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| Titel |
Characterisation and quantification of phosphorus transfer in agricultural runoff through simultaneous monitoring at nested spatial scales |
| VerfasserIn |
Clare Deasy, Louise Heathwaite, Richard Brazier |
| 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 |
250032076
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| Zusammenfassung |
| Current data available for understanding and characterising nutrient transfer are generally
collected at the catchment scale, where stream measurements integrate signals from upstream
flow pathways. However, predicting and managing nutrient transfer at this scale requires a
detailed understanding of the smaller scale processes and pathways which influence
catchment scale data. This paper presents an original dataset which characterises and
quantifies phosphorus transfer through simultaneous measurements collected at nested spatial
scales (c.0.01 to 30.6 ha) within a small catchment. Monitoring took place in a mixed land
use agricultural catchment in the UK between 2004 and 2006. Discharge was continuously
measured on a five minute timestep, at five catchment locations: a flume fed by
surface runoff (1.9 ha); three drain outfalls (1.9 ha, 2.5 ha and 3.7 ha); and the
stream catchment outlet (30.6 ha). Water samples collected through five storm events
were analysed for total phosphorus and total dissolved phosphorus, and were used
together with discharge data to calculate phosphorus loadings and area normalised
yields for the various flow pathways and scales. Data from the smallest scale, the
unbounded hillslope patch (c.0.01 ha), where flow only occurred over the field
surface during storm events, was collected using timed flow measurements and grab
samples. The results show that phosphorus transfer within the catchment is extremely
complex both spatially and temporally. In particular, variations occurred in phosphorus
concentrations, loads and yields, and in the proportion of total phosphorus transported as
dissolved phosphorus, between runoff pathways and scales and between storm
events. The highest phosphorus concentrations were recorded in data collected at
the hillslope patch scale (max. 12 mg TP l-1), while concentrations at pathways
representing larger scales were much lower; measured total P concentrations were
below 5 mg TP l-1 in surface runoff at the field scale, below 1.5 mg TP l-1 in
drainflow, and below 3 mg TP l-1in streamflow. However, although concentrations
were lower in drainflow and streamflow, phosphorus loads and yields were higher
(up to 0.6 kg TP ha-1 in streamflow) than in surface runoff, as discharge through
these flow pathways was much greater. Phosphorus transfer at the hillslope patch
scale occurred almost entirely in particulate form, but at the catchment scale, where
there was a significant baseflow contribution, dissolved phosphorus constituted
around half of the phosphorus loss. These results will help provide an improved
understanding of the processes and pathways controlling phosphorus loss at the
catchment scale, and hence enable better prediction of nutrient loss and the design and
implementation of appropriate management strategies to control diffuse pollution. |
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