The Effects of Contaminant Aging on Decontamination Efficacy for Rapid Remediation of Concrete Surfaces – 20412
Citation:
Helpler, K., M. Kaminski, N. Escamilla, AND M. Magnuson. The Effects of Contaminant Aging on Decontamination Efficacy for Rapid Remediation of Concrete Surfaces – 20412. In Proceedings, WM2020 Symposium, Pheonix, AZ, March 08 - 12, 2020. U.S. EPA Office of Research and Development, Washington, DC, 10, (2020).
Impact/Purpose:
Understanding the relationship between decontamination efficacy and contaminant aging is imperative for developing effective remediation strategies following a large-scale contamination event. Non-destructive decontamination of concrete following a contamination incident becomes more difficult with increased time between contamination and decontamination because contaminants may chemically bind to concrete and/or penetrate into the concrete subsurface. Concrete samples were aged between 1 and 59 days, with half of the coupons receiving 1 mL of artificial rainwater about once every three days. After aging, coupons were either decontaminated or analyzed to determine contaminant penetration depths. Coupons were decontaminated with 0.1 M potassium chloride (KCl) solution applied either by flowing solution across the contaminated coupon face or non-destructive power washing. Contaminant depth profiles were created by removing the top surface of the coupon at least 15 times, measuring the activity in each removed layer, normalizing the total activity removed to the measured decontamination efficacy following the last layer removal, and determining the penetration thickness using the coupon dimensions, bulk density, and mass of material removed for each layer. Pressurized washing effectively removed particles but not soluble cesium, despite the majority of Cs-137 being located within the first millimeter of the subsurface. Soluble cesium removal by flowing 0.1 M KCl solution across the contaminated surface dropped to less than 12% within the first ten days. This drop in Cs-137 removal efficacy occurred within the first five days for coupons experiencing artificial rainfall events. Flowing 0.1 M KCl solution across the contaminated face was ineffective at removing particles, likely because particles had localized in surface depressions.
Description:
In this work, we evaluated the decontamination efficacy of two decontamination methods on concrete samples contaminated with soluble cesium-137 (Cs-137) and silica particles with 0.5-μm and 2-μm diameters.