【作者】 杨洁；

【导师】 杨桂朋；

【作者基本信息】 中国海洋大学 ， 海洋化学， 2011， 博士

【摘要】 本文以中国近海有代表性的-东海、黄海、渤海和南海为研究目标,对这些海域中二甲基亚砜(DMSO)的溶解态(DMSOd)和颗粒态(DMSOp)的浓度分布特征、时空变化等进行了研究。并探讨了DMSO与环境因子(温度、盐度、营养盐等)和主要生态因子叶绿素a,以及相关的硫化物二甲基硫(DMS)、β-二甲基巯基丙酸内盐(DMSP)之间的相关关系。以初步了解DMSO浓度分布的影响因素以及在DMS生物地球化学循环中所起的作用。本论文的主要研究成果如下:1.在实验室中改进了海水中DMSO的分析方法,其检测限为0.75 nmol L-1 (40 mL样品),精密度为4%~5%,与国外同类方法相当。2.分别于2009年12~1月对东海、2010年6月和2010年11月对长江口附近海域海水中DMSOd和DMSOp进行了研究,结果表明:冬季东海表层海水中DMSOd和DMSOp的平均浓度分别为61.90±26.37和21.31±4.51 nmol L-1,夏季和秋季长江口附近海域的浓度分别为30.18±9.08、16.61±6.24和21.39±11.58、5.18±1.36 nmol L-1。由此可见,长江口DMSOd和DMSOp呈现出明显的季节变化,夏季高于秋季。在三个季节中表层海水DMSOd的浓度均表现出近岸高,远海低的趋势。在长江口附近呈现出明显的高浓度区,表明在长江口附近DMSOd的平面分布主要受到了长江冲淡水的影响。DMSOp的分布则呈现出不同的规律性,在冬季,东海东北部呈现出由近岸向远海递增的趋势,可能是由于耐高盐、暖水性的甲藻等盛产DMSO藻种的增多引起的,也有可能是由于温度的升高所引起的,主要归咎于DMSO的抗氧化作用。夏季DMSOp的分布主要是由盐度和浮游植物的种类共同决定的。秋季DMSOp的分布趋势与Chl-a的分布趋势类似,这主要可能是由于秋季硅藻占有绝对优势所引起的。由于东海复杂的水文条件,以及藻种组成的差异,从而造成在冬季和夏季DMSOp与Chl-a之间没有任何相关性,只有在秋季两者之间具有显著的相关性。DMSOp/Chl-a的比值夏季明显高于秋季,是秋季的3.41倍,这主要是由于藻种的不同所引起的。DMSOp/Chl-a的比值在冬季东海东北部与温度有着较好的线性相关性,而在夏季和秋季的相关性不明显。在夏季DMSOp/Chl-a与溶解无机氮(DIN)有着弱的负相关性,与盐度有着较好的正相关性,表明DMSO在细胞内可能会起着渗透压调节的功能。夏季DMSOd和NO3-、溶解有机碳(DOC)以及细菌数量均具有很好的相关性,而与DMSOp没有任何相关性,该结果表明DMSOd主要来源于DMS的光化学氧化和细菌氧化,而非DMSOp。另一方面,也可能说明了DMSOd与NO3-和DOC之间有着相似的来源,即长江冲淡水人为输入造成的。在秋季DMSOd与这些参数之间均没有任何线性相关性,表明DMSOd的来源相对比较复杂,不是以其中任何一个来源为主。但在两个季节中DMSOd与盐度之间均表现出较好的负相关性。冬季东海垂直分布中,DMSOd的最大值一般出现在上层水体2~25 m处,主要可能是由于UV光的照射对DMS的光化学氧化和浮游植物细胞内DMSO的释放具有促进作用,因此DMSOd的浓度会随着深度的增加而减少。DMSOp的最大值一般出现在底层,主要可能是在冬季,水体的垂直混合比较剧烈,导致沉积物的再悬浮从而造成了DMSOp值的增大。周日变化中DMSOp的最大值出现在中午附近,可能是由于其抗氧化作用导致的。DMSOd的最大值出现在夜间0:00,在白天的浓度相对较低,该结果表明白天DMSOd也存在消耗过程。3.于2010年4-5月(春季)和2010年9月(秋季)对中国黄海、渤海表层海水中DMSOd和DMSOp的时空分布及变化特征进行了研究。DMSOd和DMSOp在春季和秋季的浓度分别为16.99±1.96、17.67±2.24和10.45±1.77、17.20±3.54 nmol L-1。由此可见黄海、渤海水体中春季和秋季表层水体中DMSOd呈现明显的季节变化,春季高于秋季,而DMSOp的浓度季节变化不明显,春季略高于秋季。两个季节中,DMSOp与Chl-a都存在很好的线性相关性,表明浮游植物生物量在控制黄海、渤海DMSO的生产分布中起着重要的作用。并且春季和秋季所有站位的DMSOp与Chl-a之间仍然具有很好的相关性。DMSOd与Chl-a在春季有着较好的相关性,而在秋季不存在相关性,表明在两个季节DMSOd的主要来源有所区别。并且在春季,DMSOd与DMSOp之间存在很好的相关性,进一步说明了在春季细胞内DMSO的释放是DMSOd主要的源;在秋季,DMSOd与细菌数量有着较好的相关性,表明在秋季,DMS的细菌氧化可能是DMSOd主要的源。DMSOd在秋季与盐度之间存在显著的负相关性,与夏季和秋季东海航次的结论一致。DMSOd与温度(T)、盐度(S)、NO3-、DOC等其它环境因子之间的相关性均不显著,这可能与DMSOd复杂的来源及消耗有关。黄海、渤海春季和秋季DMSOp/Chl-a的比值变化不明显,春季略高于秋季,可能是由于在两个季节中都是硅藻占有绝对优势的原因。DMSOp/Chl-a的比值除了在秋季与盐度有着很好的正相关性外,与东海夏季的结论一致。未发现其与其它的环境因子如T、S、营养盐之间有任何的相关性。表明DMSOp/Chl-a的比值是受众多因素作用的结果。4.于2010年2月期间对冬季南海进行的大面调查,获得了南海DMSO的平面分布、影响因素等方面初步的认识。DMSOd和DMSOp在表层海水中的平均浓度分别为49.97±16.47和11.08±2.20 nmol L-1。南海表层海水中DMSOd的平面分布呈现出近岸高,远海低的趋势,在珠江入海口附近出现异常高值,表明了入海径流对DMSOd分布的影响。DMSOp的平面分布也呈现出近岸高远海低的趋势,除了受浮游植物种类的影响外,浮游植物数量也起着一定的作用,有的近岸站位沉积物的再悬浮也可能是造成DMSOp较高的原因。表层海水中DMSOp/Chl-a的比值变化范围较大,可能是由藻的种类以及粒径决定的。DMSOp/Chl-a最大值出现在甲藻和金藻(球石藻)占比例较大的海域,表明甲藻和金藻(球石藻)可能是盛产DMSO的主要藻种。DMSOp和Chl-a之间不存在任何线性相关性,进一步说明了不同的藻种产生DMSO的能力差别较大。表层海水中DMSOd和DMS之间不存在任何相关性,表明DMS可能不是DMSOd主要的源。在远离近岸的站位,DMSOd和DMSOp之间具有显著的相关性,表明DMSOp可能是DMSOd重要的来源。更多还原

【Abstract】 The spatial and temporal variations of distributions of DMSO were studied in the East China Sea (ECS), the Yellow Sea (YS), the Bohai Sea and the South China Sea (SCS). In order to obtain a preliminary feature of DMSO biogeochemistry, the possible relationships between the dimethyl sulfur compounds and the environmental factors such as temperature and salinity were also investigated. The main research results were summarized as follows:(1) A method of chemoreduction-purge-and-trap followed by gas chromatographic analysis for the determination of trace dimethylsulfoxide (DMSO) in seawater has been developed. It has a DMSO detection limit of 2.7 pmol of sulfur, corresponding to a concentration of 0.75 nM for a 40 mL sample, and has a precision of 4%~5%.(2) Distributions of DMSO were determined in the ECS from December 2009 to January 2010 and in the waters adjacent to the Yangtze Estuary in June and November 2010. The results showed that the average concentrations of DMSOd and DMSOp in the surface waters of the ECS wer 61.90±26.37 and 21.31±4.51 nmol L-1,respectively. In the waters off the Yangtze River Estuary, those were 30.18±9.08 and 16.61±6.24 nmol L-1 in summer, 21.39±11.58 and 5.18±1.36 nmol L-1 in autumn, respectively. In general, average concentrations of DMSOd and DMSOp in the ECS showed obvious seasonal variations, with higher values in summer and lower values in autumn. In the three studied seasons, the horizontal distributions of DMSOd in the ECS were obviously influenced by the Yangtze River, where high concentrations of DMSOd appeared around the mouth of it, and it decreased from inshore to offshore stations. The distribution patterns of DMSOp were compared in different seasons. In winter, it increased offshore in the northeast ECS due to the increasing temperature coupled to the change of phytoplankton species, but decreased offshore in the southwest ECS due to the poor DMSO-producer phytoplankton species in the open sea. In summer, DMSOp distributions did not show the same pattern as Chl-a which could be attributed to the seasonal change in phytoplankton community structure coupled with salinity. In autumn, DMSOp and Chl-a displayed a similar distribution pattern ascribed to the dominance of diatoms. No correlation between DMSOp and Chl-a was observed in winter and summer, while significant relationship between them was found in autumn.The ratios of DMSOp to Chl-a exhibited obvious seasonal variations, with an average value 3.41 times higher in summer than in autumn. DMSOp/Chl-a ratio correlated significantly with temperature in the northeast ECS in winter, while no relationship between them was found in summer and autumn. In summer, DMSOp/Chl-a was correlated with dissolved inorganic nitrogen and salinity, indicating that DMSO might act as an osmolyte in algal cells, while no relationship was found in autumn. DMSOd was correlated significantly with NO3-, dissolved organic carbon (DOC) and bacterial abundance in summer, but no correlation with DMSOp, indicating that DMSOd was mainly from photo-oxidation and bacterial oxidation of DMS rather than from DMSOp. DMSOd may have the same source as those materials such as the inputs of continent-derived organic matter via Yangtze River. In autumn, no relationship between DMSOd and those parameters was found, suggesting that the source of DMSOd was complicated and none of those parameters was a major source for DMSOd. Both in summer and autumn DMSOd and salinity had a significant negative relationship.The vertical profiles of DMSOd and DMSOp did not exhibit the same pattern. The maximum DMSOd was present at the depth of 2~25 m. Photochemical and biological oxidation of DMS together with the exudation of DMSO by phytoplankton might contribute to the high levels of DMSO observed near the surface. In contrast, the maximum DMSOp appeared at the bottom, probably due to the release of resuspending sediments. DMSOp and DMSOd exhibited a strong diurnal variation in the surface seawater. The highest DMSOp concentration appeared around noontime and then decreased sharply, presumably due to its antioxidant function. The DMSOd concentrations were much lower in the daytime than in the night, suggesting that there were significant loss processes of DMSOd such as microbial consumption and photo-oxidation during the daytime.(3) Distributions of DMSOd and DMSOp were determined during two cruises in the YS and the Bohai Sea in April and September 2010. The average concentrations of DMSOd in the surface waters in the two cruises were 16.99±1.96 and 10.45±1.77 nmol L-1; those of DMSOp were 17.67±2.24 and 17.20±3.54 nmol L-1, respectively. The average concentrations of DMSOd showed obvious seasonal variations, with the higher value in spring than in autumn, while seasonal variations of DMSOp were not distinct. The distribution patterns of DMSOp were controlled mainly by the phytoplankton biomass, with high DMSOp concentrations appearing in the waters containing high Chl-a levels.DMSOp and Chl-a had significant relationships in these two seasons, and even had significant relationships at all stations in two seasons, indicating that phytoplankton biomass might play a major role in controlling the distributions of DMSOp in the study area. In spring DMSOd was correlated with Chl-a, and had a significant relationship with DMSOp, suggesting that DMSOp might be the major source for the DMSOd in the surface water. In autumn, DMSOd was not correlated with Chl-a and DMSOp, but correlated with bacterial abundance, indicating that the bacterial oxidation of DMS might be responsible for the source of DMSOd. The relationship between DMSOd and other environmental factors such as temperature, NO3- and DOC concentrations was not found, which might be due to the complex production and consumption of DMSO.The seasonal variation of DMSOp/Chl-a was not distinct, because the phytoplankton were dominated by diatoms in these two seasons. In autumn, DMSOp/Chl-a and salinity had a significant relationship, similar to the results in the ECS in summer. No relationship between DMSOp/Chl-a and other environmental factors such as temperature, salinity and nutrients was found, suggesting that the biosynthesis of DMSO was influenced by many complex factors.(4) Distributions of DMSOd and DMSOp were investigated in the surface water of the SCS in January 2010. The average concentrations of DMSOd and DMSOp were 49.97±16.47 and 11.08±2.20 nmol L-1, respectively. The distribution of DMSOd was obviously influenced by Pearl River effluent, with high concentrations around the mouth of the river. The concentrations of DMSOp also decreased in the offshore direction due to the variation of phytoplankton biomass and the phytoplankton species composition. At the inshore stations the resuspending sediments might also account for the high DMSOp concentrations.The DMSOp/Chl-a ratios varied in a large range due to the different phytoplankton species. The three highest DMSOp/Chl-a values appeared at the offshore stations where Dinophyta and Chrysophyta (coccolithophores) were the dominant algal species indicating that these algal may the main DMSO producers. In the surface water DMSOd and DMS did not correlate significantly, indicating that in winter DMS was not the major source for DMSOd. At the offshore stations (depth> 50 m), DMSOd correlated significantly with DMSOp, suggesting that DMSOp might be the major source of DMSOd. No relationship between DMSOp and Chl-a, DMSOp and DMSPp was found in the SCS.更多还原