Date of Award

5-2002

Level of Access Assigned by Author

Campus-Only Thesis

Degree Name

Master of Science (MS)

Department

Civil Engineering

Advisor

Aria Amirbahman

Second Committee Member

Ivan J. Fernandez

Third Committee Member

Terry A. Haines

Additional Committee Members

Jeffery S. Kahl

Abstract

This is a study of mercury (Hg) and methylmercury (MeHg) cycling in the soils of a paired watershed system at Acadia National Park, Maine. Two watersheds were compared, Cadillac Brook watershed, burned in 1947, currently bas thin soils and primarily deciduous vegetation, and Hadlock Brook watershed, unburned, currently having thicker soil and coniferous vegetation The fue likely had a significant impact on Cadillac watershed, by altering the vegetation, raising the soil pH, and depleting the carbon pool.

Soil pH was significantly higher in all horizons of Cadillac soils than in Hadlock soils. This difference was especially significant in the 0 horizon, where on average, Cadillac soils had a pH approximately 0.40 units higher than Hadlock soils. Total Hg concentrations were higher in the 0 horizon of Hadlock soils than in Cadillac soils, most likely as a result of the fire. Cadillac and Hadlock soils contained an estimated total Hg content of 1.70 kg and 6.64 kg, respectively. Soil MeHg concentrations were higher in Cadillac than in Hadlock, also most likely as a result of the fire. Cadillac and Hadlock soils contained an estimated MeHg content of 0.0038 kg and 0.0056 kg, respectively.

Mercury adsorption isotherms indicated that at low Hg concentrations, Hg speciation is controlled by the type and concentration of dissolved organic matter (DOM), with relatively low adsorption of Hg to soil. This behavior is more significant in the organic horizons of both watersheds than in the mineral horizons. The findings fiom the adsorption study suggest that as a result of the fire, the type of DOM released into solution fiom burned soils is less efficient at binding Hg than that of the unburned soils. Given the higher lability of organic matter in the unburned soils, a higher Hg mobilization potential is expected in these soils.

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