Pacific Southwest Research Station

Particulate Emissions from Biomass Burning: Quantification of the Contributions from Residential Wood Combustion, Forest Fires, and Prescribed Fires

Proposal [pdf]

Progress Report [pdf]

Abstract

Researchers at the Desert Research Institute use instruments to sample smoke from a pile burn as part of their research to identify chemical "fingerprints" that can distinguish particles derived from residential wood combustion, wildfires, and prescribed fires. This information would help to determine how much these different sources are contributing to air quality problems in the Tahoe basin. Photo: Daniel Obrist, DRI.

The goal of this study is to develop and use a specific characterization method to differentiate between particulate matter (PM) contributions in the Lake Tahoe basin from residential wood combustion, wildfires, and prescribed fires. Deposition of PM is an important source of phosphorus (P) and sediment to Lake Tahoe, and leads to reductions in water clarity and decreases atmospheric visibility in the basin. The relative importance of PM emissions from various types of biomass combustion—i.e., domestic wood combustion, wildfires, and prescribed fires—is mainly based on seasonal observations without direct confirmation by measurements. We propose to develop a method to specifically characterize PM emissions from domestic wood combustion, wildfires, and prescribed fire emissions by combining two of the most commonly used biomass combustion tracers, soluble potassium (K+) and levoglucosan, with detailed characterization of organic compounds (i.e., carbohydrates, anhydrosugars, lignin), and particulate-bound mercury (Hg). These chemical PM fingerprints are expected to provide a powerful tool for differentiation of PM emissions from different biomass combustion sources— including in-basin versus out-of-basin contributions—and will possibly also allow for evaluation of past fire history in the basin in soil and sediment records.

Relation to Other SNPLMA Projects

The proposed study builds upon a number of earlier studies conducted in the Lake Tahoe Basin.  The SNPLMA Round 6 science project, "Development of an Air Pollutant Emissions Inventory for the Lake Tahoe Basin that Incorporates Current and Future Land Use Scenarios" prepared a more comprehensive and spatially distributed emissions inventory, which attributed similar PM10 and PM2.5 contributions to wood smoke from domestic heating, and attributed 12% and 16% of the PM10 and PM2.5 emissions to wildfires. The recently completed SNPLMA Round 7 science project, "Lake Tahoe source attribution study: receptor modeling study to determine the sources of observed ambient particulate matter in the Lake Tahoe basin" further analyzed the LTADS data to conclude that wood smoke is a major contributor to ambient PM2.5 levels, although that analysis was unable to separate contributions from the different sources of wood smoke.  Collaboration and coordination with the current SNPLMA Round 9 science project, "Effects of burning in the Tahoe Basin on soil and water quality," will allow us to assess how various pile sizes, configuration, and combustion properties (e.g., fire intensity as measured by underlying soil temperature) may impact PM emissions and help to develop strategies to reduce impacts of prescribed fires on PM related air quality issues and deposition.