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PAH-compounds in background air (PM10) and precipitation in Finland Mika Vestenius Air Chemistry Laboratory FMI

PAH-compounds in background air (PM10) and precipitation in Finland Mika Vestenius Air Chemistry Laboratory FMI. Talk outline. -Why do we measure PAH:s? -PAH-compounds -Sampling -Analysis -Measuring campaign -Results -Conclusions. Polycyclic aromatic hydrocarbons (PAH-compounds)

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PAH-compounds in background air (PM10) and precipitation in Finland Mika Vestenius Air Chemistry Laboratory FMI

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  1. PAH-compounds in background air (PM10) and precipitation in Finland Mika Vestenius Air Chemistry Laboratory FMI

  2. Talk outline -Why do we measure PAH:s? -PAH-compounds -Sampling -Analysis -Measuring campaign -Results -Conclusions

  3. Polycyclic aromatic hydrocarbons (PAH-compounds) -carcinogenic compounds -ubiquitous -formed during the incomplete combustion of organic matter -emissions from wide range of combustion sources Anthropogenic emissions: diesel and gasoline engines, fossil fuels and biomass burning (energy production), oil refining… Natural emissions include forest fires and volcanic eruptions

  4. Benzo(a)pyrene -Directive of the European parliament and the Council (2004/107/EC) requires the member states to measure PAH-compounds in the PM10-fraction in ambient air. -Benzo(a)pyrene (BaP) shall be used as a marker for the carcinogenic risk of PAH-compounds in ambient air and the limit values are set for benzo(a)pyrene Also benzo(a)anthracene, benzo(b)fluoranthene, benzo(j)fluoranthene, benzo(k)fluoranthene, indeno(1,2,3-cd)pyrene, and dibenzo(a,h)anthracene must be measured. Table 1: Limit values for benzo(a)pyrene

  5. PAH compounds: from Finlayson-Pitts & Pitts: Chemistry of the upper and lower atmosphere

  6. PAH compounds… from Finlayson-Pitts & Pitts: Chemistry of the upper and lower atmosphere

  7. PAH-compounds analyzed in the FMI: Fig. 1: Average mass percent contributions (gas + particle phase of 13 PAH:s collected in urban air from Chicago in Feb/March 1995. (From Harner and Bidleman, 1998)

  8. Sampling locations

  9. Rainwater collection

  10. PM10 and precipitation PAH-collectors

  11. The procedure Sampling Soxhlet-extraction in 60ml of CH2Cl2, minimum 8 hrs Evaporation into 1 ml Analysis in GC-MS

  12. Analysis Column: DB-5 (5%Phenyl) methylpolysiloxane (non-polar) 0,250 um x 0,5 mm ID x 50m

  13. ISTD

  14. Sample list

  15. Gas-chromatogram (SCAN)

  16. Gas-chromatogram (SIM)

  17. Benzo(a)Pyrene

  18. LOD:s and LOQ:s LOD = limit of detection LOQ = limit of quantitation MU = measurement uncertainty

  19. Total PAH-concentration at Virolahti. PM10 in 2007 (weekly samples)

  20. Benzo(a)pyrene at Virolahti PM10 in year 2007 (weekly samples)

  21. Benzo(a)pyrene at Virolahti, some daily PM10-samples in 2007

  22. PAH in precipitation at Kuhmo in 2007-2008

  23. Total PAH -concentrations in precipitation at Pallas, monthly samples in 2006, Data from IVL

  24. PAH in precipitation Data from southern Finland EVO, (SYKE/VTT), May-September Kainuun ilmanlaatu seminaari 12.5 2008

  25. gradient

  26. EXAMPLE: PAH-compounds in PM10- samples at Kuhmo, Selected days in spring 2008

  27. 3.3 2008 7.3 2008

  28. 14.3 2008 7.4 2008 13.3 2008

  29. 10.3 2008 18.4 2008

  30. Conclusions: -Traditional analysis takes time and there is a lot of work per sample, (sample preprocessing and analysis, data processing…), but -GC-MS is highly sensitive instrument for PAH-analysis LOQ (B(a)P): 0,06 ng/m3, 0,6 ppt. -Average PAH-concentrations in both rainwater and PM10 are highest in winter, due to heating and shortage of light -In PM10-fraction,mean PAH-concentrations were higher in Virolahti that in Kuhmo. Same thing with Benzo(a)Pyrene in PM10.  Concentration gradient -Total PAH in PM10 at Virolahti is 3,2 ng m-3. (yearly average) -Average benzo(a)pyrene concentration in PM10 at Virolahti was 0,25 ng m-3, which is under lower assessment level. -The average yearly PAH-deposition in Kuhmo is 3300 ng m-2, and the average PAH-concentration in PM10-fraction is 1.1 ng m-3. (spring 2008)

  31. -PAH-levels in air and in precipitation are low in Finnish background areas. -PAHs in Kuhmo come from distant sources. Take-home messages: 1. PAH-compounds are emitted to atmosphere from incomplete burning of organic compounds. 2. Offline GC-MS is labour-intensive but higly sensitive detection method for PAH-compounds in air. 3. PAH-compounds distribute to gas and aerosol phases. The distribution between the phases depends on the compounds volatility and mass. PAH-compounds containing 2-3 aromatic rings are mainly in gas phase in air, whereas compounds that have more aromatic rings go to the aerosol phase. 4. PAH-compounds decompose in photochemical reactions, which act as a sink for these compounds. These reactions are slower on the wintertime, when there is less light, compared to summertime when there is lots of light. On wintertime there is also more emissions due heating. That is why average PAH-concentrations in both PM10 and precipitation in Finland are highest on winter.

  32. Thank you! THANK YOU!

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