Research Studies
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Assessment of hydrochemical characteristics, health risks and quality of groundwater for drinking and irrigation purposes in a mountainous region of Pakistan.
Abstract
Renowned for its agriculture, livestock, and mining, Zhob district, Pakistan, faces the urgent problem of declining groundwater quality due to natural and human-induced factors. This deterioration poses significant challenges for residents who rely on groundwater for drinking, domestic, and irrigation purposes. Therefore, this novel study aimed to carry out a comprehensive assessment of groundwater quality in Zhob district, considering various aspects such as hydrochemical characteristics, human health risks, and suitability for drinking and irrigation purposes. While previous studies may have focused on one or a few of these aspects, this study integrates multiple analyses to provide a holistic understanding of the groundwater quality situation in the region. Additionally, the study applies a range of common hydrochemical analysis methods (acid–base titration, flame atomic absorption spectrometry, and ion chromatography), drinking water quality index (WQI), irrigation indices, and health risk assessment models, using 19 water quality parameters. This multi-method approach enhances the robustness and accuracy of the assessment, providing valuable insights for decision-makers and stakeholders. The results revealed that means of the majority of water quality parameters, such as pH (7.64), electrical conductivity (830.13 uScm–1), total dissolved solids (562.83 mgL–1), as well as various anions, and cations, were in line with drinking water norms. However, the water quality index (WQI) predominantly indicated poor drinking water quality (range = 51–75) at 50% sites, followed by good quality (range = 26–50) at 37% of the sites, with 10% of the sites exhibiting very poor quality (range = 76–100). For irrigation purposes, indices such as sodium percent (mean = 31.37%), sodium adsorption ratio (mean = 0.98 meqL–1), residual sodium carbonate (– 3.15 meqL–1), Kelley’s index (mean = 0.49), and permeability (mean = 49.11%) indicated suitability without immediate treatment. However, the magnesium hazard (mean = 46.11%) and potential salinity (mean = 3.93) demonstrated that prolonged application of groundwater for irrigation needs soil management to avoid soil compaction and salinity. Water samples exhibit characteristics of medium salinity and low alkalinity (C2S1) as well as high salinity and low alkalinity (C3S1) categories. The Gibbs diagram results revealed that rock weathering, including silicate weathering and cation exchange, is the primary factor governing the hydrochemistry of groundwater. The hydrochemical composition is dominated by mixed Ca–Mg–Cl, followed by Na–Cl and Mg–Cl types. Furthermore, the human health risk assessment highlighted that fluoride (F–) posed a higher risk compared with nitrate (NO3–). Additionally, ingestion was found to pose a higher risk to health compared to dermal contact, with children being particularly vulnerable. The average hazard index (HI) for children was 1.24, surpassing the allowable limit of 1, indicating detrimental health effects on this subpopulation. Conversely, average HI values for adult females (0.59) and adult males (0.44) were within safe levels, suggesting minimal concerns for these demographic groups. Overall, the study’s interdisciplinary approach and depth of analysis make a significant contribution to understanding groundwater quality dynamics and associated risks in Zhob district, potentially informing future management and mitigation strategies.
Fig. 1
Original abstract online at https://link.springer.com/article/10.1007/s11356-024-34046-7
Excerpts:
Human health risk assessment (HHRA)
Assessment of drinking water quality, especially regarding NO3– and F– exposure through ingestion and dermal contact, was conducted to evaluate non-cancer health risks among children, adult females, and adult males (Fig. 2b & Table S3) (Selvam et al. 2023; Yang et al. 2022). Consistent with previous studies, ingestion-based Hazard Quotient (HQ) values exceeded dermal HQ values across all subpopulations (Jadoon et al. 2021; Varol & Tokath, 2023). Approximately 56.67%, 10%, and 6.67% of groundwater samples exhibited ingestion HQ values exceeding the threshold value (1.0) for children, adult females, and adult males, respectively. Conversely, dermal HQ remained below 1 for all subpopulations at all sites (Fig. 2b). The total hazard quotient (THQ) calculated for NO3– and F– indicated that THQ for NO3– did not surpass 1 at any site for all subpopulations. For F–, THQ > 1 was observed at 50%, 10%, and 6.67% sites for children, adult females, and adult males (Fig. 2b). These findings emphasize the significance of the ingestion pathway and F– exposure as key contributors to potential non-cancer risk (Table S3 & Fig. S5) (Çankaya et al. 2023). Moreover, children faced the highest risk, followed by adult females and adult males (Varol & Tokatlh, 2023). Average hazard index (HI) values were 1.24.E + 00, 5.94.E-01, and 4.36.E-01 for children, adult females, and adult males, respectively (Fig. 2b). Given that average HI values for children exceeded risk thresholds, this subpopulation is susceptible to characteristic non-cancer risks. This study underscores that children face higher non-cancer risks compared to both adult groups, consistent with previous reports (Jadoon et al. 2021; Selvam et al. 2023; Varol & Tokatlh, 2023; Yang et al. 2022). Children are exposed to potential non-cancer risks at 56.67% of sites, while adult females and males face such risks at 10% and 6.67% of sites, respectively.
The HI values across all populations exhibited a significantly strong positive correlation with F– concentrations and a non-significant correlation with NO3– concentrations, indicating that F– is the primary risk factor for residents (Fig. S5) (Qu et al. 2022). Children’s increased vulnerability to groundwater NO3– and F– pollutants could be attributed to their underdeveloped metabolism and lower body weight (Qu et al. 2022).
Exceeding permissible groundwater concentrations of NO3– and F– can lead to health complications like blue baby syndrome, esophageal and gastric cancers, and dental and skeletal fluorosis (Vaiphei & Kurakalva 2021). This study’s outcomes suggest that along with other parameters, NO3– and F– pollution in groundwater could arise from water–rock interactions. The establishment of robust groundwater quality monitoring networks is crucial for effective groundwater management in the study area.
Conclusions
The study highlights the vital role of groundwater for domestic and agricultural needs in the semi-arid study area. The evaluation of water quality against established standards presents a varied outlook. While certain parameters meet WHO guidelines, the presence of contaminants is concerning. pH, EC, and TDS generally stay within limits, though exceptions exist. Elevated turbidity levels raise aesthetic and health worries. Dominant ions include bicarbonates, sulfates, chlorides, calcium, sodium, and magnesium. Although ion compositions usually align with norms, occasional excesses occur. Many physicochemical parameters surpass WHO limits, emphasizing the need for water quality enhancements. Drinking water quality varies from good to undrinkable, with no samples in the excellent range, and a notable portion falls into the poor category. TDS, calcium, magnesium, EC, and chloride contributed to drinking water quality deterioration. Irrigation indices suggest groundwater use for irrigation without initial treatment, but prolonged use without soil management may lead to sodium and magnesium hazards. Hydrochemical analysis attributes groundwater composition to rock-water interaction, primarily from silicate weathering and cation exchange. The hydrochemical facies lack a dominant water type, with mixed Ca–Mg–Cl being common, along with Na–Cl and Ca–Cl types. Fluoride poses non-cancer risks, particularly for children and adult females, underscoring the need for caution in using groundwater for drinking. In conclusion, the study emphasizes groundwater’s significance in the study area and its intricate water quality. Addressing highlighted issues is pivotal for safe and sustainable domestic and agricultural use of groundwater in the region.
Recommendation and limitations
Based on this study’s findings, it was observed that TDS, Ca2+, Mg2+, EC, Cl–, SO42-, NO3–, and F– have degraded drinking water quality, while magnesium hazard and potential salinity have affected irrigation water. Prolonged use of such compromised water poses risks to human health and soil quality, including compaction and salinity. Therefore, special attention to children is recommended to prevent future health issues and soil degradation associated with this contaminated water. This can be achieved through water treatment, regular monitoring, and construction of barriers around wells. Additional strategies include reducing soil salinity, community engagement, pre-treatment of industrial effluents, and constructing sewage treatment plants to ensure public health and improve soil quality and crop yield.
While this study offers a comprehensive assessment of drinking and irrigation water quality and associated human and environmental health risks, it has limitations. Funding constraints restricted the sample size, potentially compromising its representativeness. Additionally, the study’s reliance on a single sampling event suggests the need for seasonal evaluations to understand water quality parameters and their responses to seasonal changes more comprehensively. Future research should consider incorporating machine learning algorithms to enhance findings and predictions. Furthermore, the study may have provided only a snapshot of groundwater quality at a specific point in time, highlighting the importance of considering temporal variations for a comprehensive understanding of water quality dynamics and long-term trends.