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Human Exposure and Atmospheric Sciences

Research in Action

EPA scientists use sophisticated test chambers to simulate atmospheric conditions and understand chemical interactions

Issue
States and regions monitor nitrogen oxides, sulfur oxides, ozone, particulate matter, and other hazardous air toxics, to ensure that their concentrations do not exceed National Ambient Air Quality Standards. Additionally, states and regions need to be able to understand how emissions from various sources, such as vegetation, motor vehicles, industry, and wildfires, combine with nitrogen oxides in urban air to form secondary organic aerosol.

In order to determine the effects that emissions in ambient air have on humans and ecosystems, critical data on atmospheric gas phase and particulate phase chemistry are necessary. Furthermore, generation of these data is needed for air quality model development and improvements, as well as for global climate models.

Action
EPA scientists are using experimental laboratory studies to gather and assess these data. The scientists are using sophisticated test chambers to simulate atmospheric conditions under highly controlled conditions. This allows the scientists to observe the interactions of various chemicals and determine their transformation rates, products and fates.

Experimental results are evaluated by comparing laboratory predictions with air quality models and field measurements with respect to the formation of ozone, particulate matter, and a wide range of air toxic compounds.

Laboratory experiments include examinations of precursor-specific secondary organic aerosol mechanisms, and the interplay between several common air pollutants regulated by the Clean Air Act. In addition, research has been conducted to study the impact of nano-scale fuel borne catalysts and biofuel emissions on photochemical transformations (i.e., the interaction of chemicals with nitrogen oxides and light).

Researchers are also working on the construction and development of a new, mobile photochemical reaction chamber to be used to study the toxicity of combustion emission sources and to improve our understanding of how atmospheric reactions and transformations influence the toxicity of mixtures of air pollutants. These tests will incorporate photochemical transformation of the exhausts, thereby making the testing significantly more relevant to regulatory applications.

Results and Impact
Over the past several years, results from these experimental laboratory studies have been, and continue to be incorporated into EPA’s Community Multi-scale Air Quality model (CMAQ) which is used by states to assess implementation actions needed to attain National Ambient Air Quality Standards that are protective of human and ecosystem health. Data from these experimental laboratory studies are also incorporated into international air quality and global climate change models and used to improve, refine and evaluate the accuracy of air quality models.

Furthermore, these types of experiments can be focused on potential future atmospheric conditions, thereby making it possible for EPA to take a proactive approach in addressing major atmospheric chemistry issues of the future. Examples of this include the impact of global climate change on regional air quality and the impact of switching to biofuels on the composition and concentration of air pollutants in the atmosphere.

Technical Contact
Tad Kleindienst

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