水位波动下吐鲁番盆地地下水化学演化及风险评估

Chemical Evolution and Risk Assessment of Groundwater in the Turpan Basin under Water Level Fluctuations

摘要: 目的：吐鲁番作为中国典型的极端干旱区，降雨稀少，蒸发强烈，地下水是区域生产生活、生态维持的核心水源，其水质安全与可持续利用直接关系到区域水安全和生态稳定，系统明晰吐鲁番盆地地下水化学时空演化规律及驱动机制尤为重要。方法：以新疆吐鲁番绿洲区地下水为研究对象，通过对低水位期(2024年8月)和高水位期(2025年5月) 25个原位点共50组水样进行取样分析，采用舒卡列夫分类法、Piper图解法、Gibbs图解法、矿物饱和指数(SI)分析、梯形模糊数–蒙特卡洛随机模拟(TFN-MCSS)及PCA-APCS/MLR-PMF进行系统分析，阐明水位波动下地下水化学演化特征并进行风险评估。结果：研究区地下水整体呈弱碱性，属于微咸水；水中阳离子以Ca²⁺、Na⁺为主，阴离子以Cl⁻、$S{O}_4^{2-}$ 为主，地下水化学优势类型为SO₄·Cl-Na·Ca型，水化学形成受岩石风化与蒸发浓缩协同控制。地下水质量以I类为主，主要超标指标为$S{O}_4^{2-}$ 、TDS和$N{O}_3^{-}$ ，水质改善、恶化、稳定占比约32.0%、30.7%、37.3%，时空变化较明显；主要矿物SI均 < 0呈不饱和溶解，锰矿SI显著上升。健康风险方面，成人两期均为低风险，儿童均为中等风险，低水位期As、I风险较高，高水位期$N{O}_3^{-}$ 风险主导。结论：吐鲁番绿洲区地下水化学时空异质性由自然水文节律(水位驱动水岩作用)与人为活动(农业面源)共同驱动，核心环境问题为盐化与硝酸盐污染叠加。

Abstract: Objective: The Turpan region of Xinjiang, a typical extremely arid area with high temperatures and an arid climate, relies heavily on groundwater for social production, daily life, and ecological maintenance. The safety and sustainable utilization of its water quality are directly linked to regional water security and ecological stability. Therefore, it is of particular importance to systematically clarify the spatio-temporal evolution laws and driving mechanisms of groundwater chemistry in the Turpan Basin. Methods: Groundwater in the Turpan Oasis area of Xinjiang was selected as the research object. A total of 50 groups of water samples from 25 in-situ sites were collected and analyzed during both the low-water level period (August 2024) and the high-water level period (May 2025). The Schukarev classification method, Piper diagram, Gibbs diagram, mineral saturation index (SI) analysis, trapezoidal fuzzy number-Monte Carlo stochastic simulation (TFN-MCSS), and PCA-APCS/MLR-PMF were employed for systematic analysis to clarify the hydrochemical evolution characteristics of groundwater under water level fluctuations and to conduct a risk assessment. Results: The groundwater in the study area was generally weakly alkaline and brackish. The major cations and anions in the water were identified as Ca²⁺, Na⁺, Cl⁻, and $S{O}_4^{2-}$ , respectively. The dominant hydrochemical type was determined to be SO₄·Cl-Na·Ca, which was found to be jointly controlled by rock weathering and evaporation concentration. The groundwater quality was classified as mainly Class I, with the main exceeding-standard indicators being $S{O}_4^{2-}$ , TDS, and $N{O}_3^{-}$ . The proportions of water quality improvement, deterioration, and stability were approximately 32.0%, 30.7%, and 37.3%, respectively, showing obvious spatio-temporal variations. The saturation indices (SI) of the main minerals were all < 0, indicating unsaturated dissolution, with a significant increase observed in the SI of manganese ore. In terms of health risks, adults were found to be at low risk in both periods, while children were at medium risk. The risks of As and I were relatively higher in the low-water-level period, whereas the risk of $N{O}_3^{-}$ was dominant in the high-water-level period. Conclusion: The spatio-temporal heterogeneity of groundwater chemistry in the Turpan Oasis was found to be driven by a combination of natural hydrological rhythms (water-rock interaction driven by water level) and human activities (agricultural non-point sources). The core environmental problems were identified as the superimposed effects of salinization and nitrate pollution.