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Perchlorate retention and mobility in soils
Edward Todd Urbansky1, Stephanie K Brown
1United States Environmental Protection Agency, Office of Research and Development, National Risk Management Research Laboratory, Water Supply and Water Resources Division, Cincinnati, OH 45268, USA. eurbansky@joaptsc.navy.mil
Journal of Environmental Monitoring : JEM
|August 5, 2003
Summary
Perchlorate generally does not bind to soils, with most remaining in water. However, some soils exhibit anion exchange, requiring careful measurement methods to account for sorption.
Area of Science:
- Environmental Chemistry
- Soil Science
- Analytical Chemistry
Background:
- Perchlorate contamination is a growing environmental concern.
- Understanding perchlorate's interaction with soil is crucial for risk assessment and remediation.
- Previous studies suggest limited sorption of perchlorate in soils.
Purpose of the Study:
- To investigate the adsorption and release of perchlorate in various soils and minerals.
- To determine the perchlorate anion exchange capacity (PAEC) of different media.
- To assess the implications for perchlorate measurement in environmental samples.
Main Methods:
- Exposure of 38 different soils, minerals, and dusts to low and high aqueous perchlorate solutions.
- Quantification of perchlorate in aqueous and solid phases using ion chromatography.
- Determination of PAEC by leaching with sodium hydroxide after perchlorate exposure and rinsing.
Main Results:
- Over 90% of perchlorate remained in the aqueous phase in low-level exposure experiments.
- Measurable PAECs ranged from 4 to 150 nmol g(-1), with most media showing low sorption.
- No significant sorption was detected in some soils and minerals, but anion exchange was observed in others.
Conclusions:
- Perchlorate generally exhibits low sorption to soils, supporting its mobility being influenced by hydrologic and biologic factors.
- Intrasoil perchlorate content is likely depositional rather than sorptive in most cases.
- Accurate measurement of perchlorate in soils necessitates accounting for potential ion exchange phenomena, as water leaching alone may be insufficient.