Tracing the sources of gaseous components (222Rn, CO2 and its carbon isotopes) in soil air under a cool-deciduous stand in Sapporo, Japan

Abstract

Radon ((222)Rn) and carbon dioxide were monitored simultaneously in soil air under a cool-temperate deciduous stand on the campus of Hokkaido University, Sapporo, Japan. Both (222)Rn and CO(2) concentrations in soil air varied with atmospheric (soil) temperature in three seasons, except for winter when the temperature in soil air remained constant at 2-3 degrees C at depth of 80 cm. In winter, the gaseous components were influenced by low-pressure region passing through the observation site when the ground surface was covered with snow of ~1 m thickness. Carbon isotopic analyses of CO(2) suggested that CO(2) in soil air may result from mixing of atmospheric air and soil components of different origins, i.e. CO(2) from contemporary soil organic matter and old carbon from deeper source, to varying degrees, depending on seasonal meteorological and thus biological conditions.

Environmental forcing does not induce diel or synoptic variation in the carbon isotope content of forest soil respiration

“…Several studies have shown that trace gas transport in porous soils in a variety of ecosystems is subject to ventilation by wind or pressure pumping (e.g., Flechard et al, 2007;Fujiyoshi et al, 2010;Maier et al, 2010;Sánchez-Cañete et al, 2013) and even by thermal convection (Ganot et al, 2014). When diffusion initially dominates transport and a ventilation event follows, there should be a readily detectible isotopic effect as ventilation removes some of the small pool of diffusively enriched CO 2 within the soil (as described in Fig.…”

Soil radon (222Rn) monitoring in a forest site in Fukushima, Japan

“…Energy and efficiency calibrations were periodically carried out, as well as checking the background. Details of the measurements were described in Fujiyoshi et al (2010Fujiyoshi et al ( , 2013.…”

“…Another important and basic aspect exists in the study of 222 Rn in soil air to elucidate mechanisms of its migration in soil and transportation to the ground surface (Nazaroff 1992;Neznal and Neznal 2005;Fujiyoshi et al 2010Fujiyoshi et al , 2013. Soil radon monitoring has shown that 222 Rn activity concentration varies to a great extent depending on geological, meteorological and hydrological factors, and that its migration through the soil and rock is controlled not only by diffusion but convection It is widely recognized that both liquid and gaseous water movements are fundamental factors controlling many processes in soil.…”

“…Soil radon monitoring has shown that 222 Rn activity concentration varies to a great extent depending on geological, meteorological and hydrological factors, and that its migration through the soil and rock is controlled not only by diffusion but convection (Yakovleva 2005;Perrier and Girault 2013). Monitoring soil radon for several years since 2004 gave the results that a major factor affecting soil 222 Rn concentration was soil temperature under high atmospheric pressure region in three seasons except for winter on a campus forest site of the Hokkaido University, Japan (Fujiyoshi et al 2005(Fujiyoshi et al , 2006(Fujiyoshi et al , 2010. In contrast, lower 222 Rn concentration with small variability appeared in soil under persisting snow in winter months from December to March.…”

“…Energy and efficiency calibrations were periodically carried out, as well as checking the background. Details of the measurements were described in Fujiyoshi et al (2010Fujiyoshi et al ( , 2013.Results and discussion Pb, a 222 Rn progeny, showed a small surface enrichment, suggesting atmospheric lead deposition on the forest floor since 1981 when the construction of university buildings was finished. It should be noted here that much higher concentration of 210 Pb is usually observed in the surface layer of forest soils undisturbed for more than 100 years (Fujiyoshi et al, 2004).…”