青藏高原湖泊水质变化及现状评价

Lake water in the Tibet Plateau: Quality change and current status evaluation

为探讨青藏高原湖泊水质变化及现状,于2016年9—10月在青藏高原面上东北部G315沿线,中部S301、S302、S206沿线,南部G219、G318沿线及叶如藏布流域采集湖泊水样,通过实验最终得到33个湖泊水样数据,包括22个构造湖和11个冰湖;同时,分析了湖泊水化学指标浓度、水化学组成和湖水矿化度空间分布,并与20世纪90年代以前湖泊矿化度做对比,以揭示青藏高原近几十年湖泊水质变化及驱动因素,探讨青藏高原湖泊水质现状.结果显示:(1)青藏高原湖泊水化学指标浓度和水化学组成差异显著,构造湖水样水化学指标浓度远高于冰湖水样.按离子总量分类,22个构造湖有6个淡水湖、4个微咸水湖、1个咸水湖、11个盐湖;而11个冰湖均属于淡水湖;按湖水化学类型分类,22个构造湖有6个为Ca^(2+)(Mg^(2+))-SO_4^(2-)型湖泊,16个为Na^+(K^+)-Cl^-型湖泊,而11个冰湖均为Ca^(2+)(Mg^(2+))-SO_4^(2-)型湖泊.(2)青藏高原湖水矿化度时空差异显著,自高纬向低纬湖泊矿化度降低,与20世纪90年代前对比研究发现,青藏高原部分湖泊矿化度较90年代前降低,湖泊水体呈淡化趋势,可能与青藏高原地区气候变暖、降水量和冰川融水增加、蒸发减少有关.(3)由于受地理环境、气候条件及水化学特性的共同影响,青藏高原大部分构造湖pH值、TDS严重超标,其次有6个湖泊也受到F-的污染;冰湖水体受到Fe、Mn、Cr、Ni的污染较为严重,尤其重金属元素Cr、Ni超标极为严重,可能与人类活动有关.

To explore the water quality change and present status of lakes in the Tibet Plateau,water samples was collected from 33 lakes（ 22 tectonic lakes and 11 glacial lakes） along the highways of G315,S301,S302,S206,G219 and G318 and in the Yairu Zangbo Basin from September to October 2016. These samples were analyzed for ion concentration,chemical composition and salinity,and then the results were compared with previous studies before the 1990 s to reveal the water quality change and its driving factors. The results show that：（1） the concentration and chemical composition of water for these lakes in the Tibet Plateau are significantly different. The concentration of chemical ions of water samples in the tectonic lake is much higher than that in the glacial lake. According to the ionic strength,the 22 tectonic lakes are devided into 6 freshwater lakes,4 micro-saltwater lakes,1 salt water lake and 11 salt lakes,respectively,the 11 glacial lakes all belong to freshwater lake. According to the chemical composition of the lake,the 22 tectonic lakes contain 6 Ca2＋（ Mg2＋）-SO42- lakes and 16 Na＋ （ K＋ ）-Cl- lakes,and the 11 glacial lakes are all Ca2＋（ Mg2＋）-SO42- lakes.（2） The salinity of lake water significantly varies depending on the sampling locations and periods,and the high latitude usually shows higher lake salinity. Compared with that in the 1990 s,mineral concentration of some lakes collected in this study are less,and the desalination trend may be associated with climate warming,the increasing precipitation and glacial melt as well as decreasing evaporation in the Tibet Plateau.（3） Due to the geographical environment,climate background and water chemical characteristics,the values of pH and total dissolved solids of most tectonic lakes in the Tibet Plateau were seriously beyond the national standards of surface water quality,and six tectonic lakes are polluted by F-. The glacial lake is polluted by Fe,Mn,Cr and Ni,especiallyheavy metal elements Cr and Ni are extremely serious,which may be related to human activities.