Date of Award

1994

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Oceanography and Coastal Sciences

First Advisor

William H. Patrick, Jr

Abstract

Sediment cores were collected from coastal wetlands from the Gulf coast of North America and northern Europe to study accretion rates and heavy metal accumulation. There was a significant decrease in vertical accretion rates from low to high marsh for Gulf coast samples. Contrary to previous results, these low tidal range sites did not have negative accretion balances. Northern European samples demonstrated the utility of Chernobyl $\sp{137}$Cs as a sediment marker. There were large differences in sediment characteristics and accretion rates between Polish and western European samples. Vertical accretion rates based on $\sp{210}$Pb were lower than $\sp{137}$Cs rates for most cores. The $\sp{210}$Pb rates included effects of compaction and decomposition, and profiles of bulk density and organic content confirmed this. All European sites had positive accretion balances. Multiple regression analyses of a large data set showed that vertical accretion rates were best described by a regression using relative sea level rise, surface organic content, sediment bulk density, position within the marsh, and the interaction between relative sea level rise and position. The significance of the interaction term indicated that low marsh sites responded differently to increases in relative sea level rise than middle and high marsh sites. There was a much higher correlation between vertical accretion and organic accumulation than between vertical accretion and mineral accumulation. A computer model, using an annual cohort approach, successfully simulated sedimentation processes, including surface sediment deposition, below-ground production, decomposition, and compaction. Sensitivity analyses indicated that the most important factors affecting model-generated accretion rates were: pore space, mineral matter deposition, initial elevation, sea level rise, and below-ground production. Chronologies of sediment heavy metal concentrations for high and low marsh cores from northern Europe showed very good agreement, indicating that sediment profiles represent historic inputs of heavy metals. Some of the sediments had very high heavy metal concentrations, with peak sediment concentrations up to five times greater than found in the oldest sediment samples. Metal concentrations have recently decreased in the cores from St. Annaland and Stiffkey Marshes but remained high throughout the upper part of the cores from the Oder River.

Pages

224

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