Evidence for large average concentrations of the nitrate radical (NO3) in Western Europe from the HANSA hydrocarbon database

The nitrate radical (NO₃) was first measured in the atmosphere in the 1970s and suggestions were made that it could play a major role in oxidising many unsaturated hydrocarbons, such as those emitted from the biosphere. Analysis of the hydrocarbon mix over the North Atlantic Ocean suggested subsequently that the influence of NO₃ radical chemistry at night was even more extensive, being on a par with hydroxyl radical chemistry at some times of the year.

The paper presents a detailed analysis of an extensive database of many nonmethane hydrocarbons collected at various sites around the North Sea in the mid 1990s during the HANSA project. By comparing the relative rates of oxidation of iso and normal pentane with that of toluene and benzene it clearly shows that the efficiency of NO₃ radical chemistry and hydroxyl radical chemistry over northwest Europe are similar in springtime and predicts an average nighttime NO₃ concentration of the order of 350 pptv. It is shown that NO₃ oxidation of many unsaturated hydrocarbons can indeed be more efficient than OH oxidation, especially at times of the year outside the summer season.The consequences of these findings are profound especially as satellite measurements of nitrogen dioxide (NO₂), a major precursor to NO₃, suggest that these high average concentrations of several hundred pptv could be widespread over most of the continents.

Authors

Penkett SA , Burgess RA , Coe H , Coll I , Hov O , Lindskog A , Schmidbauer N , Solberg S , Roemer M , Thijsse T , Beck J , Reeves CE

Specifications

Publication title: Evidence for large average concentrations of the nitrate radical (NO3) in Western Europe from the HANSA hydrocarbon database
Publication date: 19 July 2007
Publication type: Publication
DOI: http://dx.doi.org/10.1016/j.atmosenv.2006.11.055
Magazine: Atmos Environ 2007; 41(16):3465-78
Product number: 92047