Fine sediment dynamics in Quesnel Lake: the regulation of contaminant and nutrient transfers from the Mt Polley mine spill

2014年8月，加拿大最大的矿难发生在不列颠哥伦比亚省Likely附近的Mt Polley铜金矿。尾矿池墙破裂，释放了25 Mm 3的尾矿、废水和建筑材料。进一步冲刷的植被和表面材料发生沿着9公里到达之前，进入西部盆地的Quesnel湖。波利湖，一个靠近尾矿池的较小的湖泊，也被投入了尾矿，但在第一年仍然禁止研究人员进入。该提案旨在评估细沉积物过程调节污染物（金属/类金属）和磷（P）的动态及其对奎斯奈尔湖和波利湖食物网的中期影响。2016年，一项岩心取样计划沿着一个湖泊样带进行了观察，该样带包含尾矿存款和更远的地方，观察结果表明，在天然沉积物或尾矿材料上方存在一层几毫米至几十厘米厚的絮凝表面材料，该材料保持松散状态。实验发现，这种材料是非常移动的，因此可能会被重新引入到水柱在不同的时间在一年中，可能在seiching（风混合）事件和秋季和冬季营业额。这种再悬浮沉积物的质量将对湖泊的功能产生影响，因为它含有大量的磷（约5%重量）以及金属，这两种物质都可能对过量的水生生物造成问题。这些污染物的生物利用度将取决于沉积物-水界面的化学和侵蚀条件。这两个变量的季节性变化将调节，如果沉积物相关的营养物质可用于在湖中的初级生产，如果沉积物相关的污染物被纳入过滤器喂养的无脊椎动物，这是一个主要的食物来源的运动和鲑鱼在湖中。 该项目的独特之处在于评估了一个提供全湖施肥的灾难性事件，但同时提供了高负荷的金属和类金属。虽然尾矿废物中引入的磷可能作为肥料增加该湖泊的初级生产，但这些生物也可能含有金属，从而放大了它们在食物网中的影响。由于波利山泄漏的大多数金属已被确定为与沉积物有关，这些未固结的絮凝沉积物在沉积物-水界面的命运是有问题的。在未来五年内，Petticrew和她的HQP将开展一系列实地和实验室项目，以解决这些问题。 该项目还将提供关于大中型湖泊生态系统对大规模扰动的复原力的宝贵信息，例如与采矿灾害有关的大规模扰动，以及原始流域的其他类似事件，从而有助于保护加拿大的水生生态系统。

In August 2014, Canada's largest mining disaster occurred at the Mt Polley copper-gold mine, near Likely, British Columbia. The tailings pond wall breached, releasing 25 Mm3 of tailings, wastewater and construction materials. Further scouring of vegetation and surface materials occurred along a 9 km reach before entering the west basin of Quesnel Lake. Polley Lake, a smaller lake adjacent to the tailings pond was also dosed with tailings but remained off limits to researchers for the first year. This proposal aims to assess fine sediment processes regulating contaminant (metals/metalloids) and phosphorus (P) dynamics and their medium-term effects on foodwebs in both Quesnel and Polley Lakes. Observations from a 2016 core sampling program along a lake transect incorporating the tailings deposit and further afield indicated a layer, several millimeters to tens of centimeters thick, of flocculated surface material that remained unconsolidated above either natural sediments or tailings material. This material was experimentally found to be very mobile and therefore likely to be reintroduced into the water column at various times of the year, potentially during seiching (wind-mixing) events and fall and winter turnovers. The quality of this resuspended sediment will have an impact on the lake functioning in that it contains a large mass of phosphorus (~5% wt) as well as metals both of which can be problematic for aquatic organisms in excess. The bioavailability of these contaminants will be dependent upon the chemical and erosive conditions at the sediment-water interface. Seasonal changes in both of these variables will regulate if sediment-associated nutrients are available for in-lake primary production and if sediment-associated contaminants are incorporated by filter feeding invertebrates, which are a main food source for the sport and salmonid fishes in the lake. The uniqueness of this proposed project is the evaluation of a catastrophic event providing full-lake fertilization, but delivered in concert with high loads of metal and metalloids. While the phosphorus introduced in the tailings waste may act as a fertilizer increasing primary production in this lake, these organisms may also incorporate metals, thereby magnifying their impact within the foodweb. As most of the metals from the Mt Polley spill have been identified as being sediment-associated, the fate of these unconsolidated flocculated sediments at the sediment-water interface is in question. A series of field and laboratory projects will be undertaken by Petticrew and her HQP over the next five years to address these issues. This project will also provide valuable information on the resiliency of large and medium-sized lake ecosystems to massive disturbances such as those associated with mining disasters, and other similar events in pristine watersheds, thereby helping to protect Canada's aquatic ecosystems.