Photochemical Ozone Pollution in Southern and Eastern PRC

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Photochemical Ozone Pollution in Southern and
Eastern PRC
Better Air Quality in Asian and Pacific Rim
Cities (BAQ 2002) 16-18 December 2002, Hong Kong
SAR

• Tao Wang, Joey Kwok, Steven Poon, A. J. Ding, C.
  H. Chueng, Tracia Wong, and Y. S. Li
• The Hong Kong Polytechnic University

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• Introduction
• Major air-pollution problems in China
• - North high PM (dust storm) and SO2
• - South acid rain
• - Emerging vehicle pollution in cities
• photochemical pollution much less understood

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• Background
• VOC NOx sunlight -gt O3
• NOx (NO NO2) is produced primarily in
  high-temperature combustion, e.g., power plant
  and vehicle exhaust.
• VOC is released from vehicle exhaust, fuel
  evaporation, industrial processes, and naturally
  from and trees.
• O3 episodes often occur in calm weather with
  high solar radiation and warm temperature

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• Unique Features of Ozone Pollution
• Several hours to form - peak in downwind areas
• Long life time - long-range transport
• Nonlinear chemistry

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Beijing
Shanghai
Hongkong
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Site Location of Linan in the Yangtze River Delta
Nanjing
Hangzhou
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Linan Baseline Air Pollution Monitoring Station
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Field study at Linan, Zhejiang, China

• Continuous measurements of O3, CO, SO2, NO, and
  NOy (China-MAP 1999-2000 TRACE-P Spring 2001)
• VOC (with Dr. Blake)
• PM2.5 (with Drs Arimoto and Baumman)

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O3 vs. CO (1300-1700)
Slope0.1
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Poor visibility on a smoggy day In summer 2001
(O3 gt 100 ppbv)
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Locations of study sites in the Pearl River delta
Guangzhou
Macau
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Tai O supersite to Study Transport of Regional
Pollution
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Field study at Tai O, Hong Kong, China

• Continuous measurements of O3, CO, SO2, NO, and
  NOy (Sept. 2001- Dec. 2002)
• Aerosol scattering and absorption (Oct. Dec.
  2002)
• VOC (with Dr. Ronald Blake)
• PM2.5 (with Drs David Cohen and Karsten Baumman)

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Multi-day Pollution Episode at Rural Tai O
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Regional pattern of ozone pollution on Sept 15,
2001 (Unit ppbv, HKAQO122)
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• Back trajectories calculated from the output of
  MM5 showing
• On 9/15, air mass coming from the PRD during
  daytime and from South China Sea at night
• On 9/16, air originating from urban Hong Kong

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Episode day
Clear day
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Correlation coef. with some tracers at Tai O
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Summary

• Measurement at the two non-urban sites in
  southern and eastern China for an extended period
  (gt 1 year) suggests ozone pollution present over
  large rural areas. The impact on human health and
  crops need to be carefully evaluated
• Concurrent measurement of other gases (CO, NOy
  and SO2, NMHCs, Halons) and aerosol composition
  provide valuable information on the causes of
  ozone pollution and on the emission
  characteristics of air pollutants. (e.g., our
  data show that emission from China is
  underestimated)

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Future research needed - regional network on
ozone and its precursors (adding non-urban
sites) - extent of transboundary transport -
NOx vs.VOC control - emission inventories -
linkage of O3, PM, and acid rain
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Thank You !
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Pearl River delta Yangtze River delta
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Linan
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Pearl River delta in southern China
Guangzhou
Hong Kong
Macau