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Elemental Versus Black Carbon: Are They Interchangeable? Insights from Extensive Measurement Campaigns in Southern California
FARAZ AHANGAR, Payam Pakbin, Sina Hasheminassab, Mohammad Sowlat, Avi Lavi, Christopher Lim, South Coast Air Quality Management District
Abstract Number: 676
Working Group: Carbonaceous Aerosol
Abstract
Elemental Carbon (EC) is one of the key components of ambient particulate matter with many adverse climate and health impacts. Traditionally, EC has been quantified by time-integrated filter-based EC measurements with subsequent laboratory analysis across the United States. In the past decade, continuous black carbon (BC) measurements are being more commonly used due to their higher time resolution and lower detection limit. While EC and BC are operationally defined, previous studies found good correlations among these two parameters. However, the relationships between EC and BC are not similar across the studies. Also, the spatial and temporal changes of EC-BC relationships are rarely explored.
In this work, we explore if the relationship between BC and EC is dependent on the characteristics of the location or whether it changes over time. We used the results from two air monitoring campaigns conducted in Southern California in 2012-2013 and 2018-2019. The data included EC measurements acquired through the IMPROVE thermal/optical reflectance method and BC measurements by seven-wavelength aethalometers at ten distinct locations in the South Coast Air Basin. The preliminary results showed that while highly correlated, BC concentrations were consistently higher than EC, especially at lower concentration levels. This is probably due to the different measurement techniques as well as the better detection limit of the aethalometers. Also, no significant trend between EC-BC relationship and the measurement season or location was observed during the study period. However, this relationship changed between the two campaigns which might be caused by the lower BC and EC levels during the second campaign, elevating the effects of higher BC-EC ratios at lower concentration levels.