Submitted to: Aquatic Geochemistry Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/18/2009
Publication Date: 9/1/2010
Citation: Uchimiya, M. 2010. Reductive transformation of 2,4-dinitrotoluene: roles of iron and natural organic matter. Aquatic Geochemistry. 16(4):547-562.
Interpretive Summary: Nitroaromatic compounds such as 2,4-dinitrotoluene are well known pollutants in surface soils of training ranges. This study investigated the effects of soil organic matter on the electron transfer interactions between 2,4-dinitrotoluene and ferrous iron, a naturally occurring reducing agent. Complex catalytic and inhibitory effects of soil organic matter was observed, depending on the ability of soil organic matter to reduce ferric iron, complex ferrous iron, and to produce reactive surface-associated ferrous iron.
Technical Abstract: This study investigated the effects of redox-active and iron-coordinating functional groups within natural organic matter (NOM) on the electron transfer interactions between Fe(II) and 2,4-dinitrotoluene (2,4-DNT), an energetic residue often encountered in aqueous environments as a propellant component and impurities in 2,4,6-trinitrotoluene (TNT). Experiments were first conducted in homogeneous phases as a function of pH in the presence of ligands that (1) complex iron (e.g., citric acid, oxalic acid), (2) complex and reduce iron (e.g., caffeic acid, ascorbic acid), and (3) humic substances with known carboxyl content and electron transfer capacity. Then, effects of these NOM components on Fe(II) reactivity in heterogeneous media were investigated by introducing goethite. Our results indicate complex catalytic and inhibitory effects of NOM components on the reaction between Fe(II) and 2,4-DNT, depending upon the ability of NOM component to (1) reduce dissolved and particulate Fe(III) (e.g., ascorbic acid), (2) form kinetically labile dissolved Fe(II) reductants (e.g., tiron and caffeic acid), and (3) produce surface-associated Fe(II) species that are accessible to 2,4-DNT.