Effect of ambient relative humidity on dry deposition of aerosol particles bearing trace elements
- Univ. of Maryland, College Park, MD (United States). Dept. of Chemistry
Aerosol particles < 15 m were size-fractionated with micro-orifice impactors at two urban (Washington, DC, area) and two rural Chesapeake Bay sites and analyzed by neutron activation analysis for 44 elements including, V, As, Se, Sb, and Zn, i.e., elements strongly associated with oil combustion, coal combustion, incineration, and intra regionally transported secondary aerosol. Size distribution parameters were determined nonparametrically and with a least-squares peak-fitting method using impactor calibration data and were used with relative humidity (RH) data and a computer model to investigate the effects of RH on particle size and deposition velocity for particles bearing the various elements. Mass mean aerodynamic diameters (mmads) for the urban samples increased continuously with increasing RH in the range 56 to 79%, but along different curves for samples influenced by local and distant sources. The mmads for samples influenced by winds from the direction of local sources were uniformly smaller than those influenced by westerly winds bearing aerosol from distant, regional, sources. At 60% RH, gmmads were As, 0.30 {+-} 0.03 and 0.46 {+-} 0.04; Se, 0.33 {+-} 0.06 and 0.54 {+-} 0.04; Sb, 0.39 {+-} 0.03 and 0.53 {+-} 0.04; and Zn, 0.39 {+-} 0.06 and 0.53 {+-} 0.08; respectively. Size spectra for Bay aerosol were more often multimodal. Mean aerosol deposition velocities determined for individual size spectra were combined with wind frequency distributions to estimate the influence of RH on annual dry particle deposition.
- OSTI ID:
- 33548
- Report Number(s):
- CONF-9410273--
- Country of Publication:
- United States
- Language:
- English
Similar Records
Size distributions parameters and hygroscopic growth of aerosol particles bearing V
Size spectra and atmospheric growth of V-containing aerosol in Washington, DC