【作者】 高学鲁；

【导师】 宋金明；

【作者基本信息】 中国科学院研究生院（海洋研究所） ， 海洋化学， 2005， 博士

【摘要】 作为地球表面最大的碳库,海洋在全球碳循环中发挥着重要作用,并在一定程度上决定了全球气候变化与全球海洋生态系统的变化走势。海水中溶解无机碳占海水总碳的85%以上,其变化趋势对海洋碳循环有异常重要的影响,因此,系统研究海水中溶解无机碳的生物地球化学特征是揭示海洋碳循环关键过程的基础,海水中溶解无机碳的研究意义重大。 本论文选择典型的陆架边缘海——长江口海域与南黄海海域,分别于 2003 年 5 月2004 年 8 月（长江口枯水与丰水季节）和 2004 年 10 月（南黄海的秋季）进行了海洋碳循环的专项调查研究,获得了包括水文、化学、生物在内的丰富样品和资料。以此为基础,比较系统地对长江口和南黄海海域水体中溶解无机碳的行为及生物地球化学特征进行了研究,确定了这两个海域作为大气二氧化碳的源/汇格局,并首次估算了长江口整个盐度梯度范围的海?气间二氧化碳通量,对这两个典型海域的无机碳化学有了一系列新的认识。 1. 在枯水季节,长江口海域由低盐区大气二氧化碳的强源逐渐过渡到高盐区的弱汇,咸淡水的混合在一定程度上决定了该区域碳源汇的格局;二氧化碳源区,浮游植物的丰度低,浮游动物主要是纯河口类群和河口性海洋类群,而汇区,浮游植物的丰度高,浮游动物主要是广盐性海洋类群。长江口丰水季节为大气二氧化碳的净源,溶解无机碳体系基本呈现枯水季节淡水区-混合区的特征。 调查期间,长江口淡水水团和混合水团西部水体混合均匀,属于均匀混合型;其他区域基本属于部分混合型。对水体 pH 值、总碱度（TA）、总二氧化碳（TCO₂）、二氧化碳分压（pCO₂）及 CO₂ 体系各分量(HCO₃^-、CO₃^2-和 CO_2（T）时空变化特征的研究表明,长江口区 CO₂体系各参数均表现出显著的时空变化特征,咸淡水的的物理混合作用是 TA、TCO₂和 HCO₃^-空间分布特征最主要的影响因素;而其他几个参数的空间分布,除了不同水团间的物理混合作用的影响,生物活动的影响也很显著。对于大多数参数,影响其随时间变化的主要因素因区域的不同而不同。pCO₂ 的空间分布总体上呈由淡水向海水逐渐降低的趋势。长江口淡水和低盐水体具有很高的 pCO₂ 值,表层水盐度<25的区域为大气CO₂的源。海-气间CO₂交换通量的变化范围为-5.8至531.5 mmol m^-2 d⁽-1_。徐六泾至口门的河口区调查过程中每天向大气中释放的 CO2的量为（7.0 ± 2.8） × 103 tC。 浮游植物和浮游动物是能够显著影响水体中溶解无机碳生物因素,因此调查过程中也对它们进行了一些研究。结果表明,浮游植物丰度呈现出显著的空间差异性,总体上沿长江径流入海方向增加;优势种随盐度的变化而变化。浮游植物丰度和 PO43??P 浓度之间的关系进一步证实了长江口透明度较高的区域,磷是浮游植物生长的限制因子;和颗粒有机碳之间的关系进一步证实了陆源输入是长江口区颗粒有机物的主体。浮游动物生物量的时间变化与潮汐有关,总体上在涨潮和退潮过程中分别呈增加和降低的趋势。更多还原

【Abstract】 As the biggest carbon reservoir on the earth surface, the oceans play a dominant role in the natural regulation of CO₂ in the atmosphere, thus exerting a powerful influence on the climate and marine ecosystem. Dissolved inorganic carbon （DIC） accounts for >85% of the total carbon in seawaters and its variability has significant influence on marine carbon cycling. So, to study DIC in seawaters systematiclly is the basis for a better understanding of the key processes of marine carbon cycling. Two typical marginal seas, namely the Changjiang Estuary and the southern Yellow Sea, were chosen as our study sites. Field observations were carried out in May 2003 and August 2004 in the Changjiang Estuary, and in October 2004 in the southern Yellow Sea. Abundant data of hydrography, chemistry and biology were gained, based on which the behaviour and biogeochemical characteristics of DIC in seawaters of these two areas were investigated. Carbon dioxide fluxes between air-sea interfaces were estimated for the first time throughout the entire salinity gradient in the Changjiang Estuary. Some new knowledge about inorganic carbon chemistry was acquired. 1. In the dry season, the Changjiang Estuary changed gradually from a strong source for atmospheric carbon dioxide in low salinity area to a weak sink in high salinity area. The physical mixing of fresh and salty water had significant influence on this carbon sink/source pattern. In the CO₂ source area, phytoplankton abundance was low and zooplankton mainly belonged to true estuary and estuary marine communities; while in the CO₂ sink area, phytoplankton was high and zooplankton mainly belonged to euryhaline marine communities. In the raniy season, the Changjiang Estuary was a net source for atmospheric CO₂, and the distribution characteristics of parameters related to DIC system were similar to those in fresh and mixed water areas in the raniy season. During the field observation, the Changjiang fresh water mass and the western turbidity maximum were well mixed, while partly mixed in other parts. Spatio-temporal variation characteristics of parameters related to carbon dioxide, i.e. pH, total alkalinity （TA）, total carbon dioxide （TCO₂）, partial pressure of carbon dioxide （pCO₂） and each of carbon dioxide species (HCO₃^-、CO₃^2- and CO_2（T）, were studied. The results indicated that physical mixing of different water masses was the most important factor influencing spatial distribution of TA, TCO₂ and HCO₃^-; while for the other parameters, the influence of biological activities on their spatial distribution was also significant besides the influence of physical mixing of different water masses. For most of the parameters, the main factors that influence their temporal variations were different in different regions. As a whole, p CO₂ decreased from the fresh water to seawater. The region where surface water salinity was below 25 was a source for atmospheric carbon dioxide, while the other region was a sink. Carbon dioxide fluxes between air-sea interface varied from -5.8 to 531.5 mmol m^-2 d^-1. The area between Xuliujing and river mouth emitted （7.0 ± 2.8） × 103 tC per day. Phytoplankton and zooplankton are biological factors that can significantly influence dissolved inorganic carbon in waters, so they were also studied during the investigation. Results indicated that phytoplankton abundance increased seaward, showing a distinct spatial difference, and the dominant species varied with salinity. Correlation between phosphorus and phytoplankton abundance further supported that phosphorus is the controlling factor in phytoplankton growth in the Changjiang Estuary where light is not; correlation between p articulate organic carbon and phytoplankton a bundance further proved the former results that a major fraction of particulate organic carbon in the Changjiang Estuary area was imported by Changjiang freshwater discharge from land. Variation characteristics in zooplankton biomass seemed to relate to tide cycles and in most cases increased during flood更多还原