title: Assessment of primary and secondary ambient particle trends using satellite aerosol optical depth and ground speciation data in the New England region, United States.
abstract: The effectiveness of air pollution emission control policies can be evaluated by examining ambient pollutant concentration trends that are observed at a large number of ground monitoring sites over time. In this paper, we used ground monitoring measurements in conjunction with satellite aerosol optical depth (AOD) data to investigate fine particulate matter (PM2.5; particulate matter with aerodynamic diameter ≤ 2.5 µm) trends and their spatial patterns over a large U.S. region, New England, during 2000-2008. We examined the trends in rural and urban areas to get a better insight about the trends of regional and local source emissions. Decreases in PM2.5 concentrations (µg/m(3)) were more pronounced in urban areas than in rural ones. In addition, the highest and lowest PM2.5 decreases (µg/m(3)) were observed for winter and summer, respectively. Together, these findings suggest that primary particle concentrations decreased more relative to secondary ones. This is also supported by the analysis of the speciation data which showed that downward trends of primary pollutants including black carbon were stronger than those of secondary pollutants including sulfate. Furthermore, this study found that ambient primary pollutants decreased at the same rate as their respective source emissions. This was not the case for secondary pollutants which decreased at a slower rate than that of their precursor emissions. This indicates that concentrations of secondary pollutants depend not only on the primary emissions but also on the availability of atmospheric oxidants which might not change during the study period. This novel approach of investigating spatially varying concentration trends, in combination with ground PM2.5 species trends, can be of substantial regulatory importance.
authors.affiliation: Exposure, Epidemiology, and Risk Program, Department of Environmental Health, Harvard School of Public Health, Boston, MA, USA. Electronic address: hlee@hsph.harvard.edu.
authors.forename: Hyung Joo
authors.initials: HJ
authors.lastname: Lee
authors.affiliation: Exposure, Epidemiology, and Risk Program, Department of Environmental Health, Harvard School of Public Health, Boston, MA, USA.
authors.forename: Choong-Min
authors.initials: CM
authors.lastname: Kang
authors.affiliation: Department of Biostatistics, Harvard School of Public Health, Boston, MA, USA.
authors.forename: Brent A
authors.initials: BA
authors.lastname: Coull
authors.affiliation: School of Forestry and Environmental Studies, Yale University, New Haven, CT, USA.
authors.forename: Michelle L
authors.initials: ML
authors.lastname: Bell
authors.affiliation: Exposure, Epidemiology, and Risk Program, Department of Environmental Health, Harvard School of Public Health, Boston, MA, USA.
authors.forename: Petros
authors.initials: P
authors.lastname: Koutrakis
mesh_terms: D000336:Aerosols / Q000145:classification*; D000397:Air Pollution / Q000032:analysis* / Q000331:legislation & jurisprudence; D004784:Environmental Monitoring / Q000295:instrumentation / Q000379:methods* / Q000592:standards; D005544:Forecasting / Q000379:methods; D006801:Humans; D009511:New England; D052638:Particulate Matter / Q000737:chemistry* / Q000145:classification; D058998:Remote Sensing Technology / Q000145:classification / Q000379:methods / Q000639:trends; D012424:Rural Population / Q000639:trends; D012621:Seasons; D014505:Urban Population / Q000639:trends
chemical_list: D000336:Aerosols; D052638:Particulate Matter
keywords: AOD; Emission; MODIS; PM(2.5); Trend analysis