The effect of chemical reaction and variable viscosity on mixed convection heat and mass transfer for Hiemenz flow over a porous wedge plate was studied in the presence of heat radiation. The wall of the wedge was embedded in a uniform Darcian porous medium to allow for possible fluid wall suction or injection and had a power-law variation of both the wall temperature and concentration. The fluid was assumed to be viscous and incompressible. Numerical calculations were carried out for different values of dimensionless parameters and an analysis of the results obtained showed that the flow field was influenced appreciably by the buoyancy ratio between species, thermal diffusion and suction/injection at wall surface. The effects of these major parameters on the transport behaviours were investigated methodically and typical results illustrated to reveal the tendency of the solutions. Representative results are presented for the velocity, temperature, and concentration distributions. Comparisons with previously published works were performed and excellent agreement between the results were obtained. It is predicted that this research might prove to be useful for study of the movement of oil or gas and water through the reservoir of an oil or gas field, in the migration of underground water, in filtration, and water purification processes.
A study to determine the impact of leachate from operating and closed landfills into the surface water and groundwater systems in the state of Selangor was conducted in the year 2009. Groundwater was a major source of water for various uses in Selangor, Malaysia and was especially important for industrial purposes. The presence of high numbers of landfill sites was seen to have increased the risk of groundwater contamination. There were 20 landfill sites in the state of Selangor and seven of them were still operating and 13 closed. The landfills are classified into four categories, which were: (a) landfills operating at critical stages without controls to prevent pollution into the environment; (b) open dumpsites that have the capacity to continue to accept waste but needed to be upgraded to manage leachate and gas; (c) landfills that were closed but no safety closure plan was carried out; and (d) engineered landfills with up to date technologies. As most of the landfills were built prior to 1989, they were not subjected to the Environmental Impact Assessment requirements, hence, they were being poorly managed and were badly sited. The non-engineered sites had no proper pollution controls such as cover materials, liner materials, groundwater monitoring wells, leachate collection ponds and treatment, and methane gas collection pipes. This study revealed that the surface water and groundwater at and nearby the landfill sites were contaminated at various levels due to the landfill sites and operation. A comparison between the current quality of surface water and groundwater with their respective standards and background levels was carried out to survey the trend of the contamination. However, the limited financial resources hindered a very thorough investigation and restricted the number of samples collected and parameters analysed.
Evaluation of the hydrogeochemical processes governing the heavy metal distribution and the associated health risk is important in managing and protecting the health of freshwater resources. This study mainly focused on the health impacts due to the heavy metals pollution in a known Cretaceous-Tertiary (K/T) contact region (Tiruchinopoly, Tamilnadu) of peninsular India, using various pollution indices, statistical, and geochemical analyses. A total of 63 samples were collected from the hard rock aquifers and sedimentary formations during southwest monsoon and analysed for heavy metals, such as Li, Be, Al, Rb, Sr, Cs, Ba, pb, Mn, Fe, Cr, Zn, Ga, Cu, As, Ni, and Co. Ba was the dominant element that ranged from 441 to 42,638 μg/l in hard rock aquifers, whereas Zn was the major element in sedimentary formations, with concentrations that ranged from 44 to 118,281 μg/l. The concentrations of Fe, Ni, Cr, Al, Cr, and Ni fell above the permissible limit in both of the formations. However, the calculated heavy metal evaluation index (HEI), heavy metal pollution index (HPI), and the degree of contamination (Cd) parameters were higher in the sedimentary formation along the contact zone of the K/T boundary. Excessive health risks from consumption of contaminated groundwater were mostly confined to populations in the northern and southwestern regions of the study area. Carcinogenic risk assessment suggests that there are elevated risks of cancer due to prolonged consumption of untreated groundwater. Ba, Sr, and Zn were found to be geochemically highly mobile due to the partitioning between the rock matrix and groundwater, aided by the formation of soluble carbonato-complexes. Factor analysis indicates that the metals are mainly derived from the host rocks and anthropogenic inputs are relatively insignificant. Overall, this study indicated that groundwater in K/T contact zones is vulnerable to contamination because of the favorable geochemical factors. Long-term monitoring of such contact zones is required to avert the potential health hazards associated with consumption of the contaminated groundwater.
The presence of radioactive elements in groundwater results in high health risks on surrounding populations. Hence, a study was conducted in central Tamil Nadu, South India, to measure the radon levels in groundwater and determine the associated health risk. The study was conducted along the lithological contact of hard rock and sedimentary formation. The concentrations of uranium (U) varied from 0.28 to 84.65 µg/L, and the radioactivity of radon (Rn) varied from 258 to 7072 Bq/m3 in the collected groundwater samples. The spatial distribution of Rn in the study area showed that higher values were identified along the central and northern regions of the study area. The data also indicate that granitic and gneissic rocks are the major contributors to Rn in groundwater through U-enriched lithological zones. The radon levels in all samples were below the maximum concentration level, prescribed by Environmental Protection Agency. The effective dose levels for ingestion and inhalation were calculated according to parameters introduced by UNSCEAR and were found to be lesser (0.235-6.453 μSvy-1) than the recommended limit. Hence, the regional groundwater in the study area does not pose any health risks to consumers. The spatial distribution of Rn's effective dose level indicates the higher values were mainly in the central and northern portion of the study area consist of gneissic, quarzitic, and granitic rocks. The present study showed that Rn concentrations in groundwater depend on the lithology, structural attributes, the existence of uranium minerals in rocks, and the redox conditions. The results of this study provide information on the spatial distribution of Rn in the groundwater and its potential health risk in central Tamil Nadu, India. It is anticipated that these data will help policymakers to develop plans for management of drinking water resources in the region.
OBJECTIVES: To characterize the bacterial community of Wind Cave's Madison aquifer through whole-genome sequencing, and to better understand the bacterial ecology by identifying genes involved in acyl-homoserine lactone (AHL) based quorum-sensing (QS) systems.
RESULTS: Genome-based taxonomic classification revealed the microbial richness present in the pristine Madison aquifer. The strains were found to span eleven genera and fourteen species, of which eight had uncertain taxonomic classifications. The genomes of strains SD129 and SD340 were found to contain the archetypical AHL QS system composed of two genes, luxI and luxR. Surprisingly, the genomes of strains SD115, SD129, SD274 and SD316 were found to contain one to three luxR orphans (solos). Strain SD129, besides possessing an archetypical AHL QS luxI-luxR pair, also contained two luxR solos, while strain SD316 contained three LuxR solos and no luxI-luxR pairs. The ligand-binding domain of two LuxR solos, one each from strains SD129 and SD316, were found to contain novel substitutions not previously reported, thus may represent two LuxR orphans that detection and response to unknown self-produced signal(s), or to signal(s) produced by other organisms.
Groundwater is defined as water that exists underground in voids or gaps in sediments and is extracted for human consumption from aquifers. It is critical to our daily lives because it contributes to the sustainability of our natural ecosystem while also providing economic benefits. Heavy metals are metallic compounds with a relatively high atomic weight and density compared to water. In Malaysia, heavy metal contamination of groundwater has become a concern due to rapid population growth, economic development, and a lack of environmental awareness. Environmental factors or their behaviors, such as density, viscosity, or volume, affect the distribution and transportation of heavy metals. The article discusses the difficulties created by the presence of heavy metals in groundwater supplies and the resulting health problems. Additionally, remediation methods are discussed for managing contaminated water to preserve the ecological environment for current and future generations, as well as their advantages and disadvantages.
The current novel work presents the optimization of factors affecting defluoridation by Al doped ZnO nanoparticles using response surface methodology (RSM). Al doped ZnO nanoparticles were synthesized by the sol-gel method and validated by FTIR, XRD, TEM/EDS, TGA, BET, and particle size analysis. Moreover, a central composite design (CCD) was developed for the experimental study to know the interaction between Al doped ZnO adsorbent dosage, initial concentration of fluoride, and contact time on fluoride removal efficiency (response) and optimization of the process. Analysis of variance (ANOVA) was achieved to discover the importance of the individual and the effect of variables on the response. The model predicted that the response significantly correlated with the experimental response (R2 = 0.97). Among the factors, the effect of adsorbent dose and contact time was considered to have more influence on the response than the concentration. The optimized process parameters by RSM presented the adsorbent dosage: 0.005 g, initial concentration of fluoride: 1.5 g/L, and contact time: 5 min, respectively. Kinetic, isotherm, and thermodynamic studies were also investigated. The co-existing ions were also studied. These results demonstrated that Al doped ZnO could be a promising adsorbent for effective defluoridation for water.
The survey data on potential aquifer was collected at two sites located in Banggi Island (i.e. Laksian Primary School [LPS] and Padang Primary School [PPS]), Malaysia on 25 and 26 April 2013. Both locations are geologically surrounded by various types of lithologies, namely, sandstone, mudstone, siltstone, shale, chert, conglomerate, lignite, tuff, limestone, terrace sand, gravel and coral. The resistivity data consisted of six-line pole-dipole short arrays and were recorded in-situ using SAS 4000 ABEM Lund Imaging System, together with a relay switching unit (Electrode Selector ES 464), six multiconductor cables, steel rod electrodes and jumpers. The data, namely electrode spacing, depth of investigation, subsurface resistivity, type of material and horizontal data coverage were used to assess the characteristics of the potential aquifer. The recorded data were then processed using RES2DINV software to obtain 2-D inversion model of the subsurface. The data were also equipped with six models of inverse resistivity section for both areas. The data obtained can be used by the government and stakeholders for groundwater exploration and extraction in order to provide water supplies for local communities, especially since access to these resources from the surrounding water treatment plants on the island is limited.
Industrial, and municipal wastes are part of the main sources of environmental hazards as well as groundwater and surface water pollutions. If not well composed, treated, and safely disposed, it could permeate through the subsurface lithologies by reaching down to the underground water aquifers, particularly in zones of unprotected aquifer units. Pollutants, most especially the landfills leachates that encompassed organic contaminants, ammonia, nitrates, total nitrogen, suspended solids, heavy metals and soluble inorganic salts, i.e., soluble nitrogen, sulphur compound, sulphate and chlorides, could posed undesirable environmental impacts due to inappropriate disposals that may give rise to gaseous fumes and leachate formations. An electrical resistivity geophysical technique utilizing the RES2D no-invasive, cost-effective and rapid method of data collection was integrated with the 3D Oasis Montaj software to approximate the volume of the generated rectangular prism model of the contaminants delineated from mixtures of the industrial, and municipal wastes plumes to be 312,000 m 3.
The Transient Electro-Magnetic (TEM) geophysical technique was deployed to map and characterized the subsurface of Pahang River Basin along the East Coast Peninsula Malaysia. The data aimed at differentiating between the massive zones and the weak zones within the region, to also assess and differentiate the subsurface structures and comes up with recommendations for policy decision, formulation and plans on the flooding impact, surface water and groundwater managements, in addition to other environmental related issues ravaging the area. The data presented in this paper, showed the properties of the subsurface rocks underlain the region as beneficial to the Agriculturists; Climatologists; Engineers; Environmentalists; Geoscientists, Hydrologists and Policy formulation officers. The TEM data collection utilized a 100 m x 100 m single loop coil for both the Transmitter (Tx) loop and the Receiver (Rx) loop to produce a total surface area coverage of 10,000 m2 per survey line along a single profile. The total area covered in the data extended across an average area of 30 km x 40 km in parts of Maran, Temerloh and Jerantut districts, within the State of Pahang, East Coast, Peninsula Malaysia. The conductivity data recorded varied from -20 mS/m to about 440 mS/m at a maximum depth of about 375 m. On the other hand, the resistivity data recorded varied from 0 Oh-m to about 1000 Oh-m. The information derived from the data are intended for potential abstraction by the Malaysian Groundwater Management Board; the Department of Mineral and Geoscience; Department of Irrigation and Drainage; the Pahang State Water Board, and the Department of Agriculture.
The effect of unmanageable construction waste is an unstable land settlement and groundwater pollution. In addition to environmental pollution, construction waste could incur construction cost. The most construction waste is the material used at sites and tile is also a part of the waste generated in construction. The objectives of this study are to determine the tile waste generated in construction stages and linear regression analysis for the amount of tile waste generated. The method used in this study was the Linear Regression Model. The regression model established in the sample data reported an R2 value of 0.793; therefore, the model can predict approximately 79.3% of the factor (area) of tile waste generation. The linear regressions can be applied as tools to predict the tile waste generated at construction sites and help the contractor to track the sources of missing waste.
Generally, non-nutritive artificial sweeteners are widely utilized as sugar substitute in various applications. With various applications, non-nutritive artificial sweeteners are now being recognized as emerging contaminants with high water persistence and are chemically stable in environment. Although non-nutritive artificial sweeteners were documented on their occurrence in environment, yet their potential impacts to environment and human health remain ambiguous. Therefore, this review was prepared to provide a more comprehensive insight of non-nutritive artificial sweeteners in environment matrixes by highlighting special concerns on human health and environmental risks. Precisely, this review monitors the exploration of non-nutritive artificial sweeteners occurrences as an emerging contaminants in environment worldwide and their associated risks to human as well as environment. At present, there are a total of 24 non-nutritive artificial sweeteners' studies with regards to their occurrence in the environment from 38 locations globally, spanning across Europe including United Kingdoms, Canada, United States and Asia. Overall, the quantitative findings suggested that the occurrence of non-nutritive artificial sweeteners is present in surface water, tap water, groundwater, seawater, lakes and atmosphere. Among these environmental matrixes, surface water was found as the most studied matrix involving non-nutritive artificial sweeteners. However, findings on non-nutritive artificial sweeteners impacts on human health and environment are limited to understanding its overall potential impacts and risks. Additionally, this review also serves as a framework for future monitoring plans and environmental legislative to better control these emerging contaminants in environment.
In low concentration, fluoride is considered a necessary compound for human health. Exposure to high concentrations of fluoride is the reason for a serious disease called fluorosis. Fluorosis is categorized as Skeletal and Dental fluorosis. Several Asian countries, such as India, face contamination of water resources with fluoride. In this study, a comprehensive overview on fluoride contamination in Asian water resources has been presented. Since water contamination with fluoride in India is higher than other Asian countries, a separate section was dedicated to review published articles on fluoride contamination in this country. The status of health effects in Asian countries was another topic that was reviewed in this study. The effects of fluoride on human organs/systems such as urinary, renal, endocrine, gastrointestinal, cardiovascular, brain, and reproductive systems were another topic that was reviewed in this study. Different methods to remove fluoride from water such as reverse osmosis, electrocoagulation, nanofiltration, adsorption, ion-exchange and precipitation/coagulation were introduced in this study. Although several studies have been carried out on contamination of water resources with fluoride, the situation of water contamination with fluoride and newly developed technology to remove fluoride from water in Asian countries has not been reviewed. Therefore, this review is focused on these issues: 1) The status of fluoride contamination in Asian countries, 2) health effects of fluoride contamination in drinking water in Asia, and 3) the existing current technologies for defluoridation in Asia.
To evaluate the current status of arsenic exposure in the Mekong River basin of Cambodia, field interview along with urine sample collection was conducted in the arsenic-affected area of Kandal Province, Cambodia. Urine samples were analyzed for total arsenic concentrations by inductively coupled plasma mass spectrometry. As a result, arsenicosis patients (n = 127) had As in urine (UAs) ranging from 3.76 to 373 µg L(-1) (mean = 78.7 ± 69.8 µg L(-1); median = 60.2 µg L(-1)). Asymptomatic villagers (n = 108) had UAs ranging from 5.93 to 312 µg L(-1) (mean = 73.0 ± 52.2 µg L(-1); median = 60.5 µg L(-1)). About 24.7 % of all participants had UAs greater than 100 µg L(-1) which indicated a recent arsenic exposure. A survey found that females and adults were more likely to be diagnosed with skin sign of arsenicosis than males and children, respectively. Education level, age, gender, groundwater drinking period, residence time in the village and amount of water drunk per day may influence the incidence of skin signs of arsenicosis. This study suggests that residents in Kandal study area are currently at risk of arsenic although some mitigation has been implemented. More commitment should be made to address this public health concern in rural Cambodia.
Uranium is a radioactive element normally present in hexavalent form as U(VI) in solution and elevated levels in drinking water cause health hazards. Representative groundwater samples were collected from different litho-units in this region and were analyzed for total U and major and minor ions. Results indicate that the highest U concentration (113 µg l(-1)) was found in granitic terrains of this region and about 10 % of the samples exceed the permissible limit for drinking water. Among different species of U in aqueous media, carbonate complexes [UO2(CO3)(2)(2-)] are found to be dominant. Groundwater with higher U has higher pCO2 values, indicating weathering by bicarbonate ions resulting in preferential mobilization of U in groundwater. The major minerals uraninite and coffinite were found to be supersaturated and are likely to control the distribution of U in the study area. Nature of U in groundwater, the effects of lithology on hydrochemistry and factors controlling its distribution in hard rock aquifers of Madurai district are highlighted in this paper.
Microbes in groundwater play a key role in determining the drinking water quality of the water. The study aims to interpret the sources of microbes in groundwater and its relationship to geochemistry. The study was carried out by collecting groundwater samples and analyzed to obtain various cations and anions, where HCO3-, Cl- and NO3- found to be higher than permissible limits in few samples. Microbial analysis, like total coliform (TC), total viable counts (TVC), fecal coliforms (FC), Vibrio cholera (V. cholerae) and total Streptococci (T. streptococci) were analyzed, and the observations reveal that most of the samples were found to be above the permissible limits adopted by EU, BIS, WHO and USEPA standards. Correlation analysis shows good correlation between Mg2+-HCO3-, K+-NO3-, TVC- V. cholerae and T. streptococci-FC. Major ions like Mg+, K+, NO3, Ca2+ and PO4 along with TS and FC were identified to control the geochemical and microbial activities in the region. The magnesium hardness in the groundwater is inferred to influence the TVC and V. cholerae. The mixing of effluents from different sources reflected the association of Cl with TC. Population of microbes T. streptococci and FC was mainly associated with Ca and Cl content in groundwater, depicting the role of electron acceptors and donors. The sources of the microbial population were observed with respect to the land use pattern and the spatial distribution of hydrogeochemical factors in the region. The study inferred that highest microbial activity in the observed in the residential areas, cultivated regions and around the landfill sites due to the leaching of sewage water and fertilizers runoff into groundwater. The concentrations of ions and microbes were found to be above the permissible limits of drinking water quality standards. This may lead to the deterioration in the health of particular coastal region.
Monitoring the groundwater chemical composition and identifying the presence of pollutants is an integral part of any comprehensive groundwater management strategy. The present study was conducted in a part of West Tripura, northeast India, to investigate the presence and sources of trace metals in groundwater and the risk to human health due to direct ingestion of groundwater. Samples were collected from 68 locations twice a year from 2016 to 2018. Mixed Ca-Mg-HCO3, Ca-Cl and Ca-Mg-Cl were the main groundwater types. Hydrogeochemical methods showed groundwater mineralization due to (1) carbonate dissolution, (2) silicate weathering, (3) cation exchange processes and (4) anthropogenic sources. Occurrence of faecal coliforms increased in groundwater after monsoons. Nitrate and microbial contamination from wastewater infiltration were apparent. Iron, manganese, lead, cadmium and arsenic were above the drinking water limits prescribed by the Bureau of Indian Standards. Water quality index indicated 1.5% had poor, 8.7% had marginal, 16.2% had fair, 66.2% had good and 7.4% had excellent water quality. Correlation and principal component analysis reiterated the sources of major ions and trace metals identified from hydrogeochemical methods. Human exposure assessment suggests health risk due to high iron in groundwater. The presence of unsafe levels of trace metals in groundwater requires proper treatment measures before domestic use.
In recent times, surface water resource in the Western Region of Ghana has been found to be inadequate in supply and polluted by various anthropogenic activities. As a result of these problems, the demand for groundwater by the human populations in the peri-urban communities for domestic, municipal and irrigation purposes has increased without prior knowledge of its water quality. Water samples were collected from 14 public hand-dug wells during the rainy season in 2013 and investigated for total coliforms, Escherichia coli, mercury (Hg), arsenic (As), cadmium (Cd) and physicochemical parameters. Multivariate statistical analysis of the dataset and a linear stoichiometric plot of major ions were applied to group the water samples and to identify the main factors and sources of contamination. Hierarchal cluster analysis revealed four clusters from the hydrochemical variables (R-mode) and three clusters in the case of water samples (Q-mode) after z score standardization. Principal component analysis after a varimax rotation of the dataset indicated that the four factors extracted explained 93.3 % of the total variance, which highlighted salinity, toxic elements and hardness pollution as the dominant factors affecting groundwater quality. Cation exchange, mineral dissolution and silicate weathering influenced groundwater quality. The ranking order of major ions was Na(+) > Ca(2+) > K(+) > Mg(2+) and Cl(-) > SO4 (2-) > HCO3 (-). Based on piper plot and the hydrogeology of the study area, sodium chloride (86 %), sodium hydrogen carbonate and sodium carbonate (14 %) water types were identified. Although E. coli were absent in the water samples, 36 % of the wells contained total coliforms (Enterobacter species) which exceeded the WHO guidelines limit of zero colony-forming unit (CFU)/100 mL of drinking water. With the exception of Hg, the concentration of As and Cd in 79 and 43 % of the water samples exceeded the WHO guideline limits of 10 and 3 μg/L for drinking water, respectively. Reported values in some areas in Nigeria, Malaysia and USA indicated that the maximum concentration of Cd was low and As was high in this study. Health risk assessment of Cd, As and Hg based on average daily dose, hazard quotient and cancer risk was determined. In conclusion, multiple natural processes and anthropogenic activities from non-point sources contributed significantly to groundwater salinization, hardness, toxic element and microbiological contamination of the study area. The outcome of this study can be used as a baseline data to prioritize areas for future sustainable development of public wells.
In recent years, groundwater quality has become a global concern due to its effect on human life and natural ecosystems. To assess the groundwater quality in the Amol-Babol Plain, a total of 308 water samples were collected during wet and dry seasons in 2009. The samples were analysed for their physico-chemical and biological constituents. Multivariate statistical analysis and geostatistical techniques were applied to assess the spatial and temporal variabilities of groundwater quality and to identify the main factors and sources of contamination. Principal component analysis (PCA) revealed that seven factors explained around 75% of the total variance, which highlighted salinity, hardness and biological pollution as the dominant factors affecting the groundwater quality in the Plain. Two-way analysis of variance (ANOVA) was conducted on the dataset to evaluate the spatio-temporal variation. The results showed that there were no significant temporal variations between the two seasons, which explained the similarity between six component factors in dry and wet seasons based on the PCA results. There are also significant spatial differences (p > 0.05) of the parameters under study, including salinity, potassium, sulphate and dissolved oxygen in the plain. The least significant difference (LSD) test revealed that groundwater salinity in the eastern region is significantly different to the central and western side of the study area. Finally, multivariate analysis and geostatistical techniques were combined as an effective method for demonstrating the spatial structure of multivariate spatial data. It was concluded that multiple natural processes and anthropogenic activities were the main sources of groundwater salinization, hardness and microbiological contamination of the study area.
Nitrate concentration in groundwater is influenced by complex and interrelated variables, leading to great difficulty during the modeling process. The objectives of this study are (1) to evaluate the performance of two artificial intelligence (AI) techniques, namely artificial neural networks and support vector machine, in modeling groundwater nitrate concentration using scant input data, as well as (2) to assess the effect of data clustering as a pre-modeling technique on the developed models' performance. The AI models were developed using data from 22 municipal wells of the Gaza coastal aquifer in Palestine from 2000 to 2010. Results indicated high simulation performance, with the correlation coefficient and the mean average percentage error of the best model reaching 0.996 and 7 %, respectively. The variables that strongly influenced groundwater nitrate concentration were previous nitrate concentration, groundwater recharge, and on-ground nitrogen load of each land use land cover category in the well's vicinity. The results also demonstrated the merit of performing clustering of input data prior to the application of AI models. With their high performance and simplicity, the developed AI models can be effectively utilized to assess the effects of future management scenarios on groundwater nitrate concentration, leading to more reasonable groundwater resources management and decision-making.