High arsenic (As) groundwater has been widely observed in the world, but the provenance, chemical weathering, and sedimentary environment of aquifer sediments hosting high As groundwater remain poorly understood. The geochemical and isotopic characteristics of high-resolution aquifer sediments were investigated to unravel the roles of provenance, chemical weathering, and sedimentary environment of the aquifer sediments. The average values of rare earth elements (REEs) showed the enrichment of light REEs and flat heavy REEs in the aquifer and the Yellow River sediments. The chemical index of alteration reflected incipient and moderate weathering (41 to 71). The δC (−27.4‰ ± 4.3‰) and C/N values (8.1 ± 5.8) indicated aquatic environment of sedimentation. Shallow aquifer sediments mostly had relatively high ΣREEs contents and negative Eu anomalies, demonstrating that the aquifer sediments were mainly derived from the Yellow River (up to 94.3% ± 5%). Deep aquifer sediments had relatively low ΣREEs contents and positive Eu anomalies, which originated from the Yinshan Mountains (up to 72.2% ± 20.4%) principally with igneous and metamorphic rocks. Moreover, recycling of the Yellow River sediments from Northeastern Tibetan Plateau enhanced the silicate weathering and increased contents of Fe/Mn oxides and As. The δC and C/N values evidenced that organisms of paleo-lake or paleo-Yellow River were responsible for abundant sedimentary organic matter. Concentrations of Fe, Mn, and As were high in shallow groundwater from the plain. The As enrichment in the shallow groundwater was jointly controlled by the provenance and chemical weathering of the aquifer sediments (14%), sedimentary environment (10%), reductive dissolution (35%) of Fe/Mn oxides, As desorption under elevated pH (20%), and competitive adsorption of (21%). This study systematically reveals the roles of provenance, chemical weathering, and sedimentary environment of the aquifer sediments and highlights joint contributions of geochemical processes and geochemical conditions to As enrichment in groundwater.

中文翻译：

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含水层沉积物的来源、化学风化和沉积环境：对地下水砷富集的影响

高砷地下水在世界范围内已被广泛观测到，但对高砷地下水的来源、化学风化和含水层沉积物的沉积环境仍知之甚少。研究了高分辨率含水层沉积物的地球化学和同位素特征，以揭示含水层沉积物的物源、化学风化和沉积环境的作用。稀土元素(REE)平均值显示含水层和黄河沉积物中轻稀土元素和扁平重稀土元素的富集。化学蚀变指数反映了早期和中度风化（41 至 71）。 δC（−27.4‰±4.3‰）和C/N值（8.1±5.8）表明沉积的水环境。浅层含水层沉积物大多具有较高的ΣREEs含量和负Eu异常，表明含水层沉积物主要来自黄河（高达94.3%±5%）。深层含水层沉积物ΣREEs含量相对较低，Eu正异常，起源于阴山山脉（高达72.2%±20.4%），主要为火成岩和变质岩。此外，青藏高原东北部黄河沉积物的循环利用增强了硅酸盐的风化作用，增加了铁锰氧化物和砷的含量。 δ13​​C和C/N值证明古湖泊或古黄河的生物是丰富的沉积有机质的原因。平原浅层地下水中铁、锰和砷的浓度很高。浅层地下水As富集受含水层沉积物物源和化学风化(14%)、沉积环境(10%)、Fe/Mn氧化物还原溶解(35%)、升高pH条件下As解吸的共同控制( 20%），竞争吸附（21%）。本研究系统地揭示了含水层沉积物的物源、化学风化和沉积环境的作用，并强调了地球化学过程和地球化学条件对地下水砷富集的共同贡献。