Heavy Metals

Amongst the range of contaminants that may be found in soils, potentially toxic elements or heavy metals are of particular interest for a number of reasons. Firstly, they show a tendency, under normal circumstances, to accumulate in soils and have a long persistence time because of the interactions with particular soil components. However, it is possible that environmental change may result in conditions, which could result in dramatic releases of stored metals, the so-called 'chemical time-bomb' effect. Secondly, they are ubiquitous in soils and arise from both natural and anthropogenic sources, with pathways including inheritance from the parent rocks, application of wastes, as well as local and long-range atmospheric and fluvial deposition of emissions from industry and mining. Finally, many of the heavy metals are essential, at low concentrations, for plant, animal and human health but, at higher concentrations, they can be toxic.

Changes in concentration of heavy metals with depth can be significantly altered within soil profiles through a number of biological and chemical processes. However, the concentration of metals in surface horizons coincides with the maximum microbiological activity in the soil and may interfere with certain key soil processes. A great deal of work has been carried out in the past on the contents of a range of heavy metals in Scottish soils but in most of these studies soil samples have been taken from the mid-point of selected soil horizons. However, in this study, samples been taken specifically from the soil surface and will maximise the impact of atmospheric deposition for the full range of pollutants.

References

• Reaves, G.A. and Berrow, M.L. (1984) Total lead concentrations in Scottish soils. Geoderma, 32, 1-8.
• Reaves, G.A. and Berrow, M.L. (1984) Total copper contents of Scottish soils. Journal of Soil Science, 35, 583-592.
• Berrow, M.L. and Reaves, G.A. (1986) Total chromium and nickel contents of Scottish soils. Geoderma, 37, 15-27.