The normalized sediment metal concentrations (10% OM, 25% clay) and their comparison to the national concentration thresholds of dredging guideline (Ministry of the Environment, 2004) are presented in Fig. 3.Most commonly the first threshold of national dredging guideline was exceeded by Cd, Ni and Zn concentrations and these sediments were classified as potentially contaminated. The mean concentrations of As, Cr and Cu also exceeded the first threshold of national dredging guideline in the R. Kyrönjoki 3, R. Perhonjoki and R. Laihianjoki study sites, respectively. Only Ni concentrations exceeded the second threshold of dredging guide in three estuary sites and those sediments were classified as contaminated. Sediment Pb concentrations exceeded neither the first (40 mg/kg) nor the second threshold (200 mg/kg) of national dredging guideline.