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Nitrogen fertilization effects on stream water cadmium concentration.
L Högbom1, H O Nohrstedt, S Nordlund
1SkogForsk, The Forestry Research Institute of Sweden, Uppsala Science Park.
Journal of Environmental Quality
|February 24, 2001
Summary
Forest nitrogen fertilization can increase soil water acidity, mobilizing metals like cadmium and zinc. However, this study found no increase in nearby stream water metal concentrations, suggesting no risk to surface water quality.
Area of Science:
- Environmental Science
- Forestry
- Geochemistry
Background:
- Previous studies unexpectedly observed high transition metal concentrations in soil water after forest nitrogen (N) fertilization.
- Preliminary findings indicated cadmium (Cd) levels exceeding drinking water health limits, raising concerns about potential risks.
Purpose of the Study:
- To investigate if elevated soil water transition metal concentrations following N fertilization are a general phenomenon.
- To determine if N fertilization could lead to increased transition metal concentrations in stream water.
Main Methods:
- Studied soil water and stream water at two N-fertilized forest watersheds in central Sweden.
- Applied nitrogen (150 kg N ha(-1)) as calcium ammonium nitrate.
- Monitored concentrations of nitrate, acidity, and transition metals (Cd, Zn, Al).
Main Results:
- Nitrogen application increased soil water nitrate and acidity, enhancing the solubility of transition metals (Cd, Zn) and aluminum (Al).
- Stream water transition metal concentrations remained unaffected by the N fertilization during the study period.
- Solubilized transition metals likely re-precipitated further down the soil profile.
Conclusions:
- Forest N fertilization at normal soil pH levels does not pose a risk of increasing transition metal levels in nearby surface waters.
- The study is the first to consider the side effect of N fertilization on transition metal mobilization and transport.