DOE-NETL is participating in a field study, managed by EPRI, to document the changes in mercury speciation that may be occurring within the plume of the coal-fired Plant Bowen power generating facility in northwest Georgia. The DOE-NETL participation is occurring in two forms: (1) under an Interagency Agreement (DE-AI26-98FT40406) with the Tennessee Valley Authority (TVA), specially-instrumented aircraft are being used to collect speciated mercury samples from within the plume at several distances downwind of the stacks at Plant Bowen; and (2) under a Cooperative Agreement (Task 54 of DE-FC26-98FT40321) with the University of North Dakota Energy and Environmental Research Center (UND-EERC), speciated mercury samples are being collected directly from the exhaust stacks at Plant Bowen.

The information from the aircraft flights will be compared to the stack sampling results to determine whether the speciation of mercury changes as it is transported downwind in the Plant Bowen plume. Preliminary evidence from an ambient monitoring site located about 15 km south of Plant Bowen had suggested that a substantial portion of the oxidized mercury (Hg²⁺) released from the plant's stacks had been reduced to elemental mercury (Hg⁰) en route to the monitoring site. The in-stack and in-plume data collected during the current collaborative effort will serve to verify the implications of the ambient monitoring data and assist in the development of atmospheric models that can more accurately represent the reactions experienced by mercury within power plant plumes.

In addition, a plume dilution sampling device developed by Frontier Geosciences, Inc. will be employed in an attempt to simulate the cooling and dilution processes experienced by the plume. Previous experiments with this device, conducted in collaboration with UND-EERC and with sponsorship by EPRI and DOE-NETL (Task 24 of DE-FC26-98FT40321), also suggested that rapid transformation of Hg²⁺ to Hg⁰ may be occurring within the plume. If it can be demonstrated that the mercury speciation changes occurring within the plume (as measured by the instrumented aircraft) can be represented accurately by the dilution sampling device, it can be employed at other power plants to determine, in a relatively inexpensive manner, whether the same types of changes are occurring in other plumes whose characteristics are different (e.g., coal type, combustion process, other flue gas treatments, etc.).