Intercommunity differences in acid aerosol (H+)/sulfate (SO4(2-) ratios

Area of Science:

• Environmental Science
• Public Health
• Atmospheric Chemistry

Background:

• Acid aerosols (H+) are linked to acute and chronic health issues.
• Previous studies monitored H+, sulfates (SO4(2-)), and ammonia (NH3) in North America.
• Spatial variations in acidity levels were investigated in Philadelphia.

Purpose of the Study:

• To characterize seasonal and daily variations of acid aerosols, sulfates, and ammonia.
• To examine factors causing spatial variation in acidity levels.
• To investigate relationships among H+, SO4(2-), ozone, and population density.

Main Methods:

• Extensive monitoring of H+, SO4(2-), and NH3 in 24 US and Canadian communities (1988 onwards).
• Summer monitoring in Philadelphia (1992-1993) and State College, Ohio.
• Analysis of summer measurements from multiple sites, including New York City region, Buffalo, and Albany.

Main Results:

• Past studies showed temporal correlation between H+ and SO4(2-).
• Spatial variations in mean acid-to-sulfate ratios were predicted using linear or quadratic models (R2 = 0.6) after accounting for population density.
• Models demonstrated satisfactory prediction of spatial variations.

Conclusions:

• Population density is a significant factor in spatial variations of acid-to-sulfate ratios.
• Developed models can aid retrospective epidemiological studies on acid aerosol health effects.
• Widely available sulfate measurements and population data can be utilized for health impact assessments.