Due to the combined influence of unique natural environment and increasing human activities, water quality in the Chinese Loess Plateau is deteriorating. Hexavalent chromium (Cr⁶⁺) contamination is a critical water environmental issue in the loess areas. In this study, surface water, spring water, Quaternary phreatic water, and soil and rock samples were collected in the middle Chinese Loess Plateau to quantify the surface water pollution and its main affecting factors. Particularly, the occurrence and potential sources of Cr⁶⁺ as well as associated health risks in surface water were thoroughly investigated. The results show that Cr⁶⁺ is widely found in Luo River, Xingzi River, Wuding River and Bali River. The upper reaches of the Luo River are the main high-Cr⁶⁺ water distribution area. For Bali River, Wuding River, Xingzi River and the downstream of the Luo River, the values of Cr⁶⁺ in surface water were below the WHO drinking water limit (0.05 mg/L). The high Cr values in the soil and rock samples indicate that the loess and mudstone are important sources of high-Cr⁶⁺ water in the area. Groundwater which is characterized by high Cr⁶⁺ concentration is also an important factor affecting Cr⁶⁺ concentration in surface water which receives recharge from groundwater. In addition to Cr⁶⁺, TDS and nitrate are also important pollutants in surface water. The hydrochemical evolution of the surface water is controlled by rock weathering and evaporation crystallization. The health risk assessment results suggest that the inhabitants in the study area face high carcinogenic risks induced by Cr⁶⁺.

中文翻译：

---

黄土高原中部的地表水污染，特别是六价铬（Cr 6+）的发生，来源和健康风险

由于独特的自然环境和人类活动增加的综合影响，黄土高原的水质正在恶化。在黄土地区，六价铬（Cr ⁶⁺）污染是关键的水环境问题。本研究收集了黄土高原中部的地表水，泉水，第四纪潜水水以及土壤和岩石样品，以定量地表水污染及其主要影响因素。特别是，对地表水中Cr ⁶⁺的发生和潜在来源以及相关的健康风险进行了彻底调查。结果表明，Cr ⁶⁺在罗河，星子河，武定河和巴厘岛河中广泛发现。River河上游是主要的高Cr ^6+配水区。对于巴厘岛河，武定河，星子河和罗河下游，地表水中的Cr ⁶⁺值低于WHO饮用水限值（0.05 mg / L）。土壤和岩石样品中的高Cr值表明黄土和泥岩是该地区高Cr ⁶⁺水的重要来源。Cr ⁶⁺浓度高的地下水也是影响从地下水中补充水的地表水中Cr ⁶⁺浓度的重要因素。除了Cr ⁶⁺，TDS和硝酸盐也是地表水中的重要污染物。地表水的水化学演化受岩石风化和蒸发结晶的控制。健康风险评估结果表明，研究区的居民面临着由Cr ⁶⁺引起的高致癌风险。