## Materials and Methods  
### Sampling and Preconcentration of TGM  
TGM was collected using a big gold-coated sand trap (BAuT) (Figure 1). A BAuT is a custom-made 50 (o.d.) \(\times\) 45 (i.d.) \(\times\) 300 mm (length) quartz tube with a 45 (o.d.) \(\times\) 5 mm (thickness) fritted quartz plate (COSMOS VID, Fukuoka, Japan). Approximately 10.5 g gold-coated sand, which traps TGM at room temperature and releases TGM as GEM at high temperatures and is reused more than 50,000 times (Nippon Instruments Corporation, Osaka, Japan) was layered on the fritted plate, and approximately 0.1 g quartz wool was then stuffed on the top of the sand. The BAuT was used vertically during sampling because the trapping material settled, but was not secured onto the fritted plate. Compared to a commercially available conventional gold-coated sand trap (a 4 (i.d.) \(\times\) 160 mm quartz tube with 0.08 g gold-coated silica sand, capable of capturing 70 ug of TGM; Nippon Instruments Corporation), the mouth of the BAuT is approximately 11 times wider, and the amount of trapping material is approximately 131 times greater, allowing a larger air flow with the same collection efficiency and capturing capacity of 9.2 mg of TGM. To meet the same linear velocities as those of the conventional trap under the typical flow rates of 0.5 and 1.0 L min\({}^{-1}\), the sampling flow rates used for the BAuT were 63.3 and 126.6 L min\({}^{-1}\), respectively. Techniques reported in the literature use sampling flow rates of 2-20 L min\({}^{-1}\) with a sampling duration of 12 h-20 days (using a carbon trap impregnated with iodine or chlorine [10; 16]), 14.4 L min\({}^{-1}\) with 2-3 days (1.8 L min\({}^{-1}\)\(\times\) 8 conventional gold traps [5; 8]), and 16 L min\({}^{-1}\) with 3 days (1 L min\({}^{-1}\)\(\times\) 16 conventional gold traps [9]). Assuming identical collection efficiencies, the BAuT sampling is 3-9-fold faster than that of the other methods. An additional advantage of the BAuT is the ease of preconditioning, its long lifetime, and the use of a single trap that makes the postsampling procedure simple. TGM was sampled by the BAuT using a diaphragm pump (N860 FTE, KNF, Freiburg, Germany or DOA-P501-DB, GAST MFG Corp., Benton Harbor, MI, USA) through a flow meter (RK230, KOFLOC, Kyoto, Japan). PTFE connectors for the BAuT were custom-made (COSMOS VID, Fukuoka, Japan), and half an inch or 3/8 of an inch (o.d.) PFA tubing (Tombo 9003-PFA, NICHIAS Corporation, Tokyo, Japan), PFA connectors (Swagelok, Solon, OH, USA), and/or PTFE connectors (Flowell 30 series, Flowell Corporation, Yokohama, Japan) were also used. Figure 1: A schematic of the large gold-coated sand trap (BAuT). TGM trapped in the BAuT was preconcentrated to a conventional gold trap prior to the plastic bag extraction. The BAuT was heated to 873 K for 1 h under a 0.5 L min\({}^{-1}\) zero air flow, which was supplied by compressed room air (super oil free BEBICON 0.4 LE-88B, Hitachi Industrial Equipment Systems Co., Ltd., Tokyo, Japan) through a dryer stuffed with silica gel (Kanto Chemical Co., Inc., Tokyo, Japan) and a mercury trap stuffed with activated charcoal (Hokuetsu MA-HG, Ajinomoto Fine Techno Co., Inc., Yokohama, Japan). The background TGM concentration in the zero air was 0.03 pg L\({}^{-1}\) or less. The flow rate was controlled using a mass flow controller (SEC-E40 and PE-D20, HORIBA, Ltd., Kyoto, Japan). The BAuT was heated by a handmade heater consisting of a nickel-chrome wire (1.0 mm (o.d. ), Sunko Corporation, Kyoto, Japan), quartz wool (GL Sciences, Tokyo, Japan), insulating glass tape (Komeri Corporation, Ltd., Niigata, Japan), variable transformer (RAS-10, Tokyo Rikosha Co., Ltd., Saitama, Japan), and temperature controller (TR-KN, AS ONE Corporation, Osaka, Japan). After preconcentration, the BAuT was baked at 853 K in a muffle furnace (FUL230 BL, Toyo Seisakusho Kaisha, Ltd., Chiba, Japan) for several days to remove organic and mercury contaminants.