Date of Award
Ph.D. in Chemistry
Chemistry and Biochemistry
Randy M. Wadkins
Mercury is a highly toxic element that is found both naturally and as an introduced contaminant in the environment. The majority of Mercury released to the environment is into the atmosphere, where because of its high volatility and long residence time is dispersed globally. In order to better understand the factors controlling the distribution and temporal patterns of atmospheric Mercury species, as well as the sources of airborne Mercury in the mid-south region, concentrations of gaseous elemental mercury (gem), gaseous oxidized mercury (gom), and particulate-bound mercury (pbm), along with meteorological parameters and other ancillary data, were collected for more than a year in Oxford, Mississippi. Mean levels of gem were 1.54 â± 0.32 ng∙m-3 and were lower and more stable in the winter and spring compared with summer and fall. Mean levels for gom and pbm were 3.87 ng∙m-3 and 4.58 ng∙m-3, respectively; levels tended to be highest in the afternoon and lowest in the early morning hours. Precipitation events greatly reduce gom and pbm levels but have little effect on gem. Gom exhibited diurnal patterns characteristic of photochemical oxidation. Atmospheric modeling revealed that higher levels of plume events for airborne hg often occur with air masses from the northern USA. Gaseous mercury exchange between terrestrial surfaces and the atmosphere was also investigated. Mercury fluxes over four landscapes representative of north Mississippi were studied. Mercury emissions were higher during the summer than the winter. The influence of environmental variables, including temperature, solar radiation, humidity, wind speed, soil moisture, and pressure, on mercury fluxes and ambient levels of atmospheric mercury were evaluated. Analytical methods were also developed to measure wet and dry deposition of mercury, and estimates were made for deposition to Enid Lake and the Yocona River watershed. The data was incorporated into a mercury mass-balance model for Enid Lake, which currently has a mercury-based fish consumption advisory. Finally gem concentrations were determined within an academic chemistry building and levels were compared to occupational safety permissible and recommended exposure limits.
Jiang, Yi, "Atmospheric Mercury Species In Northern Mississippi: Concentrations, Sources, Temporal Patterns, And Soil-Air Exchange" (2014). Electronic Theses and Dissertations. 926.