title: Plutonium immobilization and remobilization by soil mineral and organic matter in the far-field of the Savannah River Site, U.S.
abstract: To study the effects of natural organic matter (NOM) on Pu sorption, Pu(IV) and (V) were amended at environmentally relevant concentrations (10(-14) M) to two soils of contrasting particulate NOM concentrations collected from the F-Area of the Savannah River Site. More Pu(IV) than (V) was bound to soil colloidal organic matter (COM). A de-ashed humic acid (i.e., metals being removed) scavenged more Pu(IV,V) into its colloidal fraction than the original HA incorporated into its colloidal fraction, and an inverse trend was thus observed for the particulate-fraction-bound Pu for these two types of HAs. However, the overall Pu binding capacity of HA (particulate + colloidal-Pu) decreased after de-ashing. The presence of NOM in the F-Area soil did not enhance Pu fixation to the organic-rich soil when compared to the organic-poor soil or the mineral phase from the same soil source, due to the formation of COM-bound Pu. Most importantly, Pu uptake by organic-rich soil decreased with increasing pH because more NOM in the colloidal size desorbed from the particulate fraction in the elevated pH systems, resulting in greater amounts of Pu associated with the COM fraction. This is in contrast to previous observations with low-NOM sediments or minerals, which showed increased Pu uptake with increasing pH levels. This demonstrates that despite Pu immobilization by NOM, COM can convert Pu into a more mobile form.
authors.affiliation: Department of Marine Sciences, Texas A&M University , Building 3029, Galveston, Texas 77553, United States.
authors.forename: Chen
authors.initials: C
authors.lastname: Xu
authors.forename: Matthew
authors.initials: M
authors.lastname: Athon
authors.forename: Yi-Fang
authors.initials: YF
authors.lastname: Ho
authors.forename: Hyun-Shik
authors.initials: HS
authors.lastname: Chang
authors.forename: Saijin
authors.initials: S
authors.lastname: Zhang
authors.forename: Daniel I
authors.initials: DI
authors.lastname: Kaplan
authors.forename: Kathleen A
authors.initials: KA
authors.lastname: Schwehr
authors.forename: Nicole
authors.initials: N
authors.lastname: DiDonato
authors.forename: Patrick G
authors.initials: PG
authors.lastname: Hatcher
authors.forename: Peter H
authors.initials: PH
authors.lastname: Santschi
mesh_terms: D052918:Environmental Restoration and Remediation / Q000379:methods*; D006812:Humic Substances; D011005:Plutonium / Q000032:analysis / Q000737:chemistry* / Q000378:metabolism; D045483:Rivers; D012990:Soil Pollutants, Radioactive / Q000032:analysis / Q000737:chemistry* / Q000378:metabolism; D015144:Southeastern United States
chemical_list: D006812:Humic Substances; D012990:Soil Pollutants, Radioactive; D011005:Plutonium