Seasonal composition of remote and urban fine particulate matter in the United States

Abstract

Speciated aerosol composition data from the rural Interagency Monitoring for Protected Visual Environments (IMPROVE) network and the Environmental Protection Agency's urban/suburban Chemical Speciation Network (CSN) were combined to evaluate and contrast the PM2.5 composition and its seasonal patterns at urban and rural locations throughout the United States. We examined the 2005–2008 monthly and annual mean mass concentrations of PM2.5 ammonium sulfate (AS), ammonium nitrate (AN), particulate organic matter (POM), light‐absorbing carbon (LAC), mineral soil, and sea salt from 168 rural and 176 urban sites. Urban and rural AS concentrations and seasonality were similar, and both were substantially higher in the eastern United States. Urban POM and LAC concentrations were higher than rural concentrations and were associated with very different seasonality depending on location. The highest urban and rural POM and LAC concentrations occurred in the southeastern and northwestern United States. Wintertime peaks in AN were common for both urban and rural sites, but urban concentrations were several times higher, and both were highest in California and the Midwest. Fine soil concentrations were highest in the Southwest, and similar regional patterns and seasonality in urban and rural concentrations suggested impacts from long‐range transport. Contributions from sea salt to the PM2.5 budget were non‐negligible only at coastal sites. This analysis revealed spatial and seasonal variability in urban and rural aerosol concentrations on a continental scale and provided insights into their sources, processes, and lifetimes.

Composition and evolution of volcanic aerosol from eruptions of Kasatochi, Sarychev and Eyjafjallajökull in 2008–2010 based on CARIBIC observations

“…Jimenez et al (2009) report average urban organic aerosol concentrations up to 30 000 ng m −3 (Beijing, China) and, even at remote sites like Hyytiala, Finland the organic concentration exceeds one thousand ng m −3 . In a study focusing on the USA, urban regions average concentrations of several thousand ng m −3 were found and in rural areas the organic concentration was of the order 1000 ng m −3 (Hand et al, 2012). Interestingly, the Alaskan rural average organic aerosol concentration peaks in August, the month of the Kasatochi eruption, at approximately 3000 ng m −3 .…”

Aerosol loading in the Southeastern United States: reconciling surface and satellite observations

“…The IMPROVE network PM 2.5 values used in this study are the reconstructed fine mass (RCFM) determined by adding the values of ammonium sulfate, ammonium nitrate, soil, sea salt, elemental carbon and organic matter. We use 1.8 as the organic carbon to organic matter multiplier following Hand et al (2012), though we note that this could be too high or too low at specific sites as Malm and Hand (2007) have given a range of 1.2 to 2.6.…”

“…Previous studies have shown that the fine particulate matter (smaller than 2.5 µm in aerodynamic diameter, PM 2.5 ) in the region is dominated by ammonium sulfate and organic matter (OM), which together account for 60-90 % of the surface PM 2.5 concentrations (Edgerton et al, 2005;Weber et al, 2007;Hand et al, 2012;Zhang et al, 2012). Throughout most of the year, organic carbon is produced from wood combustion and diesel exhaust; while secondary production dominates in the summertime (Zheng et al, 2002).…”

Light Absorbing Properties of Brown Carbon Generated from Pyrolytic Combustion of Household Biofuels

“…Filter paper collected OA generated from biomass burning and extracted with acetone show light absorption which increases towards shorter wavelength of visible range (Kirchstetter et al, 2004, Chen andBond, 2010). Presence of organic matter in atmospheric aerosols is very profound, especially in biomass burning regions (Hand et al, 2012). Organics in atmospheric aerosols account for 10 to 70% of its total dry mass (Murphy et al, 2006).…”