title: Natural and anthropogenic geochemical signatures of floodplain and deltaic sedimentary strata, Sacramento-San Joaquin Delta, California, USA.
abstract: The geochemical history of an upper deltaic plain pending tidal wetland restoration was reconstructed to assess remobilization of redox-sensitive constituents in sediment, identify depositional processes promoting geochemical retention, and determine the extent of contamination with Hg, As, Pb, Cu, and Zn. Three 12-14-m sediment cores were analyzed for bulk sediment geochemistry using ICP-AES. Rather than showing similar stratigraphic and geochemical down-core trends, cores had a unique record indicative of strong spatial gradients in deposition processes. Each strata type (e.g. basal clay, sand channel, distal floodplain, and agriculturally impacted surficial horizon) had a unique geochemical "fingerprint". The agriculturally impacted surficial layer showed high [Hg], [As], and [Pb]. The significance is that a restored upper delta will have a complex geomorphology defying conventional criteria of "success" in a restoration framework. Also, there is a significant risk of generating toxic, bio-available CH3Hg+ that would be hazardous to fish.
authors.affiliation: Department of Land, Air and Water Resources, University of California, 211 Veihmeyer Hall, One Shields Avenue, Davis, CA 95616-8628, USA. gpast@ucdavis.edu
authors.forename: G B
authors.initials: GB
authors.lastname: Pasternack
authors.forename: K J
authors.initials: KJ
authors.lastname: Brown
mesh_terms: D001151:Arsenic / Q000032:analysis; D002140:California; D003300:Copper / Q000032:analysis; D004784:Environmental Monitoring / Q000379:methods; D004785:Environmental Pollutants / Q000032:analysis*; D019015:Geologic Sediments / Q000032:analysis*; D007854:Lead / Q000032:analysis; D008628:Mercury / Q000032:analysis; D019216:Metals, Heavy / Q000032:analysis*; D010084:Oxidation-Reduction; D013054:Spectrophotometry, Atomic / Q000379:methods; D014131:Trace Elements / Q000032:analysis; D015032:Zinc / Q000032:analysis
chemical_list: D004785:Environmental Pollutants; D019216:Metals, Heavy; D014131:Trace Elements; D007854:Lead; D003300:Copper; D008628:Mercury; D015032:Zinc; D001151:Arsenic