Volatile organic compound measurements (whole air) in selected urban areas Prof. Donald R. Blake Department of Chemistry University of California, Irvine Irvine, CA 92697 drblake@uci.edu Mexico City, Mexico Hong Kong Makkah, Saudi Arabia Volatile Organic Compounds in the atmosphere O2 RO 2 VOCs NO RO OH HO2 NO2 VOCs VOCs NOx O3 O2 Oxygenated VOCs VOCs NOx SO2 O + O2 VOCs NOx Secondary organic aerosol (SOA) VOC reactions lead to: • Tropospheric ozone (O3) • Secondary organic aerosol (SOA) These products impact: • Air quality, global climate, health Some VOCs are toxic: • e.g. Benzene is carcinogenic After: www.chem.wisc.edu/users/keutch/ and www.york.ac.uk/inst/sci/APS/backgrd_files/figure4.gif Modeled surface ozone (O3) Iran lies in a region that experiences severe O3 pollution ppbv O3 Modeled mean surface O3 in excess of 40 ppbv July-August 2006 (Lelieveld et al., ACP, 2009) UC Irvine Rowland-Blake group Measurements of volatile organic compounds (VOCs) in global ecosystems: • Global background monitoring » Pacific Basin • Areas with special conditions » Marine environments » Agriculture » Oil and natural gas » Biomass burning, etc. Pristine • World’s cities/megacities » Mecca, Saudi Arabia » Guangzhou, China » Karachi, Pakistan » Mexico City, etc. Polluted UC Irvine air sampling technique Air sampling canisters • 2-L stainless steel • Conditioned, evacuated • Bellows valve • Sampling period: 1‒2 minutes Air sampling near Rabigh, Saudi Arabia Air sampling at Canada’s oil sands mining sites Laboratory analysis Detectors: • Flame Ionization Detection (FID) » Sensitive to hydrocarbons • Electron Capture Detection (ECD) » Sensitive to halocarbons, alkyl nitrates • Mass Spectrometer Detection (MSD) » Unambiguous compound identification Each sample of air is split and sent to 5 different column-detector combinations Sample chromatogram Compound Ethane Benzene C2Cl4 LOD Precision 3 pptv 1% 3 pptv 3% 0.01 pptv 5% 1 part per trillion by volume (pptv or 10-12) is equivalent to 1 second in 320 centuries Accuracy 5% 5% 10% C9: 1,2,3-Trimethylbenzene C8: n-Octane C6: Methylcyclohexane C6: Benzene C4: i-Butane C5: i-Pentane C3: Propane C3: Propene 0 min Time (minutes) 16 min Speciated measurements of >100 VOCs, CO Alkanes Alkenes Aromatics 1. Methane 2. Ethane 3. Propane 4. i-Butane 5. n-Butane 6. i-Pentane 7. n-Pentane 8. n-Hexane 9. n-Heptane 10. n-Octane 11. n-Nonane 12. n-Decane 13. 2,2-Dimethylbutane 14. 2,3-Dimethylbutane 15. 2-Methylpentane 16. 3-Methylpentane 17. 2-Methylhexane 18. 3-Methylhexane 19. 2,3-Dimethylpentane 20. 2,2,4-Trimethylpentane 21. 2,3,4-Trimethylpentane 22. 2-Methylheptane 23. 3-Methylheptane 26. Ethene 27. Propene 28. 1-Butene 29. i-Butene 30. cis-2-Butene 31. trans-2-Butene 32. 1,3-Butadiene 33. 1-Pentene 34. cis-2-Pentene 35. trans-2-Pentene 36. 2-Methyl-1-Butene 37. 2-Methyl-2-Butene 38. 3-Methyl-1-Butene 39. 2-Methyl-1-Pentene 40. 4-Methyl-1-Pentene 41. Isoprene 42. α-Pinene 43. β-Pinene 52. Benzene 53. Toluene 54. Ethylbenzene 55. m-Xylene 56. o-Xylene 57. p-Xylene 58. Styrene 59. i-Propylbenzene 60. n-Propylbenzene 61. 2-Ethyltoluene 62. 3-Ethyltoluene 63. 4-Ethyltoluene 64. 1,2,3-Trimethylbenzene 65. 1,2,4-Trimethylbenzene 66. 1,3,5-Trimethylbenzene Alkynes 24. Ethyne 25. Propyne Alkyl Nitrates 44. MeONO2 45. EtONO2 46. i-PrONO2 47. n-PrONO2 48. 2-BuONO2 49. 2-PeONO2 50. 3-PeONO2 51. 3-Methyl-2-BuONO2 Halocarbons 75. CFC-11 76. CFC-12 77. CFC-113 78. CFC-114 79. CCl4 80. CH3CCl3 81. HCFC-22 82. HCFC-124 83. HCFC-141b 84. HCFC-142b 85. HFC-134a 86. HFC-152a 87. H-1211 Cycloalkanes/alkenes 67. Cyclopentane 68. Methylcyclopentane 69. Cyclohexane 70. Methylcyclohexane 71. Cyclopentene Sulfur Species 72. OCS 73. DMS 74. CS2 88. H-1301 89. H-2402 90. CH3Cl 91. CH3Br 92. CH3I 93. CH2Cl2 94. CHCl3 95. CHBr3 96. C2Cl4 97. CHBrCl2 98. CHBr2Cl 99. Ethylchloride 100. 1,2-DCE High precision, ultra-sensitive measurements of >100 C1-C10 volatile organic compounds (VOCs) Colman et al., An. Chem., 73, 3723-3731, 2001 Simpson et al., ACP, 10, 6445-6463, 2010 Volatile organic compound (VOC) sources Biomass burning: Fossil fuel combustion: • Ethyne • Benzene • n-Butane • Ethyne • Benzene • Ethene Biogenic: Natural gas leakage: • Isoprene • α-Pinene • β-Pinene • Methane • Ethane Industry: • Propane • i-Butane • n-Butane • C2Cl4 • HCFC-22 • HFC-134a Liquefied petroleum gas: Fossil fuel evaporation: • i-Pentane Cities studied by the Rowland-Blake group City Date Publication • Mexico City, Mexico 1993 Blake and Rowland (1995) • Santiago, Chile 1996 Chen et al. (2001) • Karachi, Pakistan 1998‒1999 Barletta et al. (2002) • 28 U.S. cities 1999‒2005 Baker et al. (2008) • 43 Chinese cities 2001 Barletta et al. (2005, 2006) • Hong Kong/Guangzhou 2004‒present Guo et al. (2004, 2006, 2007, 2009, 2012, 2013); Wang et al. (2005); Barletta et al. (2008); Jiang et al. (2010); Zhang et al. (2013) • Beijing (Olympics), PRC 2008 Wang et al. (2010) • Los Angeles, USA 2010‒present Unpublished data 2007 Unpublished data • Lahore, Pakistan 2012 Manuscript in preparation • 3 Saudi Arabian cities 2012‒2013 Manuscripts in preparation Basrah, Iraq Cities studied by the Rowland-Blake group 1993‒present Thousands of samples collected in more than 75 cities Case study 1: Mexico City What did we learn? • High levels of propane, i-butane and n-butane » Up to 45‒200 ppbv • Attributed to Liquefied Petroleum Gas (LPG) » Unburned leakage » Incomplete combustion • Significant contributor to O3 Recommendations to improve air quality: • Change LPG composition • Lower LPG leakage rates Mexico City, Mexico Case study 2: Santiago, Chile CO and tracers are good tracers for incomplete combustion Both compounds were strongly enhanced by the morning commute Case study 2: Santiago, Chile Ethyne a good tracer for incomplete combustion Propane is NOT enhanced by the morning commute Case study 2: Santiago, Chile Impact of the Leakage of Liquefied Petroleum Gas (LPG) on Santiago Air Quality Tai-Yih Chen1, Isobel J. Simpson, Donald R. Blake, and F. Sherwood Rowland Department of Chemistry, University of California, Irvine What did we learn? • First use of a grid sampling pattern to study VOCs in cities • Liquefied petroleum gas (LPG) » Major source of hydrocarbons, even during heavy traffic » Median propane up to 140 ppbv • Unburned LPG leakage » Leakage rate of 5% » Contributes 15% to excess O3 Recommendations: • Minimize LPG leakage • Change LPG formulation » Reduce alkene composition Case study 3: Hong Kong, PRC What have we learned? • Full characterization of VOC sources and concentrations over 10+ years of monitoring » Impact of vehicular sources, industry, gasoline evaporation, solvent use Mean sea level pressure and wind field on 1000 hPa between Oct 22 and Dec 1, 2007 • Impact of Asian monsoons on trace gas concentrations: » Winter maximum: continental influence » Summer minimum: oceanic influence • On-going VOC validation for Hong Kong Environmental Protection Department (HKEPD) » Calibration and intercomparisons » Expertise Hong Kong, People’s Republic of China H. Guo et al., AE, 2007 Case study 4: Karachi, Pakistan What did we learn? • Very high CH4 levels » Compare: Background < 2 ppmv » Significant natural gas leakage • High levels of propane, butanes » Liquefied petroleum gas » Lower than in Mexico City • High levels of benzene » Up to 19 ppbv » Concern for human health • Importance of vehicle exhaust Recommendations: • Improved fuel quality • Improved emission controls Karachi, Pakistan B. Barletta et al., AE, 2002 Case study 5: Mecca, Saudi Arabia What have we learned? • Very high CO and VOC levels » Especially in tunnels » Especially during Hajj • Human health concerns » Benzene: above 1-hr standards » CO: above 30-min standards • VOC sources include: » Vehicle exhaust » Gasoline evaporation » Liquefied petroleum gas (LPG) » Industry Recommendations: • Target aromatics, alkenes • Improve air quality monitoring Mecca, Saudi Arabia Case study 5: Mecca, Saudi Arabia Impact on O3 formation • VOCs are an O3 precursor • Potential for VOCs to form O3 is measured using hydroxyl radical reactivity (kOH) • Alkenes strongly contribute to O3 formation in Mecca: » Especially in tunnels •A VOC’s potential to form O3 is a function of its concentration and reactivity towards its main sink, OH: 𝑘OH = Mecca, Saudi Arabia (𝑘OH+VOCi VOC𝑖 + 𝑘OH+CO CO + 𝑘OH+NO NO + ⋯ ) VOC comparisons among megacities City comparisons (no tunnels) • VOC concentrations in cities can range over many orders of magnitude » From near pristine levels to extremely polluted • Continuing emissions of CFCs in many cities • High levels of i-pentane, especially in Mecca, indicate gasoline evaporation • High levels of benzene are a concern in many cities » Often related to traffic » Sometimes exceed 1-hour air quality standards of 150 ppbv Conclusions and future directions VOC measurements in selected urban areas • The Rowland-Blake group has measured VOCs in urban areas for more than 2 decades Santiago, Chile » Concentration assessments » Source characterization » Ozone formation potential » Specific recommendations • Our on-going work includes collaborative studies in: » Hong Kong, PR China » Los Angeles, USA » Cities in Saudi Arabia • Our group has expertise and equipment that could be used to study air quality in Iran Tehran, Iran Acknowledgments