Two distinct mechanisms of fluoride enrichment and associated health risk in springs' water near an inactive volcano, southeast Iran

Probabilistic human health risk assessment and Sobol sensitivity reveal the major health risk parameters of aluminum in drinking water in Shiraz, Iran

Overuse of aluminum salts (a.k.a., alum) in coagulation and flocculation processes in water treatment raises concerns about increased levels of aluminum (Al) in drinking water. In this study, we present a probabilistic human health risk assessment (HRA) for non-cancerogenic risks, with Sobol sensitivity analysis, to vet the concern of increased health risk from Al in drinking water in Shiraz, Iran, for children, adolescents, and adults. The results show that the concentration of Al in the drinking water in Shiraz varies significantly between winter and summer seasons and varies considerably spatially across the city irrespective of the season. However, all concentrations are below the guideline concentration. The HRA results show that the highest health risk is for children in summer, and the lowest is for adolescents and adults during winter, with generally higher health risks for younger age groups. However, Monte Carlo results for all age groups suggest no adverse health effects due to Al exposure. The sensitivity analysis shows that the sensitive parameters vary across age groups. For example, the Al concentration and ingestion rate pose the most risk for adolescent and adult groups, and children group, respectively. More importantly, the interaction of Al concentration with ingestion rate and body weight is the controlling parameters for evaluating HRA rather than Al concentration alone. We conclude that while the HRA of Al in Shiraz drinking water did not indicate significant health risk, regular monitoring and optimal operation of the coagulation and flocculation processes are essential.

Hydrogeochemical characterization and natural background level determination of selected inorganic substances in groundwater from a semi-confined aquifer in Midwestern Burkina Faso, West Africa

Hydrogeochemical processes that govern selected inorganic substances distribution in a semi-confined aquifer were characterized using traditional hydrogeochemical approaches and natural background levels (NBLs). Saturation indices and bivariate plots were used to investigate the effects of water-rock interactions on natural evolution of the groundwater chemistry, whereas Q-mode hierarchical cluster analysis and one-way analysis of variance classified the groundwater samples into three distinct groups. To highlight the groundwater status, NBLs and threshold values (TVs) of the substances were calculated using pre-selection method. Piper's diagram showed that the Ca-Mg-HCO₃ water type was the only hydrochemical facies of the groundwaters. Although all samples, except a borewell with a high NO₃^- concentration, had major ion and transition metal concentrations within the World Health Organization's recommended guideline values for drinking water, Cl^-, NO₃^- and PO₄^3- exhibited scattered distribution patterns, reflecting their nonpoint anthropogenic sources in the groundwater system. The bivariate and saturation indices revealed that silicate weathering and possible gypsum and anhydrite dissolution contributed to the groundwater chemistry. In contrast, NH₄⁺, Fe_T and Mn abundance appeared to be influenced by redox conditions. Strong positive spatial correlations between pH, Fe_T, Mn and Zn suggested that mobility of these metals was controlled by pH. The relative high F^- concentrations in lowland areas may imply the impact of evaporation on this ion's abundance. Contrary to TVs of HCO₃^-, those of Cl^-, NO₃^-, SO₄^2-, F^- and NH₄⁺ were below the guideline values, confirming the influence of chemical weathering on the groundwater chemistry. Based on the present findings, further studies that take into account more inorganic substances are required for NBLs and TVs determination in the area, thereby setting up a robust sustainable management plan for the regional groundwater resources.

A unified multivariate statistical approach for the assessment of deep groundwater quality of rapidly growing city of Maharashtra Province, India, with potential health risk

The main aim of this research is to assess the consequences of natural and anthropogenic processes on the groundwater quality of 65 deep aquifers of Nagpur city, Maharashtra Province, India, using a unified multivariate statistical approach. The dominant groundwater type recognized is Ca-HCO₃ (recharge waters) in 43.1 and 38.5% of groundwater samples of pre- and post-monsoon seasons, followed by mixed water types. The seasonal distribution of physicochemical parameters shows increase in the concentration of EC, TDS, TH, Mg²⁺, SO₄^2-, and NO₃^- signifying the high mineralization and anthropogenic loading from pre- and post-monsoon season respectively. The entropy-weight water quality index categorizes the 84.6% and 75.4% of total samples from pre- and post-monsoon seasons into moderate quality. The multiple linear regression and PCA analysis reveal the masking of rock weathering mechanism by anthropogenic activities. The % of PCA Variance varies from 79 to 83.7% from pre- to post-monsoon season. The high contributions of EC (0.76, 0.72), TDS (0.79, 0.73), TH (0.97, 0.962), Ca²⁺ (0.84, 0.78), Mg²⁺ (0.79, 0.83), Cl^- (0.73, 0.75), and NO₃^- (0.78, 0.68) in PC1 components expose high salinity and hardness in urban groundwater that signifies the consequences of urbanization on the groundwater regime. About 55.4 and 70.8% of children population as compared to the adult female (53.8%, 69.2%) and male (32.3%, 46.1%) population in PRM and POM respectively were at high non-carcinogenic health threat of NO₃^--enriched groundwater. The study is beneficial for understanding the variation in groundwater composition due to unplanned urbanization and is very useful for protecting groundwater resources in urban areas.

Comprehensive assessment of water quality and associated health risks in an arid region in south Iran

This study aims at investigating the quality of drinking water and evaluating the non-carcinogenic risk of fluoride and nitrate ions in drinking water, and fluoride in tea in Zarrin Dasht, Iran. We focus on tea since it is the most popular drink among Iranian people and in the study region. We collected and analyzed 23 drinking water samples and 23 tea samples from different locations in the study region. Based on the water quality index, the consumed drinking water does not have a good quality in most Zarrin Dasht areas. Accordingly, the water quality index (WQI) is poor and very poor in 70% and 13% of the water samples, respectively. The average fluoride concentration of the tea samples is 2.71 mg/L. The mean values of Fluoride Hazard Index (HI_fluoride) are 3.77, 2.77, and 2.33 for children, teenagers, and adults, respectively, which are higher than the safe limit of 1. The Nitrate Hazard Index (HI_nitrate) is higher than the safe limit of 1 in 8.7% of the samples. The results of the Monte Carlo simulation demonstrate that HI_fluoride and HI_nitrate are higher than 1 in all the groups, except for adults. According to the results of the sensitivity analysis, ingestion rate and body weight have a large effect on HI_fluoride and HI_nitrate, but body weight is inversely associated with sensitivity. According to the Piper diagram, saline water is the predominant type in Zarrin Dasht. Besides, the results of the principal component analysis (PCA) show a high correlation between fluoride and pH, which could be related to the effect of pH on fluoride dissolution and ion exchange. Therefore, appropriate measures are recommended to be taken in order to reduce the amount of fluoride in the drinking water resources of this region. Reduction of tea consumption can also be considered an important factor in decreasing the amount of fluoride intake.

Fluoride and nitrate contamination of groundwater in the Loess Plateau, China: Sources and related human health risks

Fluoride (F^-) and nitrate (NO₃^-) in groundwater have caused serious health problems worldwide. However, in the Chinese Loess Plateau where groundwater is the primary source of drinking water, previous studies have rarely reported the health risks from fluoride and nitrate in groundwater. Therefore, we collected 105 groundwater samples (78 from shallow aquifers and 27 from deep aquifers) from the western district of the Loess Plateau for physicochemical and isotopic analysis to investigate the sources of F^- and NO₃^- in groundwater and associated health risks. Fluoride concentration in 73.1% of shallow groundwater and 22.2% of deep groundwater exceeds 1.5 mg/L, while NO₃^- content in 76.3% of shallow groundwater and 51.9% of deep groundwater surpasses 50 mg/L. High-F^- groundwater is associated with HCO₃-Na, SO₄-Na·Mg and Cl-Na·Mg types water. Fluorine-bearing minerals dissolution, cation exchange, calcite precipitation, evaporation, and anthropogenic activities contribute significantly F^- in groundwater. Mixing with shallow groundwater is an important source of F^- in deep groundwater. The NO₃^- content is highest in Cl type water, followed by SO₄ type and HCO₃ type water. NO₃^- mainly originates from soil organic nitrogen (SON), chemical fertilizers (CF), and manure and sewage (M&S). Nitrification is the dominant transformation process of nitrogen nutrients in groundwater. The hazard index (HI) values for shallow groundwater are 0.203-9.232 for adults, 0.253-11.522 for teenagers, 0.359-16.322 for children, and 0.507-23.043 for infants, while those for deep groundwater are 0.713-5.813 for adults, 0.890-7.254 for teenagers, 1.261-10.277 for children, and 1.780-14.508 for infants. Approximately 96.2% of shallow groundwater poses non-carcinogenic risks to infants and children, followed by 92.3% to teenagers, and 89.7% to adults. All deep groundwater poses non-carcinogenic risks to infants and children, followed by 92.6% to teenagers, and 74.1% to adults. This study is helpful to develop strategies for the integrated management of high fluoride or nitrate groundwater in arid areas.

Groundwater fluoride chemistry and health risk assessment of multi-aquifers in Jilin Qianan, Northeastern China

Groundwater from deep confined aquifers is often recommended for use because of it's low fluoride health risk. Thus, this study appraised groundwater fluoride hydrochemistry in a multi-aquifer system in Jilin Qianan to determine the non-carcinogenic health risk liable from exploiting the respective aquifers. 124 samples collected from the tertiary confined aquifer (N), quaternary confined aquifer (Q₁), and quaternary phreatic aquifer (Q₃) during surveys in 2001 and 2017 was analyzed using hydrochemical, statistical, spatial, and health risk assessment methods. Results show that the dominant water facies in the respective aquifer layers was Na+K-HCO₃+CO₃ except in Q_1, where Ca+Mg - HCO₃ + CO₃ was marginally dominant. Fluoride concentrations outside the recommended guideline occurred in all the aquifers except N, where concentrations were optimum. The mean fluoride concentration of groundwater in the aquifers was of the order Q₃ (2017) > Q₃ (2001) > Q₁ > N ( mean 2.09, 2.03, 1.41 and 0.75 mg/L with 51.85%, 57.44%, 36.36% and 0% occurring beyond recommended guideline values respectively). Silicate weathering, cation exchange, and fluorite dissolution in an alkaline environment were the significant fluoride contributing processes. Evaporation and MgF⁺ complex additionally influenced Q₁ and Q₃ (2017). The total hazard quotient (THQ) from oral and dermal pathways shows fluoride health risks in the order: infant > children > adult. The associated risks likely from using water in the respective aquifer layers is of the order Q₃ (2017) > Q₃ (2001) > Q₁ > N. The mean groundwater fluoride in 2017 was marginally higher than that of 2001 ( 2.09>2.03 mg/L respectively) although the percentage of age group members disposed to fluoride risk from using water from Q₃ decreased from 2001 to 2017. Knowledge of local hydrogeology in exploiting deep groundwater free of fluoride pollution and on-site defluoridation treatment of groundwater was recommended in the study area and other areas with similar characteristics.

Non-carcinogenic health risk assessment with source identification of nitrate and fluoride polluted groundwater of Wardha sub-basin, central India

In order to understand the pollution status of groundwater with geochemical evolution and appraisal of its probable public health risk due to nitrate (NO₃^-) and fluoride (F^-), a total of 93 groundwater samples were collected during pre-monsoon (May) period from Wardha sub-basin, central India. By employing Piper plot, transition from Ca-HCO₃ type water (recharge waters) to Na-Cl (saline water) type water through mixed Ca-Na-HCO₃, mixed Ca-Mg-Cl (reverse ion exchange waters) and Ca-Cl types (leachate waters), were observed. The Geogenic processes such as silicate, dolomite, halite and carbonate weathering along with calcite precipitation and ion exchange process were identified as major controlling factors for evolution and alteration of groundwater chemistry. The Saturation index highlighted that the groundwater in the area is oversaturated with respect to the mineral calcite and dolomite, and under saturated with gypsum, fluorite and halite. The high NO₃^- and F^- concentration overpassing the permissible limit were found in 54.8% and 18.5% of samples. The plot of F^- with Na⁺/Ca²⁺, Na⁺/Mg²⁺ and F^-/Cl^- established fluoride bearing rock weathering is responsible for F^- contamination. Based on the cluster analysis, the groundwater was grouped into Cluster-I Ca-Na-HCO₃ type (61.3%) and Cluster-II Na-Ca-HCO₃-Cl type (30.1%). The total hazard index (HI) based on human health risk assessment (HHRA) model for cumulative NO₃^- and F^- toxicity through oral and dermal pathways were computed as 100%, 97.85% and 96.77% for children, female and male populations respectively. The HQ_(nitrate) > 1 through ingestion pathway were in 84.95%, 68.82% and 62.37%, and HQ_(fluoride) > 1 in 83.87%, 62.37% and 43.01% of the groundwater samples were recorded for children, female and male population respectively. The risk assessment study highlighted very high toxicity and severe health impact of ingestion of contaminated groundwater on public health.

Groundwater Pollution and Human Health Risks in an Industrialized Region of Southern India: Impacts of the COVID-19 Lockdown and the Monsoon Seasonal Cycles

Samples of groundwater were collected during a post-monsoon period (January) and a pre-monsoon period (May) in 2020 from 30 locations in the rapidly developing industrial and residential area of the Coimbatore region in southern India. These sampling periods coincided with times before and during the lockdown in industrial activity and reduced agricultural activity that occurred in the region due to the COVID-19 pandemic. This provided a unique opportunity to evaluate the effects of reduced anthropogenic activity on groundwater quality. Approximately 17% of the wells affected by high fluoride concentrations in the post-monsoon period returned to levels suitable for human consumption in samples collected in the pre-monsoon period. This was probably due to ion exchange processes, infiltration of rainwater during the seasonal monsoon that diluted concentrations of ions including geogenic fluoride, as well as a reduction in anthropogenic inputs during the lockdown. The total hazard index for fluoride in the post-monsoon samples calculated for children, adult women, and adult men indicated that 73%, 60%, and 50% of the groundwater samples, respectively, had fluoride levels higher than the permissible limit. In this study, nitrate pollution declined by 33.4% by the pre-monsoon period relative to the post-monsoon period. The chemical facies of groundwater reverted from the Na-HCO3-Cl and Na-Cl to the Ca-HCO3 type in pre-monsoon samples. Various geogenic indicators like molar ratios, inter-ionic relations along with graphical tools demonstrated that plagioclase mineral weathering, carbonate dissolution, reverse ion exchange, and anthropogenic inputs are influencing the groundwater chemistry of this region. These findings were further supported by the saturation index assessed for the post- and pre-monsoon samples. COVID-19 lockdown considerably reduced groundwater pollution by Na+, K+, Cl-, NO3¯, and F- ions due to shutdown of industries and reduced agricultural activities. Further groundwater quality improvement during lockdown period there is evidence that the COVID-19 lockdown by increased HCO3¯ ion concentration. Overall results illustrate the positive benefits to groundwater quality that could occur as a result of measures to control anthropogenic inputs of pollutants.