Spatial Characteristics of Fine Particulate Matter: Identifying Representative Monitoring Locations in Seattle, Washington

• Published in: Journal of the Air & Waste Management Association (1995) Vol. 52; no. 3; pp. 324 - 333
• Main Authors: Goswami, Emily, Larson, Timothy, Lumley, Thomas, Liu, L.-J. Sally
• Format: Journal Article
• Language: English
• Published: Pittsburgh, PA Taylor & Francis Group 01.03.2002; Air & Waste Management Association; Taylor & Francis Ltd
• Subjects: Air Pollutants - analysis; Air Pollution - prevention & control; Air. Soil. Water. Waste. Feeding; Applied sciences; Atmospheric pollution; Biological and medical sciences; Environment. Living conditions; Environmental Exposure; Environmental Monitoring - methods; Epidemiologic Studies; Exact sciences and technology; Guideline Adherence; Humans; Medical sciences; Models, Theoretical; Particle Size; Pollutants physicochemistry study: properties, effects, reactions, transport and distribution; Pollution; Public Health; Public health. Hygiene; Public health. Hygiene-occupational medicine; Public Policy; United States; North America; Washington; America; USA, Washington, Seattle; Human; Air quality; Exposure; Urban area; Spatial variation; Variance analysis; Time variation; Ambient air measurement; Suspended particle; Ambient air concentration; Surveillance; Site selection; Fine particle; Geographic information system; Statistical model; Aerosols; Air pollution; Public health
• ISSN: 1096-2247; 2162-2906
• DOI: 10.1080/10473289.2002.10470778

This study investigates how PM 2.5 varies spatially and how these spatial characteristics can be used to identify potential monitoring sites that are most representative of the overall ambient exposures to PM 2.5 among susceptible populations in the Seattle, WA, area. Data collected at outdoor sites at the homes of participants of a large exposure assessment study were used in this study. Harvard impactors (HIs) were used at 40 outdoor sites throughout the Seattle metropolitan area. Up to six sites at a time were monitored for 10 consecutive 24-hr average periods. A fixed-effect analysis of variance (ANOVA) model that included date and location effects was used to analyze the spatial variability of outdoor PM 2.5 concentrations. Both date and location effects were shown to be highly significant, explaining 92% of the variability in outdoor PM 2.5 measurements. The day-to-day variability was 10 times higher than the spatial variability between sites. The site mean square was more than twice the error mean square, showing that differences between sites, while modest, are potentially an important contribution to measurement error. Variances of the model residuals and site effects were examined against spatial characteristics of the monitoring sites. The spatial characteristics included elevation, distance from arterials, and distance from major PM 2.5 point sources. Results showed that the most representative PM 2.5 sites were located at elevations of 80-120 m above sea level, and at distances of 100-300 m from the nearest arterial road. Location relative to industrial PM 2.5 sources is not a significant predictor of residential outdoor PM 2.5 measurements. Additionally, for sites to be representative of the average population exposures to PM 2.5 among those highly susceptible to the health effects of PM 2.5 , areas of high elderly population density were considered. These representative spatial characteristics were used as multiple, overlapping criteria in a Geographic Information System (GIS) analysis to determine where the most representative sites are located.