Use of the O horizon of forest soils in monitoring metal deposition in Latvia

The concentrations of Cu, Cd, Pb, Zn, V, Ni, Cr, Fe Ca, Mg and K were determined in the organic soil layer (O horizon) of pine forests in Latvia. The concentrations were expressed on a mass, volume and surface area basis. When concentrations were calculated per unit mass of the O horizon, significant positive correlations between concentrations in the O horizon and Pleurozium schreberi were achieved for most elements (excepting Cr, Ca and K), and to lesser degrees for Cu, Pb, Zn, V, Ni and Fe when calculated on a volume or area basis. Non-rotated principal components analysis identified a major soil factor related to bulk density (volume- and area-based concentrations). The main groups of related elements defined by varimax-rotated PCA components were similar for the mass- and volume-based data, and regions with elevated levels of these elements could be related to local pollution sources, similar to the patterns previously reported from surveys based on moss.