Long-term atmospheric measurements of C1-C5alkyl nitrates in the Pearl River Delta region of southeast China

Isobel J. Simpson, Tao Wang, Hai Guo, Y. H. Kwok, Frank Flocke, Elliot Atlas, Simone Meinardi, F. Sherwood Rowland, Donald R. Blake

Research output: Journal article publicationJournal articleAcademic researchpeer-review

42 Citations (Scopus)

Abstract

Mixing ratios of seven C1-C5alkyl nitrates (RONO2) were measured during a 16-month study (August 2001-December 2002) at Tai O, a coastal site 30 km west of central Hong Kong in the Pearl River Delta, the fastest-growing industrial region in the world. The C3-C4(rather than C1-C2) RONO2were most abundant throughout the study, showing the importance of photochemical (rather than marine) RONO2production in the sampled air. A lack of methyl nitrate (MeONO2) enhancement during summer, when the prevailing winds are from the ocean, indicates that the South China Sea is not a region of strong RONO2emissions. By contrast, MeONO2levels during pollution episodes (up to 25 parts per trillion by volume (pptv)) were the highest that our group has recorded during urban photochemical RONO2production, as opposed to marine emissions or biomass burning. The highest summed RONO2level of the study (204 pptv) was measured in the afternoon of 7 November 2002, during an intense pollution episode that captured the highest ozone (O3) level ever recorded in Hong Kong (203 ppbv). During pollution episodes, the average ratio of O3to summed RONO2was roughly 1000:1 in freshly polluted air (ethyne/CO∼3-5 pptv/ppbv) and 500:1 in very freshly polluted air (ethyne/CO∼6-8 pptv/ppbv). Ozone and RONO2share a common photochemical source, and their good correlation in pollution plumes shows that RONO2can be used as a tracer of photochemical O3production. Even MeONO2showed similar diurnal variations as the C2-C5RONO2, indicating a strong photochemical source despite its very slow photochemical production from methane oxidation. The decomposition of longer-chain alkoxy radicals also does not explain the high MeONO2levels, and rough calculations show that methoxy radical reaction with NO2appears to be a viable alternate pathway for MeONO2production in polluted atmospheres, though further measurements and modeling are required to confirm this mechanism.
Original languageEnglish
Pages (from-to)1619-1632
Number of pages14
JournalAtmospheric Environment
Volume40
Issue number9
DOIs
Publication statusPublished - 1 Mar 2006

Keywords

  • Alkyl nitrates
  • China
  • Ozone
  • Photochemistry
  • Urban pollution

ASJC Scopus subject areas

  • Environmental Science(all)
  • Atmospheric Science

Cite this