Determination of the Size Distribution and Chemical Composition of Fine Particulate Semivolatile Organic Material in Urban Environments Using Diffusion Denuder Technology

Fine Particulate Chemical Composition and Light Extinction at Meadview, AZ

“…1 These data show that the quartz filter artifact originated from the reabsorption of some of the SVOCs lost from the particles during sampling and not from the collection of gas-phase organic compounds. 1,4,13 This agrees with previous results at Canyonlands National Park. 3 In contrast, in the Los Angeles Basin, the majority of the quartz filter artifact was from the collection of gas-phase organic material.…”

“…11,19,20 The origin of the "quartz artifact" can be determined by comparing the carbon collected by a second quartz filter before and after the diffusion denuder, filters Q 2,2 and Q 1,2 , respectively. 1,4 In the Project MOHAVE Meadview Study, the quartz artifact was unchanged after removal of the gas-phase organic material by a diffusion denuder. In addition, the quartz filter after a quartz filter denuder (Q 2,3 in Figure 1) collected no organic material.…”

“…4 Figure 7 displays the various average size distributions. Particle size distributions for sulfate and crustal material obtained from the DRUM were generally more gaussian in nature and had mass median diameters ϳ20% smaller than for the MOUDI results.…”

“…In Los Angeles, the artifact was markedly reduced after a diffusion denuder to remove gas-phase organic compounds. 4,13 Proper quantification of the negative artifact requires the differentiation of the organic material collected by the sorbent filter in the denuder sampler (ClF 1,1 in sampler 1, Figure 1) into gas-phase organic material that was not removed by the denuder and SVOCs lost from the particulate organic material. To determine the fraction of the volatilized carbon collected by the sorbent filter in the denuder sampler that originated from collected particles, the denuder breakthrough must be known or simultaneously measured.…”

“…However, the concentrations of both of these species determined from filter pack measurements may be in error because of sampling artifacts. Significant amounts of semivolatile organic material may be lost from fine particles during sampling [1][2][3][4] and, under some conditions, some SO 2 may be absorbed by fine particles during sample collection. 5,6 As a result of these sampling artifacts, the contribution of particulate sulfate to light extinction may be slightly overestimated and the contribution of particulate organic material significantly underestimated.…”