Carbon nanotube-based nano-biosensors for detecting heavy metals in the aquatic environment

Environmental Science and Pollution Research - The identification of harmful metal ions in aquatic environments is a global concern since these contaminants can have serious consequences for...     

Correcting common misconceptions to inspire conservation action in urban environments

Despite repeated calls to action, proposals for urban conservation are often met with surprise or scepticism. There remains a pervasive narrative in policy, practice, and the public psyche that urban environments, although useful for engaging people with nature or providing ecosystem services, are of little conservation value. We argue that the tendency to overlook the conservation value of urban environments stems from misconceptions about the ability of native species to persist within cities and towns and that this, in turn, hinders effective conservation action. However, recent scientific evidence shows that these assumptions do not always hold. Although it is generally true that increasing the size, quality, and connectivity of habitat patches will improve the probability that a species can persist, the inverse is not that small, degraded, or fragmented habitats found in urban environments are worthless. In light of these findings we propose updated messages that guide and inspire researchers, practitioners, and decision makers to undertake conservation action in urban environments: consider small spaces, recognize unconventional habitats, test creative solutions, and use science to minimize the impacts of future urban development.     

Groundwater quality assessment of Nawa Tehsil in Nagaur district (Rajasthan) with special reference to Fluoride

In recent years, the problem of fluoride in Nawa tehsil (Nagaur district) has reached at an alarming proportion. In the last decades, the water table of the Nawa tehsil has fallen. With the lowering of the water table, the amount of fluoride has increased in the subsoil water which is used by the villagers when drawn through hand pumps, tube wells etc. So the present study illustrates the groundwater quality of randomly selected villages of Nawa tehsil. The highest fluoride concentration was found in Rulaniyo ki Dhani i.e. 14.62 ppm. The excessive intake of fluoride resulted in dental and skeletal fluorosis.     

Zeolite formation from coal fly ash and heavy metal ion removal characteristics of thus-obtained Zeolite X in multi-metal systems

Zeolitic materials have been prepared from coal fly ash as well as from a SiO₂–Al₂O₃ system upon NaOH fusion treatment, followed by subsequent hydrothermal processing at various NaOH concentrations and reaction times. During the preparation process, the starting material initially decomposed to an amorphous form, and the nucleation process of the zeolite began. The carbon content of the starting material influenced the formation of the zeolite by providing an active surface for nucleation. Zeolite A (Na-A) was transformed into zeolite X (Na-X) with increasing NaOH concentration and reaction time. The adsorption isotherms of the obtained Na-X based on the characteristics required to remove heavy ions such as Ni²⁺, Cu²⁺, Cd²⁺ and Pb²⁺ were examined in multi-metal systems. Thus obtained experimental data suggests that the Langmuir and Freundlich models are more accurate compared to the Dubinin–Kaganer–Radushkevich (DKR) model. However, the sorption energy obtained from the DKR model was helpful in elucidating the mechanism of the sorption process. Further, in going from a single- to multi-metal system, the degree of fitting for the Freundlich model compared with the Langmuir model was favored due to its basic assumption of a heterogeneity factor. The Extended-Langmuir model may be used in multi-metal systems, but gives a lower value for equilibrium sorption compared with the Langmuir model.     

Morphological and Thermal Characterization of Linseed-Oil Based Polymers from Cationic and Thermal Polymerization

Linseed oil-based polymers have been synthesized via cationic and thermal polymerization and characterized through various techniques, such as SEM, DMA, DSC and TGA. The morphology of the polymer samples after extraction reveals the smooth structure of the polymer matrix. With an increase in oil content, the morphology is observed to be more loosely bound. With an increase in linseed oil content in the samples, the room temperature storage modulus (E′) varies from 10.4 × 10⁷ to 1.8 × 10⁷ Pa. The glass transition temperatures measured through DMA of the cationic samples ranges from 70 to −6 °C and the crosslink densities range from 18.4 × 10³ to 3.4 × 10³ mol/m³. The glass transition temperatures of the thermal samples range from 106 to −4 °C and the crosslink densities range from 7.7 × 10³ to 2.4 × 10³ mol/m³. The TGA results show three stages of degradation of the polymer samples and it is also revealed that these polymers are stable up to 200 °C, showing negligible decomposition.     

Effects of multi-metal toxicity on the performance of sewage treatment system during the festival of colors (Holi) in India

The present study investigated the effects of heavy metals (Ni, Zn, Cd, Cu, and Pb) toxicity on the performance of 18 MLD activated sludge process-based sewage treatment plant (STP) during celebration of Holi (festival of colors in India). The composite sampling (n?=?32) was carried out during the entire study period. The findings show a significant decrease in chemical oxygen demand removal efficiency (20%) of activated sludge system, after receiving the heavy metals laden wastewater. A significant reduction of 40% and 60% were observed in MLVSS/MLSS ratio and specific oxygen uptake rate, which eventually led to a substantial decrease in biomass growth yield (from 0.54 to 0.17). The toxic effect of metals ions was also observed on protozoan population. Out of the 12 mixed liquor species recorded, only two ciliates species of Vorticella and Epistylis exhibited the greater tolerance against heavy metals toxicity. Furthermore, activated sludge shows the highest metal adsorption affinity for Cu, followed by Zn, Pb, Ni, and Cd (Cu?>?Zn?>?Pb?>?Ni?>?Cd). Finally, this study proves the robustness of activated sludge system against the sudden increase in heavy metal toxicity since it recovered the earlier good quality performance within 5?days.     

Organ-wise accumulation of fluoride in Prosopis juliflora and its potential for phytoremediation of fluoride contaminated soil

Fluoride (F) contamination is a global environmental problem, as there is no cure of fluorosis available yet. Prosopis juliflora is a leguminous perennial, phreatophyte tree, widely distributed in arid and semi-arid regions of world. It extensively grows in F endemic areas of Rajasthan (India) and has been known as a “green” solution to decontaminate cadmium, chromium and copper contaminated soils. This study aims to check the tolerance potential of P. juliflora to accumulate fluoride. For this work, P. juliflora seedlings were grown for 75 d on soilrite under five different concentrations of F viz., control, 25, 50, 75 and 100 mg NaF kg⁻¹. Organ-wise accumulation of F, bioaccumulation factor (BF), translocation factor (TF), growth ratio (GR) and F tolerance index (TI) were examined. Plant accumulated high amounts of F in roots. The organ-wise distribution showed an accumulation 4.41 mg kg⁻¹dw, 12.97 mg kg⁻¹dw and 16.75 mg kg⁻¹dw F, in stem, leaves and roots respectively. The results indicated significant translocation of F from root into aerial parts. The bioaccumulation and translocation factor values (>1.0) showed high accumulation efficiency and tolerance of P. juliflora to F. It is concluded that P. juliflora is a suitable candidate for phytoremediation purpose and can be explored further for the decontamination of F polluted soils.     

Phase behaviors,fuel properties,and combustion characteristics of alcohol-vegetable oil-diesel microemulsion fuels

Biofuels are being considered as alternatives to fossil-based fuels due to depletion of petroleum-based reserves and pollutant emission concerns. Vegetable oils and bioalcohols have proven to be viable alternative fuels both with and without engine modification. However, high viscosity and low energy content are long-term operational problems with vegetable oils and bioalcohols, respectively. Therefore, vegetable oil-based microemulsification is being evaluated as a method to reduce the high viscosity of vegetable oils and enhance the miscibility of alcohol and oil phases. Studies have shown that microemulsification with different alcohols lead to varying fuel properties depending on their structure. The overall goal of this study was to formulate microemulsion fuels with single and mixed alcohol systems by determining the effects of water content, alcohol branching structure and carbon chain length on phase behaviors, fuel properties, and emission characteristics. It was found that microemulsion fuels using certain alcohols displayed favorable stability, properties, and emission characteristics. Flames of fuels with linear short-chain-length alcohols had larger near-burner blue regions and lower CO and soot emissions indicating the occurrence of more complete combustion. In addition to alcohol effects, the effect of vegetable oils, surfactants, and additives on emission characteristics were insightful in pursuit of appropriate microemulsion fuels as cleaner burning alternatives to both No.2 diesel and canola biodiesel.     

Effect of compression ratio,nozzle opening pressure,engine load,and butanol addition on nanoparticle emissions from a non-road diesel engine

Currently, diesel engines are more preferred over gasoline engines due to their higher torque output and fuel economy. However, diesel engines confront major challenge of meeting the future stringent emission norms (especially soot particle emissions) while maintaining the same fuel economy. In this study, nanosize range soot particle emission characteristics of a stationary (non-road) diesel engine have been experimentally investigated. Experiments are conducted at a constant speed of 1500 rpm for three compression ratios and nozzle opening pressures at different engine loads. In-cylinder pressure history for 2000 consecutive engine cycles is recorded and averaged data is used for analysis of combustion characteristics. An electrical mobility-based fast particle sizer is used for analyzing particle size and mass distributions of engine exhaust particles at different test conditions. Soot particle distribution from 5 to 1000 nm was recorded. Results show that total particle concentration decreases with an increase in engine operating loads. Moreover, the addition of butanol in the diesel fuel leads to the reduction in soot particle concentration. Regression analysis was also conducted to derive a correlation between combustion parameters and particle number emissions for different compression ratios. Regression analysis shows a strong correlation between cylinder pressure-based combustion parameters and particle number emission.