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Titel |
Measurement of N2O and CH4 soil fluxes from garden, agricultural and natural soils using both closed and open chamber systems coupled with high-precision CRDS analyzer |
VerfasserIn |
Yonggang He, Gloria Jacobson, Chris Alexander, Derek Fleck, John Hoffnagel, Bernardo Del Campo, Chris Rella |
Konferenz |
EGU General Assembly 2013
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Medientyp |
Artikel
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Sprache |
Englisch
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Digitales Dokument |
PDF |
Erschienen |
In: GRA - Volume 15 (2013) |
Datensatznummer |
250084090
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Zusammenfassung |
Studying the emission and uptake of greenhouse gases from soil is essential for
understanding, adapting to and ultimately mitigating the effects of climate change. To-date,
majority of such studies have been focused on carbon dioxide (CO2 ) , however, in 2006 the
EPA estimated that “Agricultural activities currently generate the largest share, 63
percent, of the world’s anthropogenic non-carbon dioxide (non-CO2) emissions (84
percent of nitrous oxide [N2O] and 52 percent of methane[CH4]), and make up
roughly 15 percent of all anthropogenic greenhouse gas emissions” (Prentice et al.,
2001). Therefore, enabling accurate N2O and CH4 flux measurements in the field
are clearly critical to our ability to better constrain carbon and nitrogen budgets,
characterize soil sensitivities, agricultural practices, and microbial processes like
denitrification and nitrification. To aide in these studies, Picarro has developed a
new analyzer based on its proven, NIR technology platform, which is capable of
measuring both N2O and CH4 down to ppb levels in a single, field-deployable analyzer.
This analyzer measures N2O with a 1-sigma, precision of 3.5 ppb and CH4 with a
1-sigma precision of 3ppb on a 5 minute average. The instrument also has extremely
low drift to enable accurate measurements with infrequent calibrations. The data
rate of the analyzer is on the order of 5 seconds in order to capture fast, episodic
emission events. One of the keys to making accurate CRDS measurements is to
thoroughly characterize and correct for spectral interfering species. This is especially
important for closed system soil chambers used on agricultural soils where a variety
of soil amendments may be applied and gases not usually present in ambient air
could concentrate to high levels. In this work, we present the results of analyzer
interference testing and corrections completed for the interference of carbon dioxide,
methane, ammonia, ethane, ethylene, acetylene, and water on N2O. In addition, we will
present the results of testing done with the analyzer attached to both closed and open
chamber systems to quantify fluxes of N2O and CH4 from active soil samples. The
soil samples were collected by the University of Iowa from soil test sites used for
studying the application of biochar as a soil amendment. Results will compare the
two chamber methodologies and results from several soil sample types, garden,
agricultural and natural. Preliminary results from laboratory measurements of soil core
samples taken from a garden soil sample using the closed-system chamber method
show N2O emission to be on the order of 5.67 x 10-2 μg/cm3*hr, which is in good
agreement with the open-system chamber method tested on the same soil sample, which
yielded fluxes of 6.01 x 10-2 μg/cm3*hr . Additional work presented will verify
these initial results and will be compared to literature such as Hutchinsion and
Livingston 1993 assessment of the bias of different chamber flux methodologies. |
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