Revealing the potential nutrient, ecotoxin and pathogen risks to freshwaters from livestock excreta

Livestock excreta is a major pollutant in UK freshwaters, contributing significantly to eutrophication, pharmaceutical loading, pathogen transport, and ecotoxicological risks to aquatic biota. Environmental impact is likely to depend on on-farm livestock management and farming methods, including the management of direct excreta inputs (dung, urine, slurry amendments, manure spreading to land), and connectivity of land to surface waters. Allowing livestock direct access to watercourses can also influence the rate of urination and defecation, with cattle (dairy and beef) showing a 5–10% increase in frequency compared to those voiding excreta on land. This heightened deposition in streams is exacerbated during summer low flows where streams have less dilution capacity. Meanwhile slurry amendments to fields before rainfall events can generate transport of slurry and its constituent contaminants from land to watercourses which is widely reported. Here, we report the results of a major NERC-funded research programme QUANTUM in which we have characterised the contaminant profiles of livestock excreta (including solid manure, slurry, urine and dung from dairy cattle, beef cattle and sheep farming systems) to determine their nutrient, chemical contaminant and pathogen composition, to clarify the risks these materials may pose to biota in UK freshwaters.