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

VOCs OH

HO2

NO

NO2 O + O2 O3

Oxygenated VOCs Secondary organic aerosol (SOA)

VOCs

After: www.chem.wisc.edu/users/keutch/ and www.york.ac.uk/inst/sci/APS/backgrd_files/figure4.gif

RO2

RO

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

O2

O2

VOCs NOx SO2

VOCs NOx

VOCs NOx

Modeled surface ozone (O3)

Modeled mean surface O3 in excess of 40 ppbv July-August 2006 (Lelieveld et al., ACP, 2009)

Iran lies in a region that experiences severe O3 pollution

ppbv O3

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.

• World’s cities/megacities

» Mecca, Saudi Arabia

» Guangzhou, China

» Karachi, Pakistan

» Mexico City, etc.

Pristine

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 LOD Precision Accuracy Ethane 3 pptv 1% 5% Benzene 3 pptv 3% 5% C2Cl4 0.01 pptv 5% 10%

1 part per trillion by volume (pptv or 10-12) is equivalent to

1 second in 320 centuries

C3: Propene

C3: Propane

C4: i-Butane

C8: n-Octane

C9: 1,2,3-Trimethylbenzene

C5: i-Pentane

C6: Benzene

C6: Methylcyclohexane

Time (minutes) 0 min 16 min

Speciated measurements of >100 VOCs, CO Alkanes 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

Alkynes 24. Ethyne 25. Propyne

Alkenes 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

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

Aromatics 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

Cycloalkanes/alkenes 67. Cyclopentane 68. Methylcyclopentane 69. Cyclohexane 70. Methylcyclohexane 71. Cyclopentene

Sulfur Species 72. OCS 73. DMS 74. CS2

Colman et al., An. Chem., 73, 3723-3731, 2001 Simpson et al., ACP, 10, 6445-6463, 2010

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

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

Halocarbons

High precision, ultra-sensitive measurements of >100 C1-C10

volatile organic compounds (VOCs)

Volatile organic compound (VOC) sources

Biogenic: • Isoprene

• α-Pinene

• β-Pinene

Biomass burning: • Ethyne

• Benzene

• n-Butane

Industry: • C2Cl4

• HCFC-22

• HFC-134a

Fossil fuel combustion: • Ethyne

• Benzene

• Ethene

Fossil fuel evaporation: • i-Pentane

Natural gas leakage: • Methane

• Ethane

Liquefied petroleum gas: • Propane

• i-Butane

• n-Butane

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

Basrah, Iraq 2007 Unpublished data

• Lahore, Pakistan 2012 Manuscript in preparation

• 3 Saudi Arabian cities 2012‒2013 Manuscripts in preparation

Cities studied by the Rowland-Blake group

1993‒present

Thousands of samples collected in more than 75 cities

Case study 1: Mexico City

Mexico City, Mexico

Recommendations to improve air quality:

• Change LPG composition

• Lower LPG leakage rates

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

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

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

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

Case study 3: Hong Kong, PRC

Hong Kong, People’s Republic of China

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

• 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

Mean sea level pressure and wind field on

1000 hPa between Oct 22 and Dec 1, 2007

H. Guo et al., AE, 2007

Case study 4: Karachi, Pakistan

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

B. Barletta et al., AE, 2002

Case study 5: Mecca, Saudi Arabia

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

Case study 5: Mecca, Saudi Arabia

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 = (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 » 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

Santiago, Chile

Acknowledgments