Temporal evolution of nitrate in Meoqui-Delicias aquifer in Chihuahua, Mexico

The continued input of nitrate (NO3) into groundwater is a global problem, mainly associated to excess fertilizer and improper disposal of human and livestock waste. Nitrate accumulation in oxic aquifers of semiarid areas makes these zones especially susceptible to pollution. Nitrate in Meoqui- Delicias aquifer, located in an important irrigation district in Chihuahua, Mexico, was quantified in 2021 in 63 drinking water wells. Samples collected were analyzed in laboratory and results were compared to 2003 and 2006 data available for those wells. Nitrate values varied from 0.7 to 23.2 mg/L and 22 % of the wells contained NO3 above drinking water guidelines (10 mg NO3-N/L). A low to moderate nitrate pollution index (NPI) and a slight NO3-N variation with time was observed for most wells. Values of NO3-N/Cl < 1.0 support an anthropogenic origin of nitrate. No association was found between NO3-N and well depth. The most susceptible areas to nitrate contamination were identified as those areas with high NO3-N and increasing concentration with time. The lack of a pattern of contamination suggested leakage of manure leachate at a few points as the most likely contamination source. The consistently high NO3-N content (>10 mg/L) in three deep wells constitutes a serious concern. DOI: https://doi.org/10.54167/tch.v18i1.1415