Source apportionment and health risk assessment of fluoride in water resources, south of Fars province, Iran: Stable isotopes (δ18O and δD) and geochemical modeling approaches
Graphical abstract
Introduction
Based on World Health Organization (World Health Organization, 2004) official data, globally about 80% of human diseases are associated with the consumption of low-quality drinking water. It is estimated that more than 200 million people in various parts of the world, particularly northern China, India, Sri Lanka, Mexico, western USA, Argentina, Iran, and many countries in Africa drink water with fluoride levels exceeding the World Health Organization's (World Health Organization, 2017) guideline value of 1.5 mg/L for drinking water (Adimalla and Venkatayogi, 2017; Adimalla et al., 2018a; Amini et al., 2008; Chuah et al., 2016; Edmunds and Smedley, 2013; Li et al., 2016). The US Environmental Protection Agency (EPA) determined the maximum contaminant level (enforceable limit) to be at 4 mg/L for fluoride in drinking water, although the secondary standard (non-enforceable) for United States drinking water is 2 mg/L (USEPA, 2018).
Fluorine is the 13th most abundant element in the Earth's crust (Weinstein and Davison, 2004) and its average crustal abundance is 300 mg/kg (Fawell et al., 2006; Tebutt, 1983). Weathering of F-bearing minerals in rock and soil is responsible for high F‾ concentration in water. Some such minerals include fluorite (CaF2), apatite [Ca5(PO4)3(Cl,F,OH)], topaz [Al2F2(SiO4)], cryolite (Na3AlF6), villiaumite (NaF), micas, clays, amphiboles, and epidotes (Dehbandi et al., 2017a; Keshavarzi et al., 2010). Major anthropogenic sources of fluoride contamination in the environment include excessive use of phosphate fertilizers and pesticides, aluminum smelting, glass and brick industries, industries, coal combustion, semi-conductors, and electroplating (Ali et al., 2016; Li et al., 2016).
Drinking water is typically the largest single contributor to daily fluoride intake (Chidambaram et al., 2013). Fluoride in drinking water has a narrow optimum concentration range in relation to human health. It prevents dental caries in the range of 0.7–1.2 mg/L (Farooqi, 2015). Dental and skeletal fluorosis and other diseases associated with prolonged intake of high-fluoride waters (F‾˃1.5 mg/L), are a potentially serious health problem for human and livestock (Ozsvath, 2009). Fluoride content in groundwater is related to water-rock interaction in the aquifer however, it rarely exceeds 10 mg/L. The highest natural concentration so far was measured 2800 mg/L in Lake Nakuru in Kenya (Davies, 2010).
Fluoride anomalies generally occur in special geochemical conditions such as Fe-rich soil in a humid climate, saline groundwater with high total dissolved solids, and alkaline groundwater in arid and semiarid environments (Sivasankar et al., 2016; Wen et al., 2013). Sivasankar et al. (2016) indicated that the highest fluoride levels tend to take place in semiarid climates with intense surface evaporation (>2000 mm per year), low precipitation (225–400 mm per year), and low groundwater hydraulic conductivity. Stable oxygen (18O/16O) and hydrogen (D/H) isotope ratios are used to identify the effects of evaporation on groundwater systems. A groundwater undergoing evaporation becomes enriched in heavier isotopes (Gonfiantini et al., 2018; Thivya et al., 2016).
High fluoride concentrations in groundwater are already reported form different parts of Iran such as Muteh (Keshavarzi et al., 2010), Dashtestan (Battaleb-Looie et al., 2012a), central Iran (Dehbandi et al., 2018), and Poldasht (Yousefi et al., 2018). Few studies have investigated fluoride contamination in Fars province. A recent work by Rezaei et al. (2017) in Lar area showed that fluoride had a natural source and the equilibrium reaction between calcite and fluorite was important in controlling fluoride levels in groundwater.
The main purpose of this study is to understand the causes of elevated fluoride concentrations in water resources, south of Fars province, Iran. This is essential to define consumption limits and management policies in the study area. To reach this goal, the sources of fluoride and the mechanisms that control its mobility and reactivity in aquatic systems were identified. The main geochemical reactions that influence the chemical composition of groundwater along a flow path are determined by inverse modeling using PHREEQC code. The climatic and geologic aspects of fluoride enrichment in the water resources of the study area have not been studied previously. These aspects are investigated in the present study using stable isotopes (δ18O and δD) data and leaching test, respectively. Finally, the health risk of high fluoride levels intake through drinking water is estimated.
Section snippets
Study area
The study area is located south of the Fars province, Iran (Fig. 1). Total population in the region is 465,795. Almost 350,000 of the population drink groundwater, while the rest consume surface water for drinking. The climate in the area is predominantly arid. Average annual precipitation, evaporation, and temperature in the area are 198.7 mm, 3027.6 mm, and 26.1 °C, respectively (Fars Meteorological Bureau, 2017). The majority of the rainfall occurs in the period December to March. The
Materials and methods
A total of 38 samples were collected from surface, ground, and rain water in the study area during 6th to 12th May 2017 in 1 L polyethylene bottles already washed twice with distilled water according to standard sampling procedure (APHA, 1995). The sampling points were selected considering population density and general direction of the groundwater flow. Lamerd, Lar, Mohr, Gerash, Khonj, Evaz, Alamarvdasht, Juyom, Banarouyeh, and Emad Shahr constitute the main population centers in the region.
Statistical analysis
Descriptive statistics of the chemical analyses of the water samples are presented in Table 1. The overall order of the dominance of cations is Na+˃ Ca2+ ˃Mg2+ ˃ K+ ˃ Si4+ and that of anions is Cl‾ ˃ SO42− ˃ HCO3‾ ˃ NO3‾˃ F‾ ˃ PO43−. Fluoride concentration in water samples varied from 0.06 to 4.95 mg/L averaging 1.8 mg/L. The rainwater and geothermal spring contained 0.09 mg/L and 2.23 mg/L F‾, respectively. Around 67.5% of water resources had fluoride content exceeding the permissible limit
Conclusions
This study indicated that fluoride concentration in water resources, south of Fars province, Iran range from 0.06 to 4.95 mg/L and tend to increase with general groundwater flow path. Overall, 67.57% of the analysed samples exceeded the WHO permissible limit of 1.5 mg/L and indicate a need for de-fluoridation of drinking water in this region. However, 2.7% of the samples also displayed concentrations below 0.5 mg/L which implies that fluoridation is required in these areas to protect the
Acknowledgment
The authors wish to express their gratitude to the research committee and medical geology center of Shiraz University for financial and logistic supports.
References (61)
Metamorphism of natural water in the crust of weathering
Geochem. Cosmochim. Acta
(1955)- et al.
Fluoride: a naturally-occurring health hazard in drinking-water resources of Northern Thailand
Sci. Total Environ.
(2016) - et al.
Controls on elevated fluoride and arsenic concentrations in groundwater from the Yuncheng Basin, China
Appl. Geochem.
(2011) - et al.
Fluoride concentrations in traditional and herbal teas: health risk assessment
Environ. Pollut.
(2017) - et al.
Provenance and geochemical behavior of fluorine in the soils of an endemic fluorosis belt, central Iran
J. Afr. Earth Sci.
(2017) - et al.
Geochemical sources, hydrogeochemical behavior, and health risk assessment of fluoride in an endemic fluorosis area, central Iran
Chemosphere
(2018) - et al.
A unified Craig-Gordon isotope model of stable hydrogen and oxygen isotope fractionation during fresh or saltwater evaporation
Geochem. Cosmochim. Acta
(2018) - et al.
Controls on the genesis of some high-fluoride groundwater in India
Appl. Geochem.
(2005) - et al.
Clustering Disjoint HJ-Biplot: a new tool for identifying pollution patterns in geochemical studies
Chemosphere
(2017) - et al.
Arsenic, fluoride and iodine in groundwater of China
J. Geochem. Explor.
(2013)
Health risk assessment to fluoride in drinking water of rural residents living in the Poldasht city, Northwest of Iran
Ecotoxicol. Environ. Saf.
Mechanism of fluoride enrichment in groundwater of hard rock aquifers in Medak, Telangana State, South India
Environ. Earth Sci.
Evaluation of groundwater quality, Peddavagu in Central Telangana (PCT), South India: an insight of controlling factors of fluoride Enrichment
Modeling Earth Sys. Environ.
Evaluation of groundwater contamination for fluoride and nitrate in semi-arid region of Nirmal Province, South India: a special emphasis on human health risk assessment (HHRA)
Human and Ecological Risk Assessment: Int. J.
Worldwide contamination of water by fluoride
Environ. Chem. Lett.
Statistical modeling of global geogenic fluoride contamination in groundwaters
Environ. Sci. Technol.
Standard Methods for the Examination of Water and Wastewater
Hydrogeochemical evolution of groundwaters with excess fluoride concentrations from Dashtestan, South of Iran
Environ. Earth Sci.
Geological sources of fluoride and acceptable intake of fluoride in an endemic fluorosis area, southern Iran
Environ. Geochem. Health
Petrology of Sedimentary Rocks
Assessing nitrate and fluoride contaminants in drinking water and their health risk of rural residents living in a semiarid region of northwest China
Exposure and Health
Environmental hydrogeochemistry and genesis of fluoride in groundwaters of Dindigul district, Tamilnadu (India)
Environ. Earth Sci.
Environmental Isotopes in Hydrogeology
Fluorine contamination in groundwater: a major challenge
Environ. Monit. Assess.
Medical geology in Africa
Fluoride hydrogeochemistry and bioavailability in groundwater and soil of an endemic fluorosis belt, central Iran
Environ. Earth Sci.
Profex: a graphical user interface for the Rietveld refinement program BGMN
J. Appl. Crystallogr.
Fluoride in natural waters
Arsenic and Fluoride Contamination: a Pakistan Perspective
Result of the 2016 Climatic Parameters
Cited by (31)
Salinization of shallow groundwater in the Jiaokou Irrigation District and associated secondary environmental challenges
2024, Science of the Total EnvironmentHydrogeological properties, sources provenance, and health risk exposure of fluoride in the groundwater of Batkhela, Pakistan
2022, Environmental Technology and InnovationEvaluating the genesis and dominant processes of groundwater salinization by using hydrochemistry and multiple isotopes in a mining city
2021, Environmental PollutionCitation Excerpt :The source of F− in groundwater was mainly the dissolution of fluorite and other F−bearing minerals in the rock formations (granite, gneiss, etc.). The weathering of silicate rocks could also contribute a large amount of F− (Fuge, 2019; Enalou et al., 2018; Martins et al., 2017). A longer interaction time between the groundwater and minerals in rock formations could increase the degree of mineral dissolution and promote F− enrichment in groundwater.
Hydrogeochemical and isotopic controls on the source of fluoride in groundwater within the Vea catchment, northeastern Ghana
2021, Groundwater for Sustainable DevelopmentCitation Excerpt :It is also not uncommon to associate groundwater F− enrichment to the intensity of anthropogenic activities such as industrial and agricultural activities (Kundu and Mandal, 2009). Assessment of the source of groundwater F− has been effectively conducted using conventional geochemical graphs, geochemical modeling, multivariate geostatistical analysis, and environmental isotopes (Olaka et al., 2016; Martins et al., 2018; Enalou et al., 2018; Su et al., 2019). Such an integrated approach is able to unravel groundwater flow patterns, recharge sources, effects of evaporation on hydrogeological systems, and thus, the mechanisms responsible for groundwater F− mobilization.
Two distinct mechanisms of fluoride enrichment and associated health risk in springs’ water near an inactive volcano, southeast Iran
2020, Ecotoxicology and Environmental SafetyCitation Excerpt :Iran is located in an arid/semiarid region and groundwater constitute the main water source for various consumptions particularly for drinking purposes (Mahvi et al., 2006; Esmaeili and Moore, 2012; Bazrafshan et al., 2016; Dehbandi et al., 2017b). Despite the different studies on fluoride contamination in groundwater resources in northwest (Moghaddam and Fijani, 2008; Barzegar et al., 2017, 2019; Esmaeili et al., 2018; Yousefi et al., 2019a), south (Enalou et al., 2018; Battaleb-Looie et al., 2012; Rezaei et al., 2017) and central (e.g., Aghapour et al., 2018; Dehbandi et al., 2017a; Dehbandi et al., 2017b; Dehbandi et al., 2018; Poureslami et al., 2008; Derakhshani et al., 2014; Fekri and Kasmaei, 2013) of Iran, the information on groundwater fluoride contamination in southeast of Iran is scarce. People in some districts of Sistan and Baluchestan province in southeast of Iran are suffered from endemic dental fluorosis.
Fluoride abundance and their release mechanisms in groundwater along with associated human health risks in a geologically heterogeneous semi-arid region of east India
2020, Microchemical JournalCitation Excerpt :Fluoride bearing minerals such as fluorite (CaF2), sellaite (MgF2), fluorapatite [Ca5(PO4)3F], amphiboles, cryolite (Na3AlF6), topaz [Al2SiO4(F,OH)2] and micas are found in the igneous rocks (such as granite, gneisses and pegmatite) and sediments [12]. Dissolution of such minerals constitutes a major source of F- in groundwater [13,14]. However, F- can be replaced with hydroxyl (OH-) ion and mobilized from micas (such as biotite and muscovite) and clay minerals into groundwater at alkaline condition [15].