 |
| Titel |
Inhibition of carbon transfer across the vadose zone by 20th century acid rain |
| VerfasserIn |
Søren Jessen, Dieke Postma, Rasmus Jakobsen, Majken Caroline Looms, Flemming Larsen |
| Konferenz |
EGU General Assembly 2014
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250092017
|
| Publikation (Nr.) |
 EGU/EGU2014-6340.pdf |
|
|
|
|
|
| Zusammenfassung |
| Carbon sequestration to pedogenic carbonates, forming in unsaturated zones or in aquifers
further down the flow path, relies on the downward flux of carbon with infiltrating
groundwater. During 2012, we measured seasonal dynamics of water movement, soil gas
CO2, and pore water chemistry in four multi-level profiles through a 4-6 m thick sandy
unsaturated zone of an agricultural barley field 10 km south of Ikast, Denmark. The residence
time of water in the unsaturated zone was close to one year. Soil gas CO2 concentrations were
1-3vol% during winter, increasing to 4-7vol% during summer. Post-harvest soil gas CO2
concentrations remained elevated into fall, indicating CO2 production by root decay.
CO2 production occurred primarily in the upper 0.3-0.5 m, reflecting a root zone
constrained mostly to the (moist) plow layer and not extending into the (much dryer) sand
underneath. Nevertheless, CO2 produced in the root zone was evenly distributed
over the underlying unsaturated zone by gas diffusion. Dissolved inorganic carbon
(DIC) concentrations in pore water collected below the root zone to ~2 m depth,
were up to 3.0 mM in March, increasing to 3.6 mM in September. In the same
depth range pore water pH-values were between 6 and 6.5. Below ~2 m depth,
however, a pH front was encountered, at which the pH dropped to |
|
|
|
|
|
|