Transport and retention of colloid tracers were evaluated in standard petrographic thin sections, prepared from saprolite (Cr horizons) formed from fractured sedimentary rocks, using epi-fluorescence microscopy. Thin sections prepared from dismantled hydrogeological columns revealed four domains of macropores with apparent apertures ranging from 1 to 500 Am. Colloid retention occurred within bo...

The stimulation of subsurface microbial metabolism often associated with engineered bioremediation of groundwater contaminants presents subsurface microorganisms, which are adapted for slow growth and metabolism in the subsurface, with new selective pressures. In order to better understand how Geobacter species might adapt to selective pressure for faster metal reduction in the subsurface, Geob...

We studied the effects of humic substances (HS) on the sorption of Fe(II) onto Al-oxide and clay sorbents at pH 7.5 with a combination of batch kinetic experiments and synchrotron Fe K-edge EXAFS analyses. Fe(II) sorption was monitored over the course of 4 months in anoxic clay and Al-oxide suspensions amended with variable HS types (humic acid, HA; or fulvic acid, FA) and levels (0, 1, and 4 w...

Arsenic sorbs strongly to the surfaces of Fe(III) (hydr)oxides. Under aerobic conditions, oxygen acts as the terminal electron acceptor in microbial respiration and Fe(III) (hydr)oxides are highly insoluble, thus arsenic remains associated with Fe(III) (hydr)oxide phases. However, under anaerobic conditions Fe(III)-reducing microorganisms can couple the reduction of solid phase Fe(III) (hydr)ox...

The dissimilatory Fe(III) reducer, GS-15, is the first microorganism known to couple the oxidation of aromatic compounds to the reduction of Fe(III) and the first example of a pure culture of any kind known to anaerobically oxidize an aromatic hydrocarbon, toluene. In this study, the metabolism of toluene, phenol, and p-cresol by GS-15 was investigated in more detail. GS-15 grew in an anaerobic...

In this paper, a remote O2 ion source is used for the formation of nano-oxide layers. The oxidation efficiency was measured in CoFe-oxide films, and a decrease of the oxide layer with the pan angle and the oxidation pressure is observed. For the same oxidation pressure, the oxidation efficiency depends on the O2 content in the Ar–O2 plasma. These results were applied in optimizing the fabricati...

The unique active site of flavo-diiron proteins (FDPs) consists of a nonheme diiron-carboxylate site proximal to a flavin mononucleotide (FMN) cofactor. FDPs serve as the terminal components for reductive scavenging of dioxygen or nitric oxide to combat oxidative or nitrosative stress in bacteria, archaea, and some protozoan parasites. Nitric oxide is reduced to nitrous oxide by the four-electr...

The increases in atmospheric carbon dioxide (CO(2)) concentrations can enhance plant growth and change their nutrient demands. We report that when tomato (Lycopersicon esculentum 'Zheza 809') plants were grown in iron (Fe)-limited medium (with hydrous ferric iron oxide) and elevated CO(2) (800 microL L(-1)), their biomass and root-to-shoot ratio were greater than plants grown in ambient CO(2) (...