6 research outputs found
Geochemical and Isotopic Composition of Natural Waters in the Central Main Ethiopian Rift: emphasis on the study of source and genesis of fluoride
No full textIn the Main Ethiopian Rift (MER), the supply of drinking water principally relies on groundwater wells,
springs (including some hot springs), and rivers, and is characterized by a significant problem of
fluoride (F¯) contamination. New analyses reveal that the F− geochemical anomaly is sometimes
associated with hazardous content of other potentially toxic elements such as As, B, Mo, U, Al, Fe, and
Mn. The F¯ content exceeds the permissible limit for drinking prescribed by the World Health
Organization (WHO; 1.5 mg/L) in many important wells (up to 20 mg/L), with even more extreme F
concentration in hot springs and alkaline lakes (up to 97 mg/L and 384 mg/L respectively) and is
causing prevalent endemic fluorosis disease in the region.
87 % of the groundwater wells, 38 % of rivers and 100 % of hot springs and lakes show F¯ content
above 1.5 mg/L. The groundwater and surface water from the highlands, typically characterized by low
Total Dissolved Solids (TDS) and Ca2+ (Mg2+)-HCO3¯ hydrochemical facies, do not show high F¯
content. The subsequent interaction of these waters with the various rocks of the rift valley induces a
general increase of the TDS and a variation of the chemical signature towards Na+-HCO3¯
compositions, with a parallel enrichment of F¯. The interacting matrixes are mainly rhyolites consisting
of volcanic glass and only rare F-bearing accessory minerals (such as alkali amphibole).
Comparing the abundance and the composition of the glassy groundmass with other mineral phases, it
appears that the former stores most of the total F¯ budget. This glassy material is extremely reactive,
and its weathering products (i.e. fluvio/volcano-lacustrine sediments) further concentrate the fluoride.
The interaction of these “weathered/reworked” volcanic products with water and carbon dioxide at high
pH causes the release of fluoride into the interacting water. This mainly occurs by a process of baseexchange
softening with the neo-formed clay minerals (i.e. Ca-Mg uptake by the aquifer matrix, with
release of Na+ into the groundwater). This is plausibly the main enrichment mechanism that explains
the high F¯ content of the local groundwater, as evidenced by positive correlation between F¯, pH, and
Na+, and inverse correlation between F¯ and Ca2+ (Mg2+). Saturation indices (SI) were calculated (using
PHREEQC-2) for the different water groups, highlighting that the studied waters are undersaturated in
fluorite. In these conditions, fluoride can not precipitate as CaF2, and so F¯ mobilizes freely without
forming other complexes.
On the other hand, 35 % of the 23 investigated groundwater wells and 70 % of the 12 hot springs (and
deep geothermal wells) show Arsenic concentration above the recommended limit of 10μg/L (WHO
2006). The average concentration of Arsenic is 0.9μg/L in rivers, 39μg/L in hot springs, 236μg/L in
deep geothermal wells, 21.4μg/L in groundwater wells, 77μg/L in lakes, whereas maximum
concentrations reach up to 3μg/L, 156μg/L, 278μg/L, 157μg/L and 405 μg/L respectively. Arsenic in
groundwater wells shows positive correlations with Na+ (R2=0.63) and HCO3
− (R2=0.70) as well as with
other trace elements such as Mo (R2=0.79), U (R2=0.70), V (R2=0.68) whereas no correlations are
observed with Fe and Mn. PHREEQC speciation modelling indicates that Fe and Al oxides and
hydroxides are stable in the water systems, suggesting that Fe and Al mineral phases are potential
adsorbents and thus influence the mobility of As. The oxidizing, high pH condition combined with Na+-
HCO3¯ hydrochemical facies (competing effect of HCO3
− for adsorption sites) of the MER waters play
an important role in the mobilization of arsenic.
Chemical analyses of leachates from MER rhyolitic rocks and their weathered and reworked fluviolacustrine
sediments were performed in order to evaluate their contribution as a source of the mentioned
geochemical anomalies. The leachates were obtained from a one-year leaching experiment on powdered
rocks and sediments mixed with distilled water (10g:50ml). The sediment leachates contain as much as
7.6 mg/L of F¯, 220 μg/L of As, 181 μg/L of Mo, 64 μg/L of U and 254 μg/L of V suggesting that the
local sediments represent the main source and reservoir of toxic elements. Laboratory column
experiment was also conducted in volcanic ash sample using synthetic rain water flushing, and the result
showed that significant amount of F¯ were leached out over the duration of the experiments.
This showed that these elements were originally present in the glassy portion of the MER rhyolitic
rocks, were progressively concentrated in weathered and redeposited products. It further confirms that
the pyroclastic materials are the major source and reservoir of many of the chemical elements (e.g. F¯,
As). Therefore, together with the renowned F¯ problem, the possible presence of geochemical
anomalies in As, B, Mo, V, U, Al, Fe, and Mn have to be taken into consideration in water quality issues
and future works has to investigate their possible health impact on the population of MER and other
sectors of the east African rift.
The stable δ18O, δD and radiogenic (87Sr/86Sr) isotopic composition of waters and representative
volcanic rocks (Ignimbrite and basalt) were carried out during this study. Different ranges of isotopic
values were recorded for different water groups: 10 hot spring samples show δ18O value with in the range of (-3.36‰ – 3.69‰) and δD (-0.95‰ – 24.23‰) (VSMOW), 12 groundwater wells δ18O (-
3.99‰ – 5.14‰) and δD (-19.69‰ – 32.27‰) in contrast to the 5 Lakes δ18O (3.98‰ – 7.92‰) and δD
(26.19‰ – 45.71‰). The 2 deep geothermal wells and 1 of the 2 river samples are depleted in stable
isotopic values. 87Sr/86Sr values range from 0.7045 to 0.7076 in the hot springs, and the two deep
geothermal wells have 0.7043 and 0.7054 values. These signatures are typical of water interacted with
mantle derived materials (with a minor crustal contamination), similar to the rocks widely covering the
study area. The Sr isotope values of the basalt and ignimbrite samples are 0.7063 and 0.7071
respectively. Generally, the result shows that there exists a complex surface water and groundwater
interactions that is reflected on a diversity of the stable and Sr isotopic signature in waters.
The preliminary results of the study has showed that there is a need for future extended works on the
geochemistry of solid samples (rocks, sediments and soils) as well as in waters that investigate all the
spectrum of chemical elements that are potentially detrimental to human health and environment.
Furthermore, from water resource point of view, the following works must focus on a comprehensive
study of various isotopes and geochemical data to constrain groundwater age dating, water-rock
interaction and flow path and thus help to model and systematize the hydrologic cycles in the basin
Impacts of Fine Particulate Matter Air Pollution and Health Disparities on COVID-19 Infection and Mortality
No full textBackground: Black communities, comprising 32.2% of Louisiana’s population, were disproportionately affected by the COVID-19 pandemic. Significant social disparities and a high prevalence of chronic health conditions within this demographic have heightened their vulnerability to the virus. Long-term exposure to air pollutants, along with preexisting immune and respiratory conditions, has been associated with increased susceptibility to COVID-19. This study seeks to evaluate the relationship between fine particulate matter (PM2.5) exposure and COVID-19 incidence and mortality rates in Louisiana, USA. Methods: Descriptive and multivariate regression analyses were conducted to examine the associations between PM2.5 levels and county-level COVID-19 incidence and mortality (both count and rate) in Louisiana. ArcGIS spatial analysis was utilized to perform zonal statistics, enabling a geographic assessment of the relationships between air pollution and COVID-19 outcomes. Results: Louisiana’s 19-year average PM2.5 concentration (9.1 µg/m³) exceeds the U.S. average (8.4 µg/m³). Prolonged exposure to PM2.5 has been linked to heightened COVID-19 risks. Specifically, a 1 µg/m³ increase in PM2.5 corresponded to approximately 15% higher COVID-19 incidence and a 22%-35% rise in mortality rates among Black populations, after adjusting for underlying health conditions and risk factors (p \u3c 0.05). Black communities faced approximately 20% greater COVID-19 risks compared with the total population. For exposure durations of 6-14 years, the COVID-19 risk increased by 6.5%-16.4% among Blacks and by 2.8%-10.5% overall. Preexisting health conditions, particularly those affecting diabetic kidney function, were more strongly associated with COVID-19 risks than respiratory diseases across all PM2.5 exposure durations. Conclusions: The disproportionate impacts of COVID-19 on Black communities highlight the urgent need to address air pollution and health disparities to reduce COVID-19 risks in Louisiana. Our findings underscore the importance of controlling PM2.5 levels and implementing effective public health responses to prevent COVID-19 and other future respiratory diseases at both local and state levels
Health Risk Assessment of Heavy Metal(loid)s Intake from Beverages in the United States
No full textHeavy metals in beverages can pose health risks in an exposure-dependent manner, however, few studies in the United States have evaluated their metal content and health risks. This study determined the concentrations of eight metal(loid)s, As, Al, Cd, Cr, Mn, Ni, Pb, and Zn, in 60 beverages via inductively coupled plasma[sbnd]mass spectrometry (ICPMS). The highest median concentrations (µg/kg) were found in mixed fruit juices for Ni (45.7), Cr (14.8), and As (4.5); tea for Mn (5,300), Al (730), and Pb (1.4); and plant-based milk for Zn (835) and Cd (1.1). Chronic daily intake (CDI) across age groups was calculated using the National Health and Nutrition Examination Survey (NHANES). Potential noncarcinogenic health risks were assessed via Hazard Quotients (HQ), and Hazard Indices (HI) for all elements and incremental lifetime cancer risk (ILCR) was assessed for total As, Cd, Ni, and Pb. About 58–67 % of the samples showed no noncarcinogenic risk (HQ and HI \u3c 1). HQ \u3e 1 was found in 19 samples for As, Zn, Ni, and Mn, and HI \u3e 1 in 6 additional samples (n = 25), mostly affecting children under 10, with three samples posing risk beyond adolescence. Significant carcinogenic risk (10−2 to 10−4) was found for As, Cd, and Ni across all beverage categories. This study highlights the need for consumer awareness and policy review
FLUORIDE BIOACCUMULATION AND ENAMEL FLUOROSIS FROM CHRONIC EXPOSURE THROUGH DRINKING WATER
No full textDietary contribution of essential elements from honey consumed in the United States
No full textHoney is a natural sweetener with nutritional properties, contributing minerals to the human diet. Data on U.S. honey is limited. This study analyzed the concentrations of 13 essential elements (B, Ca, Cu, Fe, K, Mg, Mn, Mo, Na, Ni, Se, Sr, and Zn) in 261 commercially available single-source honey samples from the U.S. using Inductively Coupled Plasma Mass Spectrometry (ICP-MS). The study assessed nutritional contributions, regional variations, and non-carcinogenic risks from honey consumption. On average, Se, Mo, Ni, Sr, and Cu ranged from 3.3 to 255 μg/kg, whereas Zn, Mn, Fe, B, Mg, Na, Ca, and K ranged from 0.70 to 615 mg/kg. For macroelements, K was the most abundant element, followed by Ca, with B, Fe, and Mn being highest among the microelements. Spearman correlation, Principial Component Analysis (PCA), and Kruskal-Wallis tests revealed significant inter-element relationships. Potassium and Mg were strongly correlated (r = 0.71), reflecting co-mobilization in plant nectar secretion. Moderate correlations were observed among Mg, Ca, Cu, Zn, Fe, Mo, Na, Mn, and Sr (r = 0.40-0.65), due to shared botanical and environmental influences. While significant differences between regions were identified by the Kruskal-Wallis test, PCA results showed no distinct regional clustering, indicating that the essential elemental composition of U.S. honey is not significantly influenced by geographic origin. Dietary Reference Intake (DRI) contributions were estimated for three intake levels (2 g, 21 g, and 42 g/day). At the highest level, honey provided up to 10.2 %, 11.3 %, and 16.5 % of DRI for Cu, B, and Mn, respectively, for young children. Contributions for other elements were negligible across serving sizes. Non-carcinogenic risk assessment indicated no health concerns at any intake level. This study examined the elemental composition of U.S. honey and its role as a safe, minor source of essential minerals
Origin of fluoride and arsenic in the main ethiopian rift waters
No full textIn the Main Ethiopian Rift (MER) area, rural populations often use water that exceeds the World Health Organization thresholds for fluoride (F–) and arsenic (As), two elements that are hazardous for human health. In this study, twenty-nine water samples were collected from lakes and hot and cold springs in southern MER to investigate source(s) and health-risk of the F– and As contamination. According to major ion and trace element analyses, only cold spring water is safe for consumption, whereas hot spring water is the most contaminated. Leaching tests performed with the MER rhyolitic volcanic rocks and their weathered products (fluvio-lacustrine sediments) demonstrate that the main cause of the F– and As release is geogenic, i.e., not related to anthropogenic activities. The weathering of volcanic glass and minerals (apatites, clays, hydro-oxides) by CO2-bearing alkaline water induces the mobilisation of F– and As from solid to liquid phase. This process is particularly fast, when fluvio-lacustrine sediments are involved, and can be further enhanced by hot groundwater leaching. This study, investigating the distribution, sources, and mechanisms of F– and As release in MER water, could be of interest also for other sectors of the East African Rift and other similar volcano-tectonic settings
