Modeling the impacts of alternative burning strategies on local and regional air quality

One of the main requirements land managers must follow while performing prescribed burnings is to limit smoke from reaching populated areas. We surveyed land managers and prescribed burning experts in the Southeast to identify the most relevant burning scenarios they would like us to simulate with our smoke impact prediction system. In response to the survey results, we focused on the impacts of changing: 1) frequency of burn, 2) season of burn, 3) size of burn, 4) ignition type, and 5) time of burn. The objective of this study was to find the benefits and harms associated with changing these five factors, giving guidance to land managers on alternative burn strategies that may reduce the impacts on air quality downwind.

Our smoke impact prediction system incorporates a plume dispersion model into a chemical transport model called Community Multiscale Air Quality modeling System (CMAQ). Consume (Version 3.0) was used to estimate total emissions from a burn, and Fire Emission Production Simulator (FEPS) provided time-varying emissions and important plume parameters such as fire diameter and heat flux. Weather Research and Forecasting (WRF) model provided the meteorological inputs. Daysmoke, a prescribed burning plume dispersion model, was used to track the plume at sub-grid scales. The adaptive grid version of CMAQ was used to strengthen the ability to predict air quality impacts from biomass burnings with the capability to increase grid resolution for tracking plumes at the regional scale. By adopting certain burn strategies cognizant of meteorological conditions, the dispersion and long-range transport of plumes can be altered and their effect on ground-level pollutant concentrations downwind can be controlled.

A burn conducted at Fort Benning Army Base on April 9, 2008 (Compartment F5) under southeasterly winds was used as our study case. The modeling system is evaluated with ground-level smoke measurements 2-5 km downwind of the burn and PM2.5 observations at Columbus Airport, 30 km downwind. Results of different burning strategies are analyzed based on the amounts of pollutants emitted as well as how smoke plumes are dispersed and pollutants are transported to impact downwind air quality.