Hydrogen soil deposition at an urban site in Finland

Abstract

Abstract. Hydrogen deposition velocities (v d ) 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 v d 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 v d values and radon exhalation rates. The v d 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 v d 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 v d values were observed. A snow cover also lowered v d .

A new estimation of the recent tropospheric molecular hydrogen budget using atmospheric observations and variational inversion

“…In the Northern Hemisphere, the maximum uptake is observed at the end of summer/beginning of autumn when the temperatures are mild and the moisture is weak, leading to high bacterial activity and good diffusion of air in the soil. The minimum appears to be in spring when the soils are moist and cold, leading to a smaller bacterial activity and a slower diffusion of air in the soils Seiler, 1981, 1985;Yonemura et al, 1999Yonemura et al, , 2000aLallo et al, 2008Lallo et al, , 2009Schmitt et al, 2009). …”

Calibration of atmospheric hydrogen measurements

“…In the absence of a common calibration scale for H 2 , multiple scales have been listed in the literature with Published by Copernicus Publications on behalf of the European Geosciences Union. largely unknown conversion factors (Schmidt, 1974;Khalil and Rasmussen, 1990;Novelli et al, 1999;Bonasoni et al, 1997;Francey et al, 1996). Therefore, an assessment of the comparability of the different data sets is very difficult.…”

“…Atmospheric concentration data provide key information for this understanding. A number of time series of H 2 observations at several sites with some global representation were started between the mid 1980s and the early 1990s (Khalil and Rasmussen, 1990;Novelli et al, 1999;Langenfelds et al, 2002). In the absence of a long-term trend in the past two decades the source and sink processes are believed to be in balance (Grant et al, 2010a).…”

Atmospheric hydrogen variations and traffic emissions at an urban site in Finland

“…In this article we present the variation of atmospheric hydrogen in Helsinki and calculate emissions using the H 2 / CO slope, and estimate the role of soil deposition in the daily hydrogen dynamics. The soil deposition rates in Helsinki are estimated in a companion article (Lallo et al, 2009). …”