The representativeness of the monitoring station at L1. Valby, Denmark
, has been tested. Furthermore, the relation of gaseous NOy and O-3 is
investigated. From the linear orthogonal regression analyses of Ox (s
um of O-3+NO2) and other photochemical products measured at L1. Valby
Denmark and from literature results it is estimated that the non-photo
chemical background mixing ratio of O-3 in the Northern Hemisphere is
24+/-6 ppbv. The correlation of HCOOH and CH3COOH with Ox indicates th
at these acids are of photochemical origin. A high correlation of HNO3
with Ox is also found. The anti-correlation of O-3 with MSA observed
in this study (methane sulphonic acid) indicates that O-3 at L1. Valby
, Denmark, is produced by emissions from land sources. Finally, eviden
ce is found that NO3 reactions is only a supplementary source of unide
ntified nitrogen species in the troposphere. Copyright (C) 1996 Elsevi
er Science Ltd.