Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 10.018
Filtrar
1.
J Hazard Mater ; 421: 126709, 2022 01 05.
Artículo en Inglés | MEDLINE | ID: mdl-34315021

RESUMEN

Nanoscale zero-valent iron nanoparticles (nZVI) have been used for groundwater remediation and wastewater treatment due to their high reactivity, high adsorption capacity and nontoxicity. However, side reactions generally occur in tandem with the target contaminants removal process, resulting in poor electron selectivity (ES) of nZVI, and subsequently restricting its commercial application. Major efforts to increase ES of nZVI have been made in recent years. This review's objective is to provide a progress report on the significant developments in nZVI's ES during the past decade. Firstly, the definition of ES and its quantification approaches were documented, and the intrinsic (i.e. particle size, crystallinity, and surface area) and extrinsic factors (i.e. solutions pH, target contaminant concentration, and presence of co-contaminants) affecting the ES of nZVI were reported. The latest techniques for increasing ES were summarized in detail, with reference made to sulfidation, magnetization, carbon loading and other features. Then the mechanisms of those strategies for ES enhancement were described. Finally, some constructive suggestions on future research directions concerning nZVI's ES in the future were proposed.


Asunto(s)
Restauración y Remediación Ambiental , Agua Subterránea , Contaminantes Químicos del Agua , Purificación del Agua , Electrones , Hierro , Contaminantes Químicos del Agua/análisis
2.
J Hazard Mater ; 421: 126657, 2022 01 05.
Artículo en Inglés | MEDLINE | ID: mdl-34315023

RESUMEN

The study aims to prepare a novel low-cost and environmentally friendly adsorbent by using date pits (DP) impregnated with cellulose nanocrystals (CNCs) and ionic liquid (IL), named IL-CNC@DP. The batch adsorption of lithium onto IL-CNC@DP and DP were studied at different pH values, initial lithium concentrations, and temperatures. The thermodynamics constants of the adsorption process showed that the IL-CNC@DP was exothermic, did not favor a high level of disorder, and spontaneous in nature. At pH 6, there is a significant increase in the removal efficiency where it increased to 90%. This also could be explained by the fact that electrostatic attraction forces and hydrogen bonding existed between the protonated Li+ and the less protonated IL-CNC@DP adsorbent surface, which enhanced the percentage of Li+ removal. A strong inter- and intra-hydrogen bonding (O-H) stretching absorption is seen at 3311 cm-1 that occurs in cellulose components. In conclusion, the IL-CNC@DP in comparison to the DP confirmed exceptional results proving that the modification enhanced the remediation of the Li+ from water. Furthermore, the selectivity of IL-CNC@DP towards real groundwater samples isolated in Qatar depends upon the physicochemical characteristics of each element.


Asunto(s)
Agua Subterránea , Líquidos Iónicos , Nanopartículas , Adsorción , Celulosa , Iones , Litio
3.
J Hazard Mater ; 421: 126693, 2022 01 05.
Artículo en Inglés | MEDLINE | ID: mdl-34396957

RESUMEN

Researchers interested in a paper's statement or aiming to acquire useful information from scientific papers rely heavily on references. Additionally, calculation accuracy is important for ensuring the technical soundness of scientific papers. However, inaccurate citations and calculations are common in scientific literature. A recently published paper in the Journal of Hazardous Materials reported a study on microplastics in groundwater and surface water from coastal south India (Tamil Nadu state) and the heavy metal adsorption capacities of different polymers. In this study, we identified critical calculation errors and incorrect reference citations.


Asunto(s)
Agua Subterránea , Metales Pesados , Contaminantes Químicos del Agua , Monitoreo del Ambiente , India , Microplásticos , Plásticos , Agua , Contaminantes Químicos del Agua/análisis
4.
Environ Monit Assess ; 193(10): 689, 2021 Oct 02.
Artículo en Inglés | MEDLINE | ID: mdl-34601623

RESUMEN

The objective of this study was to evaluate the occurrence of pesticides in surface and groundwater of agricultural areas of the Pampas region of Argentina and to develop an ecological risk assessment (ERA) of pesticides in freshwater ecosystems. Eight agricultural sites from south Santa Fe province, in the north of the Pampas region, were sampled seven times between 2016 and 2018. Pesticides were analysed by gas chromatography-mass spectrometry (GC/MS) and liquid chromatography-mass spectrometry (UPLC-LC/MS). Twenty compounds among herbicides, insecticides and fungicides in 84% and 79% of groundwater and surface water samples, respectively, were detected. Atrazine was the most ubiquitous pesticide, following by metolachlor, acetochlor and glyphosate, with maximum concentrations of 28, 24, 77 and 111 µg/L, respectively. An ERA was performed by employing the risk quotient (RQ) method. Atrazine, azoxystrobin, pirimiphos-methyl, acetochlor and epoxiconazole posed a high and very high risk for aquatic organisms (RQ > 1) and glyphosate, metolachlor and 2,4-D exhibited negligible to medium risk. The herbicides were the major contributors to risk. This study is the first contribution on the presence and concentration of pesticides in surface and groundwater from agricultural areas of south Santa Fe province, north Pampas region, Argentina, and a starting point for pesticide ecological risk assessment.


Asunto(s)
Agua Subterránea , Plaguicidas , Contaminantes Químicos del Agua , Argentina , Ecosistema , Monitoreo del Ambiente , Plaguicidas/análisis , Medición de Riesgo , Contaminantes Químicos del Agua/análisis
5.
J Environ Sci (China) ; 110: 38-47, 2021 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-34593193

RESUMEN

To assess groundwater nitrate contamination and its human health risks, 489 unconfined groundwater samples were collected and analyzed from Zhangjiakou, northern China. The spatial distribution of principle hydrogeochemical results showed that the average concentrations of ions in descend order was HCO3-, SO42-, Na+, Ca2+, Cl-, NO3-, Mg2+ and K+, among which the NO3- concentrations were between 0.25 and 536.73 mg/L with an average of 29.72 mg/L. In total, 167 out of 489 samples (~ 34%) exceeded the recommended concentration of 20 mg/L in Quality Standard for Groundwater of China. The high NO3- concentration groundwater mainly located in the northern part and near the boundary of the two geomorphic units. As revealed by statistical analysis, the groundwater chemistry was more significantly affected by anthropogenic sources than by the geogenic sources. Moreover, human health risks of groundwater nitrate through oral and dermal exposure pathways were assessed by model, the results showed that about 60%, 50%, 32% and 26% of the area exceeded the acceptable level (total health index>1) for infants, children, adult males and females, respectively. The health risks for different groups of people varied significantly, ranked: infants> children> adult males>adult females, suggesting that younger people are more susceptible to nitrate contamination, while females are more resistant to nitrate contamination than males. To ensure the drinking water safety in Zhangjiakou and its downstream areas, proper management and treatment of groundwater will be necessary to avoid the health risks associated with nitrate contamination.


Asunto(s)
Agua Subterránea , Contaminantes Químicos del Agua , China , Monitoreo del Ambiente , Femenino , Humanos , Masculino , Nitratos/análisis , Medición de Riesgo , Contaminantes Químicos del Agua/análisis , Contaminantes Químicos del Agua/toxicidad
6.
Environ Monit Assess ; 193(11): 712, 2021 Oct 11.
Artículo en Inglés | MEDLINE | ID: mdl-34633550

RESUMEN

Groundwater quality assessment is an important measure to determine the usability of available water based on its physical, chemical, and bacteriological properties. In the present study, 10 physicochemical parameters have been considered for the groundwater quality assessment which include potential of hydrogen (pH), electrical conductivity (EC), total dissolved solids (TDS), sodium (Na+), potassium (K+), total hardness (TH), calcium (Ca2+), magnesium (Mg2+), bicarbonate (HCO3-), and chloride (Cl-). For the analysis, 21 samples for pre- and post-monsoon periods were collected from the wells/bore wells of five designated villages, Chinna Madina, Chittiyyapalem, Typuram, Rajam, and Neelakantapuram of the Butchayyapeta Mandal (sub-district) located in Visakhapatnam District, Andhra Pradesh, for the year 2017. The Bureau of Indian Standards (BIS 2012) has been used in this study to assess the suitability of the water for drinking. The water quality index (WQI) values derived by using WAI were categorized for various levels of water quality ranging from "excellent" to "unsuitable for drinking." To get the spatial distribution pattern, the WQI values of sample points were interpolated in the Arc GIS environment. The results indicated that water quality is good in the north-western parts of the current study area during pre- and post-monsoon seasons.


Asunto(s)
Agua Subterránea , Contaminantes Químicos del Agua , Monitoreo del Ambiente , Contaminantes Químicos del Agua/análisis , Calidad del Agua , Abastecimiento de Agua
7.
Ying Yong Sheng Tai Xue Bao ; 32(9): 3267-3276, 2021 Sep.
Artículo en Chino | MEDLINE | ID: mdl-34658213

RESUMEN

Groundwater, one of the important water resources, plays an important role in maintaining sustainable social and economic development. The ecological compensation of groundwater is a beneficial tool for guaranteeing reasonable exploitation and utilization of groundwater resources. However, there is a lack of associated studies, especially compensation budget. We proposed an integrated groundwater compensation standard model, which consisted of four components: base, stimulus and punishment, research and development, and potential risk. The priority level of compensation was estimated by considering regional climate and economic conditions comprehensively. The model was applied to a total of 11 cities in Shanxi Province to calculate the groundwater ecolo-gical compensation standard. The results showed that the base compensation accounted for the largest proportion in the total compensation, with the non-market value contributing more than 60%. Our results indicated that groundwater had a high regulated service value. From 2008 to 2017, the development coefficient of each city had significantly increased, suggesting the improved regional economic level and enhanced compensation capacity. Compensation priority was affected by the non-market value of groundwater and economic level, and obvious difference in the compensation priority existed in all the cities, implying the requirement for the implement of groundwater ecological compensation. Meanwhile, we suggested that groundwater risk compensation system should be improved, special funds should be set up for supporting research projects on groundwater ecological compensation, and long-term effective compensation mechanisms should be established.


Asunto(s)
Agua Subterránea , Ciudades , Compensación y Reparación , Recursos Hídricos
8.
Environ Monit Assess ; 193(11): 722, 2021 Oct 14.
Artículo en Inglés | MEDLINE | ID: mdl-34648078

RESUMEN

Declining levels of the water table in India have become a major concern, especially with climate change and burgeoning population compounding the problem and causing a perpetual state of water crisis. A better insight into the state of these precious resources is essential for their planned exploration and usage. This study introduces a novel machine learning ensemble model (ARZ ensemble), through an implementation of majority voting-based technique over its standalone classifier constituents, namely, Automatic Multilayer Perceptron (AutoMLP), random forest (RF), and ZeroR for undertaking the groundwater potential mapping for the Jabalpur district, Madhya Pradesh. Ten groundwater influencing factors (i.e., slope, rainfall, aspect, elevation, topographic wetness index, land use, lithology, distance from rivers, plan and profile curvature) and groundwater well locations from the study area were used to construct the spatial database. In order to validate the applicability of the proposed model, its performance was compared against a conventionally employed statistical method of Shannon's entropy (SE) model. The results revealed that the ARZ ensemble model (AUC: 0.8542) outperformed SE (AUC: 0.7639). The groundwater potential map revealed that approximately 4.18% of the region has very high groundwater potential, while 47.66% belongs to a low potential zone. Such information can hold solutions for a lot of the ailments afflicting these resources and can genuinely aid in the attempts to restore them to their natural state.


Asunto(s)
Monitoreo del Ambiente , Agua Subterránea , Aprendizaje Automático , Redes Neurales de la Computación , Ríos
9.
Environ Monit Assess ; 193(11): 714, 2021 Oct 12.
Artículo en Inglés | MEDLINE | ID: mdl-34637012

RESUMEN

This paper assesses the concentrations, spatial distribution, compositional patterns, and sources of polycyclic aromatic hydrocarbons (PAHs) in the dissolved aqueous phase along the Abou Ali River course. The 16 priority PAHs, listed by the USEPA, were investigated in surface- and groundwater samples for 2 years starting August 2015 and ending in March 2017. Statistical analysis was done by using the ANOVA test at p < 0.05. The spatial distribution analysis and illustration were done using the ARC GIS software. The total PAHs concentration in surface and groundwater samples varied between not detected to 15.162 ng mL-1 and not detected to 0.635 ng mL-1, respectively. The highest concentration of PAHs in surface water was observed at site S16, downstream of the river. However, the absence of PAHs was noticed at sites S1 and S2 of the upstream. The contamination levels of PAHs were found to be high in surface water samples, and low in groundwater samples. The 5- and 6-ring PAHs were the most abundant species among others in surface water samples, whereas the 3-ring PAHs were the most abundant in groundwater. Pyrogenic inputs deriving from fuel combustion, incineration, and miscellaneous burning were found to be the main PAH sources in surface and groundwater without ignoring the contribution of petrogenic inputs in some areas.


Asunto(s)
Agua Subterránea , Hidrocarburos Policíclicos Aromáticos , Contaminantes Químicos del Agua , Monitoreo del Ambiente , Líbano , Hidrocarburos Policíclicos Aromáticos/análisis , Contaminantes Químicos del Agua/análisis
10.
Environ Monit Assess ; 193(11): 718, 2021 Oct 13.
Artículo en Inglés | MEDLINE | ID: mdl-34642861

RESUMEN

The surface resistivity method was used to appraise the protectivity of hydrogeological units and corrosivity of the top soil in Obot Akara County, southern Nigeria. A total of 28 vertical electrical sounding (VES) was undertaken in the area using the Schlumberger electrode configuration. The results of the VES data interpretation reveal 3 to 4 geoelectric layers in the study area. The resistivity of the first layer interpreted as the Motley top soil ranges from 34.7 to 929.7 Ωm with a mean value of 381.1 Ωm. The third layer, with a resistivity range of 99.4 to 2716.7 Ωm, constitutes the aquifer unit in most communities in the area, with an average thickness of 58.3 m, while the fourth layer penetrated in most communities has a resistivity range of 216.1 to 1475.7 Ωm with a mean value of 657.5 Ωm. The longitudinal conductance and resistivity reflection coefficient of the aquifer protective layers vary from 0.04 to 0.76 mhos and - 0.74 to 0.93, respectively. Analysis of these results shows that 89.3% of the hydrogeological units in the area is weakly/poorly protected, 10.7% has moderate to good protection, while 85.7% of the top soil at the sounding stations is noncorrosive and 14.3% is slightly to moderately corrosive. The implication of these results is that most of the hydrogeological units in the area are likely prone to contamination in particular by some ferrugenized materials from the overlying layers. Also, underground metal storage tanks and galvanized and steel pipes can be buried in the topmost layer in most communities in the area without any risk of failure. Although these findings are very promising especially in groundwater management and exploitation in the area, hydrogeochemical and microbiological analyses of groundwater samples from available boreholes are recommended to corroborate the results.


Asunto(s)
Cáusticos , Agua Subterránea , Monitoreo del Ambiente , Sustancias Protectoras , Suelo
11.
Sci Total Environ ; 800: 150200, 2021 Dec 15.
Artículo en Inglés | MEDLINE | ID: mdl-34625279

RESUMEN

Increases in nitrogen applications to the land surface since the 1950s have led to a cascade of negative environmental impacts, including degradation of drinking water supplies, nutrient enrichment of aquatic ecosystems and contributions to global climate change. In this study, groundwater, streambed porewater, and stream sampling were used to establish trends in nitrate concentrations and how redox gradients influence nitrate transport across diverse glacial terranes. Decadal sampling has found that elevated nitrate concentrations in shallow groundwater beneath cropland have been sustained for decades. Redox gradients established in the saturated zone using dissolved O2, iron, nitrate and excess N2 from denitrification suggest that nitrate-bearing zones are thin in glacial terranes dominated by fine materials. These thin nitrate-bearing zones lead to suboxic, low nitrate streambed porewater and limit the contributions of nitrate to streams from slow-flow groundwater. In contrast, thick oxic zones in more coarse-grained glacial terranes allow nitrate to reach deeper groundwater, resulting in streambed porewater with elevated nitrate concentrations and causing a large portion of stream nitrate to be derived from slow-flow groundwater. Groundwater age tracer data indicate that denitrification occurs more quickly in the terrane dominated by fine material than in the more coarse-grained terrane. The quicker depletion of nitrate in the more fine-grained terrane suggests that the thinner oxic zone in this terrane is due, in part, to the greater availability and reactivity of electron donors in this terrane than in the more coarse-grained terrane. Groundwater age tracer data and hydrograph separation analysis suggest that saturated zone lag times between when changes in land use practices occur and when changes in stream water are fully observed may vary widely across hydrogeologic settings.


Asunto(s)
Agua Subterránea , Contaminantes Químicos del Agua , Ecosistema , Monitoreo del Ambiente , Nitratos/análisis , Oxidación-Reducción , Ríos , Contaminantes Químicos del Agua/análisis
12.
J Environ Sci (China) ; 109: 102-113, 2021 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-34607659

RESUMEN

Antibiotics are widely used in humans and animals, but their transformation from surface water to groundwater and the impact of land uses on them remain unclear. In this study, 14 antibiotics were systematically surveyed in a complex agricultural area in Central China. Results indicated that the selected antibiotic concentrations in surface waters were higher in winter (average: 32.7 ng/L) than in summer (average: 17.9 ng/L), while the seasonal variation in groundwaters showed an opposite trend (2.2 ng/L in dry winter vs. 8.0 ng/L in summer). Macrolides were the predominant antibiotics in this area, with a detected frequency of over 90%. A significant correlation between surface water and groundwater antibiotics was only observed in winter (R2 = 0.58). This study further confirmed the impact of land uses on these contaminants, with optimal buffer radii of 2500 m in winter and 500 m in summer. Risk assessment indicated that clarithromycin posed high risks in this area. Overall, this study identified the spatiotemporal variability of antibiotics in a typical agricultural area in Central China and revealed the impact of land uses on antibiotic pollution in aquatic environments.


Asunto(s)
Agua Subterránea , Contaminantes Químicos del Agua , Animales , Antibacterianos/análisis , China , Monitoreo del Ambiente , Humanos , Estaciones del Año , Agua , Contaminantes Químicos del Agua/análisis
13.
J Environ Sci (China) ; 109: 148-160, 2021 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-34607663

RESUMEN

Filamentous fungi can enter drinking water supply systems in various ways, and exist in suspended or sessile states which threatens the health of individuals by posing a high risk of invasive infections. In this study, the biofilms formation kinetics of the three genera of fungal spores, Aspergillus niger (A. niger), Penicillium polonicum (P. polonicum) and Trichoderma harzianum (T. harzianum) isolated from the groundwater were reported, as well as the effects of water quality parameters were evaluated. In addition, the efficiency of low- concentrations of chlorine-based disinfectants (chlorine, chlorine dioxide and chloramine) on controlling the formation of fungal biofilms was assessed. The results showed that the biofilms formation of the three genera of fungi could be divided into the following four phases: induction, exponential, stationary and sloughing off. The optimum conditions for fungal biofilms formation were found to be neutral or weakly acidic at 28 °C with rich nutrition. In fact, A. niger, P. polonicum, and T. harzianum were not observed to form mature biofilms in actual groundwater within 120 hr. Carbon was found to have the maximum effect on the fungal biofilms formation in actual groundwater, followed by nitrogen and phosphorus. The resistance of fungal species to disinfectants during the formation of biofilms decreased in the order: A. niger > T. harzianum > P. polonicum. Chlorine dioxide was observed to control the biofilms formation with maximum efficiency, followed by chlorine and chloramine. Consequently, the results of this study will provide a beneficial understanding for the formation and control of fungal biofilms.


Asunto(s)
Desinfectantes , Agua Subterránea , Penicillium , Purificación del Agua , Biopelículas , Cloro , Hongos , Humanos , Hypocreales , Cinética
14.
J Hazard Mater ; 416: 125935, 2021 08 15.
Artículo en Inglés | MEDLINE | ID: mdl-34492864

RESUMEN

Carbonaceous materials (CMs) have been applied extensively for enhancing the catalytic performance of environmental catalysts, however, the self-catalytic mechanism of CMs for groundwater remediation is rarely investigated. Herein, we unveiled the catalytic ability of various CMs via Fe(III) reduction through polyvinyl alcohol-coated calcium peroxide nanoparticles (PVA@nCP) for trichloroethylene (TCE) removal. Among selected CMs (graphite (G), biochar (BC) and activated carbon (AC)), BC and AC showed enhancement of TCE removal of 89% and 98% via both adsorption and catalytic degradation. BET and SEM analyses showed a higher adsorption capacity of AC (27.8%) than others. The generation of solution-Fe(II) and surface-Fe(II) revealed the reduction of Fe(III) on CMs-surface. The role of O-containing groups was investigated by the FTIR technique and XPS quantified the 52% and 57% surface-Fe(II) in BC and AC systems, respectively. EPR and quenching tests confirmed that both solution and surface-bound species (HO•, O2-• and 1O2) contributed to TCE degradation. Acidic pH condition encouraged TCE removal and the presence of HCO3- negatively affected TCE removal than other inorganic ions. Both schemes (PVA@nCP/Fe(III)/BC and PVA@nCP/Fe(III)/AC) exhibited promising results in the actual groundwater, surfactant-amended solution, and removal of other chlorinated-pollutants, opening a new direction towards green environmental remediation for prolonged benefits.


Asunto(s)
Agua Subterránea , Nanopartículas , Tricloroetileno , Contaminantes Químicos del Agua , Preparaciones de Acción Retardada , Compuestos Férricos , Oxidación-Reducción , Contaminantes Químicos del Agua/análisis
15.
J Hazard Mater ; 416: 126119, 2021 08 15.
Artículo en Inglés | MEDLINE | ID: mdl-34492914

RESUMEN

Sulfidized nanoscale zerovalent iron (SNZVI) with improved reactivity and selectivity has shown great potential for environmental remediation. However, it is unclear if SNZVI could be applied for the remediation of soil washing solution, and how a soil-washing surfactant affects the reactivity and selectivity of SNZVI. Here, we assess the impact of Triton X-100 (TX-100) on the reactivity and selectivity of a sulfidized commercial NZVI toward tetrabromobisphenol A (TBBPA). While sulfidation of NZVI improved its reactivity and electron efficiency toward TBBPA, TX-100 could further improve these promoting effects, which was 8-21 and 4-7 times higher than those without TX-100, respectively, depending on TX-100 concentration. Because TX-100 could induce the solubilization of TBBPA, sorb onto the SNZVI surface, and favor the subsequent sorption and degradation of TBBPA. SNZVI performance for successive treatments of TBBPA contaminated water was also greatly improved by TX-100. Moreover, washing the TBBPA-contaminated soil with TX-100 could efficiently extract the TBBPA, and almost all of the TBBPA in the soil washing solution could be efficiently degraded by SNZVI. These results suggest that TX-100 is a good additive to SNZVI for improving its performance, and SNZVI coupled with TX-100 can be a promising technology for the remediation of TBBPA-contaminated soil.


Asunto(s)
Agua Subterránea , Tricloroetileno , Contaminantes Químicos del Agua , Hierro , Octoxinol , Bifenilos Polibrominados , Suelo
16.
J Hazard Mater ; 416: 126170, 2021 08 15.
Artículo en Inglés | MEDLINE | ID: mdl-34492946

RESUMEN

Dissolved arsenic typically results from chemical weathering of arsenic rich sediments and is most often found in oxidized forms in surface water. The mobility of arsenic is controlled by its valence state and also by its association with iron oxides minerals, the forms of which are both influenced by abiotic and biotic processes in aqueous environment. In this study, speciation methods were used to measure and confirm the presence of reduced arsenic species in the surface water of Frenchman creek, a gaining stream that crosses the Colorado-Nebraska border. Selective extraction analysis of aquifer and stream bed sediments shows that the bulk of the arsenic occurs with labile iron-rich oxy(hydroxide) minerals. Total dissolved arsenic in surface and groundwater ranged from ~3-18 µg L-1, and reduced arsenic species comprise about 41% of the total dissolved arsenic (16.0 µg L-1) in Frenchman creek. Leachable arsenic in the aquifer sediment samples ranged up to 1553 µg kg-1, while samples from Frenchman creek bed sediments contained 4218 µg kg-1. Dynamic surface and groundwater interaction sustains arsenite in iron-rich surface headwaters, and the implied toxicity of reduced arsenic in this hydrogeological setting, which can be important in surface water environments around the globe.


Asunto(s)
Arsénico , Arsenitos , Agua Subterránea , Contaminantes Químicos del Agua , Arsénico/análisis , Monitoreo del Ambiente , Sedimentos Geológicos , Nebraska , Ríos , Contaminantes Químicos del Agua/análisis
17.
J Hazard Mater ; 416: 126197, 2021 08 15.
Artículo en Inglés | MEDLINE | ID: mdl-34492961

RESUMEN

This study aimed to investigate the removal performance and mechanisms of dexamethasone (DEX), a representative fluoroglucocorticoid (FGC), from micro-polluted oligotrophic groundwater in a bio-electrochemical system amended with polyaniline-loaded activated carbon (PANI@AC) as three-dimensional particle electrodes (BES-3D). The BES-3D achieved a DEX removal efficiency of 95.7%, which was 39.0% and 14.1% higher than that of a single biological system (SBIO) and two-dimensional bio-electrochemical system (BES-2D), respectively. The preliminary metabolic mechanism of defluorination accounted for 53.5%, 41.1%, and 16.3% in BES-3D, BES-2D, and SBIO, respectively, which was accompanied by demethylation, side-chain fracture, and hydroxyl oxidation for ketone formation and final-ring opening. The main mechanism by which removal was improved in BES-3D was the enrichment of functional microbes and enhancement of the expression of dehalogenation genes. The relative abundance of functional microbes with electron transfer ability and reductive dehalogenating genera, i.e., Pseudomonas, Methylotenera, Desulfuromonas, Sphingomonas, and Microbacterium, in BES-3D was 3.7-6.1 times higher and the copy number of functional genes was 1.9 times higher than those of SBIO, which contributed to the high DEX removal.


Asunto(s)
Carbón Orgánico , Agua Subterránea , Compuestos de Anilina , Electrodos
18.
J Hazard Mater ; 416: 126272, 2021 08 15.
Artículo en Inglés | MEDLINE | ID: mdl-34492998

RESUMEN

The fluctuation of the groundwater table can cause upward and downward advection of soil gas within the vadose zone, just like breathing. In this study, we developed a three-dimensional numerical model and used it to investigate the role of vadose zone breathing in vapor intrusion, through which subsurface volatile chemicals migrate into the concerned building at contaminated sites. The developed model was first applied to a sand tank experiment, followed by examining the influences of fluctuation amplitude and period of water table, soil textures, and groundwater level depth. Our results suggest that the indoor pollutant concentration can be increased by about three times with the oscillatory water table of 0.4 m amplitude and 4 d period. Within one cycle of vadose zone breathing, the indoor pollutant concentration is found to vary by about 7 orders of magnitude. The results also show that, compared to the groundwater level depth, the soil texture plays a significant role in determining vapor intrusion risks. Specifically, when soil particles increase from 0.25 mm to 0.44 mm, the indoor pollutant concentration tends to increase and becomes more sensitive to groundwater table fluctuation.


Asunto(s)
Agua Subterránea , Contaminantes del Suelo , Gases/análisis , Suelo , Contaminantes del Suelo/análisis
19.
Environ Monit Assess ; 193(10): 623, 2021 Sep 03.
Artículo en Inglés | MEDLINE | ID: mdl-34477949

RESUMEN

The aim of the study was to assess the status of groundwater quality of Owerri and environs, for drinking and irrigation purposes. Twenty-two (22) groundwater samples were collected and analyzed for both chemical and physical compositions. The result of the study showed that groundwater in the area is of good quality for drinking purposes, except for pH and Fe, which had higher concentrations in some areas. A weak correlation matrix within the sampled parameters of the groundwater was observed. Hydrogeochemical studies revealed that 91% of the samples are within the geochemical zone of 4 (strong acids (SO4 + Cl) exceed weak acids (CO3 + HCO3)), while 9% are of the geochemical zone of 3 (weak acids (CO3 + HCO3) exceed strong acids (SO4 + Cl)). The study shows an ionic trend of Cl- > Ca2+ > HCO3- > Na+ + K+ > Mg2+ > SO42- and hydrogeochemical facies of Na-Cl, Ca-Cl, Ca-CO3, Mg-Cl, and Mg-HCO3 of 45.5%, 36.4%, 4.5%, 4.5%, and 9.1% respectively. Chloro-alkaline values were negative except for B4 which was positive. The water quality index (WQI) revealed water quality status of excellent (4.5%), good (27.3%), poor (40.9%), and very poor (27.3%). Contamination factor (CF) reveals that the groundwater is slightly polluted while the pollution load index (PLI) revealed no noticeable pollution. Gibbs diagram revealed that the entire samples are within the rock dominance zone. Irrigation suitability studies showed that SAR of the groundwater was of excellent quality; %Na had good quality (27.3%), permissible quality (45.4%), and doubtful quality (27.3%); MH had 86.4% of the groundwater suitable, while 13.6% are not suitable; KR had suitable groundwater (59.1%) and unsuitable (40.9%); while the Wilcox diagram had 72.7% excellent water for irrigation and 27.3% permissible for irrigation. A routine check of groundwater in the study area is recommended.


Asunto(s)
Agua Subterránea , Contaminantes Químicos del Agua , Monitoreo del Ambiente , Facies , Humanos , Nigeria , Contaminantes Químicos del Agua/análisis , Calidad del Agua
20.
Environ Monit Assess ; 193(10): 644, 2021 Sep 13.
Artículo en Inglés | MEDLINE | ID: mdl-34514527

RESUMEN

Litho-geochemical characteristics of low and high fluoride (F-) groundwater along with hydrological processes were investigated to delineate its genesis and enrichment mechanism in a watershed sedimentary basin. In this study, groundwater F- concentration ranged from 0 to 20 mg/L with a mean and standard deviation of 2.8 and ± 3.7 mg/L, respectively. Out of N = 87, 63% of samples exceeded the World Health Organization (WHO) limit of 1.5 mg/L. The order of cationic and anionic dominance in groundwater samples with mean was found in decreasing order as Na+ > Mg2+ > Ca2+ > K+ and HCO3- > SO42- > Cl- > PO43- > NO3- measured in milligrams per liter. Groundwater chemistry changed from Ca-HCO3 to Na-HCO3 type and low to high fluoride as we moved from mountain foot towards the synclinal basin. Low fluoride groundwater reflected weathering, recharge, and reverse ion exchange processes with Ca-HCO3- and Ca-Mg-Cl-type water while high fluoride groundwater revealed base ion exchange, mixing, and desorption as dominant hydrological processes with Na-HCO3 and Na-Cl types of water. Gibb's diagram showed rock weathering and mineral dissolution as the major geochemical processes controlling water chemistry with an insignificant role of evaporation in the semi-arid area. Fluoride was undersaturated with mineral fluorite, indicating fluoride in groundwater is released by secondary minerals. However, due to complex geological features, groundwater fluoride enrichment was affected by a broad-scale process across a wide area such as depth, residence time, and most important geomorphological units hosting the aquifer.


Asunto(s)
Agua Subterránea , Contaminantes Químicos del Agua , Monitoreo del Ambiente , Fluoruros/análisis , Pakistán , Contaminantes Químicos del Agua/análisis
SELECCIÓN DE REFERENCIAS
DETALLE DE LA BÚSQUEDA
...