The Influence of Discharge, pH, Dissolved Organic Carbon, and Suspended Solids on the Variability of Concentration and Partitioning of Metals in a Rural Catchment

摘要

In this study, the water draining a catchment of 65 km~2 in NW Spain was monitored over a 3-year period to examine temporal variability of five metal concentrations (Al, Fe, Mn, Cu, and Zn) in dissolved form and also in suspended solids (SS), under two different hydrological conditions-in baseflow and stormflow events. pH, SS and dissolved organic carbon (DOC) were also examined as possible factors affecting metal transport mechanisms. The results showed that Al_d, Cu_d, and Zn_D were significantly (p<0.05) higher in stormflow events than in baseflow, while in SS, all metal concentrations decreased (p<0.05) during stormflow events. The metal seasonal variability was also examined. In dissolved form, only Fe_D showed significant differences (p<0.05) between seasons, with higher concentrations in summer, independently of the hydrological conditions, while in SS, only Cu_(ss) during stormflow events showed concentrations significantly higher (p<0.05) during summer than in the remainder seasons. The partition coefficients (K_D) decreased significantly (p<0.05) for all metals during stormflow events. K_D correlations showed that SS and DOC were the main factors in controlling the K_D of all metals, except the K_D of Mn which did not depend on any of these variables in baseflow. Metal enrichment factors were significantly higher (p<0.05) during baseflow than in events which were associated to SS source and size.