富硼高温地热流体中硼的赋存形态与环境效应研究

Boron, one of the most harmful elements in high temperature geothermal fluids, has caused serious negative effects on the geothermal area and its surrounding environment as geothermal fluids discharging to the surface. The Tibet Autonomous Region is characterized by widely and intensively distributed geothermal activity and extreme enrichment of boron in geothermal waters. The discharge of geothermal water has become one of the most important sources of boron in the environment and has contaminated other types of natural water and surface soil in or near the geothermal area, seriously threatening the local residents, animals and plants. However, little systematic work has been carried out on the special forms of boron in geothermal waters, such as fluoroborate ions and polyborate ions, as well as its environmental impact, which is crucial to comprehensive understanding of environmental impact of discharging of boron-rich geothermal fluid. Therefore, this project selects Daggyai, one of the typical boron-rich geothermal system in Tibet, as the study area, and aims: 1) to delineate the boron geochemistry of geothermal water, 2) to characterize boron speciation and their mutual transformation in geothermal water, 3) to figure out the migration and accumulation of geothermal boron in the surface environmental media. This project enhances the understanding of boron speciation and its environmental impact, and provides insights for curbing geothermal boron pollution, environmental protection near the geothermal area and rational exploitation of geothermal resources.

硼，是高温地热流体中最典型的有害元素之一，伴随地热流体排放到地表后，会对地热区及周边环境造成严重的负面效应。在我国西藏自治区，广泛分布大量富硼地热系统，地热水的排放已成为环境中硼最主要的来源之一，并已污染地热区内或附近其他类型天然水体和地表土壤，严重威胁着当地居民的身体健康以及动植物的生长。然而，迄今为止，对于硼在地热水环境中的特殊赋存形态（如氟硼酸根离子、多聚硼酸根离子等）及其环境效应远未充分认识，如不考虑地热水中硼特殊形态的地球化学行为，对于刻画富硼地热水排放的环境效应必然存在片面之处。因此，本项目拟选取西藏典型富硼地热系统——搭格架为研究对象，开展地热流体硼的地球化学研究，深入分析地热水中硼的存在形式以及相互转化规律，重点研究地热水排放到地表环境介质后硼的迁移、蓄积过程，以期为我国地热成因硼污染的治理、地热田周边地区的环境保护、地热资源的合理开采提供借鉴思路和指导作用。

在我国西藏自治区，广泛分布大量富硼高温地热系统，热泉水的排泄对地表河水和沉积物都造成了不同程度污染，对当地居民及动植物的危害不容忽视。本项目以西藏地区典型富硼地热系统为研究对象，在完成不同介质（地热水、浅层地下冷水、河水、泉口沉积物、土壤等）中硼总量、硼形态、硼同位素定量测试的基础上，开展了地热流体中硼的地球化学起源及富集规律研究，查明了地热水中硼赋存形态、主控因素以及相互转化规律，总结了富硼热泉水排放到地表环境介质后的迁移蓄积过程。在此基础上，室内系统模拟了热泉水环境中硼与碳酸盐类矿物吸附与共沉淀过程，揭示了富硼热泉水排泄过程中与碳酸盐类矿物相互作用的微观机理。项目的研究方法和研究结论可为地热水环境污染与防治提供借鉴思路和科学指导。. 基于项目各项研究成果，项目负责人以第一作者身份在“Journal of Hydrology”、“Journal of Volcanology and Geothermal Research”、“地球科学”等国内外期刊发表学术论文4篇，以通讯作者身份在“Geothermics”、“沉积与特提斯地质”等期刊投稿学术论文2篇，培养硕士研究生5名。