Natural and anthropogenic geochemical signatures of floodplain and deltaic sedimentary strata, Sacramento–San Joaquin Delta, California, USA

• Published in: Environmental pollution (1987) Vol. 141; no. 2; pp. 295 - 309
• Main Authors: Pasternack, G.B., Brown, K.J.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.05.2006; Elsevier
• Subjects: agricultural land; anthropogenic activities; Applied sciences; Arsenic - analysis; bioavailability; Biological and physicochemical properties of pollutants. Interaction in the soil; Brackish; California; Copper - analysis; Deltas; Earth sciences; Earth, ocean, space; Engineering and environment geology. Geothermics; Environmental Monitoring - methods; Environmental Pollutants - analysis; Exact sciences and technology; floodplains; Freshwater; geochemistry; Geologic Sediments - analysis; leaching; Lead - analysis; Mercury - analysis; Metal accumulation; metals; Metals, Heavy - analysis; Oxidation-Reduction; pollutants; Pollution; Pollution, environment geology; sediment contamination; sediment deposition; Sedimentation; Soil and sediments pollution; Spectrophotometry, Atomic - methods; trace elements; Trace Elements - analysis; Trace metals; Wetland restoration; wetlands; Zinc - analysis; California; United States; North America; America; INE, USA, California, Sacramento-San Joaquin Delta; USA, California, Sacramento-San Joaquin Delta; Deltas; Wetland restoration; Metal accumulation; Sedimentation; Trace metals; Geomorphology; Pollutant behavior; Geochemistry; Mobility; Sediments; Tides; Coastal zone; Heavy metal; Flood plain; Pollution; Selfpurification; Delta; Wetland
• ISSN: 0269-7491; 1873-6424
• DOI: 10.1016/j.envpol.2005.08.044

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 CH 3Hg + that would be hazardous to fish. Geomorphic–geochemical linkages on an upper deltaic plain have dynamics that defy expectations for achieving restoration “success”.