 |
| Titel |
Evaluating uncertainty in 7Be-based soil erosion estimates: an experimental plot approach |
| VerfasserIn |
Will Blake, Alex Taylor, Wahid Abdelli, Leticia Gaspar, Bashar Al Barri, Nick Ryken, Lionel Mabit |
| Konferenz |
EGU General Assembly 2014
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250095200
|
| Publikation (Nr.) |
 EGU/EGU2014-10651.pdf |
|
|
|
|
|
| Zusammenfassung |
| Soil erosion remains a major concern for the international community and there is a growing
need to improve the sustainability of agriculture to support future food security. High
resolution soil erosion data are a fundamental requirement for underpinning soil conservation
and management strategies but representative data on soil erosion rates are difficult to achieve
by conventional means without interfering with farming practice and hence compromising the
representativeness of results. Fallout radionuclide (FRN) tracer technology offers a
solution since FRN tracers are delivered to the soil surface by natural processes and,
where irreversible binding can be demonstrated, redistributed in association with
soil particles. While much work has demonstrated the potential of short-lived 7Be
(half-life 53 days), particularly in quantification of short-term inter-rill erosion, less
attention has focussed on sources of uncertainty in derived erosion measurements and
sampling strategies to minimise these. This poster outlines and discusses potential
sources of uncertainty in 7Be-based soil erosion estimates and the experimental
design considerations taken to quantify these in the context of a plot-scale validation
experiment. Traditionally, gamma counting statistics have been the main element of
uncertainty propagated and reported but recent work has shown that other factors may be
more important such as: (i) spatial variability in the relaxation mass depth that
describes the shape of the 7Be depth distribution for an uneroded point; (ii) spatial
variability in fallout (linked to rainfall patterns and shadowing) over both reference
site and plot; (iii) particle size sorting effects; (iv) preferential mobility of fallout
over active runoff contributing areas. To explore these aspects in more detail, a
plot of 4 x 35 m was ploughed and tilled to create a bare, sloped soil surface at the
beginning of winter 2013/2014 in southwest UK. The lower edge of the plot was
bounded by a perforated pipe which fed into a collection bin for overland flow and
associated sediment capture. At the same time, a flat area at the top of the slope
was ploughed and tilled to create a reference site with same inventory baseline
as the slope. Rain gauges were set up at the reference and slope site. The tilled
surface had a low bulk density and high permeability at the start of the experiment
(ksat > 100 mm hr-1). Hence, despite high rainfall in December 2013 (200 mm),
notable runoff was observed only after intense rain storms during late 2013 and early
January 2014 when the soil profile was saturated. Captured eroded sediment was
analysed for 7Be and particle size. Subsequently, the plot soil surface was intensively
sampled to quantify 7Be inventory patterns and develop a tracer budget. Preliminary
results are discussed in the context of the above potential sources of uncertainty. |
|
|
|
|
|
|