Trinitrotoluene and Metabolites Binding to Humic Acid

Abstract

Systematic studies were conducted to observe the binding interactions between the class of compounds including nitroaromatic munitions pollutants trinitrotoluene (TNT) and certain of its breakdown products and dissolved Aldrich humic acid (HA), which is used as a model soil matrix. Equilibrium dialysis followed by HPLC quantitation was used to determine the effect of ligand concentration, HA concentration, pH, and ionic strength on the formation kinetics and ligand binding level of the ligand-HA complex. It was found that TNT and its byproducts 2,6-diamino-4-nitrotoluene (2,6DAmNT) and 2-amino-4,6-dinitrotoluene (2AmDNT) are all able to bind to HA at different binding levels in a slow kinetic process. The HA concentration was observed to have the same inverse effect on the binding of both TNT and 2,6DAmNT, while pH had opposite effects on binding for the two compounds. Nearly a 2-fold increase in binding of TNT to HA was observed for a 5-fold increase in ionic strength of phosphate buffer. A linear binding model represented the best fit for the 2,6DAmNT isotherm data while the Langmuir model best fit the TNT isotherms. The maximum binding density of TNT for HA calculated from the Langmuir model ranged from 6 to 30 µM TNT/µM HA of average size 5000 for all conditions studied. These facts suggest that the binding mechanisms are different for the above two ligands due to their different chemical structures.

Biotransformation of pink water TNT on the surface of a low-cost adsorbent pine bark

“…Moreover, the increasing discrepancy between the TNT input and the summarized output molar concentrations of TNT and its metabolites (ADNTs and DANTs) throughout the experiment suggests that the binding increased with the biotransformation progression. This is in line with earlier studies reporting more efficient binding with the increased number of amino groups in the aromatic ring (Daun et al 1998;Li et al 1997). By the end of experiment the biotransformation stage of TNT in batches E and F was similar to that of the non-inoculated batch D (Fig.…”

An in Situ Respirometric Technique to Measure Pollution-Induced Microbial Community Tolerance in Soils Contaminated with 2,4,6-Trinitrotoluene

“…Like heavy metals, the amended TNT can be adsorbed and bound to both clay and organic matter and, thus, be rendered unavailable to soil microorganisms (Hundal et al, 1997;Li et al, 1997;Gong et al, 1999). Clay soils may thus be less sensitive than sandy soils, as is indicated by the higher EC for the GS-3 soil compared with the RAC soil.…”

The Toxicity Assessment of Explosives Contaminated Soil using Soil Microbial Activity Tests

“…TNT와 RDX는 각각 nitroaromatic과 nitramine 계열의 화약물질을 대표하는 오염물질로 (Tan et al, 1992;Li et al, 1997;Sunahara et al, 1998) (Li et al, 1997;Mark and John, 1998;Gong et al, 1999;Frische, 2002).…”