The Importance of Iron Complexation to Organic Matter Preservation in Suboxic Sediments

在缺氧带冲击大陆架的亚氧水柱下积累的沉积物中发现了异常高的有机碳浓度。尽管有几个因素被认为是造成这种高浓度的原因，并且正在进行辩论，但仍然缺乏一种机制来解释为什么相当大一部分沉积有机物(OM)只有在亚氧水柱下才能抵抗细菌降解。PIS建议研究墨西哥海岸沉积物中的铁和OM之间的相互作用，以检验他们的假设，即沉积物中异常高的OM浓度是由更不稳定的OM在球体内的Fe-OM络合和“再分解”造成的。这个科学团队认为，络合作用的发生是因为在发生络合作用的沉积层中没有大量动力学速度更快的竞争物种，如O2、NO3-、IO3-、Mn氧化物和HS-。这项研究的结果将证明或否定这种铁络合过程是否确实是解释墨西哥海岸沉积物中异常高的OM浓度的可行机制，并提供关于竞争反应动力学的信息(即。O_2、NO_3~-、IO_3~-、Mn_2O_3和HS_3~-)导致铁在含氧、次氧和硫化物沉积物中的存在。

ABSTRACTOCE-9911364Unusually high organic carbon concentrations are found in sediments accumulating under suboxic water columns where the oxygen-deficient zone impinges on the continental shelf. Although several factors are believed to be responsible for these high concentrations and are a matter of ongoing debate, a mechanism to explain why a substantial fraction of sedimentary organic matter (OM) resists bacterial degradation only under suboxic water columns is still lacking. The PIs propose to study interactions between iron and OM in sediments from the Mexican coast to test their premise that the unusually high OM concentrations in sediments result from inner-sphere Fe-OM complexation and "refractorization" of the more labile OM. This scientific team believes that the complexation takes place because of the absence of significant amounts of kinetically faster competing species such as O2, NO3-, IO3-, Mn oxides and HS- in the sedimentary horizon where complexation takes place. Results from this study will prove or disprove whether this iron-complexation process indeed is a viable mechanism to explain the unusually high OM concentrations in sediments on the Mexican coast, as well as provide information on the kinetics of competing reactions (ie. O2, NO3-, IO3-, Mn oxides and HS-) leading to the speciation of Fe in oxic, suboxic and sulfidic sediments.