Hydrogen soil deposition at an urban site in Finland M. Lallo, T. Aalto, J. Hatakka, and T. Laurila Finnish Meteorological Institute, Helsinki, Finland
Abstract. Hydrogen deposition velocities (vd) were estimated by field chamber
measurements and model simulations. A closed-chamber method was used for
soil deposition studies in Helsinki, Finland, at an urban park inhabited by
broad-leaved trees. Radon tracer method was used to estimate the vd in
nighttime when photochemical reactions were minimal and radon gas was
concentrated in the shallow boundary layer due to exhalation from soil. A
two-dimensional atmospheric model was used for the calculation of respective
vd values and radon exhalation rates. The vd and radon exhalation
rates were lower in winter than in summer according to all methods. The
radon tracer method and the two-dimensional model results for hydrogen
deposition velocity were in the range of 0.13 mm s−1 to 0.93 mm s−1
(radon tracer) and 0.12 mm s−1 to 0.61 mm s−1 (two-dimensional).
The soil chamber results for vd were 0.00 mm s−1 to 0.70 mm s−1.
Both models and chamber measurements revealed a relation between
one week cumulative rain sum and deposition velocity. When precipitation
events occurred a few days before the chamber measurements, lower vd
values were observed. A snow cover also lowered vd.
Citation: Lallo, M., Aalto, T., Hatakka, J., and Laurila, T.: Hydrogen soil deposition at an urban site in Finland, Atmos. Chem. Phys., 9, 8559-8571, doi:10.5194/acp-9-8559-2009, 2009.