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，它们正经历着气候和大气中污染物沉积的变化，这些变化破坏了从流域到水柱的碳和污染物循环。过去的研究表明，随着广泛的酸雨问题引起的立法变化，湖泊的pH值和溶解有机碳（DOC）浓度随着酸化的恢复而增加。这些增加，原则上代表回到酸化前的状况，伴随而来的是水透明度的丧失和热分层的变化，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。在过去几十年中，氮和汞的沉积也有所减少，但减少的时间和幅度有所不同，流域中汞的持久性可能与离子和碳的持久性不同。因此，这些大气沉降趋势对加拿大温带和北方流域和湖泊的碳和汞循环的累积影响仍然知之甚少。本提案旨在通过建立在加拿大环境和气候变化处不同时空范围内的广泛数据来填补这一知识空白，这些数据包括自1984年以来每年采样的100个湖泊和4个具有对比气候和树木覆盖的流域，这些流域在加拿大东部连续数年每周监测湖泊、溪流、土壤、穿透物和降水中的地球化学性质。我们将补充这些数据集，增加对湖泊和关键流域水柱中DOC组成、营养物浓度和不同形式的总汞和甲基化汞的测量。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.