Calcium in the envionment: the highs and the lows

钙（Ca）是陆生和水生生物大量需要的必需元素。最近的观察表明，加拿大许多湖泊中的钙浓度正在下降，往往接近或超过水生生物区系的临界生物阈值。令人困惑的是，目前的地球化学模型表明，湖泊目前正在恢复到工业化前的状态，而古模型表明，目前湖泊中的钙浓度比以往任何时候都低。森林土壤中钙浓度的降低也可能导致森林生产力和森林健康的下降。然而，在其他地区，如阿萨巴斯卡油砂（AOSR）在阿尔伯塔，工业活动已导致大气中的钙沉积，这可以有效地改变天然酸性森林土壤的化学组成，具有潜在的破坏性生态后果的巨大增加。这项研究将使用最先进的技术和新颖的实验研究，以填补知识空白，需要评估加拿大环境中钙浓度变化的影响。具体而言，本研究计划将调查钙地球化学在（a）低钙前寒武纪盾地区的安大略，在那里提高矿物风化率的理解是必要的，以预测未来的钙水平在土壤和沃茨，和（B）同样低钙AOSR，相反的问题，钙富集需要进一步研究。为了评估风化是否已经或将要发生变化，将使用土壤测量结合同位素分析来量化富钙矿物（如磷灰石）对湖泊和土壤钙水平的重要性。将对湖泊沉积物岩心和树木年轮岩心进行评估，以确定在过去100-200年中，与磷灰石等矿物减少相一致的同位素变化是否明显。这些信息将用于改进风化率，用于地球化学模型，以预测未来的钙水平下的各种管理和大气沉积的情况。在钙缺乏的环境中，凋落物是土壤钙水平的最大贡献者。为了评估土地利用的变化是否有助于观察到的钙下降比较糖枫树站（当前）下的钙循环将进行比较，松树站（历史）在现场和实验室研究中的钙循环，以评估改变森林组成的影响，从物种低钙需求（和低钙凋落物输入到土壤）的高钙需求。为了解决对油砂排放引起的钙沉积升高的担忧，将使用实地调查来评估沉积增加对土壤化学和植物/树木健康的影响。结合这项研究将导致更好地了解钙的地球化学，这是必要的，以保护加拿大的北方生态区的广大地区。

Calcium (Ca) is an essential element required in large amounts by terrestrial and aquatic biota. Recent observations have shown that Ca concentrations are falling in many Canadian lakes, often approaching or exceeding reported critical biological thresholds for aquatic biota. Perplexingly, current biogeochemical models suggest that lakes are currently returning to their pre-industrial state whereas paleo-models suggest current Ca concentrations in lakes are lower than ever before. Decreasing Ca concentrations in forest soils may also lead to decreased forest productivity and forest health. Yet, in other regions, such as the Athabasca Oil Sands (AOSR) in Alberta, industrial activities have resulted in an enormous increase in atmospheric Ca deposition, which can effectively change the chemical composition of naturally acidic forest soils with potentially damaging ecological consequences. This research will use state-of-the-art techniques and novel experimental studies to fill knowledge gaps that are required to evaluate the impacts of changing Ca concentrations in Canada’s environment. Specifically, this research program will investigate Ca biogeochemistry in both the (a) low-Ca Precambrian Shield region of Ontario, where improved understanding of mineral weathering rates is necessary to predict future Ca levels in soils and waters, and (b) the equally low-Ca AOSR, where the opposite problem of Ca enrichment requires further study. To evaluate whether changes in weathering have or will occur, soil measurements combined with isotopic analyses will be used to quantify the importance of Ca-rich minerals such as apatite to lake and soil Ca levels. Lake sediment cores and tree ring cores will be evaluated to determine whether isotopic changes consistent with decreases in minerals such as apatite are evident over the past 100-200 years. This information will be used to refine weathering rates that are used in biogeochemical models to predict future Ca levels under various management and atmospheric deposition scenarios. In Ca-poor environments litter fall is the single largest annual contributor to soil Ca levels. To evaluate whether land use change has contributed to the observed Ca decline comparisons of Ca cycling under sugar maple stands (current) will be compared with Ca cycling under pine stands (historic) in field and laboratory studies to evaluate the impact of changing forest composition from species with low Ca requirements (and low Ca litter inputs to soil) to one with high Ca requirements. To address concerns over elevated Ca deposition originating from Oil sands emissions a field survey will be used to evaluate the impact of increased a deposition on soil chemistry and plant/tree health. Combined this research will result in a greater understanding of Ca biogeochemistry, which is necessary to protect vast regions of Canada's Boreal Eco zone.