This study evaluated the use of statistical randomization tests in data analysis regarding heavy metals content in sediments from the Caí River basin (Brazil). During one year, four samplings took place at eleven sites in the Caí River and tributaries. The results showed significant differences between some locations, enabling spatial segregation of sites affected by natural and anthropic sources. Considering a significance level (α) of 5%, the control station, above polluted areas, showed the best quality; Caí River station after the mouth of Pinhal/Belo stream indicated influence from the industrial complex of Caxias do Sul region, as well as copper compounds use in vineyards; and the Cadeia and Forromeco streams showed effects of natural contribution from basalts and surface runoff on naked soils. For α=10%, it was possible to identify chromium pollution by tanneries in the Cadeia stream. Long-term studies should be performed, since understanding temporal aspects such as alteration processes in sediments involves a much longer time scale.