| 1. |
- Bhattacharya, Prosun, et al.
(författare)
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Groundwater arsenic in the Lower Ganges Delta Plain in West Bengal, India and Bangladesh : A hydrogeochemical comparison
- 2010
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Ingår i: Geological Society of America. ; , s. 653-
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Arsenic contaminations in groundwater have been widely reported. The serious arsenic contamination of groundwater of Lower Ganga delta Plain (LGDP) in West Bengal, India and Bangladesh has emerged as a global natural environmental health disaster. The Bengal Delta Plain (BDP) is one of the largest deltas in the world, drained by the Ganges, Brahmaputra and Meghna river (GBM) systems. Groundwater samples were collected from 67 different sites located in the districts of 24-Parganas (S), 24-Parganas (N) and Nadia in West Bengal, India along the western margin (Bhagirathi sub-basin), and 40 different sites located in the districts of Comilla, Laxmipur, Munshiganj, Faridpur and Jhenaida districts of Bangladesh along the eastern part of the Bengal Basin (Padma-Meghna sub-basin). Groundwater in the Nadia, West Bengal is mostly of Ca–HCO3 type while in the lower part of the delta, the groundwater is of Ca-Mg-SO4 type. The concentrations of major solutes (Na+, Mg2+, Ca2+, K+, HCO3-, SO42-, NO3- and PO43- in groundwater of Meghna sub-basin is more variable than Bhagirathi sub-basin that indicating different hydrological setting in the parts of the Bengal basin. The trace element concentrations such as As, Fe and Mn also show considerable variability in the two distinct parts of the Bengal basin. Most groundwaters of the LGDP contain arsenic above the WHO and the BIS standard of 0.01 mg/L as well as in many case above the Bangladesh drinking water standard (0.05 mg/L). Both sites have moderately reducing environment, with high concentrations of dissolved organic carbon, indicating dominantly metal-reducing processes and nearly similar mechanism in As mobilization. The occurrence of elevated arsenic in groundwater is generally associated with natural biogeochemical reactions (such as reductive dissolution of iron oxides/hydroxides) by altering groundwater redox state and releasing arsenic from sediment to aqueous phase. The various redox-sensitive solutes indicate overlapping redox zones, leading to partial redox equilibrium conditions where As, once liberated from minerals of sediments, would tend to remain in groundwater because of the complex interplay among the electron acceptors. Also, microbes in organic matter environment are acting as the major electron acceptor, in the Lower Ganges Delta Plain.
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| 2. |
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| 3. |
- Bundschuh, Jochen, et al.
(författare)
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Geothermal arsenic : Occurrence, mobility and environmental implications
- 2015
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Ingår i: Renewable & sustainable energy reviews. - : Elsevier BV. - 1364-0321 .- 1879-0690. ; 42, s. 1214-1222
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Forskningsöversikt (refereegranskat)abstract
- Arsenic (As) contamination in geothermal systems has been identified in many areas of the world. Arsenic mobilization from rocks and mineral phases into geothermal fluids depends on available As sources, geochemical conditions and microbiological activity. In deep geothermal reservoirs As mobilization is predominantly from As-bearing pyrite at temperatures of 150-250 degrees C, and at higher temperatures also from arsenopyrite. Highest As concentrations, mostly in the range of thousands to tens of thousands of mu g/L and in case of Los Humeros (Mexico) even of up to 162,000 mu g/L are found in volcanic geothermal systems whereas in low- and high-enthalpy sedimentary geothermal systems they reach only about 2000 mu g/L. At many sites, uprising geothermal waters contaminate shallow water resources. From the geothermal springs, those with NaCl water type have the highest As concentrations; these waters correspond to original reservoir waters which were not significantly altered during its ascent. In the geothermal reservoir and deeper parts of hydrothermal system, As is predominantly present as neutral H3As(III)O-3 (arsenius acid) and under sulfidic conditions also as thioarsenites; close to the earth's surface oxidation through atmospheric oxygen to As(V) species may occur; however, this is a slow process. As(III) emerging in geothermal springs is oxidized quickly through microbial catalysis and often most As is present as As(V), at a distance of few meters from the spring outlet. This review highlights the occurrence and distribution of geothermal As worldwide, its sources and its mobilization and the presence of different As species in geothermal fluids considering different geological settings and processes involving geothermal fluids rising from deep geothermal reservoirs to the earth's surface where it may mix with shallow groundwater or surface waters and contaminate these resources. The microbial diversity of hot spring environments which plays an important role to mobilize the As by oxidation and reduction process in the geothermal system is also addressed.
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| 4. |
- Bundschuh, Jochen, et al.
(författare)
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Medical geology in the framework of the sustainable development goals
- 2017
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Ingår i: Science of the Total Environment. - : Elsevier BV. - 0048-9697 .- 1879-1026. ; 581, s. 87-104
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Tidskriftsartikel (refereegranskat)abstract
- Exposure to geogenic contaminants (GCs) such as metal(loid)s, radioactive metals and isotopes as well as transuraniums occurring naturally in geogenic sources (rocks, minerals) can negatively impact on environmental and human health. The GCs are released into the environment by natural biogeochemical processes within the near-surface environments and/or by anthropogenic activities such as mining and hydrocarbon exploitation as well as exploitation of geothermal resources. They can contaminate soil, water, air and biota and subsequently enter the food chain with often serious health impacts which are mostly underestimated and poorly recognized. Global population explosion and economic growth and the associated increase in demand for water, energy, food, and mineral resources result in accelerated release of GCs globally. The emerging science of "medical geology" assesses the complex relationships between geo-environmental factors and their impacts on humans and environments and is related to the majority of the 17 Sustainable Development Goals in the 2030 Agenda of the United Nations for Sustainable Development. In this paper, we identify multiple lines of evidence for the role of GCs in the incidence of diseases with as yet unknown etiology (causation). Integrated medical geology promises a more holistic understanding of the occurrence, mobility, bioavailability, bio-accessibility, exposure and transfer mechanisms of GCs to the food-chain and humans, and the related ecotoxicological impacts and health effects. Scientific evidence based on this approach will support adaptive solutions for prevention, preparedness and response regarding human and environmental health impacts originating from exposure to GCs.
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| 5. |
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| 6. |
- Herath, Indika, et al.
(författare)
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Natural Arsenic in Global Groundwaters : Distribution and Geochemical Triggers for Mobilization
- 2016
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Ingår i: CURRENT POLLUTION REPORTS. - : SPRINGER HEIDELBERG. - 2198-6592. ; 2:1, s. 68-89
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Tidskriftsartikel (refereegranskat)abstract
- The elevated concentration of arsenic (As) in the groundwaters of many countries worldwide has received much attention during recent decades. This article presents an overview of the natural geochemical processes that mobilize As from aquifer sediments into groundwater and provides a concise description of the distribution of As in different global groundwater systems, with an emphasis on the highly vulnerable regions of Southeast Asia, the USA, Latin America, and Europe. Natural biogeochemical processes and anthropogenic activities may lead to the contamination of groundwaters by increased As concentrations. The primary source of As in groundwater is predominantly natural (geogenic) and mobilized through complex biogeochemical interactions within various aquifer solids and water. Sulfide minerals such as arsenopyrite and As-substituted pyrite, as well as other sulfide minerals, are susceptible to oxidation in the near-surface environment and quantitatively release significant quantities of As in the sediments. The geochemistry of As generally is a function of its multiple oxidation states, speciation, and redox transformation. The reductive dissolution of As-bearing Fe(III) oxides and sulfide oxidation are the most common and significant geochemical triggers that release As from aquifer sediments into groundwaters. The mobilization of As in groundwater is controlled by adsorption onto metal oxyhydroxides and clay minerals. According to recent estimates, more than 130 million people worldwide potentially are exposed to As in drinking water at levels above the World Health Organization's (WHO's) guideline value of 10 mu g/L. Hence, community education to strengthen public awareness, the involvement and capacity building of local stakeholders in targeting As-safe aquifers, and direct action and implementation of best practices in identifying safe groundwater sources for the installation of safe drinking water wells through action and enforcement by local governments and international water sector professionals are urgent necessities for sustainable As mitigation on a global scale.
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| 7. |
- Ijumulana, Julian, et al.
(författare)
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Spatial uncertainties in fluoride levels and health risks in endemic fluorotic regions of northern Tanzania
- 2021
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Ingår i: Groundwater for Sustainable Development. - : Elsevier BV. - 2352-801X. ; 14
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Tidskriftsartikel (refereegranskat)abstract
- Spatial uncertainty caused by large-scale variation in fluoride (F-) occurrence remains a setback for water supply authorities in the F- belts of the world. It is estimated that approximately 80 million people in the East African Rift Valley (EARV) regions and volcanic areas exhibit a wide variety of fluorosis symptoms due to drinking water with F- concentrations higher than 1.5 mg/L (WHO guideline limit). In this study, we combined geostatistical techniques, spatial statistical methods, and geographical information systems (GIS) to (i) map the probable places with F- < 0.5 mg/L and F- > 1.5, 4.0 and 10.0 mg/L using probability kriging (PK) method, (ii) estimate the probable total population at high or low F- risk levels using univariate local Moran's I statistic, and (iii) map the spatial distribution of population at high and low F- risk levels in Manyara, Arusha and Kilimanjaro regions using GIS. It was predicted that places along the major and minor EARV mountain ranges and around the flanks of major stratovolcanoes were dominated by groundwater sources with extremely low F-(<<0.5 mg/L). In contrast, places within EARV graben were dominated by groundwater sources with F- > 1.5 mg/L. About 1 million people (similar to 20% of the total population) living around Mt. Kilimanjaro in Rombo, Moshi, and Mwanga districts are at high dental caries risk. Furthermore, it was estimated that about 2 million people (similar to 41% of the total population) in Siha, Hai, Arusha City, Hanang', Arusha, Simanjiro, and Meru districts are at high risk of dental, skeletal, and crippling fluorosis. Fluorosis, especially dental and crippling fluorosis, is an increasing disease burden at the community level due to prolonged consumption of F- contaminated water within EARV graben. The major findings of the present study are very crucial for authority to minimize the uncertainty caused by high spatial variability in geogenic F- occurrence.
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| 8. |
- Ijumulana, Julian, et al.
(författare)
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Spatial variability of the sources and distribution of fluoride in groundwater of the Sanya alluvial plain aquifers in northern Tanzania
- 2022
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Ingår i: Science of the Total Environment. - : Elsevier BV. - 0048-9697 .- 1879-1026. ; 810
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Tidskriftsartikel (refereegranskat)abstract
- Groundwater contamination from geogenic sources paces challenges to many countries, especially in the developing world. In Tanzania, the elevated fluoride (F-) concentration and related chronic fluorosis associated with drinking F- rich water arc common in the Fast African Rift Valley regions. In these regions, F- concentration is space dependence which poses much uncertainty when targeting safe source for drinking water. To account for the spatial effects, integrated exploratory spatial data analysis, regression analysis, and geographical information systems tools were used to associate the distribution of F- in groundwater with spatial variability in terrain slopes, volcanic deposits, recharge water/vadose materials contact time, groundwater resource development for irrigated agriculture in the Sanya alluvial plain (SAP) of northern Tanzania. The F- concentration increased with distance from steep slopes where the high scale of variation was recorded in the gentle sloping and flat grounds within the SAP. The areas covered with debris avalanche deposits in the gentle sloping and flat grounds correlated with the high spatial variability in F- concentration. Furthermore, the high spatial variability in F- correlated positively with depth to groundwater in the Sanya flood plain. In contrast, a negative correlation between F- and borehole depth was observed. The current irrigation practices in the Sanya alluvial plain contribute to the high spatial variability in F- concentration, particularly within the perched shallow aquifers in the volcanic river valleys. The findings of this study arc important to the overall chain of safe water supply process in historically fluorotic regions. They provide new insights into the well-known F- contamination through the use of modern geospatial methods and technologies. In Tanzania's context, the findings can improve the current process of drilling permits issuance by the authority and guide the local borehole drillers to be precise in siting safe source for drinking water.
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| 9. |
- Irunde, Regina, et al.
(författare)
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Arsenic in Africa : Potential sources, spatial variability, and the state of the art for arsenic removal using locally available materials
- 2022
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Ingår i: GROUNDWATER FOR SUSTAINABLE DEVELOPMENT. - : Elsevier BV. - 2352-801X. ; 18, s. 100746-
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Tidskriftsartikel (refereegranskat)abstract
- In the past two decades, several studies on arsenic (As) occurrence in the environment, particularly in surface and groundwater systems have reported high levels of As in some African countries. Arsenic concentrations up to 10,000 mu g/L have been reported in surface water systems, caused by human activities such as mining, industrial effluents, and municipal solid waste disposals. Similarly, concentrations up to 1760 mu g/L have been reported in many groundwater systems which account for approximately 60% of drinking water demand in rural Africa. Naturally, As is mobilized in groundwater systems through weathering processes and dissolution of As bearing minerals such as sulfides (pyrite, arsenopyrite, and chalcopyrite), iron oxides, other mineralized granitic and gneissic rocks, and climate change factors triggering As release in groundwater. Recently, public health studies in some African countries such as Tanzania and Ethiopia have reported high levels of As in human tissues such as toenails as well as in urine among pregnant women exposed to As contaminated groundwater, respectively. In urine, concentrations up to 150 mu g/L were reported among pregnant women depending on As contaminated drinking water within Geita gold mining areas in the north-western part of Tanzania. However, the studies on As occurrence, and mobilization in African water systems, as well as related health effects are limited, due to the lack of awareness. The current study aims to gather information on the occurrence of As in different environmental compartments, its spatial variability, public health problems and the potential remediation options of As in water sources. The study also aims at creating awareness of As contamination in Africa and its removal using locally available materials.
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| 10. |
- Irunde, Regina, et al.
(författare)
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The natural magnesite efficacy on arsenic extraction from water and alkaline influence on metal release in water
- 2023
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Ingår i: Applied Geochemistry. - : Elsevier BV. - 0883-2927 .- 1872-9134. ; 155, s. 105705-105705
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Tidskriftsartikel (refereegranskat)abstract
- Arsenic (As) removal studies were carried out through batch experiments to investigate the performance of the locally available calcined magnesite mineral rocks from Tanzania. Natural water from a stream source in Tanzania and the prepared synthetic water at the laboratory were used for the studies. Parameters such as initial As concentration, calcined magnesite dosage, contact time and pH were evaluated for As removal using an overhead rea×2 shaker. Arsenic concentration was reduced from 5.3 to 1.1 mg/L As(V) at 180 min when 0.5 g/L calcined magnesite was applied to a synthetic water sample, whereas the concentration of 117 μg/L As(V) and 5.2 μg/L As(III) was reduced to below 0.1 μg/L in natural water. An increase in calcined magnesite dosage resulted in increased As removal up to below 0.01 mg/L. The calcined magnesite raised the pH of the water sample from 6.8 to 10 when the applied dosage increased between 0.002 g/L and 0.05 g/L. The pH was constant at around 10 even when the amount of 0.05 g/L was added 2000 times. Despite the high pH, the amount of magnesium released in water was low. The calcination of magnesite at 500 ◦C increased surface area by 4 times as compared to the natural magnesite and X-ray diffraction showed presence of MgCO3 phase as the dominant phase at this temperature. The reaction kinetics of As removal on 0.5 g/L calcined magnesite fitted with the pseudo-second-order (R2 = 0.96). Reaction isotherm was strongly fitted with Freundlich isotherm (R2 = 0.98). Linear regression and artificial intelligence neural network showed the As removal was influenced by both contact time and pH. Arsenic can be removed from As water using calcined magnesite and will be suitable for water treatment around gold mining areas.
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