Origin and fate of Vanadium in the Hazeltine Creek Catchment following the 2014 Mount Polley mine tailings spill, British Columbia, Canada

Results are presented from the analysis of aqueous and solid-phase V speciation within 27 samples collected from the Hazeltine Creek catchment affected by the August 2014 Mount Polley 28 mine tailings dam failure, Canada. Electron microprobe and XANES analysis found that V is present 29 as V 3+ substituted into magnetite, and V 3+ and V 4+ substituted into titanite, both of which occur in the 30 spilled Mount Polley tailings. Secondary Fe oxyhydroxides forming in inflow waters and on creek 31 beds have V K-edge XANES spectra exhibiting E½ positions and pre-edge features consistent with 32 the presence of V 5+ species, suggesting sorption of this species on these secondary phases. PHREEQC 33 modelling suggests that the stream waters mostly contain V 5+ , and the inflow and pore waters contain 34 a mixture of V 3+ and V 5+ . These data, and stream, inflow and pore water chemical data, suggest that oxhydroxides, V-bearing Al(OH) 3 and/or -clay minerals may have occurred. In the circumneutral pH environment of Hazeltine Creek elevated V concentrations are likely naturally attenuated by formation of V(V)-bearing secondary Fe oxyhydroxide, Al(OH) 3 or clay mineral colloids, suggesting that the V is not bioavailable. A conceptual model is presented describing the origin and fate of V in Hazeltine Creek that is applicable to other river systems.


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Humans can be exposed to vanadium mainly through inhalation and ingestion, potentially 6 98 In this paper we focus on V due to its high environmental risk potential 2,8,9,10 and to the relative 99 lack of data on its behavior in mining-affected environments 20 . We aim to understand the geochemical 100 cycling of V in the Hazeltine Creek catchment and its implications for the origin, transport, fate and 101 potentially toxicity of V in other river systems. The objectives of the study are to determine (1) V 102 concentrations and speciation in stream, inflow and pore waters using aqueous composition data and 103 PHREEQC modeling, (2) solid-phase V concentrations and speciation in the deposited tailings and 104 secondary Fe oxyhydroxides using electron microprobe, automated mineralogy analysis and X-ray 105 absorption spectroscopy (XAS) analysis, (3) the environmental origin, fate and potential hazard of 106 the deposition of V-bearing tailings in mining-affected catchments following tailings dam failures 107 and remediation. We present, for the first time to our knowledge for natural systems, evidence that 108 dissolution of V-bearing magnetite and titanite may contribute to aqueous V. The results will also 109 inform restoration and management schemes for river systems receiving V from other natural and 110 anthropogenic sources.      (Figure 3). It is possible that these high 14 306 concentrations reflect those in initial tailings dam pore waters transported with the spilled tailings, 307 but this is unlikely for the following reasons. First, most of the tailings and interstitial water went into 308 Quesnel Lake rather than Hazeltine Creek 25 , second, we sampled in a very disturbed mixed river 309 sediment rather than undisturbed layers of tailings and third, we sampled a year after the spill and the 310 nature of the channel (high gradient, gravelly substrate) encouraged flushing by hyporheic exchange.
311 Therefore, we propose that the high filtered V concentrations at 10 and 20 cm depth arose from 312 dissolution of V-bearing phases containing these elements just below the water-sediment interface 66 .  Figure S2), 361 suggesting that fine particulate transport of V is significant in the catchment.

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The significance of the Mount Polley tailings spill on water quality and V transport are 363 illustrated in Figure S4 where V flux (kg yr -1 ) and yield (kg km -2 yr -1 ) are compared to unaffected 364 regional watersheds in British Columbia and other mining-affected watercourses around the world.
365 Transport of V in the stream is elevated compared to nearby regional streams, even when the flux