Manganese (Mn) plays a critical role in river-water quality because Mn-oxides serve as sorption sites for contaminant metals. The aim of this study is to understand the seasonal cycling of Mn in an alpine streambed that experiences large spring snowmelt events and the potential responses to changes in snowmelt timing and magnitude. To address this goal, annual variations in river-water/groundwater interaction and Mn_(aq) transport were measured and modeled in the bed of East River, Colorado, USA. In observations and numerical models, oxygenated river water containing dissolved organic carbon (DOC) mixes with groundwater rich in Mn_(aq) in the streambed. The mixing depth increases during spring snowmelt when river discharge increases, leading to a greater DOC supply to the hyporheic zone and net respiration of Mn-oxides, despite an enhanced supply of oxygen. As groundwater upwelling resumes during the subsequent baseflow period, Mn_(aq)-rich groundwater mixes with oxygenated river water, resulting in net accumulation of Mn-oxides until the bed freezes in winter. To explore potential responses of Mn transport to different climate-induced hydrological regimes, three hydrograph scenarios were numerically modeled (historic, low-snow, and storm) for the Rocky Mountain region. In a warming climate, Mn_(aq) export to the river decreases, and Mn_(aq) oxidation is favored in the upper streambed sediments over more of the year. One important implication is that the streambed may have an increased sorption capacity for metals over more of the year, leading to potential changes in river-water quality.

锰（Mn）在河水水质中起关键作用，因为Mn氧化物充当污染物金属的吸附位。这项研究的目的是了解经历大型春季融雪事件的高山流床中锰的季节性循环以及对融雪时间和幅度变化的潜在响应。为了实现这一目标，在美国科罗拉多州的东河河床中测量并模拟了河水/地下水相互作用和锰_（aq）输送量的年度变化。在观测和数值模型中，含溶解有机碳（DOC）的含氧河水与富含Mn _（aq）的地下水混合在河床中。尽管增加了氧气的供应量，但在春季融雪期间，当河流流量增加时，混合深度也会增加，从而导致向流变区提供更多的DOC，以及Mn氧化物的净呼吸。随着地下水在随后的基流期恢复上升，富含Mn _（aq）的地下水与含氧河水混合，导致Mn氧化物的净积累，直到冬季床层冻结为止。为了探索锰运移对不同气候引起的水文状况的潜在响应，对落基山地区的三种水文情景进行了数值模拟（历史，低雪和暴风雨）。在气候变暖的情况下，向河流的Mn _（aq）出口减少，而Mn _（aq）在一年中的大部分时间里，上游河床沉积物都倾向于氧化。一个重要的含义是，在一年的大部分时间里，河床对金属的吸附能力可能会增加，从而导致河水水质的潜在变化。