Organic matter effect on Fe(II) oxidation kinetics in the Labrador Sea

Abstract

Abstract The Fe(II) oxidation rate was studied in one latitudinal and one longitudinal transect crossing the Labrador Sea. The studies considered the temperature, pH, salinity and total organic carbon (TOC) content. The pseudo-first-order kinetic rate, k′ (min−1), variability was controlled by temperature (77%) when recreating in situ conditions, by pHF (75%) at a fixed temperature of 15\u202f°C and by salinity and TOC (80%) when samples were fixed in both temperature and pHF 8. Sources and characteristics of TOC affected the oxidation of Fe(II). Organic matter produced positive and negative effects on the Fe(II) oxidation rate. A theoretical approach that considers the effect of inorganic interactions and temperature on oxidation kinetics was included to explain the effects of organic ligands on the Fe(II) oxidation rate. An empirical equation for the calculation of Fe(II) oxidation rate constants was obtained, considering the in situ conditions of temperature, pHF and salinity for the North Atlantic. This article is part of a special issue entitled: “Cycles of trace elements and isotopes in the ocean – GEOTRACES and beyond” - edited by Tim M. Conway, Tristan Horner, Yves Plancherel, and Aridane G. Gonzalez.