Search

The article discusses a University of Northern British Columbia-led study of the aquatic effects of the failure of the tailings storage facility of the Mount Polley Mine in 2014. It describes the initial impacts of the disaster on the environment based on ten years of study, as well as problems encountered and lessons learned by the researchers. It explains the need to consider environmental disasters associated with human activities, such as mining, to be different from natural ones.

Stream bank erosion has been anecdotally identified as an important source of sediment in New Zealand catchments, however, there have been few attempts to quantify its contribution. Here we use a radionuclide-based sediment tracing approach to determine the relative contribution of stream bank- and hillslope-derived sediment within three catchments in the upper North Island of New Zealand. Both lithogenic (radium-226 and radium-228) and fallout radionuclides (caesium-137 and excess lead-210) were used to differentiate sediment derived from stream bank and hillslope sources. The relative contribution of stream banks and hillslopes to fluvially transported suspended sediment were predicted using a mixing model approach. Our results indicate that both fallout and lithogenic radionuclides provide good source differentiation. We demonstrate that stream bank erosion can contribute very high proportions of sediment within New Zealand catchments. We used independent assessments of bank erosion from each of the study catchments to support the sediment source fingerprinting results. Further work is required to determine the spatial and temporal variability of the contribution of sediment from stream banks. Information on the importance of different sediment sources is needed to target limited catchment rehabilitation resources where they will have the most impact. [ABSTRACT FROM AUTHOR]

On 4 August 2014, a tailings dam failure at Mount Polley Mine in central British Columbia led to the largest short‐term release of mine waste into a lake ever recorded. Once released by the breach, slurry entered the smaller of Quesnel Lake's two basins, called the West Basin, from which the lake drains northwest into the Quesnel River. An estimated 38,000 ± 11,000 tonnes of fine solids remained suspended in the West Basin on 10 September 2014, 37 days postspill. This decreased to within background levels (<300 tonnes) by June 2015, by which time ∼4,000 tonnes of sediment had flowed from the West Basin into the Quesnel River, and ∼31,000 tonnes had been transported east into the main basin, the direction opposed to the mean hydraulic gradient. Here, we evaluate sediment transport in Quesnel Lake following the Mount Polley tailings dam spill. We apply conservation of mass in two ways: using data collected between 12 August 2014 and 15 October 2020 to estimate suspended sediment mass and mass flows into and out of the West Basin; and using one‐ and two‐basin completely mixed models. Suspended sediment concentrations were highly elevated through the first three seasons postspill, then fluctuated within a gradually decreasing, seasonal cycle. The observed mass trend and an analytical mass balance model of a simplified, two‐basin system suggest that suspended sediment mass will fall to below the median prespill mass by 7 ± 5 years postspill. Plain Language Summary: The largest mine waste spill into a lake to date began on 4 August 2014, at Mount Polley Mine in central British Columbia, Canada. Within the day, nearby Quesnel Lake received a volume of waste equivalent to 2% of the volume of its smaller, downstream basin, the West Basin, where the spill flowed into the lake (0.02 km3 of waste into the 1 km3 basin). Roughly 38,000 tonnes of fine solids remained in suspension 37 days postspill, and our study evaluated the movements of this suspended sediment in Quesnel Lake and the Quesnel River using water quality data collected between 12 August 2014 and 15 October 2020. We found that the net movement of suspended sediment was opposed to that of the hydraulic gradient through the first three seasons postspill, after which the amount of sediment fluctuated seasonally each year, greatest each autumn and spring. We assessed simplified one‐ and two‐basin mathematical models, the latter of which broadly describes the two‐phased response of Quesnel Lake's two basins, and both of which predict a return to background suspended sediment concentration in the West Basin by about one decade postspill. Key Points: About 38,000 Mg of sediment was suspended in the smaller of two lake basins 1 month after a spillFour fifths of this sediment went east into the larger basin and one tenth went north to the outflowTrends show a return to background suspended sediment levels by about 7 years after the spill [ABSTRACT FROM AUTHOR]

The catastrophic August 2014 Mount Polley tailings spill, the second largest ever documented, sent ~18 Mm3 of waste plunging to the bottom of the >100 m deep West Basin of Quesnel Lake, British Columbia, a critical West Coast salmon habitat. To understand the impact of the spill on the lake, including the fate of suspended solids, we examine changes in physical water properties over 11 years (2006–2017) using water column profiles, moored timeseries, and satellite imagery. Contaminated waters were initially largely confined to the hypolimnion; however, during autumn 2014 turnover, turbid waters were mixed to the surface, resulting in the clear blue lake turning bright green. Twelve months after the spill, the lake's temperature, conductivity, and turbidity temporarily returned to pre‐spill conditions; however, initiation of mine effluent discharge in late 2015 was associated with a subsequent 15 μS cm−1 conductivity increase above historic values. Importantly, a post‐spill 1–2.5 formazin turbidity unit hypolimnetic turbidity increase was observed during spring and fall turnovers of 2015–2017, which appeared to be due to resuspension of a thin layer of unconsolidated spill‐related material from the lake bed driven by large internal seiche motions. This process implies spill contaminants may be seasonally mobilized into the water column, with potentially detrimental impacts on aquatic ecology. Our findings underscore that basin‐scale physical processes, including seasonal turnover and internal seiches, must be accounted for, even in deep lakes, to understand the long‐term impact of the ever increasing number of tailings spills into aquatic ecosystems. Plain Language Summary: The catastrophic failure of the Mount Polley copper and gold mine tailings pond dam in August 2014 was, at the time, the largest mine‐related spill ever documented. The turbid torrent of mine waste plunged to the bottom of the near pristine waters of Quesnel Lake, British Columbia, critical habitat for West Coast salmon stocks. Despite the scale of the spill, there was surprisingly little visible evidence of it at the surface of the lake in the months following. But what happened below the surface? Using 11 years of water column measurements we show that as the lake mixed from top to bottom (called turnover) that autumn the contaminated deep water was brought to the surface, abruptly changing the color of the clearblue lake to an abnormal bright green color—a change readily visible from space. Since the spill the turbidity of the lake has increased during spring and autumn turnover, apparently due to resuspension of spill material off the lake bottom driven by basin‐scale wave oscillations. This process, and the ongoing discharge of excess mine waste water directly into the lake, raises concerns over the seasonal mobilization of mine contaminants and their impact on aquatic ecosystems. Key Points: Quesnel Lake turned bright green when turbid spill material trapped in the hypolimnion mixed to the surface during autumn 2014 turnoverSeasonal turbidity increases since the spill are likely due to resuspension of spill‐related bottom sediment by internal seichesPhysical dynamics are key to understanding the long‐term impact of acute and chronic mine spills even in deep aquatic systems [ABSTRACT FROM AUTHOR]

The flow-diverted Nechako River is the second largest tributary of the Fraser River which drains 25% of mainland British Columbia, Canada. The watershed provides critical reproductive habitats for anadromous chinook salmon (Oncorhynchus tshawytscha) and sockeye salmon (O. nerka) and year-round habitat for the endangered Nechako white sturgeon (Acipenser transmontanus) population. In this study, the chemical quality of sediment in the upper Nechako River and its major tributaries was examined for polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), legacy organochlorine (OC) pesticides, polycyclic aromatic hydrocarbons (PAHs), organophosphorus and phenoxy acid herbicides, polychlorinated dibenzo-p-dioxins (PCDDs) and furans (PCDFs), labile (exchangeable) metals/metalloids, and major nutrients (N and P). ΣPCB and ΣPBDE were detected in channel bottom sediments at all Nechako River and tributary sites; hexachlorobenzene (HCB) and 4,4′-DDE (dichlorodiphenyldichloroethylene) were also detected at most sites. Organophosphorus and phenoxy acid herbicides were not detected in any samples. While ΣPCB, ΣPBDE, HCB, and 4,4′-DDE concentrations in bottom sediments were always well below provincial and federal guidelines for the protection of aquatic life, concentrations of total labile As (AsT), CrT, CuT, FeT, MnT, NiT, and ZnT in suspended and/or bottom sediments often exceeded provincial threshold effect levels (TEL) and, in some cases, approached or exceeded probable effect levels. Distinct CuT, NiT, PbT and ZnT concentration maxima in suspended sediments were linked to road and urban densities. Historical PCDD, PCDF and PAH data show that concentrations in bottom sediment samples were highest at a site in the lower Nechako River between Miworth and the City of Prince George where PCDD and PCDF concentrations exceeded the interim federal TEL. Nitrogen and P concentrations in bottom sediments were negatively correlated with water velocity and sediment texture; the evidence suggests that reductions in velocity resulting from the 1952 diversion of the Nechako River have increased the nutrient content of bottom substrates. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Water Resources Journal / Revue Canadienne des Ressources Hydriques is the property of Taylor & Francis Ltd and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The use of sediment color as a fingerprint property to determine sediment sources is an emerging technique that can provide a rapid and inexpensive means of investigating sediment sources. The present study aims to test the feasibility of color fingerprint properties to apportion sediment sources within the South Tobacco Creek Watershed (74 km²) in Manitoba, Canada. Suspended sediment from 2009 to 2011 at six monitoring stations and potential source samples along the main stem of the creek were collected. Reflectance spectra of sediments and source materials were quantified using a diffuse reflectance spectrometry, and 16 color coefficients were derived from several color space models. Canonical discriminant analysis was used to reclassify and downsize sediment source groups. After the linear additive test and stepwise discriminant function analysis, four color coefficients were chosen to fit the Stable Isotope Analysis in R model. Consistent with the conventional fingerprinting approach, the color fingerprint results demonstrated a switch in the dominant sediment source between the headwaters and the outlet of the watershed, with the main sources being topsoil in the upper reaches, whereas outcrop shale and stream bank materials dominated in the lower reaches. The color fingerprinting approach can be integrated with conventional fingerprints (e.g., geochemical and fallout radionuclide properties) to improve source discrimination, which is a key component for source ascription modeling. We concluded that the use of color fingerprints is a promising, cost-effective technique for sediment source fingerprinting. [ABSTRACT FROM AUTHOR]

Information on the Sediment Dynamics and Pollutant Mobility (SEDYMO) in River Basins Symposium on March 26 to 29, 2006 at Hamburg University of Technology in Germany is presented. The conference, which comprised 43 oral presentations and numerous poster presentations, was organized by professors Ulrich Förstner and Bernard Westrich. The event provided an opportunity for researchers to present results and findings of their sediment research.

The selective nature of interrill erosion – the preferential mobilization and transport of soil particles – can lead to the enrichment of fine-grained soil particles (< 63 μm) and organic carbon (OC) within the mobilized soil. This study investigated the effects of slope gradient, vegetative cover, soil moisture content, texture and organic matter content, as well as their interactions on soil loss, particle size distribution and organic carbon content of soil mobilized under simulated rainfall within two contrasting agricultural regions in Canada. Overall, it was found that the eroded material was enriched in both fine-grained and carbon-rich particles relative to the source soil. It was demonstrated that dispersing and sieving both the source soil and the mobilized soil to < 63 μm (i.e., removal of sand and large particulate organic matter) reduced the relative enrichment of both fine-grained soil particles and OC, which would allow for a more direct comparison of physical and biogeochemical properties between the source and mobilized soil. Furthermore, it was demonstrated that while the soil loss and the degree of enrichment were negatively correlated, there were differences in which soil surface properties had a significant effect in determining soil loss and the selectivity of both fine-grained and organic-rich soil particles and how these surface properties interacted. This suggests that while soil loss may be a good predictor of the degree of enrichment, the factors that control these two processes are different, which is important in understanding the process of selectivity. It was also shown that the OC content of both the source and mobilized soil was positively correlated to the degree of soil aggregation in addition to the silt and clay content. [ABSTRACT FROM AUTHOR]