江西武功山地区地热资源较为丰富，但地热水中氟离子浓度较高，成因机制尚不清楚。探究高氟地热水中氟的来源、分布特征及成因机制对合理开发地热资源、避免次生污染具有重要意义。为解决这一问题，中国地质科学院刘凯团队应用水文地球化学、同位素和机器学习算法，识别武功山地区中低温地热水循环演化过程、识别地热水补给来源、揭示高氟地热水成因机制等。相关成果在《Environmental Geochemistry and Health》上发表。
氟，是构成人体骨骼和牙齿的基础元素，摄入过量的氟会导致氟斑牙、氟骨病等。高氟地热水具有成因复杂、危害大、难降解等特点，其成因机制尚不明确。本研究在武功山地区共采集19组地热水样品，基于水化学和同位素测试结果，综合应用水文地球化学图解法、离子比例关系法和机器学习算法中的自组织映射神经网络等方法，分析地热水循环演化特征，探究断裂控制型中低温地热资源成藏模式，揭示高氟地热水化学特征成因机制，为该地区中低温地热资源可持续开发利用提供理论基础和科学依据。
图1 Location of geothermal groundwater samples and the hydrogeological map of Wugongshan area. Red square represents the study area. Red circles represent the sample site of geothermal groundwater samples collected from the Wugongshan area.
研究结果表明：武功山地区高氟地热水的水化学特征主要以HCO3-Na型为主（图2），氢氧同位素分析结果表明地热水的补给来源为大气降水（图3），补给高程为1000～2100m，结合研究区水文地质条件，补给区域为武功山最高峰金顶及附近山区。
应用自组织映射神经网络算法将研究区地热水划分为4个不同的种类（图4），据此分析高氟地热水成因机制：地热水中氟离子主要来源于含氟矿物风化、溶解，水岩作用控制地热水化学特征，地热水碱度、碱性地热水环境和阳离子交换作用影响氟离子富集（图5和图6）。
图2 Hydrochemical type Piper ternary diagram of geothermal groundwater in different clusters.
图3 Isotope composition of geothermal groundwater.
图4 The component planes showing weight vector values of 11 variables. The neurons in each component plane are represented by color codes, blue and yellow corresponding to the low and high values of the parameters, respectively. b The pattern of cluster formation of geothermal groundwater in the Wugongshan area. The red solid lines represent the clustering boundaries.
图5 The Gibbs diagrams of geothermal groundwater samples collected from the Wugongshan area.
The purple, green, yellow and blue circles represent the samples of Cluster I, Cluster II, Cluster III and
Cluster IV, respectively. The red arrow represents the trend of cation exchange.
图6 Relationships between hydrochemical components in geothermal groundwater of the
Wugongshan area. (a) Na+ vs Cl−, (b) Na+ vs F−, (c) CAI 1 vs CAI 2, and (d) (Ca2+ + Mg2+)-
(SO42−+ HCO3−) vs (Na++ K+–Cl−).
文章出版信息
Zhang, Shouchuan., Liu, Kai., Yu, Chenghua. et al. Identifying the genetic mechanism of medium–low temperature fluoride-enriched geothermal groundwater by the self-organizing map and evaluating health risk in the Wugongshan area, southeast China. Environ Geochem Health 46, 274 (2024). https://doi.org/10.1007/s10653-024-02058-4.
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