Anthropogenic salt sources have contributed to rising salinities in the Laurentian Great Lakes. In Lake Michigan, chloride concentrations have risen from ~ 1–2 mg L⁻¹ in the 1800s to > 15 mg L⁻¹ in 2020. The watersheds of the approximately 300 tributaries of Lake Michigan vary in size and represent a wide range of land use, from undeveloped forested watersheds to urbanized and agricultural areas. The spatial variability in both size and land cover among Lake Michigan's tributaries contributes to enormous variation in chloride concentrations and loads. We performed a spatial assessment of Lake Michigan tributaries to calculate total annual salt loading, infer future conditions based on current patterns, evaluate the use of synoptic sampling, and identify watershed characteristics that drive high chloride concentrations. We found that the tributary load to Lake Michigan is 1.08 Tg yr⁻¹ of chloride, and that chloride concentrations in Lake Michigan will likely continue to slowly rise in the coming decades.

中文翻译：

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支流氯化物流入密歇根湖

人为盐源导致劳伦森五大湖盐度上升。在密歇根湖，氯化物浓度从1800 年代的~ 1–2 mg L ⁻¹上升到 > 15 mg L ⁻¹2020 年。密歇根湖约 300 条支流的流域面积大小不一，土地利用范围广泛，从未开发的森林流域到城市化和农业区。密歇根湖支流的大小和土地覆盖的空间变异导致氯化物浓度和负荷的巨大变化。我们对密歇根湖支流进行了空间评估，以计算年度盐负荷总量，根据当前模式推断未来状况，评估天气采样的使用，并确定导致高氯化物浓度的流域特征。我们发现密歇根湖的支流负荷为 1.08 Tg yr ⁻¹氯化物，密歇根湖的氯化物浓度在未来几十年可能会继续缓慢上升。