Sorption and Oxic Degradation of the Explosive CL-20 During Transport in Subsurface Sediments
The abiotic sorption and oxic degradation processes that control the fate of the explosive CL-20, Hexanitrohexaazaisowurtzitane, in the subsurface environment were investigated to determine the potential for vadose and groundwater contamination. Sorption of CL-20 is relatively small (Kd = 0.02 to 4.2 cm3 g-1, 7 low organic carbon sediments, 12 minerals), which results in only slight retardation relative to water, so CL-20 could move quickly through unsaturated and saturated sediments to groundwater. Sorption was mainly to mineral surfaces for these low organic carbon sediments, and the resulting isotherm was nonlinear. CL-20 abiotically degrades in an oxic environment at slow rates (i.e., 10s to 100s of hours) with a wide variety of minerals, but at fast rates (i.e., minutes) in the presence of 2:1 clays (biotite, hectorite, montmorillonite, illite), ferrous iron oxides (i.e., magnetite) and manganous oxide. High concentrations of surface ferrous iron degraded CL-20 the fastest, but 2:1 clays containing no structural or adsorbed ferrous iron (hectorite) could also quickly degrade CL-20. Products of CL-20 oxic degradation included three high molecular weight compounds and anions (nitrite and formate). The 2 to 3.5 moles of nitrite produced suggests the CL-20 cage remains intact. Identification of further degradation products and CL-20 mineralization rates is needed to fully assess the impact of these CL-20 transformation rates on the risk of CL-20 (and degradation product) subsurface movement.
- Research Organization:
- Pacific Northwest National Laboratory (PNNL), Richland, WA (US)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-76RL01830
- OSTI ID:
- 860009
- Report Number(s):
- PNNL-SA-39252; 400403209
- Journal Information:
- Chemosphere, Journal Name: Chemosphere Journal Issue: 6 Vol. 56; ISSN CMSHAF; ISSN 0045-6535
- Country of Publication:
- United States
- Language:
- English
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