Distribution and migration mechanism of fluoride in groundwater in the Manas River Basin, Northwest China | Mécanisme de distribution et de migration des fluorures dans l’eau souterraine du Bassin de la Rivière Manas, Nord-Ouest de la Chine Mecanismo de distribución y migración del flúor en aguas subterráneas en la cuenca del río Manas, noroeste de China 玛纳斯河流域地下水氟的分布规律及其成因 Mecanismo de distribuição e migração de fluoreto nas águas subterrâneas na Bacia do Rio Manas, noroeste da China
2018
Liu, Yalei | Jin, Menggui | Ma, Bin | Wang, Jianjun
Elevated fluoride (F) concentration in groundwater is posing a public health risk in the Manas River Basin (MRB), Northwest China. Based on the characterization of regional groundwater flow, 90 groundwater samples from aquifers were analyzed, along with top-soil leachate and pore-water samples from aquitards. Stable oxygen (δ¹⁸O) and hydrogen isotopes, radiocarbon and hydrochemical analyses of the groundwater and pore-water samples were conducted to trace groundwater hydrological and hydrochemical processes and thereby understand the distribution and migration mechanism of F. The groundwater is recharged by meteoric precipitation through vapor condensation processes in the Tianshan Mountains. The F concentration in groundwater samples from this basin ranged from 0.11 to 48.15 mg/L (mean 2.56 mg/L). In 37 of the 90 groundwater samples, the F concentrations were above the safe level for drinking water. The F concentrations progressively increased with the residence time and well depths in the northwest of the alluvial-fluvial plain, where groundwater is overexploited for agricultural and domestic use. Positive correlations between F and sodium (Na)/calcium (Ca) indicate that the enrichment and migration of F are influenced by cation exchange processes under high-Na and alkaline pH conditions. The relationships between δ¹⁸O and F and chloride (Cl) concentrations were nonlinear due to leaching and mixing processes. This shows that vertical leaching by irrigation return flow and mixing with pore water are the dominant processes driving the migration of F in the groundwater flow system of MRB, in addition to geochemical processes.
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