AAAR 35th Annual Conference October 17 - October 21, 2016 Oregon Convention Center Portland, Oregon, USA
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Source Apportionment of PM2.5 at Multiple Northwest U.S. Sites: Using Chemically Speciated PM2.5 to Assess Regional Winter Wood Smoke Impacts from Residential Wood Combustion
ROBERT KOTCHENRUTHER, U.S. EPA
Abstract Number: 109 Working Group: Source Apportionment
Abstract Wood smoke from residential wood combustion is a significant source of elevated PM2.5 in communities across the Northwest U.S. This work uses Positive Matrix Factorization (PMF) receptor modeling to assess winter residential wood combustion impacts at 19 monitoring sites in the Northwest U.S. Each site was modeled independently. Model solutions had from 4 to 8 PMF factors, depending on the site. 15 different sources or chemical compositions were identified as contributing to PM2.5 across the 19 sites. The 6 most common were; aged wood smoke and secondary organic carbon, motor vehicles, primary wood smoke, ammonium nitrate, ammonium sulfate, and fugitive dust. Wood smoke was identified at every site, with both aged and primary wood smoke identified at most sites. Wood smoke contributions to PM2.5 were averaged for the two winter months of December and January, the months when wood smoke in the Northwest U.S. is mainly from residential wood combustion. The total contribution of primary plus aged smoke from residential wood combustion ranged from 11.4% to 92.7% of average December and January PM2.5, depending on the site, with the highest percent contributions occurring in smaller towns that have fewer expected sources of winter PM2.5.
Receptor modeling at multiple sites provided significant advantages over modeling a single site. Results from multiple sites allowed common factor chemical compositions to be identified, making it easier to evaluate when a PMF factor at a particular site represents a mix of sources versus a single source. For commonly identified factors, average chemical profiles were established. Regionally-based average profiles such as these could be used as source profile inputs in Chemical Mass Balance receptor modeling, when the availability of local source profiles is limited. Multisite results could also be used to evaluate source specific impacts in source-oriented models like CMAQ and CAMx.