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

加拿大各地对低碳电力的需求正在迅速增加，这是由于最近旨在减少人类对全球气候影响的技术和环境政策的发展。许多加拿大人认为水力发电是一种清洁的能源，但筑坝在温室气体排放和汞含量方面会产生不可忽视的环境影响，这是该国未来发展和水力发电出口的障碍。此外，这一足迹取决于碳和汞的基本基线通量，即使在没有水库的情况下也会出现这种情况，但这一基线正在迅速变化，以应对自然和人为驱动的扰动，如全球变暖、极端降水模式、大气沉积变化以及森林火灾。因此，要充分了解水力发电的净环境足迹，主要取决于两个方面：a）准确估计一段时间内水力发电水库中碳和汞的通量; B）量化水坝建成前地貌中碳和汞的自然通量。后者并不是微不足道的，因为在水资源丰富的加拿大北方生物群落中存在的估计很少，因为现有的估计忽略了不成比例的重要性，但研究不足的小水体。长期目标是从自然基线的变化中解开水库对C和Hg循环的净影响，我们的目标是，通过本项目，1）量化与水库影响相比的碳和汞通量的现代和历史变化，2）提高对碳在研究不足的小水体中从陆地到水的移动和转化的理解，以及3）更好地了解北方生物群落不同区域水生生态系统中碳和汞循环之间的关联。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碳和汞通量过去和未来的变化。这项研究所产生的知识将为工业界和管理人员提供所需的数据，以完善水力发电对环境的净影响，从而更好地评估其与其他能源以及其他国家生产的水力发电相比的竞争力。

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.