## 3 Results and Discussion
### Analysis of Elemental Compositions in Urban PMs and Incineration Asl
#### 3.3.2 Analysis of Elements of Incineration Ash and Urban PMs by the WD-XRF Method
Of these, Na and Cl are the major ionic species of airborne particulates, and their values seem to indicate the effects of sea salt, biomass burning, and road salt (K element is also 68% high.) [1,4,54]. The high Zn mass fraction appears to be associated with vehicle traffic effects because Zn is known to be associated primarily with engine oil combustion, tire debris, and brake lining [3,58,52]. In addition, Ba, Sb, and Cu are +100%, \begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & \multicolumn{2}{c}{**NIST SRM 1648a Urban PM**} & \multicolumn{2}{c}{**KRISS Urban Dust CRM Candidate**} & \multicolumn{2}{c}{**KRISS Ash CRM Candidate**} \\ \cline{2-6}
**E1.** & **WD-XRF** & **NIST Certified Values** & **WD-XRF** & **WD-XRF** & **ID-ICP/MS** \\ \cline{2-6}  & \multicolumn{2}{c}{**Mass Fraction \(\pm\) Expanded Uncertainty (mg/kg, \(k\) = 2)**} & & & \\ \hline P & 8410 \(\pm\) 588 & N/A & 1100 \(\pm\) 177 & 70,907 \(\pm\) 3686 & N/A \\ Si & 124,500 \(\pm\) 6400 & \({}^{\dagger}\) 128,000 \(\pm\) 4000 & 138,000 \(\pm\) 7700 & 182,360 \(\pm\) 9243 & N/A \\ Ni & 90 \(\pm\) 15 & 811 \(\pm\) 6.8 & 90 \(\pm\) 16 & 110.46 \(\pm\) 29 & 95.2 \(\pm\) 6.7 \\ Pb & N/A & 6550 \(\pm\) 330 & \(<\)150 & 1649 \(\pm\) 27 & 145.2 \(\pm\) 2.0 \\ \hline \multicolumn{6}{l}{The values represented as N/A are not available. \({}^{\dagger}\) Among the values certified by NIST, the mass fraction value of Si} \\ \multicolumn{6}{l}{is the reference value, and the others are certified values.} \\ \end{tabular}
\end{table} 
Table 3: Mass fractions of elements in NIST SRM 1648a urban PM, KRISS urban dust CRM candidate, and KRISS ash CRM candidate analyzed by WD-XRF and ID-ICP/MS. Figure 4: Gamma-ray spectra of KRISS urban dust CRM candidate irradiated for (**a**) 2 min and (**b**) 12 h.  
+64%, and +254% high, respectively. These elements are known to be related to fuel combustion and automotive brake wear emission [3; 50; 58; 59; 60]; Ba is particularly used in the form of BaSO\({}_{4}\), which is employed as a quantitative marker for vehicular emission [3]. A temporal variation study of airborne particulates in 2015-2016 showed that the concentrations of Zn and Ba are lower during weekends than during weekdays due to road traffic reduction; by contrast, Cu and Pb rise during weekends because of an increase in industrial emissions [58]. The elements in KRISS urban dust CRM candidate as compared to NIST SRM 1648a that showed relatively lower concentrations are Ag (\(-\)82%), As (\(-\)72%), Br (\(-\)89%), Cd (\(-\)93%), Cr (\(-\)45%), Hg (\(-\)70%), Se (\(-\)77%), Ta (\(-\)84%), U (\(-\)45%), and V (\(-\)50%). The concentrations of the elements As, Br, Cd, Cr, and Hg, which are generally known to be toxic, are relatively low compared to those in NIST SRM 1648a. According to the air quality guidelines from the World Health Organization [61], the International Agency for Research on Cancer has classified As, Cd, Cr(VI), and Ni as human carcinogens (Group 1) and Pb as probably carcinogenic to humans (Group 2A) [2; 58; 61; 62]. Cd, As, and Pb are particularly known to be associated with industrial activities, such as heavy and metallurgical industry, coal burning, and copper production [2; 58; 53]. In addition, Cd and Cr are elements of industrial origin that enter the air due to the resuspension of soil dust [52]. Hg comes mostly from industrial use, coal combustion, and waste incineration [60]. Ag is newly introduced to the environment [63]; as photo films disappear, silver emission decreases in the short term. However, predictions indicate that the emission patterns of Ag will change steadily as it is increasingly applied in electronic devices and the textile and plastic industries [64]. The source apportionment study showed that residual combustion sources are Ni and V; As, Se, and Tl are related to coal combustion [1; 4; 50; 54]. The origin of airborne particulates cannot be determined simply from the change of mass fractions of certain elements by several factors, because they are known to contribute in combination [1].