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

摘要：在缺氧区与大陆架接触的亚氧水柱下，沉积物中的有机碳浓度异常高。 虽然有几个因素被认为是负责这些高浓度，是一个正在进行的辩论的问题，一个机制来解释为什么相当大的一部分沉积有机物（OM）抵抗细菌降解，只有在亚氧水柱仍然缺乏。 PI建议研究墨西哥海岸沉积物中铁和OM之间的相互作用，以测试他们的前提，即沉积物中异常高的OM浓度是由内球Fe-OM络合和更不稳定的OM的“折射”造成的。 该科学小组认为，络合作用的发生是因为在络合作用发生的沉积层中没有大量动力学上更快的竞争物种，如O2，NO3-，IO 3-，Mn氧化物和HS-。 这项研究的结果将证明或反驳这种铁络合过程是否确实是一种可行的机制，以解释墨西哥海岸沉积物中异常高的OM浓度，以及提供竞争反应动力学的信息（即。O_2、NO_3 ~-、IO_3 ~-、Mn氧化物和HS ~-等）的存在导致了氧化、亚氧化和硫化物沉积物中Fe的形态变化。

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.