Assessing the Influence of Catchment Land-Use Patterns on the Nutrients and Major Ions Chemistry of Drainage Water

Abstract

This work describes the influence of soil use on the evolution of nutrients [ammonium (NH₄), nitrate (NO₃), nitrite (NO₂), phosphate (PO₄) phosphorus (P)] and major ions [calcium (Ca), magnesium (Mg), sodium (Na), potassium (K), silicon (Si), chloride (Cl), sulfate (SO₄)] concentrations in drainage water of a catchment with two consecutive land uses: first agricultural and then forest. This is a small catchment with previous agricultural diffuse and accidental pollution mainly due to the spreading of slurry. Ion concentrations were monitored over a period of approximately 6 years at the catchment outlet. Agricultural land use was replaced by eucalyptus plantations from mid-July 1998. Great temporal variability was observed for each ion and also among ions. The mean concentrations of studied ions were greatest during the agricultural period. The most pronounced differences occurred for NH₄, PO₄-P, NO₂, and K. All presented the greatest concentration peaks in the agricultural phase, with the exception of Ca. During this period the following concentrations (mg L⁻¹) were reached: NO₃110, NH₄ 31, NO₂ 3.76, PO₄-P 35.96, Ca 30, Mg 12.42, K 97, Na 50, Si 13.9, Cl 96, and SO₄ 16.6. The slurries seem to have contributed notably toward the increase in the concentration of nutrients and major ions in the drainage water of the catchment, affecting water quality.

Keywords:

• Drainage water
• land use
• major ions
• nutrients
• slurry