Contamination of soils and aquifers with (poly)nitroaromatic compounds ((P)NACs) is a widespread problem. This work demonstrates that (P)NACs such as the explosive 2,4,6trinitrotoluene (TNT) can be completely reduced to the corresponding aromaticpolyamines by Fe(ll) present at the surface of Fe(Ⅲ)(hydr)oxides or, less efficiently, by hydroquinone moieties of (natural) organic matter in the presence of H{sub}2S. The reduction kinetics of (P)NACs were investigated in sterile batch systems as wellas in columns containing either FeOOH-coated sand and a pure culture of the iron-reducing bacterium Geobacter metallireducens or ferrogenic consortia in aquifer sediments. The relative reactivities as well as the competition behavior of (P)NACs in batchand column systems, respectively, correlated well with their one-electron reduction potentials, E{sup}1{sub}h, which we determined for TNT and its aminonitrotoluene transformation products. A similar reactivity pattern of (P)NACs was found irrespective of the processes that (re)generated the surface-bound Fe(Ⅱ), i.e., adsorption of Fe(Ⅱ) from aqueous solution or microbial reduction of Fe(Ⅲ)(hydr)oxides. The apparent stability of the toxic arylamine products under ferrogenic conditions may compromiseintrinsic attenuation as an acceptable remediation option for (P)NAC contaminated anoxic aquifers. Iron-reducing conditions would, however, be favorable as a first step in a two-stage anaerobic/aerobic treatment of PNAC contaminated sediments sincearomatic polyamines are biodegradable and/or bind irreversibly to the solid matrix under oxic conditions.
展开▼
