Source-Receptor Relationships. Hypothesis 4.1 A complementary suite of instruments (single particle instruments, continuous composition monitors) and techniques (enhanced organic tracers, inorganic tracers) can directly determine the local air quality contributions from a broad range of sources including a) primary emissions from power plants fired by coal, oil, or gas, diesel- or gasoline-powered transportation, meat cooking, coke plants, biogenics, biomass burning, incineration, and crustal sources and b) secondary compounds emitted from power plants, and transportation systems.
Source-Receptor Relationships. During the study roughly 90% of the PM2.5 concentration came from areas outside Pittsburgh. Local transportation contributed only 7% to the average PM2.5 concentration (Xxxx et al., 2004; Xxxx et al., 2005b). [HYPOTHESIS 3.6] • While most of the PM2.5 concentration had regional sources roughly half of the particle number concentration was due to local transportation sources (Xxxx et al., 2004; Xxxxxxx et al., 2004c; Xxxx et al., 2005b). [HYPOTHESIS 3.6] • During the winter sulfate reductions will lead to increases in the nitrate concentrations. It is predicted that a 50% sulfate reduction will lead to a 10% decrease of inorganic PM2.5 mass concentrations. For a 50% reduction in ammonia availability, inorganic PM2.5 was reduced by approximately 30%, while for a 50% reduction in total nitric acid a 15-20% reduction in inorganic PM2.5 is predicted (Xxxxxxx et al., 2005). [HYPOTHESIS 3.4] • No major enhancement of the organic concentration is observed during periods when the aerosol is acidic, which suggests that acid-catalyzed SOA formation was not an important process during this study (Xxxxx et al., 2005). • Two systematic approaches (extensions of the EC tracer method) for the estimation of the SOA contribution to the OC levels were proposed by Xxxxxx et al. (2004a) and Xxxxxx et al. (2005). The first method requires semi-continuous measurements of OC and EC and is applicable to areas where most of the OC is not emitted by local sources. The use of daily average OC and EC measurements results in an under-prediction of the SOA concentration. The second approach requires also continuous VOC measurements. • Use of continuous size distribution, particle composition (sulfate, nitrate, and metals), and gas-phase concentrations in source-receptor analysis increased dramatically our ability to resolve source contributions to ambient PM2.5 concentrations. Eleven sources were identified for two summer episodes:, remote traffic, local traffic, diesel traffic, secondary sulfate, secondary nitrate 1 and 2, a lead source, coal-fired power plants, steel xxxxx, coke plants, and nucleation (Zhou et al., 2005a). [HYPOTHESIS 4.1] • An observation-based model, the thermodynamic model with removal (TMR) was developed to estimate responses of PM2.5 concentrations to changes in precursor concentrations. Use of the model requires semi-continuous measurements of sulfate, total nitrate, total ammonia, PM2.5 nitrate, and PM2.5 ammonium (Xxxxxxx et al., 2005). [HYPOTHESIS 3.4] • For ...
