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Vapor phase transport of unexploded ordnance compounds through soils
Raghunathan Ravikrishna1, Sally L Yost, Cynthia B Price
1Gordon A. and Mary Cain Department of Chemical Engineering, Louisiana State University, Baton Rouge 70803, USA.
Environmental Toxicology and Chemistry
|October 10, 2002
Summary
Evaporation of explosive compounds from unexploded ordnance (UXO) in soil is a concern. Laboratory tests show soil moisture, humidity, and temperature significantly impact contaminant flux, informing environmental risk assessments at military sites.
Area of Science:
- Environmental Science
- Geochemistry
- Chemical Engineering
Background:
- Unexploded ordnance (UXO) poses environmental risks at Department of Defense (DOD) sites.
- Understanding the fate and transport of explosive compounds from UXO is critical for site remediation.
- Evaporative flux of explosives from soil is a key pathway for environmental contamination.
Purpose of the Study:
- To quantify the evaporative flux of specific explosive compounds from different soil types.
- To investigate the influence of soil moisture, air relative humidity, and temperature on these fluxes.
- To evaluate a diffusion model for predicting chemical transport in soil pore air.
Main Methods:
- Laboratory experiments using specially designed flux chambers.
- Measurement of evaporative flux for 2,4-dinitrotoluene, 2,6-dinitrotoluene, and 1,3-dinitrobenzene.
- Controlled variation of soil moisture, air relative humidity, and soil temperature (14°C and 24°C).
- Application of a diffusion model with a fitted soil-air partition constant.
Main Results:
- Evaporative fluxes were measured under varying environmental conditions.
- Higher soil temperatures (24°C vs. 14°C) resulted in increased volatilization.
- Observed fluxes decreased more rapidly than model predictions under extremely dry conditions.
- The diffusion model qualitatively predicted experimental flux trends satisfactorily.
Conclusions:
- Soil moisture, relative humidity, and temperature are significant factors controlling explosive compound volatilization from soil.
- Higher temperatures enhance the driving force for volatilization.
- The diffusion model provides a useful, albeit approximate, tool for predicting contaminant transport, especially when soil-air partitioning is uncertain.
- Findings are crucial for assessing environmental risks and developing remediation strategies at UXO-contaminated sites.