Collaborative Research: Influences of Atmospheric Deposition, Organic Complexation and Photochemical Processes on the Redox Cycle of Iron in Surface Waters

铁的生物有效性限制了高营养、低叶绿素地区浮游植物的生产力。海洋微生物对铁的吸收似乎受到溶解铁的氧化还原和溶液形态的强烈影响，但对影响海洋铁化学和生物有效性的光化学还原、胶体形成和有机络合等物理化学过程知之甚少。为此，首席调查人员建议开展一系列以过程为导向的研究，以调查(1)墨西哥湾(GOM)100米以上铁的光化学和热化学氧化还原循环；(2)湿(降雨)和干(气溶胶)沉积提供的溶解铁的氧化还原形态，以及沉积后最初几个小时内发生的物理化学变化；(3)开放寡养GOM中胶体和低分子量溶解有机配体对Fe(III)的络合和潜在还原作用，包括天然硅藻水华、有害藻类(甲藻)水华和河流输入的陆生水生有机配体。预计这项研究的结果将进一步加深我们对铁的分布和形态调控的非生物、无机过程的理解，并提供模拟海洋铁循环所需的数据。

ABSTRACTOCE-9911339OCE-0000351Phytoplankton productivity in high nutrient, low chlorophyll areas is limited by the bioavailability of iron. Iron uptake by marine microorganisms appears to be strongly influenced by the redox and solution speciation of dissolved Fe, yet very little is known about the physical-chemical processes such as photochemical reduction, colloid formation, and organic complexation that affect Fe chemistry and bioavailability in the oceans. For this reason, the principal investigators propose to undertake a set of process-oriented studies to investigate (1) the diel photochemical and thermochemical redox cycling of Fe in the upper 100 meters of the Gulf of Mexico (GOM); (2) the redox speciation of dissolved Fe supplied by wet (rainfall) and dry (aerosol) deposition, and the physical-chemical transformations that occur within the first few hours following deposition; and (3) the complexation and potential reduction of Fe(III) by colloidal and low molecular weight dissolved organic ligands in the open oligotrophic GOM, and including ligands from natural diatom blooms, harmful algae (dinoflagellate) blooms, and from riverine input of terrestrial aquatic organic ligands. It is expected that results from this study will further our understanding of the abiotic, inorganic processes regulating the distribution and speciation of Fe, as well as provide data required to model oceanic Fe cycling.