AAAR 34th Annual Conference
October 12 - October 16, 2015
Hyatt Regency
Minneapolis, Minnesota, USA
Abstract View
Spatial Patterns and Temporal Trends of Black Carbon in Boston MA
GEORGE ALLEN, NESCAUM
Abstract Number: 465 Working Group: Carbonaceous Aerosols in the Atmosphere
Abstract Spatial patterns and temporal trends of black carbon soot (BC) in Boston, MA were evaluated using Aethalometer data from multiple sites and years. BC data were corrected for known artifacts from spot loading and instrument configuration changes over the 15-year period of data collection. Concentrations of BC decreased by almost a factor of 2 between 2002 and 2004; during this time period, the entire Boston school bus and city public transit bus fleets were either replaced or retrofitted with diesel particle filters, and State diesel Inspection and Maintenance programs were implemented. The large decrease in BC is likely due to these programs, and demonstrates their effectiveness and benefits. From 2005 to 2014, BC concentrations in Boston have not decreased at two of the three long term monitoring sites. Annual average BC at the new Boston near-road site is 1.5 micro-grams/m$^3 (2014), similar to neighborhood scale BC in 1999-2001 and twice as high as BC now measured at the urban-scale NCore site in Boston. BC is substantially higher in late summer compared to late winter, fitting the pattern of inverse monthly wind speed. There were substantial spatial gradients of annual average BC, with concentrations at core downtown sites 3 times higher than at the upwind suburban site. BC was associated with time of day and day of week traffic patterns, consistent with mobile source activity. Within the core urban area, there was substantial local scale heterogeneity. Diurnal day of week analysis identified the influence of a local emergency genset’s weekly testing operation on BC at one of the urban sites. Non-parametric wind regression analysis identified a commuter rail hub as a large source of BC.