Influence of biogeochemical reactions on inert gas fluxes between soil and the atmosphere
Résumé
In the subsurface, water content, gas solubility, organic mater
degradation as well as plant and microorganism respiration control
gas fluxes between soil and the atmosphere. Indeed, all of this
controls the partial pressures of major gas species, such as O2 and
CO2 , which controls in turn the advective and diffusive transport of
all the gaseous species, including the inert gases. Because these
processes vary in intensity with time and space, it is very
challenging to define where, when and how to measure gas fluxes
between soil and the atmosphere. This is equaly important for
detection of anomalous fluxes as well as for the calculation of
relevant mass budgets. We focus here on inert gases because of their
relevance as tracers for a large variety of processes. An
experimental setup was developed and validated at the ECOTRON
IleDeFrance research center. It is composed of a 60-cm high and 40-cm
diameter sand column placed under controlled conditions (water
content, temperature, pressure, light) in a climatic chamber. Plants
are grown at the top of the column. An inert gas (SF6) is injected at
the bottom and its flux is continuously monitored at the surface. A
similar experimental setup is run without plants. Effects of
watering, daytime/nighttime plant activity, cut out of leaves, plant
destruction as well as of other solicitations are determined and
discussed. First-order models are proposed and their results are
compared to the experimental data. These models are based on
consumption of O2 , production of CO2 with a higher solubility in
water and their effects on inert gas advection-dispersion.
Auteurs, date et publication :
Auteurs Clément Alibert , Eric Pili , Pierre Barré , Florent Massol
Date : 2018
Volume : 20
Pages : 2177