Recent developments in formulating model descriptors for subsurface transformation and sorption of trinitrotoluene

Area of Science:

• Environmental Chemistry
• Soil Science
• Environmental Remediation

Background:

• Subsurface transport of trinitrotoluene (TNT) is significantly influenced by transformation and sorption processes.
• Existing knowledge on TNT soil transformation and sorption requires further elucidation, particularly regarding influencing soil properties.

Purpose of the Study:

• To summarize the current understanding of TNT transformation and sorption in soils.
• To highlight the importance of edaphic factors, such as redox potential, in TNT transformation.
• To identify key TNT transformation products and discuss challenges in mass balance interpretation.

Main Methods:

• Review and synthesis of recently published data on TNT soil interactions.
• Analysis of factors affecting reductive transformation rates and pathways.
• Modeling of TNT sorption as an equilibrium-controlled process.

Main Results:

• Unequivocal evidence for reductive transformation of TNT in soils, particularly under anaerobic conditions.
• Identified TNT transformation products include 2A-DNT, 4A-DNT, 2,4-DANT, 2,6-DANT, and azoxytoluenes.
• TNT soil sorption is rapid and can be modeled as equilibrium-controlled, though poor mass balances complicate interpretation.

Conclusions:

• Reductive transformation and rapid sorption are critical processes governing TNT subsurface transport.
• Soil redox conditions are likely significant drivers of TNT transformation rates.
• Further research is needed to fully understand TNT transformation pathways and irreversible disappearance mechanisms.