The Lincolnshire Limestone, a regionally important aquifer in the UK, is in hydraulic continuity with rivers draining intensively farmed arable land. To assess the impact of river chemistry on groundwater quality, nutrient concentrations were monitored in surface and ground waters during a two-year period. Fertiliser applications and heavy rain resulted in winter concentrations of nitrate in rivers of up to 145 mg 1~(-1). Concentrations of dissolved organic carbon (DOC) in rivers peaked in low-flow summer conditions (2.0-13.0 mg 1~(-1)), due to algal contributions and treatment works effluents and were lowest in winter (1.9-8.5 mg l~(-1)) due to diluton. Concentrations of DOC in recharge were sufficient to reduce <40percent of recharging nitrate. Microbial consumption of DOC in the aquifer rapidly reduced DOC concentrations to 0.6-1.0 mg l~(-1) in shallow confined groundwater. The Lincolnshire Limestone has been naturally resisting fertiliser contamination, but rising concentrations of nitrate indicate that the aquifer is unable to cope with increasing loads.
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