Low Molecular Weight Carbonyls in Seawater: Formation Via Photochemical Processes and Role in the Chemistry of Humic Substances

MOPPER光引发反应在海洋的化学和生物过程中起着重要的作用，包括氧化还原反应、碳循环和光抑制。尽管光化学过程很重要，但对于海洋DOM中负责产生海洋DOM中反应位点的光化学途径和反应位点几乎一无所知，这些反应位点负责产生海洋表面的反应瞬态。重点将从海洋碳循环转移到研究LMW羰基化合物光化学形成的前体和机制，以及海洋DOM和DOM分离物（例如腐殖质）的OH自由基。一些关键的问题是：LMW羰基化合物和OH自由基主要是由初级还是次级光过程形成的？氧化剂（例如O2、超氧化物过氧化物）在海水中这些物种的光合作用中扮演什么角色？海水中DOM荧光（和吸光度）的光漂白是否伴随着腐殖质的实际损失，还是仅仅是显色性部分的损失？海洋DOM池是否可以物理分解为光反应（腐殖质）和光不反应部分？海洋DOM中发色性位点的性质是什么？该研究将为海洋DOM的光化学、化学和光谱性质提供新的基础信息。

9315821 MOPPER Light-initiated reactions play important roles in chemical and biological processes in the sea, including redox reactions, carbon cycling and photoinhibition. Despite the importance of photochemical processes, almost nothing is known about photochemical pathways and reaction sites within marine DOM that are responsible for production of reactive sites within Marine DOM that are responsible for production of reactive transients at the sea surface. The focus will be shifted from oceanic carbon cycling to the study of precursors and mechanisms involved in the photochemical formation of LMW carbonyl compounds and OH radicals form marine DOM and DOM isolates, e.g., humic substances. Some of the key questions are: Are LMW carbonyl compounds and OH radicals formed mainly by primary or by secondary photoprocesses? What is the role of oxidants, e.g., O2, superoxide peroxides, in the photoproduction of these species in seawater? Is photobleaching of DOM fluorescence (and absorbance) in seawater accompanied by an actual loss of humic substances or only of chromophoric moieties? Can the marine DOM pool be physically fractionated into photoreactive (humic) and photo-unreactive fractions? What is the nature of the chromophoric sites within marine DOM? This study will provide new basic information on the photochemical, chemical, and spectroscopic properties of marine DOM.