In Situ Monitoring of Labile Vanadium in the Mackenzie River Basin (Canada) Using Diffusive Gradients in Thin Films

Vanadium has the potential to be released as a by-product of the combustion of fossil fuels such as oil and coal in the aquatic system. Presence of tailing ponds and other mining operations may pose the largest threat to downstream users and to the long-term aquatic health of the Mackenzie River Basin (MRB, Canada). The need for developing a solid baseline for the MRB aquatic ecosystem against which future changes can be measured is urgent. In this study, 36 sets of triplicate diffusive gradients in thin films (DGT) samplers were deployed in MRB during the 2012–2014 ice-free seasons to investigate temporal and spatial changes in the concentration of DGT-labile vanadium (V) as part of a Northwest Territories community-based project. Average DGT-labile V concentration (5.9 ± 0.9 nmol L⁻¹) was comparable with non-contaminated aquatic systems, suggesting no significant impact of human activities on V speciation in MRB in 2012–2014. The V concentrations reported in this study constitutes a baseline that can be used to enhance ongoing monitoring efforts. Although the DGT samplers were deployed in collaboration with northern communities, the absence of temporal changes in DGT-labile V indicated that in situ DGT passive samplers constitute a reliable and robust alternative for community-based monitoring programs. Excitation emission matrix (EEM) fluorescence combined with parallel factor analysis (PARAFAC) validated three humic-like (C1–C3) and one protein-like (C4) fluorescent component. However, no significant relationships were apparent between DGT-labile V and dissolved organic carbon (DOC), the PARAFAC loadings, and composition (p > 0.05). Hierarchical cluster analysis revealed that DGT-labile V concentration was negatively correlated with aromatic and humified DOM (r = − 0.70 to − 0.84, p < 0.05).