X-RAY-DIFFRACTION ANALYSIS AND SOURCE APPORTIONMENT OF DENVER AEROSOL

Continuous sampling of airborne particulate matter at Commerce City in northeast metropolitan Denver was carried out for 3.5 days in late Jan. 1982. The resulting low-volume and dichotomous filter samples were analyzed by X-ray powder diffraction, X-ray transmission and optical polarizing microscopy. Major species identified in the coarse fraction included quartz, clays, 2 varieties of feldspar (1, K-rich) and muscovite. Carbonaceous matter occurred primarily in the fine fraction where 52.9% was observed in the dichotomous sample. Artifact sodium nitrate was observed deep within the fine fraction filter substrate of the dichotomous sample. A least squares effective variance source apportionment was applied to both sample sets yielding the following mass-weighted average source contributions: soil material, 47%; salt aerosol from street standing, 5%; normal vehicular combustion, 4%; and local diesel emissions, 20.5%. Also observed was 2.6% nitrate of undefined source and .apprx. 1% receptor mass, each from adjacent flour mill activities and a nearby coal-fired power plant.