Heavy metal contaminated soils in an old industrial area of Wales, Great Britain: Source identification through statistical data interpretation

A combined statistical and computergraphic approach is proposed for apportionment and attribution of soil contaminants in complex areas. The field test site lies north of Swansea, south Wales and contains two major pollutant sources, an active nickel refiner and (4 km away) the site of major base metal smelting in the nineteenth century (the Lower Swansea Valley reclamation study area). Soil samples (70 samples, 0-15 cm) were collected on a regular grid of 1000 m interval. They were extracted using 0.05 M diammonium EDTA and the extracts analysed for Cd, Co, Cu, Fe, Mn, Ni, Pb and Zn. Soil pH and %organic content were also determined. Factor analysis yielded three groups which explained 73.8% of the data variance (1: Cd, Cu, %OM, Pb, Zn, Ni; 2: Cd, Zn, Mn, pH, 3: Cu, Mn, Co, Ni, Fe). Isoline plots were classifiable into the same three groups. It was concluded that factor 3 contained those elements associated with smelter emissions, factor 1 with contamination from the Lower Swansea Valley and in factor 2 pedogenetic processes control the occurrence of the elements.