The distribution of agricultural soil leachates in the unsaturated zone of the British chalk

Abstract

In Europe the Chalk constitutes a major source of potable water supply. Its outcrop forms extensive tracts of agricultural land, where the groundwater resources largely originate as infiltrating excess rainfall. Research on the unsaturated zone of the aquifer beneath such cultivated land should allow an assessment of nutrient leaching losses from the associated highly permeable soils and the prediction of future groundwater quality trends. Pore-water profiles for nitrate and numerous other constituents from a site of exceptionally detailed study are presented and compared to results from sites elsewhere in eastern England to demonstrate the impact of modern arable agriculture. Environmental isotopes have also been investigated in depth to aid the study. The problems in evaluating the evolution of the unsaturated zone profiles are discussed.