## 3 Results and Discussion
### Tgm  
The measurement results showed that except for the sample collected on 6 April 2019, significant amounts of TGM were emitted from the noyaki events (Table 1). A comparison of the TGM concentrations with the background air revealed that the atmospheric TGM concentrations were enhanced by approximately four times. It is worth noting that the amount of TGM collected on 10 May 2021, was more than double that collected from the background air on different days. The arrival of Kosa, desert dust from China, was recorded in the Kyusyu region, therefore, this highly loaded TGM was the transboundary TGM. As discussed in the previous subsection, however, all the TGM concentrations determined by BAuT sampling may have been lower than the actual concentrations, due to the artifact from the transfer of TGM from BAuT to a conventional trap. A comparison between the concentrations determined by BAuT and conventional trap sampling made in the spring of 2021 showed lower concentrations determined by the former (Supplementary Table S6). Thus, the corrections on \(\delta^{x}\)Hg values for the biases caused by this analytical artifact were considered (see below). \begin{table}
\begin{tabular}{l c c c c c c c} \hline \hline \multirow{2}{*}{**Scheme 199**} & \multirow{2}{*}{
\begin{tabular}{c} **Total Hg** \\ **Sampled** \\ \end{tabular} } & **Conc. in air** & \multirow{2}{*}{\(\xi^{199}\)Hg} & \multirow{2}{*}{\(\xi^{200}\)Hg} & \multirow{2}{*}{\(\xi^{201}\)Hg} & \multirow{2}{*}{\(\xi^{202}\)Hg} & \multirow{2}{*}{\(\xi^{204}\)Hg} \\ \hline  & ng & \(\mathrm{ng\,m^{-3}}\) & & & & \\ \hline \multicolumn{6}{l}{_Noyaki samples_} \\ \hline
24 March 2019, Daikanpou BAuT \({}^{\star}\) & 14.5 & 3.7 & \(-0.58\) & \(-0.58\) & \(-1.01\) & \(-0.93\) & \(-1.40\) \\ \hline
6 April 2019, Namino BAuT * & 5.0 & 1.4 & \(-1.11\) & \(-0.69\) & \(-1.23\) & \(-1.37\) & \(1.18\) \\ \hline
23 March 2021, Ubuyama BAuT & 38.0 & 4.0 & \(-0.60\) & \(-0.66\) & \(-1.40\) & \(-1.34\) & \(-1.99\) \\ \hline
27 March 2021, Kitayama BAuT & 43.7 & 4.3 & \(-0.54\) & \(-0.57\) & \(-1.01\) & \(-1.03\) & \(-1.43\) \\ \hline \multicolumn{6}{l}{_Background air samples_} \\ \hline
31 March 2019, Namino BAuT \({}^{\star}\) & 5.7 & 0.8 & \(-0.05\) & 0.44 & 0.35 & 1.06 & 1.30 \\ \hline
23 May 2019, Namino BAuT \({}^{\star}\) & 15.0 & 0.7 & \(-0.02\) & 0.13 & \(-0.06\) & 0.16 & 0.49 \\ \hline
19 April 2021, Komezuka BAuT & 17.0 & 1.0 & \(-0.29\) & \(-0.15\) & \(-0.12\) & \(-0.11\) & \(-0.24\) \\ \hline
23 April 2021, Ubuyama BAuT & 18.7 & 1.0 & \(-0.34\) & \(-0.27\) & \(-0.11\) & 0.03 & \(-0.17\) \\ \hline
10 May 2021, Kitayama BAuT & 38.0 & 1.3 & \(-0.21\) & \(-0.18\) & \(-0.29\) & \(-0.28\) & \(-0.32\) \\ \hline \multicolumn{6}{l}{\({}^{\star}\)Published data [24].} \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Results of \(\delta^{x}\)Hg of TGM emitted from noyaki. Given the extent of the isotope fractionations observed in the overall recovery tests accompanying the Hg loss shown in Supplementary Table S6, the \(\delta^{\rm x}\)Hg values were corrected for the artifact fractionations (Table 2). Here, corrections for the \(\delta^{\rm x}\)Hg measurement biases observed in the recovery tests with 5.2-15.5 ng Hg (30% Hg loss) were applied to all the noyaki and background air data since the losses of Hg shown in Table S6 were larger than the loss found in the recovery tests with 41 ng Hg, and the sample size of noyaki and background air samples collected in 2019 were overall smaller than the samples collected in 2021. \(\delta^{\rm x}\)Hg values displayed that except for the \(\delta^{\rm 204}\)Hg value of the 6 April 2019, Namino sample, the \(\delta^{\rm x}\)Hg values of TGM samples emitted from noyaki were significantly smaller than those from the background air (Table 2). According to the reports for \(\delta^{\rm x}\)Hg values of Hg in plants and soils, low \(\delta^{\rm x}\)Hg values (or light isotopic compositions) have been found [31; 32; 33; 34; 35]. Our observations were consistent with their reports.