Abstract: Fluoride is a chemical element with important effects on the biosphere,lithosphere and human health. In this study,21 surface water samples,8 groundwater samples and 1 lake water sample were collected from the Keriya River Basin and the Ulugkol Lake in the Kunlun Mountains in northern marginal zone of the Tibetan Plateau in different seasons from 2014 to 2015. The fluorion content,pH values and total dissolved solids (TDS) were measured. The fluorion content of surface water varied from 0.09 and 6.08 mg·L^-1,that of groundwater ranged from 2.68 to 6.0 mg·L^-1,and that of lake water was measured as 4.81 mg·L^-1. The measured pH values of surface water and groundwater varied from 7.28 to 8.60 and from 7.26 to 7.87 respectively,and the measured pH value of lake water was 8.95. The TDS of surface water and groundwater ranged from 216 to 2 884 mg·L^-1 and from 1 113 to 3 884 mg·L^-1 respectively,and the TDS of lake water was 17 281 mg·L^-1. The results are as follows:① The Ulugkol was a lake with high fluorion content,high alkalinity and high salt content; ② There was basically no seasonal variation of chemical parameters of surface water in the upper reaches. In the middle and lower reaches,however,the fluorion content,EC value,TDS and water hardness (excluding pH valuje) were all notably lower in summer because of flood water dilution,and the fluorion content in river water was higher in winter due to groundwater recharge; ③ The fluorion content and TDS of surface water from the upper to the lower reaches of the Keriya River was holistically increased because of the dissolution of chemical elements and water evaporation. The fluorion content in river water at the upper reaches was much lower than that in the Yutian Oasis and the Daryaboy Oasis. However,the fluorion content in groundwater in the former was higher than that in the latter because of soda salinization;④ There was a good correlation between the fluorion content in river water and groundwater and TDS,but not between it and pH value; ⑤ The fluorion content in the Keriya River Basin was slightly higher than that in other drainage basins in the Tarim Basin,such as the Aksu River Basin and the Yarkant River Basin.

Key words: fluorion content, pH value, TDS, spatial distribution, Yutian Oasis, Daryaboy Oasis, Keriya River, Tarim Basin