seasonal variations. The concentrations of CHCl₃in spring are higher than that in autumn, while the concentrations of C₂HCl₃, C₂Cl₄,CHBr₂Cl and CHBr₃in autumn are higher than that in spring. The anthropogenicsource as well as biogenic source may contribute to the seasonal variations of the fiveVHCs. The high concentrations of CHCl₃in the spring may be related toanthropogenic input, whereas the high concentrations of C₂HCl₃, C₂Cl₄, CHBr₂Cl andCHBr₃may be associated with a combination impact of biogenic release andanthropogenic input. Overall, the distributions of the five VHCs in the surface waterin the North Yellow Sea and Bohai Sea during spring and autumn show significantspatial variations, with high concentrations appearing in the Yellow River estuary,southwest of the Liaodong Peninsula as well as the northwest and east of theShandong Peninsula. Elevated concentrations of the VHCs might be associated withterrestrial input such as Yellow River runoff, biological production as well as thecomplex water masses. Correlation analyses have been used to investigate possiblecontrols on the concentrations of these gases. The CHBr₂Cl concentrations appearedto be significantly correlated with chlorophyll a levels in the study area duringautumn, while other VHCs show no relationship with chlorophyll a during both seasons, suggesting that biological production are not the dominant source of theVHCs. For the physical parameters, sea surface temperature was positively correlatedwith CHBr₂Cl during spring, indicating that the distributions of CHBr₂Cl may beinfluenced by sea surface temperature. A significant correlation was observedbetween C₂HCl₃and C₂Cl₄as well as between CHBr₂Cl and CHBr₃, implied that thesource and sink patterns of C₂HCl₃and C₂Cl₄as well as CHBr₂Cl and CHBr₃in thesurface water were similar. The spatial variability in the sea-to-air fluxes of the fiveVHCs was largely controlled not only by the wind speed, but also by their surfaceconcentrations. Sea-to-air fluxes indicated that the North Yellow Sea and Bohai Seawas a source for the fiver VHCs in the atmosphere during the study periods.7. The temporal and spatial distributions of these compounds vary significantly in theEast China Sea, Yellow Sea and Bohai Sea. The mean annual concentrations of CHCl₃,C₂HCl₃and C₂Cl₄in the East China Sea and South Yellow Sea are higher than thosein the North Yellow Sea and Bohai Sea, while the mean annual concentrations ofCHBr₂Cl and CHBr₃in the East China Sea and South Yellow Sea are lower than thosein the North Yellow Sea and Bohai Sea. These variations are attributable to thedifference of these areas in latitude and longitude and environment, especially in theaspects of primary productivity and the variations of water masses and the influenceof anthropogenic activity. Based on the average fluxes of VHCs and the area of theEast China Sea and the South Yellow Sea, the annual oceanic emissions of CHCl₃,C₂HCl₃, C₂Cl₄, CHBr₂Cl and CHBr₃are estimated to be0.45Gg Cl yr^-1,0.17Gg Clyr^-1,0.12Gg Cl yr^-1,0.23Gg Br yr^-1and0.71Gg Br yr^-1by LM86, respectively.Although the East China Sea and the South Yellow Sea occupies only0.27%of thetotal world ocean area, the contribution of the East China Sea and the South YellowSea to the global oceanic emissions of CHCl₃, C₂HCl₃, C₂Cl₄, CHBr₂Cl and CHBr₃isestimated to be1.4%,8.5%,6%,5%and0.8%, respectively, which means that thecoastal shelf regions may contribute significant amount to the global oceanicemissions of these gases.更多还原