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Long-Term TNT Sorption and Bound Residue Formation in Soil

1997; Wiley; Volume: 26; Issue: 3 Linguagem: Inglês

10.2134/jeq1997.00472425002600030042x

1537-2537

Lakhwinder S. Hundal, Patrick J. Shea, S. D. Comfort, W. L. Powers, Joga Singh,

Toxic Organic Pollutants Impact

Soils surrounding former munitions production facilities are highly contaminated with 2,4,6-trinitrotoluene (TNT). Long-term availability and fate of TNT and its transformation products must be understood to predict environmental impact and develop appropriate remediation strategies. Sorption and transport in surface soil containing solidphase TNT are particularly critical, since nonlinear sorption isotherms indicate greater TNT availability for transport at high concentrations. Our objectives were to determine long-term sorption and bound residue formation in surface and subsurface Sharpsburg soil (Typic Argiudoll). Prolonged equilibration of 14C-TNT with the soil revealed a gradual increase in amount sorbed and formation of unextractable (bound) 14C residues. The presence of solid-phase TNT did not initially affect the amount of 14C sorbed during a 168-d equilibration. After 168 d, 93% of the added 14C was sorbed by uncontaminated soil, while 79% was sorbed by soil containing solid-phase TNT. In the absence of solid phase, pools of readily available (extractable with 3 mM CaCl2) and potentially available (CH3CN-extractable) sorbed TNT decreased rapidly with time and coincided with increased 14C in soil organic matter. More 14C was found in fulvic acid than in the humic acid fraction when no solid-phase TNT was present. After sequential extractions, including strong alkali and acid, 32 to 40% of the sorbed 14C was irreversibly bound (unextractable) in Sharpsburg surface and subsurface soil. Results provide strong evidence for humification of TNT in soil. This process may represent a significant route for detoxification in the soil-water environment.