WATER-UPTAKE BY AEROSOL-PARTICLES FROM AUTOMOBILE EXHAUST AND WOOD SMOKE

Water uptake by combustion aerosol particles from common anthropogenic combustion sources was estimated by weighing filter samples while var ying the relative humidity in the weighing chamber of an electronic mi crobalance. This technique was suitable for samples which weighed more than 3 mg. Significant water uptake was observed for diesel soot, gas oline exhaust, and wood smoke particles. Weights for typical diesel so ot samples increased by slightly less than 2% as relative humidity was increased from 40% to 90%. Automobile exhaust sample weights increase d by at least three to four times and wood smoke by at least three to more than five times as much as diesel soot sample weights. No effect of temperature was observed. It was concluded that atmospheric mass lo adings of particulate matter from these sources increase by a small bu t significant amount as atmospheric relative humidity increases.