SIZE SPECTRA AND ATMOSPHERIC GROWTH OF V-CONTAINING AEROSOL IN WASHINGTON, DC

Size-segregated submicrometer aerosol particles were collected with mi cro-orifice impactors (MOI) at three sites in the heavily urban, but n onindustrialized Washington, DC metropolitan area during a 40-day peri od in August and September of 1990, when atmospheric V (an important m arker of oil combustion emissions) was principally derived from commer cial and utility oil combustion. Results for 34 MOI samples, analyzed for V by instrumental neutron activation analysis, were fit with a lea st-squares technique which used impactor calibration data to determine log-normal distribution parameters, i,e., mass median aerodynamic dia meter (mmad) and geometric standard deviation (sigma(g)) for fine part icles bearing V. Geometric size distribution parameters were also dete rmined. The median mmad for 19 College Park (CP) samples was 0.361 +/- 0.006 mu m At this site, mmads for samples collected in the absence o f rain and with V concentrations > 0.61 ng/m(3) increased continuously with increasing relative humidity (RH) from 56% to 79% according to t he equation d(p)(3) = -0.0222 +/- 0,0033/ln(a(w)) - 0.013 +/- 0.009. M mads for samples collected at Andrews AFB were characteristically smal ler than those determined at CP at comparable RH, probably due to the influence of a nearby oil-fired boiler.