S.O.P. No. MLD 064 - Analysis of Anions and Cations in PM2.5 Speciation
by Ion Chromatography
In 1997, the U.S. Environmental Protection Agency created new federal air quality standards for PM2.5 and ozone, and proposed new requirements to reduce the regional haze that impairs visibility. The PM2.5 standards complement existing federal and state standards that target the full range of inhalable particulate matter (PM10). Efforts to characterize PM 2.5 and comply with the federal standards will further progress toward California's own PM10 standards.
The goal of the PM2.5 monitoring program is to provide ambient data that support the nation's air quality programs. These data include mass measurements and chemically resolved, or speciated data. Mass measurements are used principally for comparison to the PM2.5 National Ambient Air Quality Standards (NAAQS). These comparisons identify areas that do or do not meet the PM2.5 NAAQS, thereby allowing areas to be designated as attainment or nonattainment. Speciated data support the development of emission mitigation strategies intended to reduce ambient PM2.5 levels. The data are used to evaluate emissions inventory and air quality models, analyze source attribution, and track the success of emission control programs.
SUMMARY OF METHOD
Method MLD064 determines anions (nitrate and sulfate) and cations (sodium, ammonium, and potassium) collected on nylon filters exposed to ambient air, which are submitted to the laboratory by site operators. The filters are extracted in deionized water by sonicating for one hour, shaking for one hour, and storing overnight in a refrigerator. The extract is analyzed by ion chromatography using a system comprised of a guard column, analytical column, a self regenerating suppressor, and a conductivity detector. Peak analysis is determined using Dionex Peaknet Chromatography Workstation software, version 6.40.