An Analysis of Simultaneous Online GC Measurements of BTEX Aromatics at Three Selected Sites in the Greater Munich Area

During two field campaigns in 1993 and 1994, measurements of aromatic compounds [benzene, toluene, ethylbenzene, m-/p-/o-xylenes (BTEX)] were carried out at urban and rural sites in the greater Munich area. These field campaigns represent a unique study using quasi-continuous gas chromatography/flame ionization detection methods concurrently at various sites. The impact of Munich’s urban plume on photochemical processes downwind from the urbanized area was observed. Most BTEX compounds showed good correlation with other primary species such as nitrogen oxides and carbon monoxide at the rural site. High mixing ratios of primary compounds at the rural site were always correlated to transport of polluted air masses from the urban area. In addition, every time the rural site encountered the urban plume, selected BTEX ratios changed significantly and the formation of ozone and peroxyacetyl nitrate occurred. This fact demonstrates that BTEX compounds play an important role in regional photochemical smog formation. BTEX ratios may be a useful tool to assess the anthropogenically driven nonmethane hydrocarbon photochemistry in future air quality studies.