Atmospheric hydrogen variations and traffic emissions at an urban site in Finland Finnish Meteorological Institute, Climate Change Research, P.O. Box 503, 00101 Helsinki, Finland
Received: 18 May 2009 – Published in Atmos. Chem. Phys. Discuss.: 25 Jun 2009Abstract. Atmospheric hydrogen (H2) mixing ratios were observed over a one year
period from summer 2007 to 2008 in Helsinki, Finland. Relatively stable
background values of hydrogen were occasionally observed at the site, with
minimum in October and maximum between March and May. High hydrogen mixing
ratios occurred simultaneously with high carbon monoxide (CO) values and
coincided with high traffic flow periods. Carbon monoxide and radon
(222Rn) were continuously monitored at the same site and they were used
in estimation of the hydrogen emissions from traffic. The morning rush hour
slope of ΔH2/ΔCO was in average 0.43±0.03 ppb (H2)/ppb (CO). After correction due to soil deposition of H2 the
slope was 0.49±0.07 ppb (H2)/ppb (CO). Using this slope and CO
emission statistics, a road traffic emission of about 260 t (H2)/year
was estimated for Helsinki in 2007.
Revised: 01 Sep 2009 – Accepted: 08 Sep 2009 – Published: 05 Oct 2009
Citation: Aalto, T., Lallo, M., Hatakka, J., and Laurila, T.: Atmospheric hydrogen variations and traffic emissions at an urban site in Finland, Atmos. Chem. Phys., 9, 7387-7396, doi:10.5194/acp-9-7387-2009, 2009.