Geogenic sources and chemical controls on fluoride release to groundwater in the Independence Basin, Mexico

Abstract

Groundwater in the Independence Basin of Central Mexico reaches over an order of magnitude greater than the World Health Organization limit of 1.5 mg L-1 , but sources and geochemical conditions responsible for releasing fluoride into solution are unknown. Objectives of this work determined aquifer rock types containing the greatest amounts of fluoride and investigate how changes in pH and specific conductance affect fluoride release into solution. Solid phase concentrations of fluoride in well drill cuttings displayed no apparent depth dependence, but were greatest within andesitic, alluvium, and conglomerate samples. Large amounts of fluoride were bound with metal oxides/oxyhydroxides in all samples. Batch experiments examining fluoride release from aquifer materials under evolving groundwater conditions revealed that fluoride was released into solution with elevated pH. Results here may be used to better predict fluoride contamination of aquifers. This thesis contains previously published/unpublished co-authored material.

Non-Carcinogenic Health Risk Evaluation of Elevated Fluoride in Groundwater and Its Suitability Assessment for Drinking Purposes Based on Water Quality Index

“…Furthermore, the carbonate dissolution and biological decomposition of organic materials are the main factors that promote HCO 3 − in GW. The efficiency of Na + and HCO 3 − in relation to fluoride reveals that alkaline climatic conditions facilitate the dissolution of fluoride [ 57 ]. Thus, the F1 results reflect a geogenic source of contamination in the GW sources of the study area.…”

A Systems Approach to Remediating Human Exposure to Arsenic and Fluoride From Overexploited Aquifers

“…The two principal contaminants of concern considered from a human health perspective are geogenically and geothermally sourced dissolved As and F (Knappett et al., 2020 ; LaFayette et al., 2020 ). Both of these contaminants cause a wide range of serious and deadly diseases (Argos et al., 2010 ; Ayoob & Gupta, 2006 ; Sage et al., 2017 ).…”

“…The two principal contaminants of concern considered from a human health perspective are geogenically and geothermally sourced dissolved As and F (Knappett et al, 2020;LaFayette et al, 2020). Both of these contaminants cause a wide range of serious and deadly diseases (Argos et al, 2010;Ayoob & Gupta, 2006; Sage 3 of 24 reducing cavities (Rosin-Grget et al, 2013;WHO, 2019), but higher levels of exposure drives tooth and skeletal fluorosis especially in children with developing bones (Ayoob & Gupta, 2006) and may contribute to negative health outcomes in vulnerable adult populations with diabetes and chronic kidney disease (Pratap & Singh, 2013).…”

Water Quality Assessment Bias Associated with Long-Screened Wells Screened across Aquifers with High Nitrate and Arsenic Concentrations

“…In regions of the world such as central Mexico that are experiencing rapid water table declines, this problem is met by constructing production wells that extend hundreds of meters below the present water table and with either open boreholes or perforated casings across their entire length [ 11 , 12 ]. These long-screened wells may simultaneously expose the population to anthropogenic contaminants such as nitrate (NO 3 ) and geogenic contaminants such as arsenic (As) [ 11 , 13 , 14 , 15 , 16 , 17 ]. High concentrations of NO 3 in excess of the World Health Organization (WHO) recommended limit of 10 mg/L NO 3 -N can kill infants under six months old when their formula is made with water with a high NO 3 content [ 18 ].…”

“…Knappett et al (2020) [ 11 ] confirmed that this aquifer has the highest concentrations of NO 3 in the so-called Indepedence Basin. Some of these wells in the SMA area also have elevated concentrations of geogenic As and fluoride (F) which are thought to be related to the remnant geothermal heat beneath the city as it straddles the flanks of an extinct volcano and a major regional fault [ 11 , 15 , 17 , 52 ]. The spatial distribution of anthropogenically sourced NO 3 and geogenically sourced As may be useful information for the city’s water supply utility to choose the location, depth and screened interval for new production wells in this area with rapidly falling water tables of 1–2 m/year [ 53 ].…”