# Source-Based Size-Resolved Optical Properties of Carbonaceous Aerosols
## 3 Results and Discussion
Figure 4 shows the aerosol extinction and absorption coefficients of carbonaceous aerosols for each of the five sources with different \(d_{g0}\) and IRIs of HULISs. Figure 4 shows that each source has a distinct episodic peak at a different time. For example, during biogenic source-dominant periods, LBB does not contribute to emissions. During LBB source-dominant periods, SOAs as well as biogenic and mixed sources insignificantly contribute. Figure 3 also shows that the source-based \(b_{ext}\) and \(b_{abs}\) depend on the sizes and IRIs of HULISs. The \(b_{ext}\) at a \(d_{g0}\) of 0.1 \(\upmu\)m and IRI of 0.006 is the lowest compared with other sizes and IRIs. With respect to the absorption properties, \(b_{abs}\) at a \(d_{g0}\) value of 0.1 \(\upmu\)m and IRI of 0.3 is the highest compared with other sizes and IRIs. Figure 5 shows the change of the source-based extinction coefficient contribution for each sample. The sample data have different fractional contributions from different species as an input and the obtained total extinction coefficients as an output. As Figure 5 shows, the mass contribution and total extinction coefficient of each source shows similar tendencies although the detailed contribution depends on the size and refractive index of each source. Figure 4: Aerosol extinction and absorption coefficients of carbonaceous aerosols for each source with different geometric mean diameters (\(d_{g0}\): 0.1 and 0.5 μm) and imaginary refractive indices (IRIs) of HULISs (IRI of 0.006 and 0.3; \(\sigma_{g}\) = 1.5) (**a**) \(b_{cat}\), long-range biomass burning (LBB), IRI = 0.3, (**b**) \(b_{abs}\), LBB, (**c**) \(b_{ext}\), Local BB, (**d**) \(b_{abs}\), Local BB, (**e**) \(b_{ext}\), secondary organic aerosol, SOA), (**f**) \(b_{abs}\), SOA, (**g**) \(b_{ext}\), Biogenic, (**h**) \(b_{abs}\), Biogenic, (**i**) \(b_{ext}\), Mixed, (**j**) \(b_{abs}\), Mixed. Because of the lack of information regarding the source-based size distribution, we evaluated the contribution of extinction coefficients with different size. Figure 6 shows the comparison of the average source-based extinction coefficients for different \(d_{g0}\). A \(d_{g0}\) value of 0.5 \(\upmu\)m and IRI of 0.006 represent the background condition. The sources with different \(d_{g0}\) (0.1 \(\upmu\)m) were compared with the background conditions of other sources. Note that the mass concentration of each source did not change with \(d_{g0}\). Figure 6 shows that the contribution of \(b_{ext}\) differs depending on the \(d_{g0}\) value of the source. Generally, the contribution of sources decreases with decreasing \(d_{g0}\) value (\(d_{g0}\) of 0.1 \(\upmu\)m in this study). However, the magnitude of the decrease depends on the source. Based on the source-based mass concentration, the contributions can be ordered as follows: LBB > mixed > SOA > biogenic > local BB. However, Figure 6 shows that the contributions of the source-based extinction coefficients differ depending on the size distribution of the sources. Although Figure 6 shows the size dependency of source-based aerosol optical properties, this study assumed that the size distribution of each species was conserved without aggregation and this assumption may lead to potential errors as discussed in Section 2 and conclusions [20,21]. Figure 5: Contributions of source-based extinction coefficient and mass concentration with different geometric mean diameters (\(d_{g0}\) of 0.1 and 0.5 \(\upmu\)m) and imaginary refractive indices (IRIs) of HULISs (0.006 and 0.3; \(\sigma_{g}\) = 1.5) (**a**) \(b_{ext}\), \(d_{g0}\) = 0.1 \(\upmu\)m, IRI = 0.006, (**b**) \(b_{ext}\), \(d_{g0}\) = 0.5 \(\upmu\)m, IRI = 0.006, (**c**) \(b_{ext}\), \(d_{g0}\) = 0.5 \(\upmu\)m, IRI = 0.006, (**d**) \(b_{ext}\), \(d_{g0}\) = 0.5 \(\upmu\)m, IRI = 0.3, (**e**) source-based mass concentration).