TOWARD AN IMPROVED UNDERSTANDING OF AIR-SEA EXCHANGE OF GASEOUS ORGANIC CARBON AND ITS ROLE IN OCEAN CARBON FLUXES

长期以来，大气沉积一直被认为是海洋中异地氮、各种微量元素和特定有机化合物的重要来源。然而，目前输入到海洋的大气有机碳总量的大小和形式基本上是未知的。其中一个原因是，有机碳的气-海气体交换直到最近才被认为是具有全球意义的潜在来源，有机气体沉积估计超过了干湿大气沉积和有机碳向海洋的河流通量。大量大气输入的生物活性有机碳也可能足以解释观察到的亚热带东北大西洋和其他偏远海洋系统的净异养活动。因此，可以合理地断言，海-气沉积可能是海洋油气藏和活性有机质藏有机碳的一个重要来源。此外，人为排放的有机气体对当今大气的贡献可能代表着早期有机碳大量涌入海洋。在这个项目中，弗吉尼亚海洋科学研究所的研究人员将开发和验证稳健的方法来测量空气中和海水中溶解的三个可操作定义的有机碳池，以便能够定量地确定每个有机碳池的气-海气体通量。工作假设是，有机碳向海洋的气体沉积比湿大气和干大气沉积通量高一个数量级以上，大气输入在数量上类似于并可能超过河流向海洋输入的有机碳。气-海传质系数的计算表明，根据气态有机碳的气水分配特性来区分气态有机碳对于准确地量化这一不同类型的可交换有机碳的海气通量是至关重要的。为此，将开发技术来分别评估空气和地表水中挥发性、半挥发性和水溶性挥发性有机化合物。大量有机化合物测量将辅以气/液色谱分析，以评估有机化合物在每个操作定义的相中的分布，并在可能的情况下识别特定的有机化合物或化合物类别。还将在大西洋西北部的河口、沿海和开阔海域进行初步采样和有机碳气体通量估计。就更广泛的影响而言，该项目将包括教育和社区推广，并将有助于更全面地了解人类活动可能如何改变海洋中的有机碳清单。研究生、本科生和高中生，包括代表性不足群体的成员，将通过弗吉尼亚海洋科学研究所(VIMS)正在进行的几个教育项目招募工作，这两个PI都参与了该项目。将通过参加VIMS海洋科学日的实践活动、讲座和展示来实现社区推广，VIMS海洋科学日是一个年度活动，2006年有1800人参加(52/48%的儿童/成人)。拟议的研究还将有助于正在进行的国家和国际海洋碳通量方案，包括百慕大时间序列(BATS)、海洋通量方案(OFP)和表层海洋？低层大气研究(SOLAS)。

Atmospheric deposition has long been recognized as an important source of allochthonous nitrogen, various trace elements, and specific organic compounds to the oceans. However, at present the magnitude and forms of total atmospheric organic carbon (OC) inputs to the oceans are essentially unknown. One reason for this is that air-sea gas exchange of OC has only recently been recognized as a potential source of global significance, with organic gas deposition estimates exceeding both dry and wet atmospheric deposition and riverine fluxes of OC to the oceans. Large atmospheric inputs of biologically reactive OC may also be sufficient to account for the observed net heterotrophic activity of the subtropical northeast Atlantic and other remote marine systems. Thus, would be reasonable to assert that air-sea gas deposition may be an important source of OC to ocean reservoirs and reactive organic matter pools. Moreover, the contribution of anthropogenic emissions of organic gases to the present-day atmosphere may represent a significant influx of pre-aged OC to the oceans.In this project, researchers at the Virginia Institute of Marine Science will develop and validate robust methods for measuring three operationally defined OC pools in air and dissolved in seawater, so that the air-sea gas fluxes for each OC pool can be quantitatively determined. The working hypothesis is that gas deposition of organic carbon to the oceans is more than an order of magnitude higher than wet and dry atmospheric deposition fluxes, and that atmospheric inputs are similar in magnitude to, and may exceed, riverine inputs of organic carbon to the oceans. Calculations of air-sea mass transfer coefficients demonstrate that it is critical to distinguish gaseous OC according to its air-water partitioning properties in order to accurately quantify air-sea gas fluxes of this diverse pool of exchangeable OC. To this end, techniques will be developed to separately evaluate volatile, semi-volatile and water-soluble volatile OC in air and surface waters. Bulk OC measurements will be supplemented with gas/liquid chromatography analysis to evaluate the distribution of OC in each operationally defined phase, and to identify specific organic compounds or compound classes where possible. Preliminary sampling and OC gas flux estimates will also be conducted in estuarine, coastal, and open ocean waters of the northwestern Atlantic Ocean.In terms of broader impacts, the project will include education and community outreach, and will help formulate a more complete understanding of how human activity may be modifying OC inventories in the ocean. Graduate, undergraduate and high school students, including members of under-represented groups, will be recruited to work on this project through several ongoing educational programs at the Virginia Institute of Marine Science (VIMS) in which both of the PIs participate. Community outreach will be achieved through participation in hands-on activities, lectures, and displays at VIMS Marine Science Day, an annual event, which was attended by 1800 people in 2006 (52/48% children/adults). The proposed study will also contribute to ongoing national and international ocean carbon flux programs, including the Bermuda Time Series (BATS), the Ocean Flux Program (OFP), and the Surface Ocean ? Lower Atmosphere Study (SOLAS).