High-arsenic (As) groundwater was first discovered in the Yanchi region, Northwest China, which is an arid or semiarid area, and the groundwater quality seriously affects the health of local residents. A comprehensive understanding of the spatiotemporal distribution characteristics, water quality, and health risk of high-As groundwater is indispensable for the sustainable utilization of groundwater sources and resident health. Seventy-nine groundwater samples were collected from different aquifers and seasons. The hazard quotient (HQ) and carcinogenic risk (CR) of As for adults and children were assessed. Moreover, the effects of groundwater sampling site and seasonal change on As concentration were investigated. Then, the random forest method was used to evaluate the importance of the indicators and the influence of these important indicators on groundwater classification. Thirty-three percent of the groundwater samples had HQ values > 1, and the CR values of all groundwater > 1.00 × 10⁻⁶ for children, representing a serious health risk. Twenty-one percent of the groundwater samples had health risk for adult. High-As groundwater is present at depths less than 60 m, and groundwater As concentrations are slightly affected by seasonal changes. The random forest shows that the most important indicators that affect groundwater quality are Na, TDS, TH, and F, and the least important is As. Furthermore, the optimal set of indicators contained all four of the most important indicators obtained by the random forest model, which achieved a classification accuracy of 88.21% for groundwater quality.

高砷（As）地下水是在干旱或半干旱地区的西北盐池地区首次发现的，地下水质量严重影响当地居民的健康。全面理解高砷地下水的时空分布特征，水质和健康风险对于可持续利用地下水源和居民健康必不可少。从不同的含水层和季节收集了79个地下水样品。评估了成人和儿童的砷的风险商（HQ）和致癌风险（CR）。此外，还研究了地下水采样点和季节变化对砷浓度的影响。然后，采用随机森林法评估指标的重要性以及这些重要指标对地下水分类的影响。33％的地下水样品的HQ值> 1，所有地下水的CR值> 1.00×10^-6为儿童，表示严重的健康风险。百分之二十一的地下水样本对成年人有健康风险。高砷地下水存在于小于60 m的深度，而地下水砷浓度受季节变化的影响很小。随机森林显示，影响地下水质量的最重要指标是Na，TDS，TH和F，最不重要的是As。此外，最优指标集包含通过随机森林模型获得的所有四个最重要指标，这些指标对地下水质量的分类精度为88.21％。