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
Received: 13 Jul 2015 – Discussion started: 16 Oct 2015
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.
Revised: 05 Jan 2016 – Accepted: 06 Jan 2016 – Published: 01 Feb 2016
Lloyd, C. E. M., Michaelides, K., Chadwick, D. R., Dungait, J. A. J., and Evershed, R. P.: Runoff- and erosion-driven transport of cattle slurry: linking molecular tracers to hydrological processes, Biogeosciences, 13, 551-566, doi:10.5194/bg-13-551-2016, 2016.