Hydrogeochemistry and water-rock interactions in the urban area of Puebla Valley aquifer (Mexico)

Abstract

The urban area of Puebla Valley aquifer is seated in Puebla City and neighbor municipalities. Puebla is the fourth largest city in Mexico, where there are significant industrial zones and a large population. Water needs are almost exclusively met by groundwater, which has brought intense exploitation of groundwater resources and water quality degradation. The present study investigates the hydrogeochemical changes in groundwater, particularly focuses on the chemical changes produced by upwelling mineralized water. These concentrations may represent potential risks to the health of the population. The groundwater presented five types of families Ca-HCO 3 , Mg-HCO 3 , Mix-HCO 3 , HCO 3-Ca-SO 4 and Ca-SO 4. The high concentrations of sulphates, calcium and magnesium are reflected in high TDS and Total Hardness. The samples collected showed detectable concentrations of F − , Fe, Mn, Ba, Sr, Cu, Zn, B and Li. The limitations for its use as drinking water are given by the high values of TDS, sulphates, total hardness and Mn. Geochemical modeling using Geochemist's Workbench (GWB) and PHREEQC software enabled the computation of the saturation index of mineral phases with ions in solution and speciation ions. Groundwater was initially in equilibrium with calcite; however, due to the changes in hydrogeological conditions, gypsum and dolomite are being dissolved until new equilibrium conditions are met. The additional calcium and carbonate in the water causes calcite to become oversaturated and to precipitate. Evidence of dedolomitization reactions and common ion effect is illustrated by concurrent increases in calcium and magnesium concentrations in the groundwater.

Hydrogeochemical Characteristics and Assessment of Drinking Water Quality in the Urban Area of Zamora, Mexico

“…The procedure takes place in three stages. In the first stage an individual weight (wi) between 1 and 5 is assigned to 13 parameters (pH, Total Dissolved Solids (TDS), Cl − , SO 4 2− , HCO 3 − , Ca 2+ , Mg 2+ , Na + , K + , Total Hardness, F − , NO 3 − and N-NH 3 ) depending on its importance in the evaluation of water quality [3].…”

“…The presence of phosphorus was observed in both samplings. The most abundant chemical form of this element in water is PO 4 3− , considered one of the primary nutrients in the water, and together with HCO 3 − , Cl − and SO 4 2− , it is one of the major anions that contribute to the ionic equilibrium of water along with the cation group. Except for evaporites and rocks of marine origin, rocks usually have a low proportion of Cl − .…”

“…The importance of the determination of N-NO 3 − and N-NH 3 is that they are some of the main indicators of ancient (NO 3 − ) and recent (N-NH 3 ) organic contamination, expressing the excellent oxidation in the water. Moreover, being very soluble and movable, both are the most common forms of nitrogen in groundwater [4]. N-NH 3 appears as a trace species in natural groundwater, increasing its concentration when the medium is strongly reducing.…”

“…Fe is a trace element present in most groundwater. It is an essential element in human nutrition [4]. All sites are within the limit established by the Mexican regulations of 300 µg/L.…”

“…3 45 Clastic material, rock pieces, scoria, and cineritic material, with sandy-clay sediments, and low saturation. 4 150 Extrusive rocks of fractured basaltic composition, with saturation possibility.…”