Urban-scale Spatial-temporal Variability of Black Carbon and Winter Residential Wood Combustion Particles

Abstract

It has been suggested that certain organic aerosol components of wood smoke have enhanced ultraviolet absorption at 370 nm relative to 880 nm in two-wavelength aethalometer black carbon (BC) measurements. This enhanced absorption could serve as an indicator of wood combustion particles (“Delta-C” = UVBC370nm – BC880nm). From August 2009 to October 2010, week-long mobile monitoring campaigns were conducted during each season in Rochester, New York. The temporal and spatial variations of BC and Delta-C were investigated at twelve monitoring sites. A portable two-wavelength aethalometer housed in Clarkson’s Mobile Air Pollution Lab was used for data collection. The average BC concentrations were 0.94 µg/m 3 , 0.68 µg/m 3 , 0.47 µg/m 3 , and 0.81 µg/m 3 in summer, winter, spring, and fall, respectively. BC and DeltaC hotspots were identified. Coefficients of divergence (COD) and correlation coefficients (r) were calculated between site pairs to assess the spatial and temporal heterogeneity. High spatial divergence but uniform temporal variation in BC were found for these sites. Winter residential wood combustion (RWC) particles exhibited high spatial heterogeneity as well. In epidemiological studies, BC particles data from a central monitoring site are generally used as the basis in population exposure estimation. These results suggest that one central monitoring site may not adequately represent the actual BC and RWC particle exposure over a whole urban area.