Multivariate statistical analysis for fluoride occurrence in groundwater in the Northern region of Ghana
Highlights
► Groundwater from parts of Northern region of Ghana has excess fluoride which can cause fluorosis. ► The source and mechanism of fluoride enrichment has not been well studied. ► Principal component analysis, Person's correlation and thermodynamic calculations helped explain the enrichment mechanism. ► Fluorite dissolution, F–/OH– anion exchange and evapotranspiration processes were found as predominant mechanisms. ► The study results may help in planning strategies for safe drinking water for the population at risk.
Introduction
Over 90% of rural domestic water requirements in the Northern region of Ghana is being met from groundwater sources, due to its many advantages (CWSA-NR, 2007, Gyau-Boakye and Dapaah-Siakwan, 2000). The presence of fluoride in groundwater in parts of the region at levels above 1.5 mg/L, the WHO guideline value has however, resulted in the closure of many otherwise successful boreholes in order to avoid the incidence of fluorosis (CWSA-NR, 2007, WHO, 2008).
Fluoride is known to have both beneficial and detrimental effects to human health (Biswas et al., 2007, Fawell et al., 2006, Karro et al., 2006, WHO, 2008). Ingestion of low concentrations of fluoride (about 1 mg/L) in drinking water can prevent the incidence of dental caries. Intake of excess fluoride for long periods can, however, result in the incidence of dental and skeletal fluorosis as well as other adverse health effects including growth retardation, loss of mobility, changes in DNA structure, lowering of IQ of children and even death when doses reach very high levels (about 250 mg/L) (Apambire et al., 1997, Brunt et al., 2004, Fawell et al., 2006, Reddy et al., 2010, Shomar et al., 2004).
A limited fluorosis survey conducted in six selected communities in the eastern corridor of the Northern region of Ghana, where the presence of high fluoride in groundwater is most prominent, revealed the incidence of dental fluorosis (tooth mottling). The prevalence rate in some of the communities was found to be as high as 61%. The severe type of dental fluorosis based on Dean's fluorosis index classification criteria, which is characterized by brown stains, discrete or confluent pitting of the dental enamel was observed. The possible emergence of skeletal fluorosis (bone deformation and painful brittle joints in older people) was also observed in some of the affected communities (Ayugane, 2008, Mandinic et al., 2010).
The presence and distribution of elevated concentrations of fluoride in groundwater and the related health impacts in other parts of Ghana, particularly the Bongo and Bolgatanga districts in the Upper East region, have also been reported and well studied (Anongura, 1995, Apambire et al., 1997). The fluoride concentrations in the area were found to range between 0.11 and 4.60 mg/L. The fluoride enrichment was also found to be most probably associated with the dissolution of the mineral fluorite (CaF2), found in the Bongo granites in the area, and also from both the dissolution and anion exchange from micaceous minerals and their altered clay products.
Even though groundwater remain the most important source for rural water supply in the Northern region of Ghana, little is known about the natural and any anthropogenic factors that control the groundwater chemistry, and hence the groundwater quality and fluoride contamination. The aim of this paper is to study the groundwater chemistry in the Northern region with a focus on the occurrence and genesis of high fluoride waters in the eastern corridor of the region. Piper graphical classification, Pearson's correlation, principal component analysis (PCA) and thermodynamic calculations were used as an approach to gain an insight into the groundwater chemical composition and the dominant mechanisms influencing the occurrence of high fluoride waters. Spatial join procedure was used to examine the relationship between fluoride and the underlying geology of the study area.
Section snippets
Factors controlling fluoride enrichment in groundwater
Fluoride occurs in practically all natural groundwaters, in concentrations varying from trace to as high as 2800 mg/L in environments such as the Soda Lakes of the East African Rift System. The dominant factors that control the concentration of fluoride in natural groundwater include: the geological setting and types of rocks/minerals traversed by groundwater, solubility of fluorine-bearing minerals in the aquifer matrix and the amount of leachable fluorine they contain, anion exchange capacity
The study area
The eastern corridor of the Northern region of Ghana (the study area) is located between latitudes 8° 30″ and 10° 30″ N and longitudes 1° 0″ W and 1° 0″ E. It comprises eleven administrative districts (West Mamprusi, East Mamprusi, Bunkpurugu-Yunyo, Gushegu, Karaga, Saboba/Cheriponi, Zabzugu Tatale, Yendi, Nanumba North and South (Fig. 1)), and covers an area of about 27,900 km2 with a population of about 1,150,000.
Temperatures in the Northern region of Ghana are relatively high, ranging from a
Descriptive statistics
A univariate statistical analysis of the hydrochemical data of the groundwater samples collected from the area, which include the lower quartile (Q1), median (Q2), upper quartile (Q3) and the inter-quartile range (IQR) are presented in Table 1.
The concentration of fluoride in the groundwater samples ranged from 0.0 to 11.6 mg/L, with a mean value of 1.13 mg/L and a standard deviation of 1.24 mg/L. A relatively high percentage (23%) of the samples were found to have fluoride concentrations
Genesis of high and low fluoride groundwaters in the eastern corridor of Northern region
The presence of fluoride at concentrations up to 11.6 mg/L in the groundwater samples suggests that favorable conditions exist for the dissolution of fluorine‐bearing minerals that may be present in the study area, as well as other processes which results in fluoride enrichment. A review of the PCA results, the equilibrium state of the groundwater based on the saturation indices and the direct relationship between fluoride and calcium concentrations (Fig. 2) highlights the following with regard
Conclusions
Twenty three percent (23%) of 357 groundwater samples from the eastern corridor of the Northern region of Ghana for which the physico-chemical parameters were studied were found to have fluoride concentrations exceeding 1.5 mg/L, the WHO guideline for drinking water, with concentrations as high as 11.6 mg/L. Human consumption of water from these wells can result in the incidence of fluorosis. Fifty two percent (52%) of the groundwater samples were within the acceptable fluoride concentration
Acknowledgment
The authors of the paper are greatly indebted to the UNESCO—IHE UPaRF project for the financial sponsorship which made this study possible. The authors are also very grateful to the management and staff of the following organizations: (i) Community Water and Sanitation Agency, Tamale and Accra, Ghana, (ii) Water Research Institute, Tamale and Accra, Ghana, (iii) Church of Christ Rural Water Project, Yendi, Ghana, (iv) UNIHYDRO Ltd, Accra, Ghana and many other organizations and individuals who
References (50)
- et al.
Hydrochemical characteristics of aquifers near Sutherland in the Western Karoo, South Africa
Journal of Hydrology
(2001) - et al.
Fluorine geochemistry in bedrock groundwater of South Korea
Science of the Total Environment
(2007) - et al.
Multivariate statistical evaluation of trace elements in groundwater in a coastal area in Shenzhen, China
Environmental Pollution
(2007) - et al.
Geochemical processes controlling the elevated fluoride concentrations in groundwaters of the Taiyuan Basin, Northern China
Journal of Geochemical Exploration
(2007) - et al.
Fluoride in drinking water and dental fluorosis
Science of the Total Environment
(2010) - et al.
Geochemical factors controlling the occurrence of high fluoride water in the Nagar Parkar area, Sindh, Pakistan
Journal of Hazardous Materials
(2009) - et al.
Fluoride dynamics in the granitic aquifer of the Wailapally watershed, Nalgonda district, India
Chemical Geology
(2010) Groundwater classification using multivariate statistical methods: Southern Ghana
Journal of African Earth Sciences
(2010)- et al.
Hydrochemical evaluation of Voltain system—the Afram Plains area, Ghana
Journal of Environmental Management
(2008) - et al.
Hydrogeological and hydrochemical framework of shallow groundwater system in the southern Voltain Sedimentary Basin, Ghana
Hydrogeology Journal
(1998)
Sandstone petrology and the provenance of the Neoproterozoic Voltain Group in the southern Voltain Basin, Ghana
Sedimentary Geology
Water quality analysis of groundwater in crystalline basement rocks, Northern Ghana
Environmental Geology
Fluorosis Survey of Bongo District of Upper East Region—Ghana: Report Submitted to Action Research Committee
Geochemistry, genesis, and health implications of fluoriferous groundwaters in the upper regions of Ghana
Environmental Geology
Standard Methods for the Examination of Water and Wastewater
Geochemistry, Groundwater and Pollution
Ethno-pedology Surveys in the Semi-arid Savanazone of Northern Ghana. An ILEIA Initiated Project Report 97/04
Adsorption kinetics of fluoride on iron (III)–zirconium hybrid oxide
Adsorption
Fluoride in Groundwater: Probability of Occurrence of Excessive Concentration on Global Scale
The scree test for number of factors
Multivariate Behavioral Research
Preparation and characterization of granular ceramic containing dispersed aluminum and iron oxides as adsorbents for fluoride removal from aqueous solution
Journal of Hazardous Materials
Geostatistical and principal component analysis of ground chemistry and soil-salinity data, San Joaquin Valley, California. Regional characterization of water quality
Fluoride in Drinking Water
Cited by (84)
Comments on “Hydrogeochemical and isotopic controls on the source of fluoride in groundwater within the Vea catchment, northeastern Ghana” (Musah Saeed Zango, Kenneth Bayetimani Pelig-Ba, Maxwell Anim-Gyampo, Abass Gibrilla, Emmanuel Daanoba Sunkari, 2021)
2022, Groundwater for Sustainable DevelopmentHydrochemical appraisal of fluoride contamination in groundwater and human health risk assessment at Isa Khel, Punjab, Pakistan
2022, Environmental Technology and Innovation