Nitrate pollution of groundwater in western Europe

In groundwater recharge areas with large portions of agricultural land, the nitrate concentration of well water has shown rising trends in many countries within the last 2–3 decades. Nitrate leaching from agricultural land must be considered as an important non-points source for nitrate contamination of the groundwater. In the humid regions of Europe, nitrate leaching takes place mainly during autumn, winter and early spring. Site- and land-use-specific data for the mean nitrate N concentration of the annual groundwater recharge show rather high concentrations for sandy soils with arable crops, intensively managed grazed grassland and field cropping of vegetables. These concentrations can exceed the European drinking water limit of 11.3 mg nitrate N l−1 (=50 mg nitrate l−1) by a factor of between 2 and >4. Moreover, conversion of permanent grassland to arable land causes strongly enhanced nitrate leaching for a limited time period. To reduce the nitrate load of groundwater it is very important to minimize the residual nitrate content in the root zone at harvest time, to preserve the nitrate during the main leaching period in the form of biologically fixed plant N within the N cycle and to minimize the nitrate input of the total recharge area of a groundwater well (by enlarging areas with low nitrate inputs at the expense of areas with high nitrate inputs). Results of a closer coordination of fertilizing with the N supply of the soil (nitrate in the root zone in spring, N mineralization) and of cropping of winter catch crops are shown. The site- and time-specific nitrate leaching risk during the leaching period is quantified. Nitrate losses by microbial denitrification in the grsundwater can play an important role. Quantitative understanding of the complex processes determining the final nitrate concentration of a groundwater well is crucial. All agricultural and groundwater management measures should be applied to secure a sufficient water quality.

[1]  J. Germon,et al.  Management systems to reduce impact of nitrates , 1989 .

[2]  W. V. Duijvenbooden,et al.  Vulnerability of soil and groundwater to pollutants , 1987 .

[3]  K. Howard.  Denitrification in a major limestone aquifer , 1985 .

[4]  J. Wehrmann,et al.  The Nmin‐method – an aid to integrating various objectives of nitrogen fertilization , 1986 .

[5]  K. O'Carroll.  Nitrates in water , 1987 .

[6]  J. C. Ryden,et al.  Nitrogen relationships in intensively managed temperate grasslands , 1984 .

[7]  A. Cripps,et al.  Nitrate Leaching to Groundwater , 1982 .

[8]  G. Wessolek,et al.  Evapotranspiration and groundwater recharge – A case study for different climate, crop patterns, soil properties and groundwater depth conditions - , 1986 .

[9]  W. Werner,et al.  Untersuchungen über den Einfluss langjähriger Gülledüngung auf N-Fraktionen und N-Nachlieferung des Bodens , 1985 .

[10]  O. Strebel,et al.  Redoxpotential und Eh/pH-Diagramme von Stoffumsetzungen in reduzierendem Grundwasser (Beispiel Fuhrberger Feld) , 1986 .

[11]  O. Strebel,et al.  Quantitative und qualitative Veränderungen im A‐Horizont von Sandböden nach Umwandlung von Dauergrünland in Ackerland , 1988 .

[12]  Kurt Overgaard.  Trends in nitrate pollution of groundwater in Denmark , 1984 .

[13]  John A. Cherry,et al.  An in-situ study of the occurrence and rate of denitrification in a shallow unconfined sand aquifer , 1986 .

[14]  E. A. Garwood,et al.  Nitrate loss through leaching and surface runoff from grassland: effects of water supply, soil type and management , 1986 .

[15]  Jürgen Wollring,et al.  Der Nitratgehalt in der Halmbasis als Maßstab für den Stickstoffdüngerbedarf bei Wintergetreide , 1990 .

[16]  J. Steenvoorden,et al.  Nitrogen losses from animal manures: from grazed pastures and from applied slurry , 1987 .

[17]  M. Renger,et al.  A FIELD STUDY WITH NITROGEN‐15 OF SOIL AND FERTILIZER NITRATE UPTAKE AND OF WATER WITHDRAWAL BY SPRING WHEAT , 1980 .

[18]  W. H. M. Duynisveld,et al.  Nitrogen supply to cereals and sugar beet by mass flow and diffusion on a silty loam soil , 1989 .

[19]  J. Steenvoorden,et al.  Losses of nitrogen from intensive grassland systems by leaching and surface runoff , 1986 .

[20]  J. Böttcher,et al.  Solute input into groundwater from sandy soils under arable land and coniferous forest: Determination of area-representative mean values of concentration , 1989 .

[21]  J. Boettcher,et al.  Reduced sulphur compounds in sandy aquifers and their interactions with groundwater , 1990 .