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| Titel |
Using organic biomarkers to trace the transport pathways of livestock-derived organic matter in the soil subsurface. |
| VerfasserIn |
Charlotte Lloyd, Katerina Michaelides, Richard Evershed, David Chadwick, Jennifer Dungait |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250042233
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| Zusammenfassung |
| We explore the use of organic biomarkers as tracers for different components of
livestock-derived organic matter (LD-OM) at two different spatial scales. We conducted six
small-scale rainfall simulation experiments on a 30 Ã 30 Ã 30Â cm soil lysimeter, following
an application of bovine slurry at a rate of 5 l m-2. Throughout the experiment timed samples
of leachate from the base of the lysimeter were collected, then soil cores were taken
following the rainfall simulation. These samples were analysed in order to identify the most
suitable biomarkers to trace dissolved and sediment-bound LD-OM respectively. The results
showed that ammonium was an important tracer compound for dissolved LD-OM, along
with other key low molecular weight compounds such as carbohydrates and amino
acids. Analysis of the soil cores confirmed that compounds 5-β sigmastanol and 5-β
epistigmastanol (5-β stanols) could be used very effectively to trace the sediment-bound and
colloidal component of LD-OM. These specific organic compounds, which are
identifiable by GC/MS analysis, only occur due to biohydrogenation of plant sterols in a
ruminant gut, providing a unique opportunity to trace bovine faecal matter via sediment
pathways.
These tracers were then applied to a larger 3-D hillslope system by using University of
Bristol’s TRACE (Test Rig for Advancing Connectivity Experiments) facility. TRACE is a
large-scale dual axis soil-slope measuring 6 m long à 2.5 m wide à 0.3 m deep accompanied
by a 6-nozzle rainfall simulator. In these experiments slurry was only applied to the top 1 m
section of the hillslope, in order to trace how the LD-OM was transported in the soil system.
The slope allows the collection of leachate from the soil surface, from lateral through-flow
and infiltrated water which reached the soil base (indicating deeper pathways). This enabled
the distinction between LD-OM transported via different hydrological pathways.
Soil cores were also taken across the soil surface and analysed for 5-β stanols, this
allowed the spatial distribution of LD-OM to be determined following the rainfall
event.
The results showed that not only is LD-OM transported on the surface of the hillslope via
overland flow, but the dissolved component infiltrates through the soil profile and is
transported via deeper hydrological flowpaths. 5-β stanol analysis showed that soil
erosion processes were extremely important, as LD-OM was found downslope of
the application area and in eroded material lost from the base of the experimental
hillslope.
These experiments provided new insights into how LD-OM interacts with the
soil-water system and allows quantification of the contamination risk posed. This is
important as 90 million tonnes of LD-OM is applied to land annually in the UK.
It is well known that there is a potential for contamination of water courses by
nitrate, ammonium and other faecal-derived pollutants such as E. Coli through
runoff from treated land. Pollution from LD-OM has now been shown to extend to
the contamination of subsurface pathways and potentially groundwater resources. |
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