| Aerosol growth technology is used to collect sub-hourly samples of ambient aerosol particles for subsequent chemical analyses by graphite furnace atomic absorption spectrometry. Ambient air is sampled at a flow rate of 170 L·min−1, and particles are grown by condensation of water vapor in a condenser maintained at 0.5°C after saturation by direct injection of steam. The resulting droplets are concentrated 13.6-fold using a twin-nozzle virtual impactor and collected as a liquid slurry at a flow rate of about 0.2 mL·min−1 with a real impactor in an all-glass and plastic system. The prototype system's collection efficiency was tested with 0.084 to 3 μm diameter monodisperse fluorescent polystyrene latex particles. Particles initially 0.084 to 0.5 μm in diameter are collected with an overall efficiency of 40% which gradually increases with size to 68% for 3 μm particles.; Simultaneous multielement graphite furnace atomic absorption spectrometry is used to determine Al, As, Cd, Cr, Cu, Fe, Mn, Ni, Pb, Sb, Se, and Zn in three analytical groups. Instrumental detection limits are reported and are generally 3- to 8-fold greater than single-element literature values, due to compromise of furnace conditions. Detection limits in aerosol samples are further limited by system reagent blanks. Analyses of NIST SRM 1643d, Trace Elements in Water, agree well for all elements, except for Al. Analyses of NIST SRM 1648, Urban Particulate Matter, were typically within 10% of expected values for all elements except Al, Cr, and Fe, presumably due to incomplete atomization of refractory particles. This problem will be reduced for urban fine particulate matter samples (PM2.5), which typically contain much smaller amounts of coarse particles.; The prototype system was used to collect 30-min ambient air samples in College Park, MD. Measured concentrations in the samples were typically 2- to 5-fold greater than system blanks and 2- to 16-fold greater than laboratory blanks. From visual inspection of the 30-min samples, the temporal changes in the influences of major local sources, including motor vehicle traffic, coal- and oil-fired power plants, and municipal incineration, are clearly evident. Factor analysis of the 30-min samples provides excellent resolution of seven sources: urban dust, meteorology (i.e., wind speed and direction and mixing height), municipal incineration, coal- and oil-fired power plants, and an unknown As source. Factor analysis of 2.5-h averages of the 30-min samples failed to resolve the oil-fired power plant source. This clearly shows the utility of greater temporal resolution by increasing the power of factor analysis to resolve sources. |
