Cornwall has numerous derelict Cu-Sn mine sites scattered throughout the county-a legacy of past intensive mining activity. Due to the toxic concentrations of heavy metals many sites are poorly vegetated which leads to continued dispersion of toxic metals into the surrounding farming environment. The aim of this research is to establish the extent of contamination, to determine its form, and to ascertain how much dispersion is currently occurring. A case study of the Tresavean Mine near Redruth, west Cornwall, UK, has shown that the distribution of As and Cu from the mine extends up to 150 m. An extensive soil survey of the farmland surrounding the mine revealed two distinct distribution patterns for As and Cu. Arsenic distribution appears to correlate with the prevailing wind direction at the site, whereas the Cu distribution follows the down slope drainage pattern. Sequential extractions were made on soil samples taken at intervals along a transect from the mine to determine which soil fractions Cu and As are held in; i.e. water-soluble, exchangeable, adsorbed, organic, Fe-Mn oxides or residual. These sequential extractions indicate the Cu is held mainly in the residual and organic fractions and As is held mainly in the residual and iron-organic fractions. Although the absolute concentrations of As and Cu decrease with distance from the mine site, as expected, the percentage of As and Cu in each fraction does not follow this pattern in every case.
Several inherent characteristics of metalliferous mine wastes inhibit the establishment of vegetation: nutrient deficiency, acidity, poor water retention, metal toxicity, instability, and poor soil structure. They may be overcome by in situ amendments. Most reclamation programs in west Cornwall, UK, involve extensive treeplanting schemes. Alder species are usually a major component of such schemes because of their N-fixing capability. A pot experiment (based on a quarter replicate of a full 2 7 factorial design) was established at the Camborne School of Mines, to investigate the effects of seven amendments (and their interactions) on the growth of common alder (Alnus glutinosa (L.) Gaertner). The amendments were ammonium nitrate, mineral phosphate and potash fertilizers, calcareous sea sand, dewatered sewage sludge, diatomaceous earth, and a superexpanding polyacrylamide gel polymer. The waste was analyzed for total and ammonium acetate-extractable metals and nutrients, pH, and total exchangeable bases at the outset of the experiment, and was found to contain 0.3% As and very low concentrations of the major nutrients. Tree heights and survival were recorded monthly for two growing seasons. Leaf, stem, and root dry weights were recorded after harvesting, from which various resource allocation ratios were calculated. Sewage was the best amendment, followed by diatomaceous earth. The N, P, and K fertilizers, sand, and gel had little effect, being deleterious in some cases. Of the interactions, the traditional mineral phosphate-calcareous sand treatment was ineffective. The importance of soil structure improvement by organic material was apparent.
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