Electronic Theses and Dissertations

Date of Award


Document Type


Degree Name

M.S. in Chemistry


Chemistry and Biochemistry

First Advisor

James Cizdziel

Second Advisor

James Cizdziel

Third Advisor

Murrell Godfrey

Relational Format



Mercury (Hg) is a global pollutant with human-health and ecological impacts. Gaseous Hg exchange between the atmosphere and aquatic or terrestrial surfaces serves as an important, but not well understood, route for Hg to enter and exit ecosystems. To better understand the role of gaseous Hg exchange in the biogeochemical cycling of Hg, we investigated Hg0 fluxes over natural wetlands (Sky Lake) and artificial wetlands (UM Field Station) using a dynamic flux chamber and an Hg vapor analyzer based on atomic fluorescence (Chapter 1). We also examined the effect of activated carbon and biochar on Hg emissions from soils for potential remediation purposes (Chapter 2). Finally, we studied the concentration of total-Hg in rain in Oxford, Mississippi, as a function of season and cloud-type (Chapter 3). Mercury emission fluxes from soils varied diurnally, with higher fluxes during the day, and lower and more stable fluxes during the night. Emission of Hg was correlated (p<0.05) with solar radiation for both soil (r=0.81) and water (r=0.95). Mean ambient levels of total gaseous mercury (TGM) at the Field Station and Sky Lake were 1.57 ± 0.67ng m-3 h-1 and 1.23 ± 0.58ng m-3 h-1, respectively. Mercury emission was generally greater from terrestrial (soil) surfaces compared to aquatic (water) surfaces. For example, the mean flux at the Field Station was 4.5ng m-3 h-1 over soil versus 2.3ng m-3 h-1over water during the same period. Emission of Hg from soils was greatly reduced when the soil was mixed with biochar or activated carbon at 5% weight. We observed that a 1-2% sorbent-soil ratio appears to be the most cost-effective approach for potential remediation purposes. While reduction in Hg emissions was size-dependent with the greatest reduction for the finest fraction (<125?m), the larger size-fraction and crude fraction also reduced soil-Hg emissions. For biochar, the mean Hg flux was reduced from 0.70ng m-3 h-1 to -0.86ng m-3 h-1 indicating that not only were emissions from the soil decreased but also that Hg in the ambient air was being adsorbed on the biochar. Similarly, activated carbon changed the Hg flux from a net emission to a net deposition. These results show that amending soils with these sorbents can be effective to minimize Hg emissions from contaminated soils. Concentrations of total-Hg in rain from Oxford, Mississippi were greater (p<0.05) in the spring and summer during thunderstorms (38 ± 10pg/g) compared to the fall and winter during non-thunderstorms (6.7 ± 3.9pg/g). This supports the hypothesis that cumulonimbus (thunderstorm) clouds, which reach higher altitudes, are effective at scavenging gaseous oxidized Hg species that accumulate in the upper troposphere.

Included in

Chemistry Commons



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