Identifying environmental and geochemical variables governing metal concentrations in a stream draining headwaters in NW Spain

Headwater stream, draining from a rural catchment in NW Spain, was sampled during baseflow and storm-event conditions to investigate the temporal variability in dissolved and particulate Al, Fe, Mn, Cu and Zn concentrations and the role of discharge (Q), pH, dissolved organic carbon (DOC) and suspended sediment (SS) in the transport of dissolved and particulate metals. Under baseflow and storm-event conditions, concentrations of the five metals were highly variable. The results of this study reveal that all metal concentrations are correlated with SS. DOC and SS appeared to influence both the metal concentrations and the partitioning of metals between dissolved and particulate. The SS was a good predictor of particulate metal levels. Distribution coefficients (KD) were similar between metals (4.72–6.55) and did not change significantly as a function of discharge regime. Stepwise multiple linear regression analysis reveals that the most important variable to explain storm-event KD for Al and Fe is DOC. The positive relationships found between metals, in each fraction, indicate that these elements mainly come from the same source. Metal concentrations in the stream were relatively low.