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Metal fractionation in a contaminated soil after reforestation: temporal changes versus spatial variability
Bernd Nowack1, Rainer Schulin, Jörg Luster
1Institute of Terrestrial Ecosystems, ETH Zürich, Universitaetstrasse 16, CH-8092 Zürich, Switzerland. nowack@empa.ch
Environmental Pollution (Barking, Essex : 1987)
|August 21, 2010
Summary
Tree activity in metal-contaminated soils significantly alters metal solubility and fractionation, especially within the first six months. Spatial variations in soil composition are more critical than time for understanding metal behavior.
Area of Science:
- Environmental Science
- Soil Science
- Geochemistry
Background:
- Industrial activities, such as non-ferrous metal smelting, release filter dust that pollutes topsoils with heavy metals.
- Understanding metal speciation and fractionation in contaminated soils is crucial for assessing environmental risk and developing remediation strategies.
Purpose of the Study:
- To investigate the long-term effects of tree presence on the fractionation and solubility of copper (Cu), zinc (Zn), cadmium (Cd), and lead (Pb) in polluted soils.
- To compare metal speciation changes over time in planted versus plant-free contaminated soils.
Main Methods:
- A lysimeter experiment was conducted using topsoils polluted with smelter filter dust.
- Sequential extraction techniques were employed to analyze metal fractionation over 42 months.
- Plant-free and uncontaminated soils were used as controls.
Main Results:
- Significant changes in metal speciation occurred within the first 6 months in contaminated and planted soils.
- A linear relationship was observed between certain metal fractions, indicating systematic redistribution.
- Plant activity appeared to maintain metals in more soluble forms compared to plant-free soils, which showed higher proportions in refractory phases after 30 months.
Conclusions:
- Spatial heterogeneity in total metal content plays a more significant role than temporal variations in determining metal fractionation and solubility in contaminated soils under natural conditions.
- Plant activity is a key factor influencing the long-term speciation and bioavailability of metals in polluted ecosystems.
