Risk assessment for the distribution and levels of fluoride and nitrate in groundwater in a semi-arid area of northern Mexico

Abstract

This study assessed groundwater quality and associated risks in a semi-arid region located in a city in the Northern zone of Mexico. To conduct this study, we collected 92 groundwater samples and analyzed 14 physicochemical parameters across 18 sectors. Only fluoride (F−) and nitrate (NO3–N) exceeded Mexican regulations and WHO guidelines for drinking water. Approximately 65 % of samples surpassed the 1.5 mg/L permissible limit for F−, with the highest recorded concentration reaching 3.60 mg/L in two sectors among the 18 studied, 34 % of samples exhibited NO3−-N concentrations in the 10.64–17.27 mg/L range across three sectors, surpassing permissible levels. Pearson Correlation Analysis revealed strong positive correlations with HCO3−, EC, Mg2+, Ca2+, NO3−, Cl−, SO42−, and Na+. Moderate correlations existed for the total hardness, alkalinity, Cl−, NO3−, SO42−, Na+, Mg2+, and EC. K+ showed weak correlations. PIG values indicated significant pollution of F− in all of 18 sectors (PIG <1). HQ for F− exceeded tolerable levels in 14 adult and 16 child sectors, posing an intolerable risk. Nitrate's HQ was below <1 for all age groups, suggesting non-carcinogenic effects. THI indicated high F− and NO3−-N exposure risks for children in the study area. It is recommended to implement effective water treatment technologies, such as reverse osmosis or adsorptive materials, in those sectors reported as a potential risk to human health to ensure access to safe drinking water.