There is increasing concern over the negative ecological impacts caused by falling calcium (Ca) concentrations in lakes, particularly in central Ontario, Canada. Forecasting regional changes in lake Ca concentrations relies on accurate estimates of mineral weathering rates that are not widely available. In this study, bulk atmospheric deposition, surface water and soil chemistry along with ⁸⁷Sr/⁸⁶Sr isotope measurements were used to provide regional insight into weathering controls on Ca concentrations in lakes. Regionally, Ca concentrations in 90% of 129 lakes sampled in central Ontario were <0.1 mmol L⁻¹ and the Ca/Sr ratio in lakes increased and the K/Sr ratio decreased with increasing Sr concentration, which is indicative of greater Ca sources from calcite or apatite in the higher Ca lakes. Significant relationships between ⁸⁷Sr/⁸⁶Sr ratios and Ca/Sr rations in dilute acid (0.1 M HCl) soil extracts are also indicative of the presence of trace amounts of calcite or apatite in surficial soils. Within the low (<0.7 mmol L⁻¹) Ca lakes, defined in this study that are considered most at risk from falling Ca concentrations, ⁸⁷Sr/⁸⁶Sr ratios fell within the range observed in weak acid soil extracts and were also significantly related to Ca/Na and K/Sr ratios in surface waters. There were large inconsistencies however, between Ca/Na ratios and Ca/Sr in surface waters and soil acid extracts that suggest differences in ⁸⁷Sr/⁸⁶Sr ratios in surface waters of the low Ca lakes do not simply reflect differences in Ca derived from non-silicate minerals in surficial soils and that that Ca sources from deeper soil or bedrock are also important contributors to surface water Ca in these low Ca lakes.

人们越来越关注湖泊（尤其是加拿大安大略省中部地区）的钙（Ca）浓度下降所造成的负面生态影响。预测湖泊中Ca浓度的区域变化取决于对矿物风化率的准确估算，而目前尚无法获得。在这项研究中，大量的大气沉积，地表水和土壤化学，以及⁸⁷ Sr / ⁸⁶ Sr同位素测量被用来为湖泊中Ca浓度的风化控​​制提供区域性见识。从区域来看，安大略省中部采样的129个湖泊中90％的Ca浓度<0.1 mmol L ^-1随着Sr浓度的增加，湖泊中Ca / Sr的比例增加，而K / Sr的比例降低，这表明较高Ca的湖泊中方解石或磷灰石的钙源更多。稀酸（0.1 M HCl）土壤提取物中⁸⁷ Sr / ⁸⁶ Sr比与Ca / Sr比之间的重要关系也表明表层土壤中存在痕量方解石或磷灰石。在本研究中定义的低（<0.7 mmol L ^-1）Ca湖泊中，Ca浓度下降风险最大，为⁸⁷ Sr / ⁸⁶Sr比值落在弱酸性土壤提取物中观察到的范围内，并且还与地表水中的Ca / Na和K / Sr比值显着相关。但是，地表水和土壤酸提取物中的钙/钠比与钙/锶之间存在很大的不一致，这表明低钙湖泊地表水中⁸⁷ Sr / ⁸⁶ Sr比的差异并不能简单地反映出源自非钙离子的钙的差异。在这些低钙湖泊中，表层土壤中的硅酸盐矿物以及钙来自深层土壤或基岩的原因也是造成地表水钙的重要因素。