ABSTRACT Water data collected from 33 lakes across the Upper Midwest in two sampling regimes spanning ~ 20 years were used to detect changes in water chemistry. Significant increases in chloride, total dissolved solids, and pH, and decreases in magnesium were observed between the two datasets. Rates of change per year were greatest for Cl (0.088 mg L−1 yr−1) and TDS (1.88 mg L−1 yr−1), with road salt application and an increase in impervious surfaces related to urbanization being the suggested causes. The decrease in atmospheric sulphate deposition over the time period was a likely driver for higher pH. Principal component analyses of 10 water chemistry variables for each sampling period were compared using Procrustes rotation, with sample scores from 2013 representing the change in water chemistry (ΔWC). Correlations between mean annual temperature (r = 0.545, p = 0.001) and total annual precipitation (r = −0.672, p = 0.000) with ΔWC warranted the development of a regression model that explained 50% of the variance in the ΔWC (adjusted r2 = 0.50, p < 0.001). The two datasets, collected 20 years apart, reveal trends similar to those observed in other studies.

中文翻译：

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过去 20 年人为和气候变化对湖水化学的影响，美国中西部上游

摘要 使用跨越约 20 年的两个采样方案从中西部上游的 33 个湖泊收集的水数据用于检测水化学的变化。在两个数据集之间观察到氯化物、总溶解固体和 pH 值的显着增加以及镁的减少。Cl (0.088 mg L-1 yr-1) 和 TDS (1.88 mg L-1 yr-1) 的年变化率最大，其中道路盐的应用和与城市化相关的不透水表面的增加是建议的原因。在此期间，大气硫酸盐沉积的减少可能是提高 pH 值的一个驱动因素。使用 Procrustes 旋转比较每个采样周期的 10 个水化学变量的主成分分析，2013 年的样本分数代表水化学的变化 (ΔWC)。年平均温度 (r = 0.545, p = 0.001) 和年总降水量 (r = -0.672, p = 0.000) 与 ΔWC 之间的相关性保证了回归模型的发展，该模型解释了 ΔWC（调整后的 r2 = 0.50，p < 0.001）。这两个相隔 20 年收集的数据集揭示的趋势与其他研究中观察到的趋势相似。