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

艾伯塔省东北部油砂地区最近的工业活动导致硫磺和氮氧化物排放量增加，有可能使周围对酸敏感的生态系统(森林和湖泊)酸化。土壤酸化可导致盐基阳离子的淋溶增加，并使铝和其他痕量金属等潜在有毒元素被动员起来。在酸敏感地区，土壤的逐渐酸化最终会导致地表水酸化，因为土壤的缓冲能力减弱。然而，在酸化过程中考虑时间尺度是至关重要的，特别是在工业活动寿命有限的情况下。在艾伯塔省的油砂地区，估计酸敏感生态系统的“作用时间”是极其重要的，该地区的酸排放量预计将在几十年内居高不下。这项研究方案的目的是使用动态酸化模型来确定在各种未来排放情景下，该区域土壤和淡水的临界化学限量(不利影响的指标)是否会超过。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“影响时间”；并辅之以若干相关任务，包括动态模型比较研究和矿物风化估计的详细评估。还将通过实地研究将酸化模型中使用的临界化学限量与水生生态系统的生物效应联系起来。此外，还将对酸敏土壤和淡水进行详细的区域临界负荷评估，重点关注与氮素动态和临界化学限值相关的不确定性，以确保将动态模型应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攸关方，并用于帮助制定艾伯塔省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.