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BAY REGION ATMOSPHERIC CHEMISTRY EXPERIMENT (BRACE)
Citation:
Landis, M S. BAY REGION ATMOSPHERIC CHEMISTRY EXPERIMENT (BRACE). Presented at Science Forum 2003, Washington, DC, May 5-7, 2003.
Impact/Purpose:
The overall research objective of this task is to improve our understanding of the emission, transport, transformation, and deposition of atmospheric mercury. Information garnered from this research is used to improve and evaluate EPA deterministic models that are used to investigate the (i) relative impact to local, regional, and global sources to atmospheric mercury deposition, and (ii) benefits of various emission reduction scenarios.
Specifically, individual research project objectives are listed below:
(1) Evaluate the ability of speciated mercury (Hg0, Hg2+, HgP) measurements to aid source apportionment models in identifying anthropogenic source contributions to atmospheric mercury deposition
(2) Elucidate the contribution of coal combustion sources to observed mercury wet deposition in the Ohio River Valley
(3) Obtain atmospheric profiles (200 - 12,000 ft) of speciated ambient mercury off the south Florida Coast
- Evaluate the role of long range transport of RGM to Florida in the marine free troposphere.
- Identify any vertical mercury gradients that might indicate the presence of rapid mercury chemistry in air or in cloud water.
(4) Conduct research at Mauna Loa Observatory to elucidate elemental mercury oxidation in the remote marine free troposphere.
(5) Conduct laboratory kinetics experiments to determine the rate constants of elemental mercury oxidation to gaseous inorganic divalent mercury species from atmospheric halide species (e.g. BrO, ClO).
Description:
The Tampa Bay Estuary Program (TBEP) was formed in 1991 to assist the community in developing a comprehensive plan to restore and protect Tampa Bay. The ecological indicator of the health of the Bay is the coverage of seagrasses, historically in decline, which are important to the Bay's aquatic habitat and food web. Seagrass decline is linked to excess of plant-stimulating forms of nitrogen to the bay, promoting algae growth, which shades out light needed to sustain seagrasses. One element of the TBEP is a private-local-state, multi-agency Nitrogen Management Consortium that seeks to limit nitrogen loading to the Bay to the 1992-1994 average. Present estimates suggest atmospheric deposition comprises ~ 30% of the nitrogen budget of the Bay. This estimate is based, however, on limited ambient monitoring data and simple models.
In BRACE USEPA NERL will join with Florida DEP and TBEP to increase the intensity, sophistication and spatial scope of monitoring and modeling and provide better information on air quality in the Tampa Bay area. The result will be improved estimates of the effects of local and regional emissions of oxides of nitrogen (NOx) on the Bay and the benefits to be gained from implementation of emissions reduction strategies. The two primary objectives of BRACE are to (i) provide TBEP with robust estimates of deposition of biologically active forms of nitrogen to Tampa Bay and its watershed and (ii) assess the Tampa Bay air quality before and after the TECO Gannon Station re-powering from coal to natural gas. EPA NERL is contributing to BRACE by participating in atmospheric monitoring and modeling activities. Specifically NERL will conduct source apportionment modeling to identify the sources of observed NOx and PM2.5 and run a state-of-the-art model to evaluate the formation of ozone and secondary aerosols.