10th International Aerosol Conference
September 2 - September 7, 2018
America's Center Convention Complex
St. Louis, Missouri, USA

Abstract View


Long-Term, Continuous Aethelometer Monitoring Data Reveal Unexpected Black Carbon and Brown Carbon Sources

K. MAX ZHANG, George Allen, Philip K. Hopke, James Schwab, Oliver Rattigan, H. Dirk Felton, Cornell University

     Abstract Number: 1612
     Working Group: Combustion-Generated Aerosols: the Desirable and Undesirable

Abstract
Rochester, NY has one of the longest uninterrupted monitoring of light-absorbing PM in the world. A two-wavelength Aethalometer (model AE-22) has been operating continuously at an urban site since 2004. Our recent analysis of the existing data revealed some surprising findings. First, our examination of temporal patterns showed a consistent late nighttime (around 10 pm) peak of BC (880 nm) in all seasons, which was not consistent with traffic patterns in Rochester. Further analysis clearly demonstrated that the dominant wind direction for high nighttime BC almost perfectly align with a railway line near the monitoring site. It is likely that some nighttime idling and switching activities of diesel locomotives in the railway yard about 1.5 km from the monitor lead to the observed elevated BC concentrations . Second, our analysis indicated that daily mean DC (= BC(370nm)-BC(880nm)) values are statistically higher on weekend days than weekdays during summertime. Since DC has been shown a good woodsmoke (or Brown Carbon) indicator, we originally believed that the DC signals should be quite low in summertime in the absence of heating demand. Zooming into the time series of BC (880 nm) and DC reveals that spikes of synchronized PM2.5, DC and BC(880 nm) around midnight on weekend days. These results strongly suggest a non-negligible contribution of recreational wood burning to PM2.5 during summertime by source apportionment analysis. The potential sources could include camp fires, chimineas, and fire pits. Our findings support the benefits of long-term, continuous light-absorbing PM monitoring on air quality management.