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Sediment budget-based estimates of trace metal inputs to a Chesapeake estuary (1993)

Marcus, W. A. ; Nielsen, C. C. ; Cornwell, J. C.

Springer

Environmental geology 22 (1993), S. 1-9

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ISSN: 1432-0495

Keywords: Metals budget ; Sediment ; Chesapeake estuary

Source: Springer Online Journal Archives 1860-2000

Topics: Geosciences

Notes: Abstract This article evaluates whether a sediment budget for the South River, Maryland, can be coupled with metals data from sediment cores to identify and quantify sources of historic metal inputs to marsh and subtidal sediments along the estuary. Metal inputs to estuarine marsh sediments come from fluvial runoff and atmospheric deposition. Metal inputs to subtidal sediments come from atmospheric deposition, fluvial runoff, coastal erosion, and estuarine waters. The metals budget for the estuary indicates that metal inputs from coastal erosion have remained relatively constant since 1840. Historical variations in metal contents of marsh sediments have probably resulted primarily from increasing atmospheric deposition in this century, but prior to 1900 may reflect changing fluvial sources, atmospheric inputs, or factors not quantified by the budget. Residual Pb, Cu, and Zn in the marsh sediments not accounted for by fluvial inputs was low to moderate in 1840, decreased to near zero circa 1910, and by 1987 had increased to levels that were one to ten times greater than those of 1840. Sources of variability in subtidal cores could not be clearly discerned because of geochemical fluxes, turbulent mixing, and bioturbation within the cores. The sediment-metal budgeting approach appears to be a viable method for delineating metal sources in small, relatively simple estuarine systems like the South River and in systems where recent deposition (for example, prograding marshes) prevents use of deep core analysis to identify “background” levels of metal. In larger systems or systems with more variable sources of sediment and metal input, however, assumptions and measurement errors in the metal budgeting approach suggest that deep core analysis and normalization techniques are probably preferable for identifying anthropogenic impacts.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00775277

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Differences in trace metal concentrations among fluvial morphologic units and implications for sampling (1998)

Ladd, S. C. ; Marcus, W. A. ; Cherry, S.

Springer

Environmental geology 36 (1998), S. 259-270

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ISSN: 1432-0495

Keywords: Keywords Trace metal ; Sediment ; Pollution modeling ; Hydraulics ; Morphology ; Classification ; Sampling ; Spatial autocorrelation

Source: Springer Online Journal Archives 1860-2000

Topics: Geosciences

Notes: Abstract This study examines the segregation of trace metals within and between fluvial morphologic units in sand-sized and finer bed sediments in a cobble bed stream. The types of fluvial morphologic units sampled are low gradient riffles, high gradient riffles, glides, eddy drop zones, lateral scour pools, attached bars, and detached bars. Three to nine samples were collected from ten of each type of morphologic unit. All 12 metals show significantly different concentrations between some morphologic units in sediments smaller than 2 mm. Eddy drop zones and attached bars consistently have the highest metal concentrations, while low gradient riffles, high gradient riffles, and glides typically have the lowest concentrations. Metals showing the greatest between-unit variability are Al, Cr, Fe, Cu, and Ti, followed by Co, Mn, and Pb, while Mg, Mn, V, and Zn display relatively few differences between units. Lateral and longitudinal variations of metals within units are not significant, and there was no consistent, predictable variation in metal concentrations with distance downstream. Results indicate that metal studies in other gravel- and cobble-bed streams should include a reconnaissance survey to determine variations between morphologic units, stratify sampling by morphologic unit, and analyze spatial autocorrelation to determine sample spacing.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/s002540050341

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