『Abstract
Surface runoff transporting sediment with high phosphorus (P)
concentrations has been identified as a major hydrological pathway
for sediment-associated P delivery to surface waters and is considered
a major threat to water quality, due to the ability of P to cause
eutrophication in fresh water. Not all P-rich sediment that is
mobilised by erosion will however be delivered directly to the
channel. Some may instead be deposited in intermediate storage
away from its source area. The aim of this contribution was to
determine the influence of land use and soil type on the P content
of surface runoff sediment and sediment deposited in intermediate
storage and was undertaken in the largely agricultural and rural
catchments of the Rivers Frome and Piddle in Sorset, UK. The study
formed part of a larger investigation of hydrological and hydrogeochemical
processes and fluxes in lowland permeable catchments in the UK
(LOCAR). Soil samples were collected from the main land use types;
freshly deposited sediment was sampled from ditches, hedge boundaries
and depressions in fields, and sediment-laden runoff was collected
during heavy rainfall events. The concentrations of total phosphorus
(TP) and the P fractions found in the surface runoff sediment
were significantly different from those measured in the original
source soils, with a greater degree of enrichment associated with
surface runoff sediment from cultivated land than from pasture
land. For cultivated land, concentrations of TP and the P fractions
in deposited sediment were higher than those in the original source
material, while for pasture soils, concentrations of TP and the
P fractions tended to be lower than in the original; source soils.
The relative importance of the P fractions associated with surface
runoff sediment and sediment deposits also differed from that
for the original soil samples. Surface runoff sediment was finer
than source pasture and cultivated soils, reflecting the particle
size selectivity of sediment mobilisation and transport. Soil
physical properties and land use can both influence the P content
of surface runoff and deposited sediment.
Keywords: Runoff; Sediment; Land use; Erosion; Transport; Selectivity;
Phosphorus; Enrichment; Deposited sediment; Runoff sediment; Soil
type』
1. Introduction
2. Methods
2.1. Study catchments
2.2. Sampling methods
2.3. Laboratory analysis
3. Results and discussion
3.1. The phosphorus content of pasture and cultivated topsoils
3.2. The phosphorus content of sediment recovered from surface
runoff
3.3. The phosphorus content of deposited sediment
3.4. The specific surface area of sediment in surface runoff
and deposited sediment
4. Conclusion
Acknowledgements
References