## 3 Results and Discussion
### Methodology Tests
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & **This Method** & **[PERSON] et al. [14]** & **[PERSON] et al. [13]** & **[PERSON] et al. [5]** & **[PERSON] et al. [15]** \\ \hline Tested Hg quantity & 103 & unknown & 0.5–2.7 & 30–80 & 4.7–200 \\ (ng) & 40\% inversed aqua & 1\% KMnO4 in 5\% & & & \\ the extraction & regia & H\({}_{2}\)SO4 & & inversed aqua regia & 1\% KMnO4 & 0.03–1\% KMnO4 or 40\% HNO3:BrCl \\ Extraction time (h) & 24 & 2 & unknown & unknown & 0.7 \\ Extraction method & plastic bag & purging under the programmed heating & purging under the programmed heating & purging under the programmed heating & purging under the \\ Recovery yield (\%) & 100–103 & 99.1–99.6 & 75–102 & heating & pregium \\ \hline \hline \end{tabular}  
\end{table} 
Table 3: Comparison of acid extraction methods for gaseous elemental mercury. The reported scaling factors for the masses of 199, 200, 201, and 204 were 0.2520, 0.5024, 0.7520, and 1.493, respectively. The calculated \(\Delta^{\rm x}\)Hg values for the background-corrected TGM from the 24 March Noyaki showed a slightly, but significantly, odd MIF (Table 5). This may imply that such light isotopic compositions may be associated with the isotopic fractionations that occur in the evaporation process during the burning of a field, and the process may involve a small MIF. Such an MIF was not observed in the 6 April Noyaki sample, and the \(\Delta^{\rm 199}\)Hg and \(\Delta^{\rm 204}\)Hg varied widely, i.e., \(-\)2.3% and 2.9%, respectively. The reason for the variation is unknown, and further research is needed. Analysis of the TGM from the laboratory and clean room air showed the sufficient collection of TGM (116 and 85 ng, respectively) and the successful analysis of their \(\delta^{\rm x}\)Hg values, ranging from \(-\)0.11% to \(-\)0.59% (Table 4). The collection of GEM from the outdoor air was also successful (88 ng) and sufficient for creating a sample solution for isotope measurements, showing a range from \(-\)0.12% to 0.48%. The \(\delta^{\rm x}\)Hg values in the clean room air were the lightest, and this may be attributed to the isotope fractionation that occurred at the surface of mercury absorbent used for cleaning the air. The \(\Delta^{\rm x}\)Hg values for all of these air samples showed a consistent trend--a higher \(\Delta^{\rm x}\)Hg value for a greater mass (Table 6). The \(\delta^{\rm x}\)Hg of the residual GEM after the reaction with OH radicals exhibited large isotope fractions--from \(-\)1.63% to 9.96% at the 44% extent of Hg reaction estimated from the concentration of the extract (Table 4). A saw-tooth pattern was clearly seen in the \(\delta^{\rm x}\)Hg profile between \({}^{199}\)Hg and \({}^{202}\)Hg. With the exception of \({}^{204}\)Hg, this pattern was due to MDF and MIF on odd- and even-numbered masses, respectively: for the odd-numbered masses, the light mercury isotope--\({}^{198}\)Hg--reacted faster than the heavy isotopes of \({}^{199}\)Hg and \({}^{201}\)Hg, resulting in heavy \(\delta^{\rm x}\)Hg values in the residual GEM; meanwhile, for the even-numbered masses, the heavy isotopes of \({}^{200}\)Hg and \({}^{202}\)Hg reacted faster than \({}^{198}\)Hg, resulting in light \(\delta^{\rm x}\)Hg values. The \(\delta^{204}\)Hg value is an exception, as this even-numbered \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Sample** & \(\Delta^{\rm 199}\)**Hg (\%)** & \(\Delta^{\rm 200}\)**Hg (\%)** & \(\Delta^{\rm 201}\)**Hg (\%)** & \(\Delta^{\rm 201}\)**Hg (\%)** & \(\Delta^{\rm 204}\)**Hg (\%)** \\ \hline Outdoor air & 0.11 & 0.55 & 0.71 & 1.87 \\ Laboratory air & 0.12 & 0.36 & 0.48 & 1.23 \\ Clean room air & 0.00 & 0.27 & 0.25 & 0.80 \\ Reactor GEM & 8.96 & \(-\)1.43 & 5.44 & 10.52 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Calculated \(\Delta^{\rm x}\)Hg values for the air and laboratory experimental samples.