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Appraising groundwater quality and probabilistic human health risks from fluoride-enriched groundwater using the pollution index of groundwater (PIG) and GIS: a case study of adama town and its vicinities in the central main Ethiopian rift valley.
| RSC Advances | Shube H, Karuppannan S, Haji M, Paneerselvam B, Kawo N, Mechal A, Fekadu A. | Issue 41

Abstract

This research’s main objective is to identify the level of contamination in drinking water in Adama town and its environs by employing PIG, GIS and HHRA. The physical–chemical parameters of groundwater were determined, and the results were compared to regional and global drinking water quality guidelines. The pH of groundwater is alkaline, and the contents of Ca2+, Na+, HCO3–, and F– in the majority of samples surpassed the permissible drinking limit. The hydrochemical facies were identified in the following order: Ca–Mg–HCO3, Na–Ca–HCO3, and Na–HCO3. Cation exchange and Rock–water interaction are the major dominant natural mechanisms controlling groundwater chemistry. Using IDW interpolation methods with Arc GIS 10.8, spatial analysis of the physico-geochemical content of water divulged that TDS, pH, TH, EC, Mg2+, Ca2+, K+, Na+, Cl–, HCO3–, F–, and SO42- all exhibit a positive trend in the direction of groundwater flow from the upland to the lowland (rift floor). As per PIG, the results show that 57%, 33%, 7% and 3% of the samples were found in the insignificant, low, moderate and high, correspondingly. The total hazard index (THI) is calculated from hazard quotients (HQIntake and HQDermal) results showing 83%, 73%, and 57% of the samples exceed the non-carcinogenic health threat of fluoride THI >1 in drinking water for children, women and men. Children are more susceptible to danger than either males or women, according to the THI data, based on body weights and consumption rates. Similarly, females are also more vulnerable to health risks than men.

Full-text article online at https://pubs.rsc.org/en/content/articlelanding/2024/ra/d4ra02890b
Excerpts:
In the MER (Main Ethiopian Rift), groundwater is intensively utilised for the provision of drinking water.42 The aquifers throughout the RV (Rift Valley) and the highlands have diverse hydrochemistry. Several researchers have observed high F- levels in RV groundwater,43,44 and it is the primary geological problem for the supply of drinking water. Due to the presence of mica aquifers, amphiboles, and pyroxene, fluoride may be discovered in the groundwater of the research area.45 Furthermore, anthropogenic activities like urban sewage, industrial, as well as agricultural intensification are affecting the quality of surface and groundwater in Adama Woreda, (MER). In spite of the fact that millions of people living along the MER depend on groundwater supplies for their survival, there was no groundwater quality monitoring system in place, nor were there any aquifer or well-head protection zones. For the purpose of efficiently developing new groundwater schemes and managing groundwater resources in the area under investigation, it is required to have a regional variation map of the principal cations and anions. The study’s goals are to analyze groundwater quality for drinking applications. …

2.1. Portrayal of research site

2.1.1. Location and climate

Adama Woreda is positioned inside the north-central part of the Main Ethiopian Rift (CMER), within the East Showa area of the Oromia. The geographical location of the town ranges from 8027.5′ N–8035.7’N and 39?013.5’E–39019’E with an altitude that generally ranges from 1360–2338 m above sea level (Fig. 1). It’s located in the East African Rift Valley (EARV), about 99.5 km southeast of the Ethiopian capital city of Finfinnee (Addis Ababa). It’s nestled between two mountain ridges in the Great Rift Valley on generally flat lowland, which is located in the Awash River basin. Adama is the fourth largest city in Ethiopia and one of the most important cities in the Oromiya region. This country’s second-most populous city has seen tremendous growth. It is the most populous and rapidly urbanising city in the Oromia Region, which is centrally located on the express highway connecting Addis Ababa and Djibouti and has a plethora of industries and manufacturing enterprises, making it a major commercial and transportation hub. In the Adama woreda, the annual rainfall ranges from 1200 mm to 800 mm. It has bimodal rainfall patterns, with the main rainy season, the summer monsoon, extending from June to September, and the dry period extending between October and February. There is a short rainy season between February and May, with an average rainfall of 800 mm. The mean annual temperature ranges between 8 and 28 °C. The month of May has the highest recorded temperature. The mean relative humidity is 61.3% (National meteorological service agency)…

 

Fig. 5 Spatial variation map of Cl– (a), SO42- (b), HCO3– (c), and F– (d).

The F– content in the study site varies from 1 to 10.5 mg L-1, with a mean of 4.2 mg L-1 (Table 4). Most water samples were found to be unsuitable for humans to consume, as per WHO norms. Unfit samples are most widely found in the southern and southeastern parts of the research area (Fig. 5d). When the level of F? in natural water is between 0.5 and 1.5 mg L-1, the enamel of the teeth is strengthened. F– Concentrations in natural drinking water above 4 mg L-1, above 1.5 mg L-1, and above 10 mg L-1 are associated with skeletal fluorosis, dental fluorosis, and crippling skeletal fluorosis, correspondingly.64,65 Fluoride levels in groundwater may be elevated as a result of fluoridated water salts percolating through acidic volcanic rocks (unwelded tuffs, lacustrine sediments, pyroclastic deposits, rhyolitic lava flows and ignimbrite) and geothermal water in this investigated region.44,66–68 The content of groundwater is overhauled as it moves down from the highlands to the lowlands of the rift valley. In highland aquifers, F– content is typically low, but it increases along the groundwater flow line in rift floor aquifers.

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