Abstract A channel head is a zone where hydrological changes occur that shape the chemical features of water, during the final stage of underground flow and the beginning of the surface water cycle. The study aims were as follows: (i) to characterise spatial water chemistry patterns; (ii) to establish the role played by the hyporheic zone in the chemical transformations associated with the groundwater that supplies the first-order stream; and (iii) to identify the factors that control the chemical composition transformations that occur in headwater alcoves. The analysis was performed on three sets of samples taken at the Żarnowo channel head situated in the young glacial landscape of the Parseta drainage basin (NW Poland). The performed hydrochemical measurements showed that the waters found in the alcoves displayed a mosaic pattern, with spatial variability in the levels of trace metals and nutrients. In turn, geogenic ions featured in the mineralogical-petrographic compositions of deposits found in headwater catchments, such as Ca2+, HCO3−, Mg2+, and Na+, showed low temporal variability and small differences among the various sampled headwater alcoves. These results indicated that the majority of spatial variance associated with the chemical composition of water is driven by the transformation of groundwater discharges in the hyporheic zone. The locations of hydrochemical transformation hotspots can be explained by the influences of critical physical variables, such as the intensity of seepage erosion, sediment texture, bottom microtopography, groundwater discharge characteristics, water temperatures, and the diversity of groundwater-fed vegetation. Hydrochemical studies performed in the ground- and surface-water contact zones within a channel head can identify the underlying causes of changes to water chemistry, which, in turn, can facilitate the protection of water resources against unfavourable changes that may affect the water quality at the headwater catchment.

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源到主流：年轻冰川区河道头的水化学水变化（波兰波美拉尼亚湖区）

摘要 河道头是在地下水流的最后阶段和地表水循环的开始阶段发生水文变化的区域，形成水的化学特征。研究目的如下： (i) 表征空间水化学模式；(ii) 确定下流带在与供应一级河流的地下水相关的化学转化中所起的作用；(iii) 确定控制发生在水源壁龛中的化学成分转变的因素。对在位于 Parseta 流域（波兰西北部）年轻冰川景观中的 Żarnowo 河道头采集的三组样本进行了分析。进行的水化学测量表明，在壁龛中发现的水显示出马赛克图案，微量金属和营养物质水平的空间变异性。反过来，在源头集水区发现的沉积物的矿物学-岩相组成中的地质成因离子，如 Ca2+、HCO3-、Mg2+ 和 Na+，在不同的采样源头凹室之间显示出较低的时间变异性和小的差异。这些结果表明，与水的化学成分相关的大部分空间变化是由下流带地下水排放的转变驱动的。水化学转化热点的位置可以通过渗流侵蚀强度、沉积物质地、底部微地形、地下水排放特征、水温和地下水补给植被的多样性等关键物理变量的影响来解释。