Abstract <p>The main distribution patterns of metals and metalloids (MM: Sc, V, Cr, Fe, Mn, Zn, Cu, Ni, Co, Pb, Cd, Sr, Ba, Sb, As, Hg) in bottom sediments (BS) and silt waters of small rivers of St. Petersburg, which are under the influence of industrial wastewater discharges, have been studied. MM concentrations in the solid and liquid phases of bottom sediments exceed background values by <i>n</i> × 10–10² times. The leading influence of chemical specialization of enterprises on their composition has been shown. Near the discharge of wastewater from the production of lead–acid batteries in the Yekateringofka River, the Pb content in interstitial water reaches 14.5 mg/L, and under the influence of the production of Ni–Cd batteries (Karpovka River), the Ni concentration is 8.56 mg/L. Correlation, factor and cluster analyses were used to measure a relationship between the MM concentration in bottom sediments and silt water and complete identity of the main paragenetic associations. The risks of secondary pollution of rivers were established: diffusion flows from bottom sediments into water and opening of the pore space during bottom cleaning operations. Based on Fick law, the intensity of MM diffusion flows (μg/(m² day)) was estimated, the maximum average values of which are characteristic of Fe (9985), Ba (322), Zn (169), Mn (131), and the minimum, of As (0.9), Cd (2.4), and Co (4.4). Calculations showed that in most cases the intensity of secondary pollution through diffusion entry of pollutants prevails over mechanical pollution.</p>