Environment and Climate Change Canada, Cold Regions Research Centre, Wilfrid Laurier University, 75 University Ave West, Waterloo, ON N2L 3E5, Canada.
Environment and Climate Change Canada, National Hydrology Research Centre, 11 Innovation Blvd, Saskatoon, SK S7N 3H5, Canada.
Sci Total Environ. 2020 Dec 20;749:141393. doi: 10.1016/j.scitotenv.2020.141393. Epub 2020 Aug 1.
Contaminant loads to rivers of the Canadian oil sands region are linked to industrial and natural sources. To date, biomonitoring studies have been unable to unequivocally assess potential environmental impacts associated with this development. As part of the Joint Alberta-Canada Oil Sands Monitoring initiative, we aimed to assess cumulative effects of anthropogenic activities and exposure to natural bitumen geology on benthic macroinvertebrate assemblages in the lower Athabasca River. We examined associations among macroinvertebrates and environmental correlates, such as nutrients, ions, metals, polycyclic aromatic compounds, and total suspended solids. The study design included sites within and outside the mineable bitumen deposits, within and outside of the active mining and extraction area, and above and below municipal sewage effluents. We predicted observing a negative association between ecological condition of the river and exposure to natural bitumen and oil sands activity. However, contaminant concentrations in water and sediment were far below known toxicity thresholds, and benthic macroinvertebrate assemblages in sites exposed to oil sands mining activities appeared more affected by nutrient enrichment from the MSE than contaminants from mining or natural bitumen. Although sites within the area of intense oil sands activity showed signs of mild environmental stress, assemblage pattern was more strongly associated with MSE nutrient enrichment than to diffuse contamination from either natural bitumen or oil sands mining. Enrichment likely increases food resources available to consumers, thereby potentially masking toxic responses of consumers to contaminants. Current regulations prohibit the direct release of oil sands contaminants to waterways, with diffuse atmospheric deposition of aerial emissions and fugitive dust the main contaminant pathways to freshwaters. As the storage capacity of tailings ponds is reached, this nutrient-contaminant pattern could change if the river receives the proposed direct release of treated oil sands process water. Focused investigation-of-cause studies are required to better assess the consequences of cumulative interactions and ecological effects of nutrients and contaminant exposure in this system.
加拿大油砂区河流的污染物负荷与工业和自然来源有关。迄今为止，生物监测研究还无法明确评估与这一发展相关的潜在环境影响。作为联合艾伯塔省-加拿大油砂监测倡议的一部分，我们旨在评估人为活动的累积效应以及暴露于天然沥青地质对阿萨巴斯卡河下游底栖大型无脊椎动物群落的影响。我们研究了大型无脊椎动物与环境相关性（如养分、离子、金属、多环芳烃和总悬浮固体）之间的关系。研究设计包括可开采沥青矿床内和矿床外、活跃采矿和开采区内外以及市政污水排放口以上和以下的地点。我们预测，在暴露于天然沥青和油砂活动的情况下，河流的生态状况与暴露于这些物质之间存在负相关关系。然而，水中和沉积物中的污染物浓度远低于已知的毒性阈值，并且暴露于油砂开采活动的地点的底栖大型无脊椎动物群落受到来自 MSE 的养分富化的影响似乎比来自采矿或天然沥青的污染物更大。尽管在油砂活动强烈的区域内的地点显示出轻微的环境压力迹象，但组合模式与 MSE 养分富化的关系比与来自天然沥青或油砂采矿的扩散污染的关系更紧密。富化可能会增加消费者可获得的食物资源，从而可能掩盖消费者对污染物的毒性反应。目前的法规禁止将油砂污染物直接排放到水道中，大气排放和扬尘的扩散沉积是向淡水输送污染物的主要途径。随着尾矿池的储存容量达到极限，如果河流接收提议的处理后的油砂工艺水的直接排放，这种养分-污染物模式可能会发生变化。需要进行有针对性的因果研究，以更好地评估该系统中养分和污染物暴露的累积相互作用和生态影响的后果。
