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Статті в журналах з теми "Groundwater – Arsenic content – Vermont"
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Lu, Shuai, Xiaoyu Feng, and Xiaosi Su. "Geochemical characteristics of arsenic in groundwater during riverbank filtration: a case study of Liao River, Northeast China." Water Supply 20, no. 8 (September 4, 2020): 3288–300. http://dx.doi.org/10.2166/ws.2020.213.
Повний текст джерелаАнотація:
Abstract Affected by groundwater exploitation in the riverside, the infiltration of river water to recharge groundwater will cause changes in the groundwater environment, which has an important impact on the geochemical behavior of arsenic in groundwater. In this study, the groundwater environment zones in the process of river water infiltration were divided, and the arsenic content in groundwater in the study area had a good correlation with the environment zones. In the weak oxidation environment zone and the weak reductive environment zone, as the distance from the riverbank increased, the arsenic content gradually increased. In the reduction environment zone, there was a decreasing trend in arsenic content in groundwater. The arsenic content in groundwater varied significantly with the seasons, and its dynamic characteristics were closely related to the water level. The arsenic content in groundwater decreased with the rise in groundwater level, and it responded obviously to the change of water level in the shallows. Overall, arsenic entered the groundwater from the solid phase through adsorption and desorption of exchangeable arsenic and exchangeable iron, and reductive dissolution of iron or manganese oxides bound iron in the medium during riverbank filtration.
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Gwachha, Sushila, Bishwa Nath Acharya, Agni Dhakal, Sujen Man Shrestha, and Tista Prasai Joshi. "Assessment of Arsenic Content in Deep Groundwater of Kathmandu Valley, Nepal." Nepal Journal of Science and Technology 19, no. 1 (July 1, 2020): 69–77. http://dx.doi.org/10.3126/njst.v19i1.29785.
Повний текст джерелаАнотація:
The contamination of groundwater by arsenic is one of the major problems in Nepal. This study was conducted in 20 deep groundwater (>200m) samples of Kathmandu valley to assess the arsenic content of different groundwater zones and to determine the relationship of arsenic with physico-chemical parameters. Samples were collected in the post-monsoon season of 2016. The random sampling method was applied to the collection of water samples.Standard methods as APHA 2005 was followed for the analysis of the water sample.Arsenic concentration showed spatial variation. The maximum concentration of arsenic was found in Central Groundwater Zone at Patan (27040’07.3” and 85019’14”). Karl Pearson’s correlation coefficient revealed that moderate positive correlation of arsenic concentration withelectrical conductivity (μS/cm) (r = 0.58and p =0.01) and turbidity (NTU)(r = 0.67 and p = 0.01). Groundwater consumers of the central zone of the valley are at risk of arsenic-based health issues.
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Vu, Thi Duyen, Thi Mai Tran, Thi Kim Trang Pham, Mai Lan Vi, Manh Phu Dao, Hung Viet Pham, and Dieke Postma. "Spatial distribution of arsenic in groundwater in the northwestern Hanoi." Ministry of Science and Technology, Vietnam 63, no. 11 (November 24, 2021): 19–23. http://dx.doi.org/10.31276/vjst.63(11db).19-23.
Повний текст джерелаАнотація:
Arsenic contamination in groundwater is commonly found in alluvial plains of major river basins, in which the Red river delta has also been reported to be contaminated with high levels of arsenic. In this study, groundwater from 50 household wells was collected to study the spatial distribution of arsenic in northwestern Hanoi. The results showed that arsenic concentration in groundwater varied in a wide range of less than 5 to 334 μg/l, of which up 62% of the wells exceeded the WHO guideline value of 10 μg/l for arsenic content in drinking water. Arsenic groundwater in this area is unevenly distributed throughout the area, high arsenic concentrations are found in a narrow band between Red river and Day river. This pattern of arsenic distribution is strongly related to the sediment age, sedimentary processes, and it is also modified by local groundwater flow parts and the occurrence of hydraulic connection between aquifers, which are observed in the study area. Arsenic is released into the groundwater during the reductive dissolution of arsenic-bearing minerals under the presence of organic matter.
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Saha, Sudip, A. H.M. Selim, and Mrinal Kanti Roy. "The geological setting of arsenic enrichment in groundwater of the shallow aquifers of the Tista Floodplain, Rangpur, Bangladesh." International Journal of Advanced Geosciences 8, no. 2 (October 22, 2020): 231. http://dx.doi.org/10.14419/ijag.v8i2.31116.
Повний текст джерелаАнотація:
Arsenic is present in water samples within the studied active floodplain areas of the Tista river, Rangpur Division, Bangladesh. All the water samples contain less arsenic than the WHO prescribed limit of 10 μg/L. 93.33% groundwater samples have higher Mn content than the permissible limit of 0.01 mg/L of WHO. The heavy metal concentrations of water can be expressed as Fe>Mn>Zn>As on the basis of their mean content. The heavy metals are negatively correlated with the well depth which is indicative of the influence of the anthropogenic activities on the concentrations of heavy metals. The arsenic concentration in water samples is higher in the central part of the study area. The coarser grain size, dominance of physical weathering, elevated topography and the effective flushing of groundwater resulted low concentration of arsenic in the groundwater. The EDS study reveals that arsenic occurs as coating materials of the silicate minerals. The river waters also have arsenic content lower than WHOs permissible limit. The factor analysis reveals that the iron and arsenic is released by the chemical weathering of arsenic bearing minerals like pyrite and arsenopyrite. The Fe and Mn derived in the groundwater by the chemical weathering of iron and manganese bearing minerals such as iron rich clay, silicate minerals and iron sulfides.
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Liu, Fan, Guanxing Huang, Jichao Sun, Jihong Jing, and Ying Zhang. "Distribution of arsenic in shallow aquifers of Guangzhou region, China: natural and anthropogenic impacts." Water Quality Research Journal 49, no. 4 (June 23, 2014): 354–71. http://dx.doi.org/10.2166/wqrjc.2014.014.
Повний текст джерелаАнотація:
To elucidate the distribution of arsenic in shallow aquifers of the Guangzhou region (South China), 85 groundwater samples were collected and 18 chemical parameters of them were analyzed. The arsenic concentration of groundwater ranged from below detection limit to 0.13 mg/L. The results showed that those areas with high arsenic concentration were characterized by porous aquifers, low-lying, relief topography and close proximity to fault belt and rivers. The reductive dissolution of Fe (hydr)oxides is the main control mechanism for arsenic enrichment in the river delta region where groundwater is mainly characterized by a reducing environment. This mechanism was well embodied in the areas with these geological and geographical features. Agricultural fertilizer could produce high levels of nitrate in groundwater and the reduction of it could restrain the enrichment of arsenic. Industrial effluents, sewage irrigation and the probable leakage from sewers could promote the arsenic content in groundwater by lateral flow and infiltration. In addition, the effect of ion competition between phosphate and arsenic occurred in sewer leakage areas characterized by middle-high construction leading to the elevation of arsenic concentrations. The arsenic distribution in groundwater was caused by these natural and anthropogenic factors jointly.
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Ren, Minghua, José Alfredo Rodríguez-Pineda, and Philip Goodell. "Arsenic Mineral in Volcanic Tuff, a Source of Arsenic Anomaly in Groundwater: City of Chihuahua, Mexico." Geosciences 12, no. 2 (February 1, 2022): 69. http://dx.doi.org/10.3390/geosciences12020069.
Повний текст джерелаАнотація:
Arsenic is a naturally occurring trace element that causes many health effects when present in drinking water. Elevated arsenic concentrations in water are often attributed to nearby felsic volcanic sequences; however, the specific rock units to which the groundwater anomalies can be accredited are rarely identified. The groundwater from wells around the city of Chihuahua, Mexico, contains high arsenic content. Arsenic in groundwater increases toward the base rock containing Tertiary volcanic rocks. Through detailed scanning electron microscope (SEM) and electron microprobe (EMP) work, arsenic minerals are identified in the cavities of the Tertiary volcanic tuff from the northeast part of the Tabalaopa Basin, city of Chihuahua. Arsenic minerals, the As–Sr–Al phase (a possible arsenogoyazite–arsenoflorencite group mineral) crystallized in the vesicles of the tuff and the As–Y bearing phase included in biotite, prevail in the studied Tertiary volcanic outcrops. Based on the current study, the arsenic anomaly in the Tabalaopa–Aldama aquifer corresponds to these arsenic phases in the Tertiary volcanic rocks.
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Magalona, Maritess L., Milagros M. Peralta, Marivic S. Lacsamana, Veronica C. Sabularse, Amado B. Pelegrina, and Constancio C. De Guzman. "Analysis of Inorganic Arsenic (As(III) and Total As) and Some Physicochemical Parameters in Groundwater Samples from Selected Areas in Bulacan, Batangas, and Laguna, Philippines." KIMIKA 30, no. 2 (December 1, 2019): 28–38. http://dx.doi.org/10.26534/kimika.v30i2.28-38.
Повний текст джерелаАнотація:
Numerous cases of arsenic (As) poisoning from contaminated groundwater have been reported worldwide including the Philippines. The maximum contamination limit has been set by World Health Organization (WHO) for arsenic in drinking water at 10 ppb. This study determined the As(III) and total As content of groundwater samples in selected sites of Bulacan, Batangas, and Laguna by differential pulse anodic stripping voltammetry (DPASV). The pH, temperature, conductivity, total solids, turbidity, and salinity of the groundwater samples were also determined during sample collection. Groundwater samples from Laguna were naturally warm, with collection temperatures exceeding 30 oC, compared to water samples from Batangas and Bulacan ((T = 27 to 29.5 ˚C). The pH and turbidity of all samples were found to comply with the limits based on acceptability set by the WHO and the Philippine National Standards for Drinking Water (PNSDW). However, some samples had total dissolved solids and salinity beyond the limits set by the WHO and PNSDW guidelines. Moreover, some of the samples tested contained arsenite As(III), the more toxic form of arsenic, above 10 ppb whereas only one water sample tested had less than 10 ppb total arsenic content.
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Armienta, M. A., R. Rodríguez, and O. Cruz. "Arsenic Content in Hair of People Exposed to Natural Arsenic Polluted Groundwater at Zimapán, México." Bulletin of Environmental Contamination and Toxicology 59, no. 4 (October 1, 1997): 583–89. http://dx.doi.org/10.1007/s001289900519.
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Trung, Dang Tran, Nguyen Thi Nhan, Than Van Don, Nguyen Kim Hung, Jolanta Kazmierczak, and Pham Quy Nhan. "The controlling of paleo-riverbed migration on Arsenic mobilization in groundwater in the Red River Delta, Vietnam." VIETNAM JOURNAL OF EARTH SCIENCES 42, no. 2 (May 9, 2020): 161–75. http://dx.doi.org/10.15625/0866-7187/0/0/14998.
Повний текст джерелаАнотація:
In the Red River Delta, the concentrations of Arsenic in groundwater of alluvial dominated systems are very high, exceeding the WHO’s permissible. The correlation between the Arsenic concentrations in groundwater and the age of Holocene sediment as a key controlling groundwater Arsenic concentration in the Red River delta has been investigated. The evolution of sediments in the Holocene is closely related to paleo-riverbed migration in the past. A combination of methods is implemented including remote sensing, multi-electrode profiling (MEP), gamma-logging, drilling, soil sample and groundwater modeling. The resul has identified the shape, sediment compositions and location of the six paleo-riverbed periods. The age of the paleo-riverbed is determined by drilling, soil sampling and optically stimulated luminescence (OSL) in the laboratory. The oldest sediments is 5.9±0.4 ka BP in Phung Thuong near the mountain, the youngest one is from 0.4÷0.6 ka BP in H-transect near the Red River and the rest of the other is around 3.5 ka BP. The modeling results by using MODFLOW and MT3D show that the dynamics of paleo-riverbeds controlling Arsenic mobilization in groundwater in the Red River Delta. When the river moved to another position, the current river position at that time was filled with younger sediments and became paleo-riverbed formation with reducing conditions, Arsenic content which was adsorbed in the previous stage then released into groundwater. Therefore, Arsenic concentration in groundwater of young Holocene sediments is higher than in older ones which elucidates that paleo-riverbed migration controls on Arsenic mobilization in groundwater in the study area.
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Trung, Dang Tran, Nguyen Thi Nhan, Than Van Don, Nguyen Kim Hung, Jolanta Kazmierczak, and Pham Quy Nhan. "The controlling of paleo-riverbed migration on Arsenic mobilization in groundwater in the Red River Delta, Vietnam." VIETNAM JOURNAL OF EARTH SCIENCES 42, no. 2 (May 9, 2020): 161–75. http://dx.doi.org/10.15625/0866-7187/42/2/14998.
Повний текст джерелаАнотація:
In the Red River Delta, the concentrations of Arsenic in groundwater of alluvial dominated systems are very high, exceeding the WHO’s permissible. The correlation between the Arsenic concentrations in groundwater and the age of Holocene sediment as a key controlling groundwater Arsenic concentration in the Red River delta has been investigated. The evolution of sediments in the Holocene is closely related to paleo-riverbed migration in the past. A combination of methods is implemented including remote sensing, multi-electrode profiling (MEP), gamma-logging, drilling, soil sample and groundwater modeling. The resul has identified the shape, sediment compositions and location of the six paleo-riverbed periods. The age of the paleo-riverbed is determined by drilling, soil sampling and optically stimulated luminescence (OSL) in the laboratory. The oldest sediments is 5.9±0.4 ka BP in Phung Thuong near the mountain, the youngest one is from 0.4÷0.6 ka BP in H-transect near the Red River and the rest of the other is around 3.5 ka BP. The modeling results by using MODFLOW and MT3D show that the dynamics of paleo-riverbeds controlling Arsenic mobilization in groundwater in the Red River Delta. When the river moved to another position, the current river position at that time was filled with younger sediments and became paleo-riverbed formation with reducing conditions, Arsenic content which was adsorbed in the previous stage then released into groundwater. Therefore, Arsenic concentration in groundwater of young Holocene sediments is higher than in older ones which elucidates that paleo-riverbed migration controls on Arsenic mobilization in groundwater in the study area.
Дисертації з теми "Groundwater – Arsenic content – Vermont"
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Uddin, G. M. Saleh. "Groundwater contamination by arsenic in Bangladesh : causes, consequences and solutions." Title page, table of contents and abstract only, 2001. http://web4.library.adelaide.edu.au/theses/09ENV/09envu18.pdf.
Повний текст джерела
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Choudhury, Zubaida Akhtar. "Groundwater arsenic pollution in Bangladesh : a study of water consumption behaviour and decision-making processes within rural communities." Thesis, University of Cambridge, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.610220.
Повний текст джерела
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Ferreira, Gabriela Ribeiro de Sena. "Arsenic Mobilization from Silicic Volcanic Rocks in the Southern Willamette Valley." PDXScholar, 2016. http://pdxscholar.library.pdx.edu/open_access_etds/2752.
Повний текст джерелаАнотація:
Volcanic tuffs and tuffaceous sediments are frequently associated with elevated As groundwater concentrations even though their bulk As contents (~ 5 mg kg-1; Savoie, 2013) are only marginally greater than the average crustal abundance of 4.8 mg g-1 (Rudnick & Gao, 2003). Thus, As mobilization must be facilitated by conditions particular to these rocks. Alkaline desorption, anionic competition, reactive glass dissolution, and reductive dissolution of iron oxides are proposed processes of As release from volcanic rocks. Geogenic As contamination of groundwater in the southern Willamette Valley in western Oregon has been well-documented since the early 1960s, and previous studies have identified the Little Butte Volcanics Series and Fisher and Eugene Formations as the source of As contamination.
This study examines 19 samples from 10 units of ash flow tuffs and tuffaceous sediments within the Fisher Formation and Little Butte Volcanics Series, representing a range of weathering and devitrification, to determine conditions of mobilization and mineralogical constraints that control As release into solution. Leachate studies were conducted over a range of pH from 7 to 11, phosphate concentrations from 10 μM to 100 mM, and in time series from 4 to 196 hours. Results demonstrate that silicic volcanic tuffs are capable of mobilizing As in concentrations above regulatory limits at pH conditions produced naturally by the tuffs (pH 8-9) or with moderate concentrations of P (10-100 μM). Alteration products, e.g. zeolites and clays, appear to be the primary host phases for mobile As. Samples that do not contain these alteration products tend to produce concentrations of As well below regulatory limits and often below the instrument detection limits of this study. The type of alteration may influence As mobilization: tuffs containing more clays tend to mobilize As through surficial desorption, and tuffs containing more zeolites tend to mobilize As by dissolution or formation of colloids. Additionally, one volcaniclastic sample demonstrates that extremely elevated concentrations of As, up to 1000 μg/L are possible as a result of oxidative dissolution of As-bearing sulfide phases.
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CHENG, PEI-CHENG, and 程培正. "Arsenic Content in Arsenic-enriched Soil Crops and Methods for Reducing Arsenic in Groundwater." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/a526vx.
Повний текст джерелаАнотація:
碩士朝陽科技大學
環境工程與管理系
106
According to the EPA survey, most of the main causes of arsenic pollution in agricultural land in China are caused by long-term arsenic-based groundwater irrigation. The pollution range is mainly distributed in the Lanyang Plain, the Zhuoshuixi Alluvial Fan, the Jianan Plain and the Pingtung Plain, covering a wide area. In the face of so many arsenic-rich agricultural land caused by geological factors, the cost of rectification is quite large. If the geological factors are not improved, the safety of planting edible vegetables in arsenic-rich soils needs to be evaluated. Biochar has the function of changing soil properties and carbon sequestration, and is agronomic material that is currently actively promoted in agriculture and environmental protection. In this study, biochar was prepared from agricultural waste rice husks, and biochar was applied at a weight ratio of 0%, 5%, 10%, and 15% to investigate the effect of biochar application on the absorption of arsenic in vegetable crops. In addition, reducing the arsenic concentration of irrigation water can slow down the accumulation rate of arsenic concentration in agricultural land. In this study, twelve kinds of materials were selected for the adsorption test of arsenic-rich aqueous solution, and the adsorption capacity of different materials for arsenic was explored, thereby developing a treatment technology for reducing arsenic in irrigation water. The results showed that in addition to hydroponic water, the application of biochar in the other five experimental vegetable crops could increase the yield, and the arsenic content of the edible parts of the five vegetable crops was lower than the white rice inorganic arsenic consumption limit published by the Ministry of Health and Welfare. Mg/kg, showing that arsenic-rich agricultural soils are planted with vegetable crops, and the cumulative concentration of arsenic in edible parts is not high. The arsenic content of water amaranth is much higher than that of the other five vegetable plants. It is recommended that arsenic-rich agricultural land should not plant aquatic food crops as much as possible. The application of biochar has a tendency to increase the arsenic concentration in the roots and shoots of crops. If phyto-contaminated soil is improved by phytoremediation, the application of biochar has the potential to accelerate the rate of arsenic removal. The ultra-deep-burning ceramsite made in Taiwan has a very high adsorption capacity for arsenic in both bulk and powder form. For 0.25-1.0 ppm arsenic aqueous solution, the arsenic removal efficiency can reach more than 99%. The self-prepared calcium chloride modified biochar can also remove more than 60% of arsenic. In the future, it can continue to explore its feasibility as an arsenic removal technology for irrigation water.
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Teclu, Daniel Ghebreyo. "Bioremediation of arsenic contaminated groundwater." Thesis, 2008. http://hdl.handle.net/10413/342.
Повний текст джерелаАнотація:
Sulphate-reducing bacteria (SRB) mediate the reduction of metals/metalloids directly or indirectly. Bioremediation of arsenic contaminated water could be a cost-effective process provided a cheap carbon source is used. To this end, molasses was tested as a possible source of carbon for the growth of sulphate-reducing bacteria (SRB). Its chemical composition and the tolerance of SRB toward different arsenic species [As (III) and As (V)] were also investigated. Batch culture studies were carried out to assess 1, 2.5 and 5 g l-1 molasses as suitable concentrations for SRB growth. The results indicate that molasses does support SRB growth, the level of response being dependent on the concentration; however, growth on molasses was not as good as that obtained when lactate, the usual carbon source for SRB, was used. The molasses used in this study contained several metals including Al, As, Cu, Fe, Mn and Zn in concentrations ranging from 0.54-19.7 ìg g-1, but these levels were not toxic to the SRB. Arsenic tolerance, growth response and sulphate-reducing activity of the SRB were investigated using arsenite and arsenate solutions at final concentrations of 1, 5 and 20 mg l-1 for each species. The results revealed that very little SRB growth occurred at concentrations of 20 mg l-1 As (III) or As (V). At lower concentrations, the SRB grew better in As (V) than in As (III). Batch cultures of sulphate-reducing bacteria (SRB) in flasks containing pine bark, sand and polystyrene as support matrices and Postgate medium B were used to study formation of biofilms. The effects of the support matrices on the growth of the organisms were evaluated on the basis of pH and redox potential change and the levels of sulphide production and sulphate reduction. Characterisation of the matrix surfaces was done by means of environmental scanning electron microscopy (ESEM). A consortium of SRB growing on polystyrene caused a 49% of original sulphate reduction whereas on sand a 36% reduction occurred. Polystyrene was further examined for its durability as a long-term support material for the growing of SRB in the presence of As(III) and/or As(V) at concentrations of 1, 5 and 20 mg l-1. Both sulphate reduction and sulphide production were greater in this immobilised system than in the matrix-free control cultures. With pine bark as support matrix no significant sulphate reduction was observed. The kinetics of sulphate reduction by the immobilised cells were compared with those of planktonic SRB and found to be superior. The leaching of organic compounds, particularly phenolic substances, from the pine bark had a detrimental effect on the growth of the SRB. Different proportions of pine bark extract were used to prepare media to investigate this problem. Growth of SRB was totally inhibited when 100% pine bark extract was used. Analysis of these extracts showed the concentration of phenolics increased from 0.33 mg l-1 to 7.36 mg l-1 over the extraction interval of 15 min to 5 days. Digested samples of pine bark also showed the presence of heavy metals. The effects of nitrate, iron and sulphate and combinations thereof were investigated on the growth of a mixed culture of sulphate-reducing bacteria (SRB). The addition of 30 mg l-1 nitrate does not inhibit the production of sulphide by SRB when either 50 or 150 mg l-1 sulphate was present. The redox potential was decreased from 204 to -239 mV at the end of the 14 day batch experiment in the presence of 150 mg l-1 sulphate and 30 mg l-1 nitrate. The sulphate reduction activity of the SRB in the presence of 30 mg l-1 nitrate and 100 mg l-1 iron was about 42% of original sulphate, while if no iron was added, the reduction was only 34%. In the presence of 20 mg l-1 either As(III) or As(V), but particularly the former, growth of the SRB was inhibited when the cells were cultured in modified Postgate medium in the presence of 30 mg l-1 nitrate. The bioremoval of arsenic species [As(III) or As(V)] in the presence of mixed cultures of sulphate-reducing bacteria was investigated. During growth of a mixed SRB culture adapted to 0.1 mg l-1 arsenic species through repeated sub-culturing, 1 mg l-1 of either As(III) or As(V) was reduced to 0.3 and 0.13 mg l-1, respectively. Sorption experiments on the precipitate produced by batch cultured sulphate-reducing bacteria (SRB-PP) indicated a removal of about 77% and 55% of As(V) and As(III) respectively under the following conditions: pH 6.9; biomass (2 g l-1); 24 h contact time; initial arsenic concentration,1 mg l-1 of either species. These results were compared with synthetic iron sulphide as adsorbent. The adsorption data were fitted to Langmuir and Freundlich isotherms. Energy dispersive x-ray (EDX) analysis showed the SRB-PP contained elements such as sulphur, iron, calcium and phosphorus. Biosorption studies indicated that SRB cell pellets removed about 6.6% of the As(III) and 10.5% of the As(V) from water containing an initial concentration of 1 mg l-1 of either arsenic species after 24 h contact. Arsenic species were precipitated out of synthetic arsenic-contaminated groundwater by reacting it with the gaseous biogenic hydrogen sulphide generated during the growth of SRB. The percentage removal of arsenic species was dependent on the initial arsenic concentration present. Lastly, laboratory scale bioreactors were used to investigate the treatment of arsenic species contaminated synthetic groundwater. A mixed culture of SRB with molasses as a carbon source was immobilised on a polystyrene support matrix. The synthetic groundwater contained either As(III) or As(V) at concentrations of 20, 10, 5, 1 or 0.1 mg l-1 as well as 0.1 mg l-1 of a mixture with As(III) accounting for 20, 30, 40, 60 and 80% of the total. More that 90% and 60% of the As(V) and As(III) respectively were removed by the end of the 14-day experiment. At an initial concentration of 0.1 mg l-1 total arsenic had been reduced to below the WHO acceptable level of 10 ìg l-1 when the proportion of As(III) was 20 and 30%, while at 40% As(III) this level was reached only when the treatment time was increased to 21 days. The efficiency of As(III) removal was increased by first oxidising it to As(V) using MnO2.Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2008.
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Mozumder, Rajib Hassan. "Impacts of pumping on the distribution of arsenic in Bangladesh groundwater." Thesis, 2019. https://doi.org/10.7916/d8-1w98-7737.
Повний текст джерелаАнотація:
Chronic exposure to naturally occurring arsenic (As) in groundwater threatens the health of >150 million villagers in S/SE Asia. In Bangladesh, low As aquifers offer the best hope of reducing the exposure of 35-40 million remain exposed to elevated levels of As in drinking water (>10 μg/L). These low As aquifers could be affected, however, by massive pumping from shallow (<30 m) depths for growing rice and overexploitation of deeper aquifer for municipal water supply. The goal of this dissertation is to assess the impacts of groundwater pumping on the distribution in groundwater of dissolved As, reactive carbon, and redox-sensitive elements in anoxic aquifers of Bangladesh based on long-term hydrologic measurements, geochemical analyses, and numerical flow modeling.
In the second chapter, changes in the well-water As concentrations within a 25 sq. km area over a 10+ year timespan are assessed on the basis of continuous time series for 18 monitoring wells, a set of 271 wells resampled three times, and a large dataset obtained from blanket surveys of several thousand wells in the region. The two larger data sets both show a 10% decline in the initial areal mean As of 100 μg/L. This decline can be explained by flushing of As in the shallow aquifer by low-As recharge water, evidently compensated to some extent by the desorption of sediment-bound As. The presence of a large exchangeable pool of As in the sediment therefore seems to buffer changes in the distribution of As in the face of large perturbation in groundwater flow, albeit not enough to prevent some trends indicated by the detailed time series. The third chapter provides a complementary perspective on groundwater-sediment interactions by quantifying the rates of adsorption and desorption of As with column experiments conducted in the field for two different types of sediments: grey reduced Holocene sands and orange oxidized Pleistocene sands. The data show that, contrary to widely held beliefs, retardation of As transport by adsorption is quite similar in Holocene and Pleistocene sediments, even if Holocene sands initially contain a much larger pool of easily mobilizable As. The field column experiments also showed significant changes in solid phase speciation that affected As retention within a timespan of only a few weeks. Detailed field observations and flow modeling in the fourth chapter examine how perturbed flow paths can draw either As or reactive carbon into a Pleistocene aquifer. A groundwater flow model, constrained by head measurements and isotopic tracer data shows that certain portions of the aquifer are becoming increasingly contaminated with As as a result of municipal pumping, but against a background of redox transformation in the aquifer that probably preceded this perturbation.
Overall, the research conducted for this thesis shows that alteration of the hydrological system due to local and regional forcing is affecting the distribution of As in groundwater. These changes do not affect all wells yet and, if they do, the increase in As concentrations observed so far are gradual because of the buffering capacity of the sediment. Lowering exposure by targeting low As aquifer should therefore definitely continue in Bangladesh, with particular attention paid to regular monitoring using vulnerability criteria this research has helped to identify.
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Wovkulich, Karen. "Laboratory and Field Studies Directed toward Accelerating Arsenic Remediation at a Major US Superfund Site in New Jersey." Thesis, 2011. https://doi.org/10.7916/D87M0FXW.
Повний текст джерелаАнотація:
Arsenic is a prevalent contaminant at a large fraction of US Superfund sites. Therefore, establishing techniques for accelerating As remediation could benefit many contaminated sites. Remediation of As contaminated groundwater by conventional methods, i.e. pump and treat (P&T), can be impeded by slow desorption of As from Fe and Al (hydr)oxides in aquifer solids. Through experimentation at different physical scales (grain, bench, and field scale), the potential for chemical additions to increase As release from sediments and possibly accelerate P&T remediation is examined. The work described here focuses on As contamination and remediation at the Vineland Chemical Co. Superfund site in southern NJ. The site is extensively contaminated with As resulting from decades of poor chemical storage and disposal practices by the Vineland Chemical Co., which manufactured As-based biocides from 1949-1994. Despite significant intervention, including groundwater remediation by P&T and treatment of solids via soil washing, sufficient site clean up could require many decades with current technologies. Chemical amendments that either compete with As for sorption sites or dissolve Fe and Al (hydr)oxides can increase As mobility and potentially improve P&T remediation efficiency. Simple extrapolations from bench scale column experiments based on pore volumes suggest that treatment with 10 mM oxalic acid could lower the time necessary for clean up at the Vineland site from 600 years (with current techniques involving just groundwater) to potentially on the order of 4 years. Small scale (<1 mm2) X-ray fluorescence maps from columns performed within the synchrotron beamline showed As release during oxalic acid treatment that was consistent with the bulk column materials and suggested that microscale processes can be predictive of the larger system. Finally, during a 3-month pilot study at the Vineland site, oxalic acid was injected into a section of the aquifer via an injection manifold system that was designed and built for the experiment. Groundwater samples indicate that introduction of oxalic acid led to increased As release at a sampling well and pump and treat recovery well in the study area. Addition of oxalic acid shows promise for accelerating treatment of a highly contaminated site.
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"Potentially harmful trace elements (PHTEs) in the groundwater of Greater Giyani, Limpopo Province, South Africa: possible health implications." Thesis, 2015. http://hdl.handle.net/10210/15089.
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M.Sc. (Geology)Most rural communities in developing countries rely on borehole water as their only source of water. Since borehole water comes from underground, it is often considered pure and clean, but this is frequently not the case. Groundwater contains certain amounts of trace elements that may become deleterious to human health. The objectives of this investigation were to assess the concentration levels of Potential Harmful Trace Elements (PHTEs) and their spatial distribution patterns in borehole water in the Greater Giyani area of Limpopo, South Africa, and the potential human health risks associated with this. The method of research comprised two phases: (I) In the first phase, I assessed the occurrence and distribution patterns of PHTEs in the boreholes of the Giyani area. A total of 29 water samples were collected from boreholes (including 15 community boreholes and 14 primary school boreholes) in the Greater Giyani area during the dry season (July/August 2012), and for comparison another 27 samples (including 15 community boreholes and 12 schools boreholes) from the same localities during the wet season (March 2013). The samples were analysed for the trace elements arsenic (As), cadmium (Cd), chromium (Cr), selenium (Se) and lead (Pb) using the Inductively Coupled Plasma Mass-Spectrometry (ICPMS) technique. In order to assess the groundwater quality, PHTEs concentrations were compared with the South African National Standard of Drinking water (SANS 241-1:2011). (II) In the second phase, I evaluated the geographic variation between PHTEs and associated human health effects. This involved acquisition of data on a total of 100 cancer cases recorded during the period 2011-2014 at Nkhensani Hospital. ArcGIS Spatial analyst tool was used to create thematic maps illustrating spatial distribution of clinical data and arsenic concentrations in boreholes.
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Mon-LinChou and 周孟麟. "Impact of Arsenic-Rich Soil and Groundwater Productionof Selected Crops and Remediation Strategies forReducing Arsenic Content in Crops." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/81059740543713963443.
Повний текст джерелаАнотація:
博士國立成功大學
地球科學系
104
Arsenic (As), a toxic substance in the environment, is a major public health concern worldwide. High concentrations of As have also been linked to cancers of the nasal cavity, lung, liver, bladder, kidney, and prostate, and can lead to hypertension and diabetes. Peripheral vascular gangrene, also known as Blackfoot disease (BFD), was first reported in Chianan Plain of southwestern Taiwan in the 1960s. Since 1980, As-rich groundwater has no longer been consumed as drinking water in Taiwan, although it is still widely used for irrigation, aquacultural, and industrial purposes, and hence deserves our continued attention. Rice is the staple food for nearly one-half of world’s population including those living in Taiwan, China, Japan, Korea, and other Asian countries. However, rice uptakes As into grains are much more readily occurred than other cereal crops. The present study geochemically investigates As-rich groundwater, soil, and rice plants from paddy fields in Chianan Plain of southwestern Taiwan, an area which is mainly used for rice cultivation. The stable isotopes of oxygen-18 and deuterium were used to identify different sources of water in a soil layer in rice paddy during the rice growing season in 2014. This study can help us understand that the level of As in rice plants can be affected by the groundwater used for irrigation, type and concentration of As in the soil, and soil properties of paddy fields. In addition, experimental results by means of stable isotopes technique clarified the infiltration of rainfall in the complicated process that can be affected by soil structure, texture, moist and extent of heterogeneity. Results show that the total As concentrations in the groundwater used for irrigation of the sampled paddy fields at Hsuechia, Yichu, and Budai in the Chianan Plain are in the range of 32.9 to 175.7 μg L–1, which is higher than the permissible drink limit (10 μg L–1) recommended by the World Health Organization (WHO) and irrigation limit (50μg L–1) recommended by agricultural authorities of Taiwan. The percentages of As in different parts of the rice plants found in the current study are in the range of 88.3 to 92.8% in roots, 2.8 to 4% in shoots, 1.5 to 5.2% in leaves, 1 to 1.7% in husks, and 0.8 to 1.2% in grains. This study investigated the impacts of various types of irrigation practices with As-contaminated groundwater on the extent of As accumulation within rice plant parts during development and rice crop production at maturity. Three types of irrigation practices were applied to As-rich paddy fields: flooded irrigation, aerobic irrigation, and alternate wetting and drying irrigation (AWDI). Results show that the arsenic concentration in different parts of rice plants varied with growth stage and irrigation practices in both cropping seasons. Lower levels of As in rice were found in AWDI and aerobic irrigation than in flooded irrigation. Different irrigation practices can change the oxidation and reduction conditions of the paddy field, which lead to As release or absorption in the soil, thus influencing the uptake of As by plants. The chemical immobilization of As-rich soil by using ethylenediaminetetraacetic acid ferric sodium salt (EDTA-Fe) and calcium peroxide (CaO2) as stabilizing agents was investigated in Chianan Plain of southwestern Taiwan. The As-rich soil was amended with EDTA-Fe, at the rates of 0, 0.35, 0.7 and 1.4 Mg/ha, or with CaO2, at the rates of 0, 0.38, 0.76 and 1.52 Mg/ha, and grown with radish (Raphanus sativus L.), lettuce (Lactuca sativa), Chinese cabbage (Brassica rapa) and Arden lettuce (Lactuca sativa L.). Results showed that those amended with EDTA-Fe at 0.35 and 0.7 Mg ha−1 can significantly reduce As accumulation in vegetables. Moreover, the uptake of As in vegetables decreased more in soil amended with CaO2 relative to that amended with EDTA-Fe. As indicated, applications of EDTA-Fe at the rate of 0.7 Mg ha−1 and CaO2 at the rate of 1.52 Mg ha−1 can obtain optimal effect on suppressing As uptake by vegetables. Present study aimed to assess the presence and availability of As in paddy field of the Chianan Plain. Arsenic content was determined in soils and pore water sampled at 5 sampling depths (20, 40, 60, 80, 90 cm) in paddy field. The As concentrations in the experimental field soil varied slightly with sampling depths. Total As concentration positively and significantly (p 〈 0.05) correlated with the soil properties including free Fe (Fed), free Mn (Mnd), amorhous Fe (Feo), amorhous Mn (Mno), cation capacity exchange, and clay content. The sequential extraction of soil As showed that As was mainly fixed by both amorphous and crystalline Fe/Mn oxides, which may be ascribable to that As has a high affinity for Fe/Mn oxides under reduction regime of groundwater. As a consequence, As probably would become soluble due to the usage of groundwater and the change of redox regime. In addition, coarse texture of study soil, the flow path of irrigation water, and the gravity impact are factors affecting As movement in the soil layers. The soil As was concentrated on the surface soil and gradually decreased with soil depth. Therefore, total As in subsoils was lower than topsoil because As was adsorbed and accumulated by abundant Fe/Mn oxides in surface soil after irrigation. Based on the measured deuterium and oxygen-18 in soil water, rainwater and groundwater in the paddy field of the Chianan Plain of southwestern Taiwan, in the wet season, the relationship between δD and δ18O in soil water and groundwater recharge after typhoon rainfall (event water) was investigated in the present study. The soil water at different depths before and after event water varied in hydrogen and oxygen isotope ratios. The top soil layer (〈 30 cm depth) had more depleted isotopic compositions as a result of the higher rate of evaporation. Similar soil water isotope composition profiles were observed in shallow soil layers. More depleted fractions of isotopes were found in groundwater as those in rainwater, suggesting that the groundwater primarily came from the rainwater. However, the isotope compositions of hydrogen and oxygen in groundwater is still slightly deviated from the local meteoric water line in southwestern Taiwan. The proposed conceptual model for the interaction among soil, plant and arsenic in the study area can help understand the mechanism that arsenic was released in the subsurface environment. The remedial measure and strategy for reducing arsenic content in selected crops is also proposed in this research.
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Sun, Jing. "Developing Improved Strategies of Remediating Arsenic Contaminated Aquifers." Thesis, 2015. https://doi.org/10.7916/D8D50MPW.
Повний текст джерелаАнотація:
Groundwater arsenic contamination is currently a global problem, and also a concern at numerous former industrial sites, agricultural sites, landfill sites and mining operations in the U.S. This dissertation aims to develop improved strategies of remediating these arsenic contaminated aquifers. It focuses on two distinct approaches of remediation: (1) mobilizing arsenic from contaminated aquifer sediments to decrease the quantity of arsenic at the source of contamination; and (2) immobilizing arsenic in situ, to decrease the mobility and bioavailability of this arsenic. Optimal remediation may well involve combinations of these two approaches.
Arsenic mobilization using oxalic acid is effective because oxalic acid dissolves arsenic host minerals and competes for sorption sites on those minerals. In this dissertation, oxalic acid treatment was tested using sediments with contrasting iron mineralogies and arsenic contents from the Dover Municipal Landfill and the Vineland Chemical Company Superfund sites. Oxalic acid mobilized arsenic from both sites and the residual sediment arsenic was less vulnerable to microbial reduction than before the treatment. Oxalic acid thus could improve the efficiency of widely used pump-and-treat remediation. Oxalic acid did not remove all of the reactive iron(III) minerals in Vineland sediment samples, and thus released significant quantities of arsenic into solution under reducing conditions than the Dover samples. Therefore, the efficacy of pump-and-treat must consider iron mineralogy when evaluating its overall potential for remediating groundwater arsenic.
Arsenic immobilization occurs by changing the chemical state, or speciation, of arsenic and other elements in the system. Arsenic is often assumed to be immobile in sulfidic environments. In this dissertation, sulfate reduction was stimulated in sediments from the Vineland Superfund site and the Coeur d'Alene mining district. Sulfate reduction in the Coeur d'Alene sediments was more effective at removing arsenic from solution than the Vineland sediments. The Vineland sediments initially contained abundant reactive ferrihydrite, and underwent extensive sulfur cycling during incubation. As a result, arsenic in the Vineland sediments could not be effectively converted to immobile arsenic-bearing sulfides, but instead a part of the arsenic was probably converted to soluble thioarsenates. Therefore, coupling between the iron and sulfur redox cycles must be fully understood for arsenic immobilization by sulfate reduction to be successful.
Arsenic can also be immobilized by retention on magnetite (Fe3O4). Magnetite is stable under a wide range of aquifer conditions including both oxic and iron(III)-reducing environments. In this dissertation, a series of experiments were performed with sediments from the Dover and Vineland Superfund sites, to examine the potential of magnetite for use in arsenic immobilization. Our data suggest that the formation of magnetite can be achieved by the microbial oxidation of ferrous iron with nitrate. Magnetite can incorporate arsenic into its structure during formation, forming a stable arsenic sink. Magnetite, once formed, can also immobilize arsenic by surface adsorption, and thus serve as a reactive filter when contaminated groundwater migrates through the treatment zone. Reactive transport modeling is used for investigating the magnetite based arsenic immobilization strategy and for scaling laboratory results to field environments. Such modeling suggests that the ratio between iron(II) and nitrate in the injectant regulates the formations of magnetite and ferrihydrite, and thus regulates the long-term evolution of the effectiveness of the strategy. The results from field-scale models favor scenarios that rely on the chromatographic mixing of iron(II) and nitrate after injection.
The studies in this dissertation demonstrate that the environmental fate of arsenic depends on the biogeochemical cycling of arsenic, iron, and to a lesser extent, sulfur. The development of effective groundwater arsenic remediation strategies depends on a good understanding of each of the involved processes, and their combinations.
Книги з теми "Groundwater – Arsenic content – Vermont"
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De, Sirshendu. Arsenic removal from contaminated groundwater. New Delhi: The Energy Resources Institute, 2012.
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H, Welch Alan, and Stollenwerk Kenneth G, eds. Arsenic in ground water. Boston: Kluwer Academic Publishers, 2003.
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3
Abul, Khair. A study on development of an arsenic test kit and some arsenic contamination issues. Dhaka: ITN-Bangladesh, 2003.
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4
Farhana, Sultana, Mannan Fatema, and Bangladesh. Arsenic Policy Support Unit., eds. Selected papers on the social aspects of arsenic and arsenic mitigation in Bangladesh. Dhaka: Arsenic Policy Support Unit, 2006.
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5
Jalila, Ābadula. Effectiveness of alum in removing arsenic from groundwater. Dhaka: International Training Network Centre, BUET, 2007.
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6
Bibhāga, Bangladesh Sthānīẏa Sarakāra. Situation analysis of arsenic mitigation, 2009. Dhaka: Local Government Division, Govt. of Bangladesh, 2010.
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7
Deshpande, Leena S., 1963- , joint author, ed. Arsenic in aquatic environment. Delhi: Daya Pub. House, 2010.
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8
Arsenic in ground water, the hidden catastrophe: A comprehensive review, Bangladesh perspective. Dhaka: Md. Azizur Rahman, 2004.
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9
Peryea, Frank J. Leaching of lead and arsenic in soils contaminated with lead arsenate pesticide residues. Wenatchee, Wash: Tree Fruit Research and Extension Center, Washington State University, 1989.
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10
Andrews, William J. Pilot study of natural attenuation of arsenic in well water discharged to the Little River above Lake Thunderbird, Norman, Oklahoma, 2012. Reston, Va: U.S. Department of the Interior, U.S. Geological Survey, 2013.
Знайти повний текст джерелаЧастини книг з теми "Groundwater – Arsenic content – Vermont"
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Chandrasekhar, V., A. Joshi, and D. Chandrasekharam. "Arsenic content in groundwater and soils of Ballia, Uttar Pradesh." In Water-Rock Interaction. Taylor & Francis, 2007. http://dx.doi.org/10.1201/noe0415451369.ch212.
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Chowdhury, Subhashis, Souvik Chakraborty, and Rajashree Lodh. "Analysis of Rainwater Harvesting Method for Supply of Potable Water: A Case Study of Gosaba, South 24 Pargana, India." In Advances in Green Electronics Technologies [Working Title]. IntechOpen, 2022. http://dx.doi.org/10.5772/intechopen.106537.
Повний текст джерелаАнотація:
In Gosaba, a village on the outskirts of South 24 Parganas, West Bengal, India, people experience a lot of problems related to shortage of potable water due to salinity and arsenic contamination in the supplied water. Rapid growth of industrialization, increased population, saline water intrusion etc. is causing a decrease in fresh water. Due to overuse of groundwater, GWT is declining rapidly in the Gosaba region. Moreover, seawater is intruding into the groundwater, causing pollution of surface water and a rise in Fe content, Cl content, arsenic content and salinity content in groundwater of that location. The runoff available from that amount of received precipitation is estimated using two empirical equations derived by Sir Aiexander Binnie; Ingels-De Souza and T.G. Barlow and the calculation confirms a good amount of runoff that can be utilized for harvesting in order to decrease the water scarcity of the location. The scarcity of fresh water in the Gosaba location can be minimized by adopting the rainwater harvesting (RWH) method, a sustainable process to obtain disinfected water at a very low cost. The technical part of the present study is to adopt RWH where rainwater is collected from rooftop of an institute building and to design tank where water can be stored and utilized further at minimum costs.