Impact/Purpose:

1. Based on the best available information in the literature, recommend chemical mechanisms for EPA models that can be used to estimate ambient concentrations of the 33 classes of air toxic compounds identified by OAQPS in the Urban Air Toxics Strategy.

2. Develop a research plan for carrying out laboratory and computational chemistry studies to fill in the gaps and reduce uncertainties in the atmospheric mechanistic data of the 33 classes of air toxic compounds.

Description:

A full assessment of the impact of the release of air toxic compounds into the atmosphere requires a detailed understanding of their atmospheres lifetimes and fates. The objective of this task is to begin to develop such data for the 33 classes of air toxic compounds identified by OAQPS in the Urban Air Toxics Strategy. Along with emission rates, atmospheric lifetimes are needed to determine (1) ambient concentrations that can affect human exposure levels and (2) dry and wet deposition rates that control uptakes of air toxic compounds to ecologically sensitive land surfaces and aquatic bodies. A literature survey will be carried out first to identify gaps and uncertainties in atmospheric lifetimes, deposition rates, and mechanistic data for 33 classes of air toxic compounds. Based on the available literature, chemical mechanisms will be developed for the air toxic compounds for inclusion into EPA models. The first set of compounds to be investigated are mercury compounds. After recommending literature-based chemical mechanisms for each of the 33 classes of air toxic compounds, a research plan for carrying out laboratory and computational chemistry studies to fill in the gaps and reduce uncertainties in the atmospheric lifetime and mechanistic data will be developed. These studies will be carried out under a follow-on task to begin in FY04.

Record Details:

Record Type:PROJECT

Start Date:10/01/2000

Completion Date:09/01/2003

Record ID: 56187

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Project Information:

Progress :During FY01 the review of the atmospheric chemistry of mercury compounds (FY01 APM 220) was completed and submitted. The review included (1) evaluation of equilibrium constants, rate constants, reaction product data of key chemical reactions in gas and aqueous phases; (2) assessments of the roles of gas-aerosol phase partitioning and chemical reactions in aqueous aerosols; (3) review of chemical process modeling studies; (4) recommendations for what should be included in atmospheric chemical mechanisms; (5) research recommendations for reducing gaps and uncertainties in the chemical mechanisms. During FY02 similar reviews were conducted for the following 10 classes of compounds: formaldehyde, acetaldehyde, acrolein, 1,3-butadiene, acrylonitrile, benzene, hexachlorbenzene, 1,2-dichloropropane, hydrazine and ethylene oxide.

- FY01 APM 220 Develop chemical process and product mechanisms for some important classes of air toxics, suitable for incorporation into EPA models.

- Report: Atmospheric Chemistry of Mercury Compounds 9/01

Relevance :The information provided under this task will be used to develop chemical mechanisms for air quality models for predicting ambient concentrations and deposition loadings of the 33 air toxic compounds identified in the Urban Air Toxics Strategy (Table 1). Such information is needed as input to models that can be used to evaluate strategies for reducing risk associated with exposure to airborne air toxic compounds The first class of compounds investigated were mercury compounds. In FY01 a chemical mechanism was recommended for predicting ambient concentrations of mercury compounds (FY01 APM 446). The complete set of first generation chemical mechanisms for the 33 classes of air toxic compounds, that will be based on a review of the literature, constitute FY03 APM 20.

Clients : OAQPS Jawad Touma

Project IDs:

ID Code :6058

Project type :OMIS