空氣中臭味還原性硫化物線上濃縮與分析 On-line enrichment and analysis of reduced sulfur compounds in the atmosphere

1. 空氣中臭味還原性硫化物線上濃縮與分析On-line enrichment and analysis of reduced sulfur compounds in the atmosphere 報告者:林岱縈 指導老師:王家麟 教授

2. Reduced sulfur compounds • H2S/ COS/ CH3SH/ C2H5SH/ CS2/ CH3SCH3/ CH3SSCH3 • (DMS) (DMDS) S Oxidation RSCs SO42- CCN Regional Temperature aerosol

3. Source Natural emission Volcano Ocean S R C H2S, SO2 DMS Anthropogenic emission Factory Wastewater treatment H2S, SO2, C2H5SH, DMS, DEDS…. H2S, CH3SH, DMS, CS2….

4. Preconcentration methods Cryogenic trapping 易沾黏、反應性高 Loss 背景濃度低 Detection limit Solid sorbents S S Au Sorption on metal surface Molecular sieve 5A/ Tenax TA H2S other RSCs LN2 Anal. Chem. 1978, 50, 992-996/ AnalyticaChimica Acta,1995, 306, 259-266 / USEPA, Method 15/ Atmospheric Science for Environmental Scientists

5. The research goal Solid sorbent Cryogenic trap 電子降溫至-20°C Find a better sorbent Molecular sieve 5A/ Tenax (USEPA, Method 15)

6. Experimental setup Sampling Injection Sample Sample N2 N2 GC He He GC -20°C Cool Heat GC/ PFPD pump MFC pump MFC

7. Principle of PFPD 2 Ignition 3 Propagation 4 Combustion 5 Extinction 1 Filling 點火室 燃燒室 Combustor gas H2/ zero air Wall gas H2/ zero air hʋ S2* 2200°C 燃燒室時劑圖 Time-delay 7

8. (可調控以改變稀釋倍率) 4 L/min Calibration system MFC III H2S Zero air MFC I 50 mL/min (固定) 混合室 C2H5SH DMS DMDS 滲透管 烘箱30°C 滲透管實圖 MFC II 1 mL/min (固定) 滲透管 CS2 vent 水冷機1°C

9. Stability test of permeation tube Tenax TA N=3 N=3 N=3 N=3

10. Stability test of permeation tube Tenax TA N=3 N=3 N=3 N=3 • 滲透管已可作為標準氣體使用，改變稀釋比例並不影響滲透管穩定輸出的能力

11. Results and discussion • Light RSC (H2S) Challenge Volatile Reactivity H2O Desorption temperature Look for the best material to compare with Molecular sieve 5A Micro (<2 nm) Meso (2-50 nm) Macro ( >50 nm) Non 2. Heavy RSCs (C2H5SH/ DMS/ CS2/ DMDS) Trapping T. Stability Calibration Meso (2-50 nm) Macro ( >50 nm) Desorption temperature Trapping T. Stability Calibration Look for the best material to compare with Tenax TA

13. 1. Light RSC (H2S) Unibeads 1S H L L H

14. SiO2 VS carbonin H2S Micro Meso Carboxen 1016 推測碳材比SiO2對H2S有較強作用力，因此脫附效率不佳!

15. Desorption temperature

16. Trapping temperature/ Calibration(Unibeads 1S vs. MS-5A) H2O 5.12ppb 12.4ppb N=3 • 約70次實驗後，Glass sand 氣通量不足 16

17. 0.5-25ppbv H2S Chromatogram 25 ppbv N=3 0.5 ppbv LOQ (10σ) for H2S: 0.17 ppbv LOD (3 σ) for H2S: 0.13 ppbv

18. 2. Heavy RSCs (C2H5SH/ CS2/DMS/ DMDS)

19. The chosen material for heavy RSCs Desorption temperature of C2H5SH / CS2 / DMS / DMDS Compared with Tenax TA

20. Desorption Temperature N=3 N=3 150°C 150°C N=3 N=3 150°C 150°C

21. Byproduct: C2H5SSC2H5 (DEDS) 2C2H5SH→ C2H5SSC2H5 + H2 DEDS at 150°C DEDS Tenax TA Unibeads 1S

22. CS2 Ranking DMS Normalization = Normalization = Tested Material (peak area at 150°C) Tested Material (peak area at 150°C) Tenax TA (peak area at 150°C) Tenax TA (peak area at 150°C) Desorption at 150°C Porapak Q Haysep D Unibeads 2S Unibeads 1S Tenax TA • Unibeads 1S compared with Tenax TA in C2H5SH/ DMS/ CS2/ DMDS

23. Trapping Temperature(Unibeads 1S vs. Tenax TA) Trapping temperature Stability ( -20 °C )

24. Calibration N=3 N=3 N=3 N=3

25. Summary • An on-line TD-GC/PFPD was developed for analyzing ambient RSCs. • Of all the RSCs, H2S is the most difficult RSC to be enriched due to its high volatility and reactivity. • Unibeads 1S shows significantly better sorption characteristics than MS 5A and Tenax TA to enrich H2S with LOQ = 0.17 ppbv. • For other higher boiling RSCs, Unibeads 1S shows comparable sorption characteristics to the conventional MS 5A or Tenax TA. • Sorbents with smaller pore sizes may reduce the formation of DEDS from C2H5SH. • Unibeads 1S has never been used as a sorption material for RSCs, and previously it is being used as a packing material for GC columns.

26. Thanks for your attention !