Volume 13, issue 2 | Copyright
Biogeosciences, 13, 551-566, 2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 01 Feb 2016

Research article | 01 Feb 2016

Runoff- and erosion-driven transport of cattle slurry: linking molecular tracers to hydrological processes

C. E. M. Lloyd1,2, K. Michaelides2, D. R. Chadwick3, J. A. J. Dungait4, and R. P. Evershed1 C. E. M. Lloyd et al.
  • 1Organic Geochemistry Unit, Bristol Biogeochemistry Research Centre, School of Chemistry, University of Bristol, Cantocks Close, Bristol, BS8 1TS, UK
  • 2School of Geographical Sciences, University of Bristol, University Road, Bristol, BS8 1SS, UK
  • 3School of Environment, Natural Resources and Geography, Bangor University, Deiniol Road, Bangor, Gwynedd, LL57 2UW, UK
  • 4Department of Sustainable Soils and Grassland Systems, Rothamsted Research-North Wyke, Okehampton, EX20 2SB, UK

Abstract. The addition of cattle slurry to agricultural land is a widespread practise, but if not correctly managed it can pose a contamination risk to aquatic ecosystems. The transport of inorganic and organic components of cattle slurry to watercourses is a major concern, yet little is known about the physical transport mechanisms and associated fluxes and timings of contamination threats. Therefore, the aim of the study was to ascertain the importance of flow pathway partitioning in the transport (fluxes and timing) of dissolved and particulate slurry-derived compounds with implications for off-site contamination. A series of rainfall–runoff and erosion experiments were carried out using the TRACE (Test Rig for Advancing Connectivity Experiments) experimental hillslope facility. The experiments allowed the quantification of the impact of changing slope gradient and rainfall intensity on nutrient transport from cattle slurry applied to the hillslope, via surface, subsurface, and vertical percolated flow pathways, as well as particulate transport from erosion. The dissolved components were traced using a combination of ammonium (NH4+) and fluorescence analysis, while the particulate fraction was traced using organic biomarkers, 5β-stanols. Results showed that rainfall events which produced flashy hydrological responses, resulting in large quantities of surface runoff, were likely to move sediment and also flush dissolved components of slurry-derived material from the slope, increasing the contamination risk. Rainfall events which produced slower hydrological responses were dominated by vertical percolated flows removing less sediment-associated material, but produced leachate which could contaminate deeper soil layers, and potentially groundwater, over a more prolonged period. Overall, this research provides new insights into the partitioning of slurry-derived material when applied to an unvegetated slope and the transport mechanisms by which contamination risks are created.

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Our interdisciplinary research brings together methodologies from hydrology, soil science and biogeochemistry to address key questions about the transport of cattle slurry in the environment. The paper provides a novel approach to trace dissolved and particulate components of cattle slurry through an experimental hillslope system. This work provides one of the first examples of using biomarkers to assess the effects of slope gradient and rainfall intensity on the movement of slurry derived-OM.
Our interdisciplinary research brings together methodologies from hydrology, soil science and...