The release of carbon and pollutants from eastern canadian watersheds in response to atmospheric deposition and climate change

加拿大的温带和北方景观是地球上湖泊数量和密度最高的地区之一。这些湖泊大多距离人类直接活动数百至数千公里，正在经历气候变化和大气污染物沉积，扰乱了从流域到水柱的碳循环和污染物循环。过去的研究表明，随着酸化的恢复，湖泊的pH值和溶解有机碳(DOC)的浓度一直在上升，这是在普遍存在的酸雨问题之后立法发生变化之后的结果。这些增加--原则上意味着恢复酸化前的条件--伴随着水透明度的丧失和热分层的转变、水生生态系统温室气体排放的增加以及与饮用水处理有关的经济和健康问题。氮和汞的沉积在过去几十年中也有所减少，但这种下降的时间和幅度不同，流域中汞的持久性可能不同于离子和碳的持久性。因此，大气沉积的这些趋势对加拿大温带和北部流域和湖泊的碳和汞循环的累积影响仍然知之甚少。这一建议旨在利用加拿大环境和气候变化部现有的不同空间和时间范围的大量数据，填补这一知识空白，其中包括自1984年以来每年对100个湖泊进行采样，以及对加拿大东部气候和树木覆盖率不同的4个流域进行每周监测，以了解湖泊、溪流、土壤、穿透雨和降水的水中的地球化学性质。我们将补充这些数据集，增加对DOC组成的测量，以及湖泊水柱和关键流域隔间中营养物质和不同形式的总汞和甲基化汞的浓度。这样，我们将能够更好地了解工业活动如何在不同的空间和时间尺度上影响水质的多个方面。

Canada's temperate and boreal landscapes host among the highest amounts and densities of lakes on earth. These lakes, most of them being hundreds to thousands of kilometers away from direct human activities, are experiencing changes in climate and atmospheric deposition of pollutants that disrupt the carbon and contaminant cycles, from their watershed to their water column. Past research has shown that lakes pH and concentrations of dissolved organic carbon (DOC) have been increasing in response to recovery from acidification, following legislation changes in the wake of widespread acid rain issues. These increases, which would in principle represent a return to pre-acidification conditions, have been accompanied by a loss in water transparency and shifts in thermal stratification, an increase in greenhouse gases emissions from aquatic ecosystems, and economic and health issues regarding drinking water treatment. Deposition of nitrogen and mercury have also decreased over the last decades, but the timing and amplitude of this decrease differed, and mercury persistence in watersheds may differ from that of ions and carbon. The cumulative effects of these trends in atmospheric deposition on the carbon and mercury cycles of Canadian temperate and boreal watersheds and lakes thus remain poorly understood. This proposal aims at filling this knowledge gap by building on extensive data available at Environment and Climate Change Canada at different spatial and temporal extents, including 100 lakes that have been sampled yearly since 1984 and 4 watersheds with contrasting climate and tree cover that have been monitored on a weekly basis since for several years in eastern Canada for geochemical properties in the water of lakes, streams, soils, throughfall and precipitation. We will complement these datasets by adding measurements of the composition of DOC as well as the concentrations of nutrients and different forms of total and methylated mercury in the water column of lakes and in key watershed compartments. Doing so, we will be able to better understand how industrial activities affect multiple facets of water quality at different spatial and temporal scales.