Long-term stability of organic carbon-stimulated chromatereduction in contaminated soils, and its relation to manganese redoxstatus

Journal Article · Tue Mar 13 04:00:00 EDT 2007 · Environmental Science and Technology

DOI:https://doi.org/10.1021/es062874c· OSTI ID:923420

Tokunaga, Tetsu K; Wan, Jiamin; Lanzirotti, Antonio; Sutton, Steve R; Newville, Matthew; Rao, William

In-situ reduction of toxic Cr(V1) to less hazardous Cr(II1)is becoming a popular strategy for remediating contaminated soils.However, the long term stability of reduced Cr remains to be understood,especially given the common presence of MnfIIIJV) oxides that reoxidizeCr(II1). This 4.6 year laboratory study tracked Cr and Mn redoxtransformations in soils contaminated with Cr(V1) which were then treatedwith different amounts of organic carbon (OC). Changes in Cr and Mnoxidation states within soils were directly and nondestructively measuredusing micro X-ray absorption near edge structure spectroscopy. Chromatereduction was roughly lst-order, and the extent of reduction was enhancedwith higher OC additions. However, significant Cr(||1) reoxidationoccurred in soils exposed to the highest Cr(V1) concentrations (2,560 mgkg"'). Transient Cr(II1) reoxidation up to 420 mg kg1 was measured at 1.1years after OC treatment, followed by further reduction. Chromateconcentrations increased by 220 mg kgm1a t the end of the study (4.6years) in one soil. The causal role that Mn oxidation state had inreoxidizing Cr was supported by trends in Mn K-edge energies. Theseresults provide strong evidence for longterm dependence of soil Croxidation states on balances between OC availability and Mn redoxstatus.

• Research Organization: Ernest Orlando Lawrence Berkeley NationalLaboratory, Berkeley, CA (US)
• Sponsoring Organization: USDOE Director. Office of Science. Basic EnergySciences
• DOE Contract Number: AC02-05CH11231
• OSTI ID: 923420
• Report Number(s): LBNL--62676; BnR: KC0303020
• Journal Information: Environmental Science and Technology, Journal Name: Environmental Science and Technology Journal Issue: 12 Vol. 41; ISSN ESTHAG; ISSN 0013-936X
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
ABSORPTION
AVAILABILITY
CARBON
CHROMATES
MANGANESE
OXIDES
SOILS
SPECTROSCOPY
STABILITY
TRANSFORMATIONS
TRANSIENTS
VALENCE