title: Evaluation of sorbent amendments for in situ remediation of metal-contaminated sediments.
abstract: The present study evaluated sorbent amendments for in situ remediation of sediments contaminated with two divalent metals. A literature review screening was performed to identify low-cost natural mineral-based metal sorbents and high-performance commercial sorbents that were carried forward into laboratory experiments. Aqueous phase metal sorptivity of the selected sorbents was evaluated because dissolved metals in sediment porewater constitute an important route of exposure to benthic organisms. Based on pH-edge sorption test results, natural sorbents were eliminated due to inferior performance. The potential as in situ sediment amendment was explored by comparing the sorption properties of the engineered amendments in freshwater and saltwater (10 PPT salinity estuarine water) matrices. Self-assembled monolayers on mesoporous supports with thiols (Thiol-SAMMS) and a titanosilicate mineral (ATS) demonstrated the highest sorption capacity for cadmium (Cd) and lead (Pb), respectively. Sequential extraction tests conducted after mixing engineered sorbents with contaminated sediment demonstrated transfer of metal contaminants from a weakly bound state to a more strongly bound state. Biouptake of Cd in a freshwater oligochaete was reduced by 98% after 5-d contact of sediment with 4% Thiol-SAMMS and sorbed Cd was not bioavailable. While treatment with ATS reduced the small easily extractable portion of Pb in the sediment, the change in biouptake of Pb was not significant because most of the native lead was strongly bound. The selected sorbents added to sediments at a dose of 5% were mostly nontoxic to a range of sensitive freshwater and estuarine benthic organisms. Metal sorbent amendments in conjunction with activated carbon have the potential to simultaneously reduce metal and hydrophobic contaminant bioavailability in sediments.
authors.affiliation: Department of Civil and Environmental Engineering, University of Maryland Baltimore County, 5200 Westland Blvd., Baltimore, Maryland 21227, USA.
authors.forename: Seokjoon
authors.initials: S
authors.lastname: Kwon
authors.forename: Jeff
authors.initials: J
authors.lastname: Thomas
authors.forename: Brian E
authors.initials: BE
authors.lastname: Reed
authors.forename: Laura
authors.initials: L
authors.lastname: Levine
authors.forename: Victor S
authors.initials: VS
authors.lastname: Magar
authors.forename: Daniel
authors.initials: D
authors.lastname: Farrar
authors.forename: Todd S
authors.initials: TS
authors.lastname: Bridges
authors.forename: Upal
authors.initials: U
authors.lastname: Ghosh
mesh_terms: D000042:Absorption; D000327:Adsorption; D000818:Animals; D002413:Cations, Divalent / Q000737:chemistry; D052918:Environmental Restoration and Remediation / Q000379:methods*; D005618:Fresh Water / Q000737:chemistry; D019015:Geologic Sediments / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D008670:Metals / Q000032:analysis / Q000737:chemistry* / Q000378:metabolism; D009835:Oligochaeta / Q000378:metabolism; D012623:Seawater / Q000737:chemistry; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000737:chemistry* / Q000378:metabolism
chemical_list: D002413:Cations, Divalent; D008670:Metals; D014874:Water Pollutants, Chemical