THE INFLUENCE OF TEMPERATURE AND NACL ON CADMIUM, COPPER AND ZINC PARTITIONING AMONG SUSPENDED PARTICULATE AND DISSOLVED PHASES IN AN URBANRIVER

Distribution coefficients (K-d) were used to estimate the most importa nt geochemical phases within the suspended particulate matter (SPM) po ol for sorption of Cd, Cu and Zn. Given that pH effects were expected to be minimal, as the Don is a well buffered system, the possible infl uence of secondary environmental variables [temperature, dissolved org anic carbon (DOC), dissolved Ca2+ and NaCl] on trace metal partitionin g between SPM and the dissolved phase was evaluated using a series of multiple linear regressions for total (KdT)as well as the phase specif ic (K(d)L leachable phase; K(d)R reducible phase; and KdO oxidizable p hase) distribution coefficient estimates. The three metals varied in t heir sorptions patterns. Cd and Zn showed the same relative affinities for three SPM pools (leachable = reducible > oxidizable), while Cu af finities ranked oxidizable = leachable > reducible. Secondary environm ental factors were identified as more important influences on trace me tal partitioning than pH. Temperature and NaCl (from road salt runoff) were found to be key environmental variables influencing trace metal partitioning. A decrease in water temperature caused decreases in the accumulation of Cd, Cu and Zn in the particulate pool. Increasing NaCl concentrations decreased the concentrations of Cd and Zn associated w ith the particulate leachable phase and the Cd, Zn and Cu content in t he oxidizable SPM phase. These results suggest that in running waters during winter months, or even during summer months in the hypolimnia o f sufficiently deep lakes, a relatively higher proportion of these met als remains in the dissolved and potentially more bioavailable pool.