Variations Of Surface Water Chemistry And Stable Isotopes In Summer In The YairuZangbo Basin

The chemical characteristics of surface water can reflect the climate and environmental background of the region.Ascomponents of water molecules,stable hydrogen and oxygen isotopes(¹⁸O and D)are nature tracers describing hydrological processes,and are one of the hot topics in studies of global change.In order to investigate the hydrochemical characteristics in the northern slope of the middle Himalayas,24 water samples of glacial lake,river,wetland and precipitationwere collected in the Yairu Zangbo Basin in September 2015,and then analyzed in the State Key Laboratory of Cryospheric Sciences,Chines Academy of Sciences.The results showed that:?1?The hydrochemical characteristics exhibited a significant spatial diversity in the Yairu Zangbo Basin.The pH and TDS values of water samples presented a weak decrease trend as elevation rises.All the samples belonged to fresh water except one identified as brackish water.The preponderant cation of surface water was Ca²⁺and the main anion was SO₄^2-,followed by HCO₃^-.This meant that the water was characterized by Ca²⁺-SO₄^2-in the Yairu Zangbo Basin.There were different correlations among all the ions.In particular,four ions including Cl^-,HCO₃^-,Na⁺and K⁺had a strong co-originality.However,cations originated from different sources.For instance,Na⁺and K⁺mainly came from bicarbonate,Ca²⁺was mainly from sulfate,and the source of Mg²⁺was wide.?2?Meanwhile,it was revealed that the main ions mainly originated from terrestrialdust using the sea-salt ions tracer method in the Yairu Zangbo Basin.According to the influence of terrestrial dust,the order of ions was:Na⁺<Mg²⁺<SO₄^2-<Ca²⁺<K⁺<HCO₃^-.This implied that the hydrochemical process was mainly controlled by rock weathering in this basin,especially the natural weathering of carbonate rock.The human activities such as herding and fertilization had a growing impact on hydrochemical characteristics of river and wetland at the downstream area below the Qiangmu Village.?3?Yairu Zangbo Basin particles average particle size of 1.32 microns,ultrafine particle number for the entire watershed was 95.35%,the average of super quality of coarse particle average of 86.27%.The spatial difference of particle number in the basin water by local atmospheric environmental impact,but the terrain blocking effect is larger.In addition,Yairu Zangbo Basin upstream of high mountain glacial lake region,the lake ice insoluble particle size is tiny.?4?Isotope values of the Yairu Zangbo Basin surface water are-19.56^-9.35‰for?¹⁸O,and average valueis-17.10‰.Due to the strong evaporation fractionation effect,isotope values of south are all higher than those in north.Presented the relationship of?¹⁸O and?D for precipitation?LMWL?in Yairu Zangbo Basin:?D=4.5832*?¹⁸O-52.328?R²=0.9708?.