Marine Photochemistry: Particles versus Solutes

有机物的光化学转化对海洋中碳、氮和微量气体的循环有着深远的影响。以往对海洋光化学的研究主要集中在溶解有机物(DOM)，对颗粒有机物(POM)的研究较少。然而，我们和其他实验室的初步测试表明，基于POM的光化学通量具有生态和环境意义。这项拟议研究的首要目标是评估POM光降解对海洋碳、氮和痕量气体循环的影响。通过对溶解有机碳(DOC)、有色DOM(CDOM)、一氧化碳(CO)、溶解无机碳(DIC)和氨(NH3)这五种主要光产物的研究，本研究试图1)量化作为POC汇和DOC和CDOM源的POM光降解，并评估它们的季节和区域变化；2)量化POM光降解作为DIC、CO和NH3的来源，并评价它们的季节和区域变化；3)评估颗粒物类型(陆地和海洋)和环境变量(水温、pH和盐度)对这些POM光过程的影响；4)阐明了基于POM的DIC、CO和NH3的光产生相对于相应的基于DOM的光产生术语的意义。将在河口、沿海和公海水域的不同地理区域进行实地研究。实地调查的结果将通过建立POM光过程与环境变量之间的定量经验关系而外推到区域范围。通过探索一个迄今很少被探索的具有潜在巨大生物地球化学重要性的区域，这项拟议的研究有望创造出化学海洋学、海洋生态学和海洋光学之间相互关联的新的研究领域。它将填补我们对POM和DOM光化学在海洋水域碳、氮和痕量气体循环中的作用以及它们对海洋生态系统功能的影响的理解方面的空白。

Photochemical transformations of organic matter have profound influences on the cycling of carbon, nitrogen, and trace gases in the ocean. Previous studies of marine photochemistry have mostly focused on dissolved organic matter (DOM) with little attention paid to particulate organic matter (POM). Preliminary tests in our and other laboratories, however, suggest that POM-based photochemical fluxes are of ecologically and environmentally significance. The overarching goal of this proposed research is to evaluate the impacts of POM photodegradation on marine cycles of carbon, nitrogen, and trace gases. Through studying five key photoproducts, dissolved organic carbon (DOC), colored DOM (CDOM), carbon monoxide (CO), dissolved inorganic carbon (DIC), and ammonia (NH3), this research program will seek to 1) quantify POM photodegradation as a sink of POC and as sources of DOC and CDOM and evaluate their seasonal and regional variability; 2) quantify POM photodegradation as sources of DIC, CO, and NH3 and evaluate their seasonal and regional variability; 3) assess the influences of particle type (terrestrial vs. marine) and environmental variables (water temperature, pH, and salinity) on these POM photoprocesses; 4) elucidate the significance of POM-based photoproduction of DIC, CO, and NH3 relative to the corresponding DOM-based photoproduction terms. Field studies will be carried out in diverse geographical regions covering estuarine, coastal, and open-ocean waters. Results from the filed surveys will be extrapolated to regional scales by establishing quantitative empirical relationships between the POM photoprocesses and environmental variables. By exploring a heretofore little explored area with potentially great biogeochemical importance, this proposed research is expected to create new research niches interrelating among chemical oceanography, marine ecology, and ocean optics. It will fill in gaps in our understanding of the roles of POM and DOM photochemistry in the cycling of carbon, nitrogen, and trace gases in marine waters and hence of their impacts on the functioning of marine ecosystems.