Relationships between ozone and other photochemical products at Ll. Valby, Denmark

The representativeness of the monitoring station at Ll. Valby, Denmark, has been tested. Furthermore, the relation of gaseous NO y and O 3 is investigated. From the linear orthogonal regression analyses of Ox (sum of O 3 + NO 2) and other photochemical products measured at Ll. Valby Denmark and from literature results it is estimated that the non-photochemical background mixing ratio of O 3 in the Northern Hemisphere is 24 ± 6 ppbv. The correlation of HCOOH and CH 3COOH with Ox indicates that these acids are of photochemical origin. A high correlation of HNO 3 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 Ll. Valby, Denmark, is produced by emissions from land sources. Finally, evidence is found that NO 3 reactions is only a supplementary source of unidentified nitrogen species in the troposphere.