Photochemical Oxygen Consumption in Marine Waters

海洋氧化光化学反应是陆地来源的DOM修饰和再矿化的重要步骤，具体例子和间接的机理证据都表明了这一点。重要的海洋派生DOM类也可能进入这个循环。该项目将通过(1)在灵敏度允许的情况下直接测量氧气吸收，以及(2)使用对“蓝水”和低反应性沿海水研究足够敏感的间接方法，将总光氧化过程量化为氧气消耗。该结果将为光氧化在海洋碳氧循环中的作用提供急需的定量评价。与DOM氧化密切相关的耗氧量将在沿海和河口水域以及疏水吸附浓缩的有机物中进行测量。直接氧摄取将使用脉冲极谱电极与自动数据采集来测量。一种灵敏的新间接技术，根据经验对直接测量进行校准，将量化“蓝色”和低活性沿海水域中主要耗氧物种的通量。研究了波长、光强、温度、氧浓度和长时间光解等变量对O2消耗率的影响，以了解它们的（生物）地球化学意义，并确定涉及O2摄取/C再矿化的主要机制。

Oxidative marine photochemical reactions are an important step in modifying and remineralizing terrestrially-derived DOM, as shown in individual examples and indirect mechanistic evidence. Important classes of marine-derived DOM probably also enter this cycle. This project will quantify total photooxidative processes as oxygen consumption, by (1) direct O2 uptake measurements where sensitivity permits, and (2) using an indirect method sensitive enough for "blue water" and for low-reactivity coastal water studies. The results will provide much-needed quantitative evaluation of the role of photooxidation in oceanic carbon and oxygen cycles. Oxygen consumption, closely related to DOM oxidation, will be measured in coastal and estuarine waters and in organic matter concentrated by hydrophobic adsorption. Direct O2 uptake will be measured using pulsed polarographic electrodes with automated data acquisition. A sensitive new indirect technique, calibrated empirically against direct measurements, will quantify fluxes of the primary O2 -consuming species in "blue" and low-activity coastal waters. Effects of variables such as wavelength, light intensity, temperature, oxygen concentration, and prolonged photolysis on O2 consumption rates will be investigated to understand their (bio) geochemical significance and to identify the major mechanisms involved in O2 uptake/C remineralization.