Fluoride and Arsenic in an Alluvial Aquifer System in Chihuahua, Mexico: Contaminant Levels, Potential Sources, and Co-occurrence


The objectives of this study were to identify potential sources of As and F within an alluvial aquifer system in central Chihuahua, to evaluate their change in concentrations with time, and to determine their degree of co-occurrence. The As content in rock, sediment, and groundwater samples was first determined in 2004; later on, in 2007 and 2010, the content of As and F in groundwater was measured. From 34 wells sampled, seven had As levels above the Mexican maximum contaminant level of 0.025 mg L-1, and 13 wells surpassed the F value of 1.5 mg L-1, all of these near the town of Aldama. The surrounding rocks contained enough As and F to support a geogenic origin of these contaminants, especially evident in rhyolites. A correlation between As and F suggests a co-occurrence of these two contaminants (r = 0.720; p < 0.001). The minor variations of As and F in the measured events indicate a stable evolution for As and F. Yearly monitoring the content of As and F is recommended, in order to observe the behavior of these elements within the aquifer, especially as land use is changing and the demand for groundwater (drinking water, irrigation) is increasing.


Geography, Geology, and Planning

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Water, Air, & Soil Pollution