Hydrochemical Characteristics and Influencing Factors of Surface Water in Layuequ Watershed

SHAO Jie; TENG Chao; CHEN Xiqing; YANG Xinjie; ZHANG Zechen; CAO Jun; ZHU Ning; XIAO Deng; SUN Siyuan; LYU Fei

doi:10.19672/j.cnki.1003-6504.1326.23.338

Abstract：In order to probe into the hydrochemical characteristics and influencing factors of surface water of the Layuequ River basin in southeast Tibet,samples of surface water(25 groups incl.two groups of hot-spring)and rainwater(two groups)were collected in the study area,and anions and cations in the water samples were measured.Analytic tools including the Pip-er triplex graph,Gibbs model,Ca/Na and TDS logarithmic relationship model and the correlation analysis were used to ana-lyze the testing results.As a result,the analysis showed that the mean values of four cations(Ca2+,Mg2+,Na+ and K+)of the 23 groups(surface water except hot-spring)were 13.90,1.43,1.65 and 1.56 mg/L,respectively,and the mean values of the five anions(HCO3-,SO42-,NO3-,Cl-and F-)were 27.57,14.88,2.92,5.40 and 0.24 mg/L,respectively,while pH values were in the range of 7.05-7.96,indicating that the water was weak alkaline.As for the two groups of rain-water samples,the mean values of four cations(Ca2+,Mg2+,Na+ and K+)were 1.94,0.01,0.12 and 0.18 mg/L,respectively,and the mean values of five an-ions(HCO3-,SO42-,NO3-,Cl-and F-)were 0.10,4.38,2.48,5.26 and 0.00 mg/L,respectively,with pH values ranging from 7.56 to 7.60.So the contents of cations and ions in rain-water samples were markedly lower than the mean values of 23 groups surface water samples.On the other hand,the contents of anions and cations in two groups of hot-spring water from deep underground was significantly higher than the mean values of 23 groups surface-water samples,except for NO3-content(0.00 mg/L).For hydro-chemical type e.g.,HCO3-Ca or HCO3-Ca·Mg,the correlation coefficients of TDS versus Ca2+ and TDS versus HCO3-were 0.930 and 0.924,respectively.With respect to the control factors which were mainly the rock weather-ing and dissolution,supplemented by atmospheric precipitation,while the action of cations alternating adsorption and evapora-tion and concentration was very weak.Furthermore,the hydro-geochemical evolution of surface water was still in the natural evolution stage,and the interference factors of human activities could be ignored;the main ions contained in the surface water were rather strongly controlled by the weathering dissolution of silicate and carbonate rocks,but controlled by the weathering dissolution of evaporative rocks comparatively weak.