WATER-UPTAKE BY SUNLIGHT AND OZONE EXPOSED DIESEL EXHAUST PARTICLES

Two types of experiments were conducted to investigate the effect of a erosol aging on water uptake by diesel soot particles. First, in three experiments diluted diesel soot was exposed to sunlight for up to 10 hours in a 190 m(3) Teflon film smog chamber and filter samples were c ollected at various time intervals. Second, diesel soot filter samples were exposed to 2 to 4 ppm ozone concentrations for 3 hours in a stai nless steel chamber. Water uptake was measured by weighing the filter samples from each type of experiment by varying relative humidity in t he weighing chamber of an electronic microbalance. When relative humid ity was increased from 40% to 90% weights of fresh diesel soot samples from the smog chamber increased by less than 2% and sample weights of diesel soot aged in the chamber for 9 to 10 h increased by 7 to 8%. S ample weights for diesel soot filter samples aged in the stainless ste el chamber in the presence of ozone in the dark increased by less than 2.5% over the same relative humidity range. Copyright (C) 1996 Elsevi er Science Ltd