Photochemical Modeling of Ethylene and Propylene Emissions

Introduction

Massive and frequent spikes of ozone, which appear to be directly associated with release of reactive unsaturated hydrocarbons, were detected by a wide variety of experimental measurements during the recent TexAQS 2000 summer campaign in the Houston-Galveston non-attainment area. Compared with typical ozone concentration evolution patterns in a clear summer day in other US cities, several monitoring sites in the Houston-Galveston area show rapid transient high ozone events (THOEs) that significantly violate the National Ambient Air Quality Standards. Since December 2000, when TNRCC submitted a State Implementation Plan (SIP) for Houston based on 100% NOx reduction, various scientific, legal and political factors have caused a dramatic shift of focus back to VOC emissions, inventory, and chemical reactivity.

Objective

The main objective of this project is to study the reactive unsaturated carbon plume chemistry for the Houston-Galveston area based upon modeling tools such us MM5 meteorological model, EPA’s state-of-science Models-3 CMAQ urban-regional air quality model, and Houston inventory prior to recent shift of focus. The project is focused on (A) the TNRCC “primary” modeling episode of August 25-September 1 (which occurs in the middle of the TexAQS intensive data collection period), and (B) ethylene and propylene plumes released for the vicinity of the Houston Ship Channel, evidence for which was detected unambiguously by experiments.

Goals

1. characterize the EPA’s CMAQ’s performance in identifying THOEs with current model configuration and input data;
2. utilize TNRCC’s detailed emissions inventory for reactive unsaturated hydrocarbon to compare mechanism differences between Carbon-Bond 4 and SAPRC-99 chemical mechanism;
3. develop an improved emitted hydrocarbon speciation method for use with the SAPRC-99 chemical mechanism;
4. recommend improved Eulerian air quality model configurations enabling THOE simulations.

Input data
Emission simulation results (SMOKE)
Air Quality simulations results (CMAQ)