Computational analysis of turbulence enhancement in a compression ignition engine with modified inlet design

Environmental Science and Pollution Research - This study aims to enhance the turbulence of direct injection (DI) diesel engine by modifying the inlet manifold design with an inclined nozzle-like...     

Titanium dioxide nanoparticles induce bacterial membrane rupture by reactive oxygen species generation

Nano-titania is widely used in the food industry due to its efficient antimicrobial activity. However, the mechanism of microbial toxicity of nano-titania is poorly known. Here, nano-TiO₂ has been fabricated by microwave-irradiation chemistry, a new method, and then tested for antimicrobial activity. Mutagenicity of nano-TiO₂ was evaluated using Salmonella typhimurium histidine-auxotrophic strains. The reactive oxygen generation test was performed using 2,7-dichlorofluorescein diacetate dye. To test membrane permeabilization, E. coli cultures were grown in nutrient broth at an optical density of 0.3–0.5 at 610 nm, harvested by centrifugation at 11,000g for 10 min, washed and resuspended in 0.5 % NaCl solution. We also analyzed superoxide formation and membrane integrity, and we used scanning electron microscopy. Results show that nano-TiO₂ has a minimum inhibitory concentration of 15 µg/mL, and a minimum bactericidal concentration of 20 µg/mL for E. coli. The bacterial inner wall was ruptured, and cytoplasmic content was released after 5 min of treatment in a dose-dependent manner. Notably, superoxide formation was not observed, which establishes the fact that reactive oxygen generation and alteration of membrane integrity, as well as permeability, is the major mechanism of antimicrobial activity of nano-TiO₂.     

Lithological and hydrochemical controls on distribution and speciation of uranium in groundwaters of hard-rock granitic aquifers of Madurai District,Tamil Nadu (India)

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.     

Taxonomy of groundwater quality using multivariate and spatial analyses in the Tuticorin District,Tamil Nadu,India

A holistic appraisal of the quality of groundwater from the Tuticorin District has been conducted using multivariate statistical and spatial analyses. The objectives of the study were to delineate the spatial and temporal variabilities in groundwater quality and to understand its suitability for human uses. A total of 100 groundwater samples were collected and analyzed for major cations and anions during pre-monsoon and post-monsoon. Water quality index rating was calculated to quantify overall water quality for human consumption. The PRM samples exhibit poor quality in greater percentage when compared with POM due to the dilution after rainfall. Correlation, factor analysis, and plot of the factor scores reflect the seawater intrusion and weathering process. The mineral stability diagrams indicated that the groundwater is in equilibrium with kaolinite and Ca-montmorillonite, whereas Gibbs plot showed that the chemical composition of groundwater in both districts is controlled by the natural weathering processes irrespective of seasons. The major water type identified in this study is the Ca²⁺–Mg²⁺–HCO₃ ^? type, which degrades into predominantly Na⁺–Cl^?–SO₄ ^2? more saline groundwater toward the coast.     

Applications of nanotechnology in agriculture and water quality management

Due to their small size and unique physico-chemical characteristics, nanomaterials have gained importance in the agri-food sector, notably in preservation and packaging. Future applications will focus on shelf life, food quality, safety, fortification and biosensors for contaminated or spoiled food, irrigating water and drinking water. Different types and shapes of nanomaterials are being used depending upon the needs and nature of the work in agriculture and water quality management. Here we review the application of nanotechnology in agriculture. The major points discussed are: (1) Nanomaterials for agriculture and water quality management. (2) Research interests such as nanoscale carriers, fabricated xylem vessels, nanolignocellulosic materials, clay nanotubes, photocatalysis, bioremediation of resistant pesticides, disinfectants, agricultural wastewater treatment, nanobarcode technology, quantum dots for staining bacteria and nanobiosensors. (3) Nanotechnological applications for agriculture, which includes nanolignodynamic metallic particles, photocatalysis, desalination, removal of heavy metals and wireless nanosensors.     

A study on evaluation of probable sources of heavy metal pollution in groundwater of Kalpakkam region, South India

This study investigates the heavy metal pollution vulnerability of the groundwater in the coastal aquifers of Kalpakkam region in the state of Tamilnadu, India. Integrated-approach includes pollution evaluation indices, principal component analysis (PCA), and correlation matrix (CM) to evaluate the intensity and source of pollution in groundwater. The data have been used for the calculation of heavy metal pollution index (HPI) and degree of contamination (C _d). The mean metal levels in groundwater followed a descending order as: Zn?>?Ba?>?Fe?>?Al?>?Se?>?Mn?>?Cu?>?Ni?>?Pb?>?Cr?>?Mo?>?As?>?Cd?>?Sb?>?Be. The concentrations of Fe, Cd, Zn, Se, Ba, Mn, Ni, Pb, and Al in some of the groundwater samples exceed the maximum admissible concentration (MAC). The HPI and C _d yield different results despite significant correlations between them. The following elemental associations were obtained from PCA and CM: Fe?CMn?CNi?CCr?CPb?CCd?CZn?CBe?CAl, Cu?CAs, Sb?CAs, Al?CBa and Se?CMo, which could be linked to anthropogenic sources (i.e., processes of tannery and dying industries with some contribution from the landfill leachate and municipal sewage). GIS-based factor score maps suggest that the activities of tannery industries and landfill leachate are pervasive processes in the area. This study has provided the evidence that effluents discharged from the tannery and auxiliary industries and landfill leachate are the main sources of heavy metal pollution in the groundwater. The high metal concentrations observed in the groundwater may have serious public health and potential environmental hazard implications.     

Three-phase partitioning for the separation of proteins,enzymes, biopolymers,oils and pigments: a review

Environmental Chemistry Letters - Modern biomass and organic waste are becoming major, carbon-neutral sources of fine chemicals, biomolecules and fuels to replace fossil fuel products. As a...     

A study on mountain front recharge by using integrated techniques in the hard rock aquifers of southern India

Mountain front recharge (MFR) is the contribution of mountains to recharge the aquifers in the adjacent basins. The estimation of MFR is essential to obtain a detailed investigation of recharge of the groundwater at the mountain front. This study summarises the current understanding of recharge processes by comparing daily groundwater fluctuation to daily rainfall and identifies the recharge rates. The recharge rates vary with time due to difference in water table depth and travel time. Thus to understand the MFR along the foothills of Courtallam, a total of 14 surface water, rainwater and groundwater samples were collected and measured for stable isotopes. The isotopic data were used to investigate the recharge process and to identify the elevations to recharge. The study findings also suggest that predominantly rainfall along the foothills contributes recharge to the riparian zone (basin block region), whereas foothill regions receive recharge from rainfall over mountain block.     

Application of water quality index for groundwater quality assessment: Thirumanimuttar sub-basin, Tamilnadu, India

An attempt has been made to understand the hydrogeochemical parameters to develop water quality index in Thirumanimuttar sub-basin. A total of 148 groundwater samples were collected and analyzed for major cations and anions. The domination of cations and anions was in the order of Na>Mg>Ca>K for cations and Cl>HCO₃ >SO₄ in anions. The hydrogeochemical facies indicate alkalis (Na and K) exceed alkaline earths (Ca and Mg) and strong acids (Cl and SO₄) exceed weak acid (HCO₃). Water quality index rating was calculated to quantify overall water quality for human consumption. The PRM samples exhibit poor quality in greater percentage when compared with POM due to effective leaching of ions, over exploitation of groundwater, direct discharge of effluents and agricultural impact. The overlay of WQI with chloride and EC correspond to the same locations indicating the poor quality of groundwater in the study area. SAR, Na%, and TH were noted higher during both the seasons indicating most of the groundwater locations not suitable for irrigation purposes.     

Thermal co-reduction approach to vary size of silver nanoparticle: its microbial and cellular toxicology

In recent years, silver nanoparticles (AgNPs) have attracted considerable interest in the field of food, agriculture and pharmaceuticals mainly due to its antibacterial activity. AgNPs have also been reported to possess toxic behavior. The toxicological behavior of nanomaterials largely depends on its size and shape which ultimately depend on synthetic protocol. A systematic and detailed analysis for size variation of AgNP by thermal co-reduction approach and its efficacy toward microbial and cellular toxicological behavior is presented here. With the focus to explore the size-dependent toxicological variation, two different-sized NPs have been synthesized, i.e., 60 nm (Ag60) and 85 nm (Ag85). A detailed microbial toxicological evaluation has been performed by analyzing minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), diameter of inhibition zone (DIZ), growth kinetics (GrK), and death kinetics (DeK). Comparative cytotoxicological behavior was analyzed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. It has been concluded by this study that the size of AgNPs can be varied, by varying the concentration of reactants and temperature called as “thermal co-reduction” approach, which is one of the suitable approaches to meet the same. Also, the smaller AgNP has shown more microbial and cellular toxicity.