Microbial oxidation of Fe(II)-natural organic matter complexes

铁的形态，特别是铁（III）矿物和在铁（II）氧化过程中形成的溶解的铁（III）复合物的特性和性质，强烈影响吸附，从而影响砷、镉、铜和汞（Hg）等有毒元素的流动性和生物利用度，从而影响水、土壤和沉积物的质量。众所周知，铁（III）矿物的性质各不相同，1)取决于铁（II）是通过非生物氧化还是生物氧化（通过铁（II）氧化细菌），2)取决于天然有机物（如腐殖质化合物）的存在与否。然而，Fe(II)-氧化细菌是否能氧化含有天然有机物分子作为配体的Fe(II)-配合物尚不清楚。此外，在这种微生物氧化铁（II）络合物过程中形成的铁（III）化合物的特性和反应性尚不清楚。因此，本提案的目标是首先合成具有小有机配体和纯化黄腐酸和腐植酸的确定的铁(II)-有机物配合物。在第二步中，我们将确定嗜微氧、硝酸盐还原和光养铁（II）氧化细菌是否可以氧化这些铁（II）复合物。第三，我们将确定形成的Fe（III）化合物的身份、性质和反应性。最后，我们将从土壤中分离出Fe（II）复合物，并确定它们是否可以被Fe（II）氧化细菌氧化，以及在此过程中形成什么样的Fe（III）化合物。本提案的结果将最终增加我们对污染物的环境命运的认识。它将特别提高我们对铁(II)-氧化细菌和铁(II)-天然有机物复合物在形成与环境中污染物相互作用的活性铁（III）化合物中的作用的理解。

Iron speciation and in particular the identity and properties of Fe(III) minerals and dissolved Fe(III)-complexes formed during Fe(II) oxidation strongly impact sorption and thus the mobility and bioavailability of toxic elements such as arsenic, cadmium, copper and mercury (Hg) and thereby affect the quality of water, soils and sediments. It is known that the properties of Fe(III) minerals vary i) depending on whether the Fe(II) is oxidized abiotically or biotically (via Fe(II)-oxidizing bacteria) and ii) depending on the presence and absence of natural organic matter (e.g. humic compounds). It is unknown, however, whether Fe(II)-oxidizing bacteria can oxidize Fe(II)-complexes that contain natural organic matter molecules as ligands. Furthermore, the identity and reactivity of the Fe(III) compounds formed during such a microbial oxidation of Fe(II)-complexes are unknown.The objectives of the present proposal therefore are first to synthesize defined Fe(II)-organic-matter complexes with small organic ligands and purified fulvic and humic acids. In a second step we will determine whether microaerophilic, nitrate-reducing and phototrophic Fe(II)-oxidizing bacteria can oxidize such Fe(II) complexes. Thirdly, we will determine the identity, properties and reactivity of the Fe(III) compounds formed. Finally, we will isolate Fe(II) complexes from a soil and also determine whether they can be oxidized by Fe(II)-oxidizing bacteria and what kind of Fe(III) compounds are formed during this process. The results from the present proposal will ultimately increase our knowledge regarding the environmental fate of contaminants. It will in particular improve our understanding of the role of Fe(II)-oxidizing bacteria and Fe(II)-natural-organic matter complexes for the formation of reactive Fe(III) compounds that interact with contaminants in the environment.