Chemical Evaluation of Groundwater from Supply Wells in the State of Coahuila, México

Abstract

The present study i s conducted with the purpose of determining the chemical characteristics of groundwater that supplies 16 wells in the state of Coahuila, which are used for different human activities. Sampling was conducted in January 2011. For 56% of the fifteen wells tested, analysis did not detect the presence of aluminum; however, wells 2, 3, 6, 8 and 13 had concentrations above the permissible limit established by the Mexican standard NOM-127-SSA1-1994. For cadmium, only the well 3 was above the Norm. Meanwhile, iron was above the permissible limit in eight wells (2, 4, 5, 6, 9, 12, 13 and 15). Lead exceeded the limit in wells 6, 7, 9, 10, 11 and 12. In general, for the rest of the parameters listed in the Norm, values were below allowable limits. By using Piper diagrams, it was observed that in general, the waters tested showed characteristic calcium bicarbonate. By establishing a matrix of correlations between chemical parameters , it was observed that the highest significant correlations occurred among carbonate hardness, calcium, lead and total alkalinity, with r 2 values greater than 0.82. Also, high correlations were found between some metal species, suggesting a common origin. The allowed Principal Component Analysis and Cluster Analysis establish the associations between all analyzed physicochemical parameters, and they also determine the wells with similar characteristics.