Geochemical processes controlling the groundwater chemistry and fluoride contamination in the aquifer systems on the eastern, western and northern flanks of Mount Meru, Tanzania

In the Arusha volcanic region in northern Tanzania, within the eastern branch of the East African Rift, water shortage is common and much of the surface water carries unacceptable levels of dissolved fluoride; hence groundwater is the main source of drinking water. Unfortunately, the quality of groundwater in this region is also very poor due to a high fluoride (F⁻) content because of natural contamination from the surrounding geological environment. Consumption of this water leads to dental and skeletal fluorosis among the local population. Existing borehole completion reports and field stratigraphic description of sub-surface sediments during the digging of new hand dug wells were used to characterise the geology of aquifers. On the western flank, the main aquifer is a fractured and weathered basalt while on the south-western and north-eastern flanks the aquifers are composed of volcanic deposits (ash, tuffs, pumice, lapilli) and fractured and weathered basalt. A total of 158 groundwater samples from 113 water points (61 hand-dug wells and 52 springs) were collected for chemical analysis. Laboratory results show Sodium (Na+) and bicarbonate (HCO3⁻) are the dominant ions hence the main water type in this area is Sodium bicarbonate (NaHCO3). Preliminary results show strong contrasts in pH, EC, TDS and F⁻ concentration across the study area, with some spatial patterns for water samples from springs (on the north-eastern flank) where pH, EC, TDS and F⁻ concentration increase with a decrease in elevation. In all 158 groundwater samples, 91% (143 samples) have F⁻ concentration higher than the WHO limit (1.5 mg/l) recommended for drinking water. The 9% (15 samples) with F⁻ concentration lower than the WHO limit are water from the springs found in the recharge area at higher elevation on the eastern flanks of Mount Meru inside the Arusha National Park. The chemistry of the groundwater shows that weathering and dissolution of silicate minerals (especially chemical weathering of Na-K-rich volcanic rocks), dissolution of fluoride-rich minerals and calcite precipitation play great roles on the chemical evolution of groundwater in the study area while long residence time and nature of the geological formations (including degree of weathering) play great roles in the groundwater fluoride contamination in the area

Assessing the biological reactivity of organic compounds on volcanic ash: implications for human health hazard

Exposure to volcanic ash is a long-standing health concern for people living near active volcanoes and in distal urban areas. During transport and deposition, ash is subjected to various physicochemical processes that may change its surface composition and, consequently, bioreactivity. One such process is the interaction with anthropogenic pollutants; however, the potential for adsorbed, deleterious organic compounds to directly impact human health is unknown. We use an in vitro bioanalytical approach to screen for the presence of organic compounds of toxicological concern on ash surfaces and assess their biological potency. These compounds include polycyclic aromatic hydrocarbons (PAHs), polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and dioxin-like polychlorinated biphenyls (dlPCBs). Analysis of ash collected in or near urbanised areas at five active volcanoes across the world (Etna, Italy; Fuego, Guatemala; Kelud, Indonesia; Sakurajima, Japan; Tungurahua, Ecuador) using the bioassay inferred the presence of such compounds on all samples. A relatively low response to PCDD/Fs and the absence of a dlPCBs response in the bioassay suggest that the measured activity is dominated by PAHs and PAH-like compounds. This study is the first to demonstrate a biological potency of organic pollutants associated with volcanic ash particles. According to our estimations, they are present in quantities below recommended exposure limits and likely pose a low direct concern for human health

Assessment of leachable elements in volcanic ashfall : a review and evaluation of a standardized protocol for ash hazard characterization.

Volcanic ash presents a widespread and common hazard during and after eruptions. Complex interactions between solid ash surfaces and volcanic gases lead to the formation of soluble salts that may be mobilized in aqueous environments. A variety of stakeholders may be concerned about the effects of ash on human and animal health, drinking water supplies, crops, soils and surface runoff. As part of the immediate emergency response, rapid dissemination of information regarding potentially hazardous concentrations of soluble species is critical. However, substantial variability in the methods used to characterize leachable elements makes it challenging to compare datasets and eruption impacts. To address these challenges, the International Volcanic Health Hazard Network (www.ivhhn.org) organized a two-day workshop to define appropriate methods for hazard assessment. The outcome of this workshop was a ‘consensus protocol’ for analysis of volcanic ash samples for rapid assessment of hazards from leachable elements, which was subsequently ratified by leading volcanological organizations. The purpose of this protocol is to recommend clear, standard and reliable methods applicable to a range of purposes during eruption response, such as assessing impacts on drinking-water supplies and ingestion hazards to livestock, and also applicable to research purposes. Where possible, it is intended that the methods make use of commonly available equipment and require little training. To evaluate method transferability, an interlaboratory comparison exercise was organized among six laboratories worldwide. Each laboratory received a split of pristine ash, and independently analyzed it according to the protocol for a wide range of elements. Collated results indicate good repeatability and reproducibility for most elements, thus indicating that the development of this protocol is a useful step towards providing standardized and reliable methods for ash hazard characterization. In this article, we review recent ash leachate studies, report the outcomes of the comparison exercise and present a revised and updated protocol based on the experiences and recommendations of the exercise participants. The adoption of standardized methods will improve and facilitate the comparability of results among studies and enable the ongoing development of a global database of leachate information relevant for informing volcanic health hazards assessment

Impact of mine waste on environment and human health, Otavi Mountainland, Namibia : master’s thesis

Predmet istraživanja ovog diplomskog rada su jalovina i tlo onečišćeno rudarskim aktivnostima na području rudnika Berg Aukas i Tsumeb u Namibiji. Cilj istraživanja bio je utvrditi stupanj zagađenja, rizik za okoliš te biopristupačnost potencijalno toksičnih metala sa svrhom procjene utjecaja rudarskih aktivnosti na zdravlje djece. Uzorkovanje tala i jalovine obavili su prof.dr.sc. Marta Mileusnić i prof.dr.sc. Benjamin Mapani na lokacijama najučestalije aktivnosti djece u istraživanom području, tijekom srpnja 2012. godine. Laboratorijske analize uzoraka uključivale su ekstrakciju zlatotopkom, sekvencijsku ekstrakcijsku analizu te ekstrakciju u tjelesnim tekućinama (želučanom i crijevnom). Analiza potencijalno toksičnih metala u navedenim ekstraktima obavljena je primjenom atomske apsorpcijske spektrometrije, od kojih su najznačajniji izmjereni metali As, Cd, Cu, Hg, Pb i Zn. Rezultati istraživanja statistički su obrađeni te su izračunati indikatori stupnja zagađenja tla, stupanj rizika za okoliš te dnevni unos onečišćivala za djecu. Budući da su rezultati pokazali visok stupanj zagađenja i rizik za okoliš za istraživane metale u svim analiziranim uzorcima, tla u oba istraživana područja nisu prihvatljiva za korištenje u poljoprivredne i rezidencijalne svrhe. S obzirom na procijenjeni dnevni unos onečišćivala, djeca koja žive na području Berg Aukasa ugrožena su olovom, kadmijem i cinkom, a djeca na području Tsumeba potencijalno su ugrožena radi količina unesenog arsena i olova.Abstract: The subject of this thesis are tailings and soils contaminated by mining activities in the area of the mines Berg Aukas and Tsumeb in Namibia. The aim of this study was to determine the degree of pollution, environmental risk and bioaccessibility of potentially toxic metals in order to estimate the impact of mining activities on the health of children. Soil and tailings sampling was performed in July 2012 by prof. Marta Mileusnić and prof. Benjamin Mapani, at locations where children spend most of their time. Laboratory analysis of samples included aqua regia extraction, sequential extraction and body fluids (gastric and intestinal) extraction. Potentially toxic metals (As, Cd, Cu, Hg, Pb and Zn) in extracts were analyzed using atomic absorption spectrometry. Indicators of soil contamination, environmental risk and daily intake of contaminants for children were calculated. Considering high level of pollution and environmental risk for the studied metals in all samples, soils from both study areas are not acceptable for agricultural and residential use. Given the estimated daily intake of contaminants, children living in the Berg Aukas are threatened by lead, cadmium and zinc, whereas children in Nomtsob township of Tsumeb are potentially threatened by intake of arsenic and lead

Impact of mine waste on environment and human health, Otavi Mountainland, Namibia : master’s thesis

Predmet istraživanja ovog diplomskog rada su jalovina i tlo onečišćeno rudarskim aktivnostima na području rudnika Berg Aukas i Tsumeb u Namibiji. Cilj istraživanja bio je utvrditi stupanj zagađenja, rizik za okoliš te biopristupačnost potencijalno toksičnih metala sa svrhom procjene utjecaja rudarskih aktivnosti na zdravlje djece. Uzorkovanje tala i jalovine obavili su prof.dr.sc. Marta Mileusnić i prof.dr.sc. Benjamin Mapani na lokacijama najučestalije aktivnosti djece u istraživanom području, tijekom srpnja 2012. godine. Laboratorijske analize uzoraka uključivale su ekstrakciju zlatotopkom, sekvencijsku ekstrakcijsku analizu te ekstrakciju u tjelesnim tekućinama (želučanom i crijevnom). Analiza potencijalno toksičnih metala u navedenim ekstraktima obavljena je primjenom atomske apsorpcijske spektrometrije, od kojih su najznačajniji izmjereni metali As, Cd, Cu, Hg, Pb i Zn. Rezultati istraživanja statistički su obrađeni te su izračunati indikatori stupnja zagađenja tla, stupanj rizika za okoliš te dnevni unos onečišćivala za djecu. Budući da su rezultati pokazali visok stupanj zagađenja i rizik za okoliš za istraživane metale u svim analiziranim uzorcima, tla u oba istraživana područja nisu prihvatljiva za korištenje u poljoprivredne i rezidencijalne svrhe. S obzirom na procijenjeni dnevni unos onečišćivala, djeca koja žive na području Berg Aukasa ugrožena su olovom, kadmijem i cinkom, a djeca na području Tsumeba potencijalno su ugrožena radi količina unesenog arsena i olova.Abstract: The subject of this thesis are tailings and soils contaminated by mining activities in the area of the mines Berg Aukas and Tsumeb in Namibia. The aim of this study was to determine the degree of pollution, environmental risk and bioaccessibility of potentially toxic metals in order to estimate the impact of mining activities on the health of children. Soil and tailings sampling was performed in July 2012 by prof. Marta Mileusnić and prof. Benjamin Mapani, at locations where children spend most of their time. Laboratory analysis of samples included aqua regia extraction, sequential extraction and body fluids (gastric and intestinal) extraction. Potentially toxic metals (As, Cd, Cu, Hg, Pb and Zn) in extracts were analyzed using atomic absorption spectrometry. Indicators of soil contamination, environmental risk and daily intake of contaminants for children were calculated. Considering high level of pollution and environmental risk for the studied metals in all samples, soils from both study areas are not acceptable for agricultural and residential use. Given the estimated daily intake of contaminants, children living in the Berg Aukas are threatened by lead, cadmium and zinc, whereas children in Nomtsob township of Tsumeb are potentially threatened by intake of arsenic and lead

Impact of mine waste on environment and human health, Otavi Mountainland, Namibia : master’s thesis

Predmet istraživanja ovog diplomskog rada su jalovina i tlo onečišćeno rudarskim aktivnostima na području rudnika Berg Aukas i Tsumeb u Namibiji. Cilj istraživanja bio je utvrditi stupanj zagađenja, rizik za okoliš te biopristupačnost potencijalno toksičnih metala sa svrhom procjene utjecaja rudarskih aktivnosti na zdravlje djece. Uzorkovanje tala i jalovine obavili su prof.dr.sc. Marta Mileusnić i prof.dr.sc. Benjamin Mapani na lokacijama najučestalije aktivnosti djece u istraživanom području, tijekom srpnja 2012. godine. Laboratorijske analize uzoraka uključivale su ekstrakciju zlatotopkom, sekvencijsku ekstrakcijsku analizu te ekstrakciju u tjelesnim tekućinama (želučanom i crijevnom). Analiza potencijalno toksičnih metala u navedenim ekstraktima obavljena je primjenom atomske apsorpcijske spektrometrije, od kojih su najznačajniji izmjereni metali As, Cd, Cu, Hg, Pb i Zn. Rezultati istraživanja statistički su obrađeni te su izračunati indikatori stupnja zagađenja tla, stupanj rizika za okoliš te dnevni unos onečišćivala za djecu. Budući da su rezultati pokazali visok stupanj zagađenja i rizik za okoliš za istraživane metale u svim analiziranim uzorcima, tla u oba istraživana područja nisu prihvatljiva za korištenje u poljoprivredne i rezidencijalne svrhe. S obzirom na procijenjeni dnevni unos onečišćivala, djeca koja žive na području Berg Aukasa ugrožena su olovom, kadmijem i cinkom, a djeca na području Tsumeba potencijalno su ugrožena radi količina unesenog arsena i olova.Abstract: The subject of this thesis are tailings and soils contaminated by mining activities in the area of the mines Berg Aukas and Tsumeb in Namibia. The aim of this study was to determine the degree of pollution, environmental risk and bioaccessibility of potentially toxic metals in order to estimate the impact of mining activities on the health of children. Soil and tailings sampling was performed in July 2012 by prof. Marta Mileusnić and prof. Benjamin Mapani, at locations where children spend most of their time. Laboratory analysis of samples included aqua regia extraction, sequential extraction and body fluids (gastric and intestinal) extraction. Potentially toxic metals (As, Cd, Cu, Hg, Pb and Zn) in extracts were analyzed using atomic absorption spectrometry. Indicators of soil contamination, environmental risk and daily intake of contaminants for children were calculated. Considering high level of pollution and environmental risk for the studied metals in all samples, soils from both study areas are not acceptable for agricultural and residential use. Given the estimated daily intake of contaminants, children living in the Berg Aukas are threatened by lead, cadmium and zinc, whereas children in Nomtsob township of Tsumeb are potentially threatened by intake of arsenic and lead

The Late Quaternary Eruptive History of Meru Volcano, Northern Tanzania

info:eu-repo/semantics/publishe

Identification of low fluoride areas using conceptual groundwater flow model and hydrogeochemical system analysis in the aquifer system on the flanks of an active volcano: Mount Meru, Northern Tanzania

Co-auteur étrangerInternational audienceThis study investigates the localities of low and high F- groundwaters in the aquifer system on the flanks of Mount Meru to come up with guidelines to provide groundwater that can be used for drinking water supply without health impacts on the population. Our study focuses on parts of the flanks which were only partially or not at all covered by previous research. Results show that the groundwater chemistry of F--rich NaHCO3 alkaline groundwater in the area is controlled by dissolution of weathering aluminosilicate minerals, dissolution of F--bearing minerals, the precipitation of carbonate minerals as secondary products and the dissolution of magmatic gases. The low F- groundwaters which can be used for drinking water supply without health impacts under the WHO limit (1.5 mg/L) are the low-fluoride springs from the high altitude recharge areas on the eastern and north-western flanks of Mount Meru inside Arusha National Park, whereas on the western flank the groundwater meets the Tanzanian limit (4.0 mg/L). On the south-western flank, the shallow aquifer composed of alluvium deposits at lower elevations, shows F- values that meet the Tanzanian limit. One of the three investigated deep boreholes on this flank also meets the Tanzanian limit, suggesting a possibility of finding relatively low F- groundwaters in the deep aquifer. Yet, in general, the deposits at lower elevations are found to contain high to very high F- values, whereas the deposits at high elevations contain groundwater of low F- values. Thus, the internal texture and grain size of geological formations, the burial depth of these formations and the water residence times are the factors determining the groundwater mineralisation and F- concentrations in the area. The study identified that the deep hydrothermal system has influence on the high F- groundwaters on the eastern and north-eastern flanks of Mount Meru

Hydrochemical Characterisation of High-Fluoride Groundwater and Development of a Conceptual Groundwater Flow Model Using a Combined Hydrogeological and Hydrochemical Approach on an Active Volcano: Mount Meru, Northern Tanzania

co-auteur étrangerInternational audienceThis study characterises high-fluoride groundwater in the aquifer system on the flanks of Mount Meru, focusing on parts of the flanks that were only partially or not at all covered by previous research. Additionally, we analyse the impact of rainwater recharge on groundwater chemistry by monitoring spring discharges during water sampling. The results show that the main groundwater type in the study area is NaHCO3 alkaline groundwater (average pH = 7.8). High F− values were recorded: in 175 groundwater samples, the concentrations range from 0.15 to 301 mg/L (mean: 21.89 mg/L, median: 9.67 mg/L), with 91% of the samples containing F− values above the WHO health-based guideline for drinking water (1.5 mg/L), whereas 39% of the samples have Na+ concentrations above the WHO taste-based guideline of 200 mg/L. The temporal variability in F− concentrations between different seasons is due to the impact of the local groundwater recharge. We recommend that a detailed ecohydrological study should be carried out for the low-fluoride springs from the high-altitude recharge areas on the eastern and northwestern flanks of Mount Meru inside Arusha National Park. These springs are extracted for drinking purposes. An ecohydrological study is required for the management of these springs and their potential enhanced exploitation to ensure the sustainability of this water extraction practice. Another strategy for obtaining safe drinking water could be to use a large-scale filtering system to remove F− from the groundwater