Land use impacts on trace metal concentrations of suburban stream sediments in the Helsinki region, Finland.

The purpose of this study was to statistically analyze the effect of different suburban land use types on trace metal contamination of suburban streams. Acid extractable metal concentrations (Cu, Zn, Pb, Cd) of stream bed sediments (<63 μm) and high-flow suspended sediments were determined for 61 suburban and six baseline catchments in the Helsinki metropolitan region, Finland. Our results showed that the average suburban metal concentrations were 3-5-fold compared to baseline values for stream bed sediments and 2-9-fold for suspended sediments. Correlation analyses revealed moderate relationships between the land use parameters of the contributing catchment and the metal concentrations. Metals, particularly Zn and Cu, were most strongly correlated with proportions of dense suburban land use and imperviousness. In addition, industrial land use appeared to be particularly important for describing the variations of suspended sediment metal concentrations. Our findings present statistical evidence that the intensity of urbanization and industrial land use provides an indication of metal contamination even within the suburban environment.