玉龙雪山—丽江水体水化学和同位素特征及其变化规律与成因

Hydrochemical and isotopic characteristics, changes andcontrolling factors of waters in the Yulong Snow Mountain-Lijiang area, China

水体水化学与同位素组成受自然和人为因素共同控制,研究其组成及变化成因对流域水资源合理利用和科学管理具有重要意义。本文系统采集了玉龙雪山—丽江地区地表—地下水水化学、氘氧(δD/δ18O-H_(2)O)和碳(δ13C-DIC)同位素样品,重点分析上述指标沿径流方向的空间演化,并对比2005年与2021年水化学组分浓度变化,探讨人类活动影响区域水环境的时空差异。结果表明:①流域地表—地下水以大气降水和冰雪融水补给为主,水化学类型主要为Ca·Mg-HCO_(3)和Ca-HCO_(3)型,部分民井受人类活动影响,Na^(+)、K^(+)、Cl^(−)和SO_(2)^(4−)浓度上升。②受自然和人为因素共同影响,δD和δ18O-H_(2)O值沿地表—地下水径流方向增加,δ13C-DIC值减小,Na^(+)、K^(+)、Cl^(−)和SO_(2)^(4−)在流经主城区后因污废水输入而浓度明显增加。③玉河河水流经大研古镇后由III类水降低至IV类水(NH4^(+)超标),且古镇内井水Na^(+)^(+)K^(+)与δ13C-DIC、Cl^(−)^(+)SO2−4与δ13C-DIC显著性负相关,揭示了古城旅游活动对水环境的负面影响。④与2005年相比,受市政污水补给的漾弓江Na^(+)、K^(+)、Cl^(−)和SO_(2)^(4−)浓度增长速率大于拉市海、玉峰寺泉和团山水库。研究揭示人类活动对玉龙雪山—丽江水环境产生了一定的负面影响,为流域水资源保护提供了基础数据;同时证实同位素和水化学相结合是研究水环境变化及控制因素的重要手段。

The hydrochemical and isotopic compositions of water are controlled by natural and anthropogenic factors,therefore,it is of great significance to study the hydrochemical and isotopic compositions,changes and contributing factors for the rational utilization and scientific management of water resources within a watershed.Hydrochemistry,water(δD/δ18O-H_(2)O)and carbon(δ13C-DIC)isotope samples from surface-groundwater in the Yulong Snow Mountains-Lijiang area,China,were analyzed to reveal the spatial evolution of the above indicators along the water flow direction,to compare the changes of water chemical compositions between 2005 and 2021,and to explore the spatio-temporal differences of regional water environment affected by human activities.Results showed that:(1)In the basin,surface water and groundwater were mainly recharged by local atmospheric precipitation and glacier-snow meltwater,and the water chemistry types were mainly Ca·Mg-HCO_(3) and Ca-HCO_(3),while the concentrations of Na^(+),K^(+),Cl^(−)and SO_(2)^(4−)increased in some wells due to human activities;(2)Under the influence of natural processes and human activities,δD/δ18O-H_(2)O values increased along the direction of the surface-groundwater flow,while the value ofδ13C-DIC decreased.Concentrations of Na^(+),K^(+),Cl^(−)and SO_(2)^(4−)increased significantly after water flows through the main urban area;(3)Water quality of the Yuhe River was reduced from class III to class IV(NH4^(+)exceeded the standard)after the river flows through the Dayan ancient town,and significant negative correlation between Na^(+)^(+)K^(+)andδ13C-DIC,Cl^(−)^(+)SO_(2)^(4−)andδ13C-DIC occurred in wells from the ancient town,which revealed the negative impact of tourism activities on the water environment;and(4)Compared with 2005,the growth rates of Na^(+),K^(+),Cl^(−)and SO_(2)^(4−)concentrations in the Yanggong River,which were fed by urban sewage and wastewater,were greater than those of Lashi Lake,Yufengsi Spring and Tuanshan Reservoir waters.Our study revealed that human activities had a certain negative impact on the water environment in the Yulong Snow Mountain-Lijiang area,which provided basic data for water resources protection in the river basin and also confirmed that the combination of isotopes and water chemistry is an important means to study the water environment change and the contributing factors.