Chemical remobilization of contaminant metals within floodplain sediments in an incising river system: implications for dating and chemostratigraphy
✍ Scribed by Hudson-Edwards, K. A.; Macklin, M. G.; Curtis, C. D.; Vaughan, D. J.
- Publisher
- John Wiley and Sons
- Year
- 1998
- Tongue
- English
- Weight
- 370 KB
- Volume
- 23
- Category
- Article
- ISSN
- 0360-1269
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✦ Synopsis
Metals such as Pb, Zn, Cd and Cu from historical mining activity have been used as stratigraphic markers for dating and provenancing vertically accreted, fine-grained floodplain overbank deposits. This study presents evidence for chemical remobilization of these metals within overbank sediments in the Tyne basin, UK. The evidence includes: breakdown of metal-bearing minerals (sulphides, carbonates, iron and manganese oxyhydroxides); shifts of chemical fractions within zones of relatively low pH towards more soluble and reactive phases; and accumulation of secondary iron and manganese oxyhydroxides at levels related to fluctuating water-table levels or to the breakdown of organic matter. All of this suggests that fine, centimetre-scale, chemostratigraphy using metal concentrations and ratios is unlikely to provide reliable data in river systems that have experienced, or are experiencing, major changes in water-table levels, or pedogenesis. Coarse tens of centimetre-to metre-scale, chemostratigraphy, when applied with caution, may still provide a means of delineating contaminated units.