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可能附近的波利山铜金矿。尾矿库围墙破裂，泄漏了25mm3的尾矿、废水和建筑材料。在进入奎斯奈尔湖西部盆地之前，对9公里范围内的植被和地表材料进行了进一步的冲刷。与尾矿库毗邻的波利湖是一个较小的湖泊，也被投放了尾矿，但第一年仍然禁止研究人员进入。该提案旨在评估调节污染物(金属/类金属)和磷(P)动态的细微沉积物过程及其对奎斯奈尔湖和波利湖食物网的中期影响。2016年，在一个包括尾矿库和更远地区的湖泊样带上进行的岩心采样项目的观察显示，有一层几毫米到几十厘米厚的絮状表面物质，在天然沉积物或尾矿材料上方保持松散。实验发现，这种物质具有很强的流动性，因此很可能在一年中的不同时间被重新引入水柱，可能是在浮沉(混合风)事件以及秋季和冬季的倒流期间。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(~5wt%)和金属，这两种元素都可能对过量的水生生物造成问题。这些污染物的生物有效性将取决于沉积物-水界面的化学和侵蚀条件。这两个变量的季节变化将调节与沉积物相关的营养物质是否可用于湖泊中的初级生产，以及与沉积物相关的污染物是否通过滤食无脊椎动物并入，无脊椎动物是湖中鱼类和鲑鱼的主要食物来源。*这一拟议项目的独特之处在于对提供全湖施肥的灾难性事件进行了评估，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一种肥料增加了这个湖的初级产量，但这些生物也可能吸收金属，从而放大它们在食物网中的影响。由于波利山漏油事件中的大多数金属已被确定为与沉积物有关，这些松散的絮状沉积物在沉积物-水界面的命运还有待商榷。佩蒂克鲁和她的总部基地将在未来五年内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干扰的复原能力的宝贵信息，例如与采矿灾害有关的干扰，以及原始流域的其他类似事件，从而帮助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. **