Hydrogeochemical Behavior And Numerical Modeling Of Fluorine

Xingtai piedmont plain in Hebei Province is an area representative of the formation and dis-tribution of shallow high fluorine groundwater in North China. Taken Xingtai piedmont plain asa typical study area, the important live element—fluorine of shallow ground water system is cho-sen as the object of study in this article. On the basis of a large of the previous study work, thequantitative study method of groundwater geochemistry—geochemical modeling of groundwa-ter, developed in several years, as well as the theory and method of the coupled model of hydro-logic dispersive transport and chemical reaction in reactive multispecies components systems areintroduced. Through field study—simulating laboratory—numerical simulation, several prob-lems are studied as follow in the article:1. On the basis of analysing the natural environment of the formation of shallow high fluo-rine groundwater in Xingtai piedmont plain, geochemical behavior of fluorine in shallow ground-water system is discussed. The effect of the physcial and chemical characteristics of unsaturatedsoils on fluorine source intensity, fluorine supply potential of unsaturated soils, and migration,transformation and concentration of fluorine between unsaturated soils and shallow groundwaterare studied in detail.2. Based on the dynamic state laboratory for migration and concentration of fluorine in wa-ter—heterogeneous unsaturated soils system, the law of migration, transformation and concen-tration of fluorine in water—heterogeneous unsaturated soils system under rainfall infiltration isstudied. Chemical equilibrium or chemical kinetic reaction models for aqeous complexation, disso-lution/precipiation and adsorption/desorption are established. Considering hydrologic transportand chemicai reaction of fluorine, the coupled model of hydrologic transport and chemical reactionof fluorine in water—heterogeneous unsaturated soils system under rainfall infiltration is estab-lished. Using the coupled model, the change of fluorine with time and space in water—heteroge-neous unsaturated soils system in the processes of rainfall infiltration is quantitatively simulated.3. Using the quantitative study method of groundwater geochemistry—geochemical model-ing of ground water, Chemical equlibrium reaction model and mass balance reaction model of flu-orine in shallow ground water are established. The speciation of fluorine and other elements inshallow ground water is calculated. The net masses of minerals dissolved and/or precipiated alongflow path from the leaching—migration zone to the concentration zone of fluorine, as well asthe saturated state and the tendency of dissolution/precipiation of several solid deposits in shallowground water are quantitatively defined. The relation between speciation of F,Ca,Mg and en-demic fluorosis is discussed.