The changing boreal carbon cycle at the land-water-sediment interfaces

由于旨在减少人类对全球气候影响的技术和环境政策最近的发展，加拿大各地对低碳电力的需求正在迅速增加。水力发电被许多加拿大人视为一种清洁的电力来源，但筑坝在温室气体排放和汞水平方面带来了不容忽视的环境足迹，这是该国未来发展和水力发电出口的障碍。此外，这一足迹取决于即使在没有水库的情况下也会出现的碳和汞的基本基线通量，但这一基线正在迅速变化，以应对自然和人类驱动的扰动，例如全球变暖、极端降水模式、大气沉积的变化以及森林火灾。因此，充分了解水电的净环境足迹取决于两个主要方面：a)准确估计一段时间内水电站水库中碳和汞的通量，以及b)在修建水坝之前对地貌中碳和汞的自然通量进行量化。后者并不是微不足道的，因为在富含水的加拿大北部生物群中几乎没有估计，而且现有的估计忽略了不成比例重要但未得到充分研究的小型水体。我们的长期目标是将水库对碳和汞循环的净影响从自然基线的变化中分离出来，通过这个项目，我们的目标是：1)与水库的影响相比较，量化碳和汞通量的现代和历史变化；2)提高对碳在未被研究的小水体中从陆地到水的移动和转化的理解；以及3)更好地了解在北方生物群不同区域发现的水生态系统中碳和汞的循环之间的联系。为此，我们将开展实地工作，重点是对魁北克北部三个主要水电活动地区的小湖泊、湿地和湿地的水和沉积物进行采样。我们将进一步利用现有的地理和实地数据来模拟过去和未来碳和汞通量的变化。这项研究产生的知识将为行业和管理人员提供必要的数据，以完善水电对环境的净影响，以便更好地评估其与其他能源以及与其他国家生产的水电相比的竞争力。

The demand for low-carbon power is rapidly increasing across Canada due to recent developments in technologies and environmental policies that aim at reducing human impacts on the global climate. Hydro-power is perceived as a clean source of power by many Canadians, but damming carries an environmental footprint in terms of greenhouse gases emission and mercury levels that cannot be ignored, which is a hurdle for future developments in the country and exports of hydro-electricity. Moreover, this footprint depends on the underlying baseline fluxes of C and Hg that would occur even in the absence of reservoirs, but this baseline is rapidly changing in response to natural and human driven perturbations such as global warming, extremes in precipitation patterns, changes in atmospheric deposition, as well as forest fires. Full understanding of the net environmental footprint of hydro-power hence relies on two main aspects: a) accurate estimations of the fluxes of carbon and mercury in hydro-electric reservoirs over time and b) quantification of the natural fluxes of carbon and mercury at the landscape before dams were constructed. The latter is not trivial because very few estimates exist in the water-rich Canadian boreal biome and because existing estimates ignore the disproportionately important but understudied small water bodies. With the long term goal of disentangling the net effects of reservoirs on the cycling of C and Hg from shifts in natural baselines, we aim, with this project, to 1) quantify the modern and historical variation in carbon and mercury fluxes in comparison to the effect of reservoirs, 2) improve understanding of the movement and transformation of carbon from land to water across under-studied small water bodies, and 3) better understand the association between the cycling of carbon and mercury in aquatic ecosystems found in different regions across the boreal biome. To do so we will conduct field work focusing on the sampling of water and sediments of small lakes, wetlands in three regions of boreal Québec where there are major hydro-electric activity. We will further leverage existing geographic and field data to model past and future changes in the fluxes of carbon and mercury. The knowledge generated by this research will provide industries and managers with the data needed to refine the net environmental impacts of hydro-power for a better assessment of its competitiveness compared to other sources of energy as well as to hydro-power produced in other countries.