Comparison and evaluation of methods to apportion ambient PM2.5 to residential wood heating in Fairbanks, AK

Abstract

Biomass burning for residential heating significantly contributes to ambient PM2.5 burdens in many areas, making source apportionment to wood heater emissions an important issue. This study compares and evaluates Chemical Mass Balance (CMB), levoglucosan analysis, and14C analysis methods for apportionment. Results suggest that the CMB method appears to overestimate the contribution of residential wood heating in Fairbanks, perhaps due to non-representativeness of emissions source profiles. Carbon-14 analysis allows for apportionment to biomass sources, but must be corrected for non-carbon PM2.5 content. Levoglucosan analysis has the advantage of being relatively inexpensive, but there is considerable uncertainty in determining conversion factors to calculate wood smoke levels from measured levoglucosan concentrations. Conversion factors in the range of 9.1 to 13.3 are calculated from previously published and experimental mass fractions of levoglucosan in wood smoke PM2.5. Conversion factors in the range of 10.7 to 12.9 are determined from analysis of independent field measurements of 14C and levoglucosan in Fairbanks. The calculated and measured conversion factors are consistent and are similar to previously-reported values. The three apportionment methods (focused on residential wood smoke contributions) are complementary and collectively provide a means to evaluate or confirm apportionment results.