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A comparison of HONO budgets for two measurement heights at a field station within the boreal forest in Finland

Journal Article


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Abstract


  • Atmospheric concentrations of nitrous acid (HONO), one of the major precursors of the hydroxyl radical (OH) in the troposphere, significantly exceed the values predicted by the assumption of a photostationary state (PSS) during daytime. Therefore, additional sources of HONO were intensively investigated in the last decades. This study presents budget calculations of HONO based on simultaneous measurements of all relevant species, including HONO and OH at two different measurement heights, i.e. 1 m above the ground and about 2 to 3 m above the canopy (24 m above the ground), conducted in a boreal forest environment. We observed mean HONO concentrations of about 6.5 × 108 molecules cm−3 (26 ppt) during daytime, more than 20 times higher than expected from the PSS of 0.2 × 108 molecules cm−3 (1 ppt). To close the budgets at both heights, a strong additional source term during daytime is required. This unidentified source is at its maximum at noon (up to 1.1 × 106 molecules cm−3 s−1, 160 ppt h−1) and in general up to 2.3 times stronger above the canopy than close to the ground. The insignificance of known gas phase reactions and other processes like dry deposition or advection compared to the photolytic decomposition of HONO at this measurement site was an ideal prerequisite to study possible correlations of this unknown term to proposed HONO sources. But neither the proposed emissions from soils nor the proposed photolysis of adsorbed HNO3 contributed substantially to the unknown source. However, the unknown source was found to be perfectly correlated to the unbalanced photolytic loss of HONO.

UOW Authors


  •   Fischer, H (external author)
  •   Konigstedt, R (external author)
  •   Oswald, R (external author)
  •   Ermel, M (external author)
  •   Hens, K (external author)
  •   Novelli, A (external author)
  •   Ouwersloot, H G. (external author)
  •   Paasonen, P (external author)
  •   Petaja, T (external author)
  •   Sipila, M (external author)
  •   Keronen, P (external author)
  •   Back, J (external author)
  •   Beygi, Z. Hosaynali (external author)
  •   Williams, Jonathan (external author)
  •   Hoffmann, T (external author)
  •   Trebs, I (external author)
  •   Sorgel, M (external author)
  •   Bohn, B (external author)
  •   Martinez, M (external author)
  •   Harder, H (external author)
  •   Kubistin, Dagmar C.

Publication Date


  • 2015

Citation


  • Oswald, R., Ermel, M., Hens, K., Novelli, A., Ouwersloot, H. G., Paasonen, P., Petaja, T., Sipila, M., Keronen, P., Back, J., Konigstedt, R., Beygi, Z. Hosaynali., Fischer, H., Bohn, B., Kubistin, D., Harder, H., Martinez, M., Williams, J., Hoffmann, T., Trebs, I. & Sorgel, M. (2015). A comparison of HONO budgets for two measurement heights at a field station within the boreal forest in Finland. Atmospheric Chemistry and Physics, 15 (2), 799-813.

Scopus Eid


  • 2-s2.0-84921481984

Ro Full-text Url


  • http://ro.uow.edu.au/cgi/viewcontent.cgi?article=3869&context=smhpapers

Ro Metadata Url


  • http://ro.uow.edu.au/smhpapers/2847

Has Global Citation Frequency


Number Of Pages


  • 14

Start Page


  • 799

End Page


  • 813

Volume


  • 15

Issue


  • 2

Abstract


  • Atmospheric concentrations of nitrous acid (HONO), one of the major precursors of the hydroxyl radical (OH) in the troposphere, significantly exceed the values predicted by the assumption of a photostationary state (PSS) during daytime. Therefore, additional sources of HONO were intensively investigated in the last decades. This study presents budget calculations of HONO based on simultaneous measurements of all relevant species, including HONO and OH at two different measurement heights, i.e. 1 m above the ground and about 2 to 3 m above the canopy (24 m above the ground), conducted in a boreal forest environment. We observed mean HONO concentrations of about 6.5 × 108 molecules cm−3 (26 ppt) during daytime, more than 20 times higher than expected from the PSS of 0.2 × 108 molecules cm−3 (1 ppt). To close the budgets at both heights, a strong additional source term during daytime is required. This unidentified source is at its maximum at noon (up to 1.1 × 106 molecules cm−3 s−1, 160 ppt h−1) and in general up to 2.3 times stronger above the canopy than close to the ground. The insignificance of known gas phase reactions and other processes like dry deposition or advection compared to the photolytic decomposition of HONO at this measurement site was an ideal prerequisite to study possible correlations of this unknown term to proposed HONO sources. But neither the proposed emissions from soils nor the proposed photolysis of adsorbed HNO3 contributed substantially to the unknown source. However, the unknown source was found to be perfectly correlated to the unbalanced photolytic loss of HONO.

UOW Authors


  •   Fischer, H (external author)
  •   Konigstedt, R (external author)
  •   Oswald, R (external author)
  •   Ermel, M (external author)
  •   Hens, K (external author)
  •   Novelli, A (external author)
  •   Ouwersloot, H G. (external author)
  •   Paasonen, P (external author)
  •   Petaja, T (external author)
  •   Sipila, M (external author)
  •   Keronen, P (external author)
  •   Back, J (external author)
  •   Beygi, Z. Hosaynali (external author)
  •   Williams, Jonathan (external author)
  •   Hoffmann, T (external author)
  •   Trebs, I (external author)
  •   Sorgel, M (external author)
  •   Bohn, B (external author)
  •   Martinez, M (external author)
  •   Harder, H (external author)
  •   Kubistin, Dagmar C.

Publication Date


  • 2015

Citation


  • Oswald, R., Ermel, M., Hens, K., Novelli, A., Ouwersloot, H. G., Paasonen, P., Petaja, T., Sipila, M., Keronen, P., Back, J., Konigstedt, R., Beygi, Z. Hosaynali., Fischer, H., Bohn, B., Kubistin, D., Harder, H., Martinez, M., Williams, J., Hoffmann, T., Trebs, I. & Sorgel, M. (2015). A comparison of HONO budgets for two measurement heights at a field station within the boreal forest in Finland. Atmospheric Chemistry and Physics, 15 (2), 799-813.

Scopus Eid


  • 2-s2.0-84921481984

Ro Full-text Url


  • http://ro.uow.edu.au/cgi/viewcontent.cgi?article=3869&context=smhpapers

Ro Metadata Url


  • http://ro.uow.edu.au/smhpapers/2847

Has Global Citation Frequency


Number Of Pages


  • 14

Start Page


  • 799

End Page


  • 813

Volume


  • 15

Issue


  • 2