Improved microbial reduction of biogenic and abiogenic goethite by diesel soot

Abstract

The biogeochemical cycling of iron is crucial to plenty of environmental processes, and is often influenced by black carbon with high electrical conductivity and abundant functional groups. This study for the first time revealed that diesel particulate matter (DPM), a typical black carbon material which often caused serious environmental effects, could significantly promote dissimilatory reduction of both abiogenic and biogenic goethite (CGt and BGt) by Shewanella oneidensis MR-1. In 7 days, Fe(II) production in CGt systems containing 0.5, 5, 10, 25, and 50 mg/L of DPM were 1.2, 1.3, 1.8, 1.9, and 2.7 folds higher than that in the system without DPM (0.12 mM), respectively. During the bioreduction of BGt, Fe(II) concentrations were 2.4–3.4 folds higher than those in the CGt systems, and were increased by 4.8%− 41.7% with the addition of 0.5–50 mg/L DPM. X-ray diffraction (XRD) analysis demonstrated that goethite was the sole mineralized product during the bioreduction of CGt, while vivianite appeared gradually during the microbial transformation of BGt. DPM enhanced electron transfer between cells and goethite via serving as electron shuttles. The results of this study would improve our understanding of interactions among microbes, natural minerals, and black carbon in the natural environments.