Behaviors of nitrogen, iron and sulfur compounds in contaminated marine sediment

Abstract

The marine sediment sustains from the anoxic condition due to increased nutrients of external sources. The nutrients are liberated from the sediment, which acts as an internal source. In hypoxic environments, anaerobic respiration results in the formation of several reduced matters, such as N2 and NH4 + , N2O, Fe 2+ , H2S, etc. The experimental results have shown that nitrogen and sulfur played an influential, notable role in this biogeochemical cycle with expected chemical reductions and a 'diffusive' release of present nutrient components trapped in pore water inside sediment toward the bulk water. Nitate/ammonium, sulfate/sulfides, and ferrous/ferric irons are found to be the key players in these sediment-waters mutual interactions. Organonitrogen and nitrate in the sediment were likely to be converted to a form of ammonium. Reductive nitrogen is called dissimilatory nitrate reduction to ammonium and denitrification. The steady accumulation in the sediment and surplus increases in the overlying waters of ammonium strongly support this hypothesis as well as a diffusive action of the involved chemical species. Sulfate would serve as an essential electron acceptor so as to form acid volatile sulfides in present of Fe 3+ , which ended up as the Fe 2+ positively with an aid of the residential microbial community.

Anaerobic carbon oxidation in sediment of two Brazilian mangrove forests: the influence of tree roots and crab burrows

“…The excess DIC generated at OF may not be delivered solely by SR but can, as mentioned above, also be generated by fermentation of fatty acids (Valdemarsen and Kristensen, 2010). The shutdown of sediment Fe(III) availability and FeR by anthropogenic discharges has been observed in other mangrove environments, even in the presence of oxidizing biogenic structures (Penha-Lopes et al, 2010;Kraal et al, 2015;Khirul et al, 2020).…”