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

[摘要] The addition of cattle slurry to agricultural land is a widespread practise,but if not correctly managed it can pose a contamination risk to aquaticecosystems. The transport of inorganic and organic components of cattleslurry to watercourses is a major concern, yet little is known about thephysical transport mechanisms and associated fluxes and timings ofcontamination threats. Therefore, the aim of the study was to ascertain theimportance of flow pathway partitioning in the transport (fluxes and timing)of dissolved and particulate slurry-derived compounds with implications foroff-site contamination. A series of rainfall–runoff and erosion experimentswere carried out using the TRACE (Test Rig for Advancing ConnectivityExperiments) experimental hillslope facility. The experiments allowed thequantification of the impact of changing slope gradient and rainfallintensity on nutrient transport from cattle slurry applied to the hillslope,via surface, subsurface, and vertical percolated flow pathways, as well asparticulate transport from erosion. The dissolved components were tracedusing 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 flashyhydrological responses, resulting in large quantities of surface runoff, werelikely to move sediment and also flush dissolved components of slurry-derivedmaterial from the slope, increasing the contamination risk. Rainfall eventswhich produced slower hydrological responses were dominated by verticalpercolated flows removing less sediment-associated material, but producedleachate which could contaminate deeper soil layers, and potentiallygroundwater, over a more prolonged period. Overall, this research providesnew insights into the partitioning of slurry-derived material when applied toan unvegetated slope and the transport mechanisms by which contaminationrisks are created.

[学科分类] 地球化学与岩石