Spatial and temporal impacts of acid disposition in the Oil Sands Region: estimating time-to-effects for soils and freshwaters using dynamic simulation models

阿尔伯塔东北部油砂地区最近的工业活动导致硫和氮氧化物排放量增加，有可能使周围酸敏感的生态系统（森林和湖泊）酸化。土壤酸化可导致碱性阳离子的沥滤增加，以及铝和其他微量金属等潜在有毒元素的移动。在酸敏感地区，土壤的逐渐酸化最终将导致地表沃茨酸化，因为土壤的缓冲能力降低。然而，考虑酸化过程的时间尺度至关重要，特别是当工业活动的寿命有限时。在阿尔伯塔油砂地区，酸排放量预计将在几十年内保持高位，估计酸敏感生态系统的“时间效应”是极其重要的。该研究方案的目标是利用动态酸化模型来确定在未来各种排放情景下是否会超过该区域土壤和淡水的关键化学品限值（不利影响指标）。主要任务将侧重于估计酸沉降超过其临界负荷的生态系统的“产生影响的时间”;由一些相关任务提供支持，包括动态模型比较研究和矿物风化估计的详细评价。还将通过实地研究解决酸化模型中使用的关键化学限值与水生生态系统中的生物效应之间的关系。此外，还将对酸敏感土壤和淡水进行详细的区域临界负荷评估，重点是与氮动态和临界化学品限值有关的不确定性，以确保动态模型适用于酸排放风险最大的地区。 这项研究的结果将传达给利益相关者，并用于帮助制定阿尔伯塔油砂地区的排放控制战略，以防止对水生和陆地生态系统的负面影响。

Recent industrial activity in the Oil Sands Region of north-eastern Alberta has led to increased emissions of sulphur and nitrogen oxides with the potential to acidify surrounding acid-sensitive ecosystems (forests and lakes). Acidification of soils can lead to increased leaching of base cations and the mobilisation of potentially toxic elements such as aluminium and other trace metals. In acid-sensitive regions, the gradual acidification of soils will ultimately cause surface waters to acidify as the soils buffering capacity diminishes. However, consideration of time-scale in the acidification process is of vital importance, particularly when industrial activities only have a finite lifespan. Estimating the 'time-to-effects' for acid-sensitive ecosystems is extremely important in the Alberta Oil Sands Region where acid emissions are predicted to remain elevated for several decades. The objective of this research programme is to use dynamic acidification models to identify whether critical chemical limits (indicators of adverse impacts) for soil and freshwaters in the region will be exceeded under various future emission scenarios. The principal task will focus on estimating 'time-to-effects' for ecosystems that receive acid deposition in excess of their critical load; supported by a number of related tasks including a dynamic model comparison study and a detailed evaluation of mineral weathering estimates. Relating the critical chemical limits used in acidification models to biological effects in aquatic ecosystems will also be addressed through field studies. In addition, a detailed regional critical load assessment of acid sensitive soils and freshwaters will be carried out, focusing on uncertainties associated with nitrogen dynamics and critical chemical limits to ensure that dynamic models are applied to the areas most at risk from acid emissions.  Results from this research will be communicated to stakeholders and used to help formulate emission control strategies for the Alberta Oil Sands Region to prevent negative effects on aquatic and terrestrial ecosystems.