Impact/Purpose:

The objective of this research is to develop and evaluate methods for accurately representing the complex atmospheric chemistry involved in the formation of ozone, secondary air toxics, photochemical aerosol precursors and other problems of importance to EPA. This task will produce updated, state-of-the-art photochemical mechanisms that will be used in regulatory and research air quality models at EPA. These new and accurate chemical mechanisms are required by OAQPS and state agencies to produce the FY 2003 State Implementation Plans for ozone, as well as by EPA to study upcoming problems of interest to the Agency.

Description:

Air quality models that realistically describe the formation of ozone, secondary air toxics, and other photochemical pollutants are needed by EPA and state agencies to predict current and future concentrations of these pollutants and develop ways to decrease their concentrations below harmful levels. The atmospheric chemistry of ozone is complex, involving the interactions of tens of thousands of different chemical reactions. Including this complex chemistry in a regulatory air quality model swamps even the most powerful computers, therefore we must develop ways to perform these calculations more efficiently without losing accuracy in the predictions. In this task we are developing, evaluating, and applying a method, the Morphecules Approach, to formulate complete chemical mechanisms which can efficiently and accurately describe the atmospheric chemistry of ozone and other photochemical pollutants in regulatory and research Air Quality models. In addition, we are evaluating thoroughly updated versions of current condensed mechanisms for appropriate use in EPA's regulatory and research models. These evaluations of the chemical mechanism will help to reduce uncertainty in the predictions of chemical mechanisms that are used in air quality models.

Record Details:

Record Type:PROJECT

Start Date:10/01/1998

Completion Date:09/01/2001

Record ID: 56179

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Project Information:

Progress :The final version of the software to implement the Morphecules method for computing atmospheric chemistry was delivered in June, 1999. Evaluation and analysis tasks have started immediately. However, progress in FY00 was slower than originally planned due to a loss of staff and the implementation of an ORD hiring freeze.

In tandem with the evaluation of the Morphecules mechanism, we have obtained thoroughly updated versions of three major condensed chemical mechanisms that are in wide use in air quality models both inside and outside of EPA. In FY00, we received two entirely updated version of the CB4 chemical mechanism, which is the photochemical mechanism used in EPA's regulatory air quality models. Because this is such an important mechanism, it is imperative that we rigorously evaluate it for replacement in regulatory models. In August, 1999, we received a new version of the SAPRC mechanism, which is used widely in regulatory models in California. In October 2000, we acquired a new version of the RACM2 mechanism, a revised version of the RADM2 mechanism currently being used in the Models3/CMAQ tests.

We have initiated protocol development for comparison studies of multiple chemical mechanisms, involving not just ozone concentrations, but through using a Process Analysis method for studying the cycling of radicals and NOy species.

ABSTRACT/ORAL: Date Cleared: 26-MAY-00

Tonnesen, G.S., and Luecken, D.J. Intercomparison of photochemical mechanisms using response surfaces and process analysis.

Abstract presented at: Millenium NATO/CCMS International Technical Meeting on Air Pollution Modeling and Its Application,

Boulder, CO, May 15-19, 2000.



Relevance :This research directly supports the Agency's Goal of Clean Air (Goal 01) and achievement of Objective 1: "By 2010 improve the air quality for Americans living in areas that do not meet the National Ambient Air Quality Standards for ozone and particulate matter."

Tropospheric ozone has been identified in ORD's Strategic Plan as an area of high importance that will continue to be a major part of ORD's research program. A better understanding of the concentrations of secondary pollutants and the atmospheric degradation of VOCs will help ORD develop more scientifically sound approaches for assessing and characterizing environmental exposure and risk. This research contributes to the chemical, physical, and biological processes element of the exposure component of ORD's Risk Assessment paradigm under ORD's Strategic Plan.

These studies will support the NARSTO program, a public-private consortium for ozone and particulate pollution research, and will also furnish important information for the Models 3 program and for other EPA offices. In particular, OAQPS will benefit from the improved predictions of atmospheric photochemistry implemented in regulatory models and the improvements in the scientific basis by which they evaluate ozone and other air pollutant control strategies.

Clients : OAQPS; NARSTO, state and regional EPA offices, any scientist who uses Models3/CMAQ

Project IDs:

ID Code :5669

Project type :OMIS