Fjölrit RALA - 15.06.2004, Page 121

Distribution and bioavailability of heavy metals in Icelandic Soils.
Julian J.C. Dawson1, Olafur Arnalds2 and Graeme I. Paton1
'Soil Science Group, School of Biological Sciences, Cruickshank Building, University of Aberdeen
2Agricultural Research Institute, Reykjavík, Iceland
Introduction
Heavy metals perhaps pose their greatest threat when derived from anthropogenic sources.
There is a wide distribution of these contaminants throughout the world derived from a wide
range of sources including fuels, paints, cosmetics, tyres, sewage and animal wastes, piping
and industrial effluents. However, metals and metalloids occur at elevated concentrations in a
wide range of environments and are the focus for significant ecological monitoring. The
minerals associated with Andolsols are known to contain elevated levels of a range of metals
and metalloids. As the soils mature through weathering, these metals become distributed
throughout the soil profile. To fully assess the presence of metals and their likely
environmental impact an intense sample regime was undertaken. The correlation between
target elements, Fe and A1 can be used to assess if the source is geochemical or
anthropogenic. Analysis of vegetation can be used to evaluate food chain transfer impacts
and the burden that the metals impose upon plant responses.
Aims and objectives
The aims of this study were to-
• Assess the concentration of metals and metalloids in Icelandic soils and vegetation
• Relate the doses of analytes to the soil types
• Quantify the bioavailable fraction of the target metals and metalloids
• Consider the likely source of these pollutants.
Materials and Methods
Sampling
An intense samphng regime was developed in Iceland in September 2000. Samples were
collected from thirty four locations representing a range of soil types, topography, vegetation
and altitude. Inert sampling procedures were used to avoid cross contamination of the soils
and vegetation and the samples were taken back to Aberdeen under controlled conditions.
Analysis
Metal analysis was carried out using a standard Aqua Regia digestion followed by ICP-MS
analysis. Confirmatory analysis was also carried out by hand-held XRF. The same
techniques were used to analyse vegetation samples. Water extractions were also performed
and correlated with the other measurements.
Toxicity assessments
Bioluminescence-based biosensors were used to assess the bioavailabihty of residual metal
fractions in the samples (Tiensing et al., 2001; Flynn et al., 2003).
Results and discussion
Elevated levels of metals and metalloids were most prevalent in the Andosols. Although they
were also detected in the Histosols, it was likely that the source was the ash deposits, visible
in the profiles. The desert soils showed Uttle evidence of elevated metal levels. In the soils,
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