Streamwater phosphorus and nitrogen across a gradient in rural–agricultural land use intensity

摘要: Abstract This paper provides an overview of the impacts rural land use on lowland streamwater phosphorus (P) and nitrogen (N) concentrations P loads sources in streams. Based weekly water quality monitoring, agriculture N hydrochemistry were examined along a gradient rural–agricultural use, by monitoring three sets ‘paired’ (near-adjacent) headwater streams, draining catchments which are representative major geology, soil types rural/agricultural large areas Britain. The magnitude timing inputs assessed load apportionment model (LAM) was applied to quantify ‘continuous’ (point) source ‘flow-dependent’ (diffuse) contributions these results show that intensive arable farming had only comparatively small impact total (TP loads), with highly consistent stream diffuse-source TP yields ca. 0.5 kg-P ha −1  year for predominantly both clay loam soils, compared 0.4 kg-P ha low agricultural intensity grassland/woodland similar types. In contrast, livestock heavy soils resulted dramatically higher 2 kg-P ha . livestock-dominated catchment characterised high organic P, C fractions, associated manure slurry sources. Across study sites, human settlement clearly identifiable effluent from septic tanks sewage treatment works resulting large-scale increases soluble reactive (SRP) concentrations. At sites heavily impacted settlements, SRP under baseflow conditions reached several hundred μg-P L Load modelling demonstrated significant ‘point-source’ streams even where there no within upstream catchment. indicates that, sparsely populated catchments, settlements isolated groups houses sufficient cause nutrient pollution tank systems serving communities actually operating as multiple point sources, rather than diffuse input.