Field performance evaluation during fog-dominated wintertime of a newly developed denuder-equipped PM1 sampler

This study presents the performance evaluation of a novel denuder-equipped PM₁ (particles having aerodynamic diameter less than 1 μm) sampler, tested during fog-dominated wintertime, in the city of Kanpur, India. One PM₁ sampler and one denuder-equipped PM₁ sampler were co-located to collect ambient PM₁ for 25 days. The mean PM₁ mass concentration measured on foggy days with the PM₁ sampler and the denuder-equipped PM₁ sampler was found to be 165.95 and 135.48 μg/m³, respectively. The mean PM₁ mass concentration measured on clear days with the PM₁ sampler and the denuder-equipped PM₁ sampler was observed to be 159.66 and 125.14 μg/m³, respectively. The mass concentration with denuder-fitted PM₁ sampler for both foggy and clear days was always found less than the PM₁ sampler. The same drift was observed in the concentrations of water-soluble ions and water-soluble organic carbon (WSOC). Moreover, it was observed that the use of denuder leads to a significant reduction in the PM positive artifact. The difference in the concentration of chemical species obtained by two samplers indicates that the PM₁ sampler without denuder had overestimated the concentrations of chemical species in a worst-case scenario by almost 40 %. Denuder-fitted PM₁ sampler can serve as a useful sampling tool in estimating the true values for nitrate, ammonium, potassium, sodium and WSOC present in the ambient PM.     

QSAR modeling for predicting mutagenic toxicity of diverse chemicals for regulatory purposes

The safety assessment process of chemicals requires information on their mutagenic potential. The experimental determination of mutagenicity of a large number of chemicals is tedious and time and cost intensive, thus compelling for alternative methods. We have established local and global QSAR models for discriminating low and high mutagenic compounds and predicting their mutagenic activity in a quantitative manner in Salmonella typhimurium (TA) bacterial strains (TA98 and TA100). The decision treeboost (DTB)-based classification QSAR models discriminated among two categories with accuracies of >96% and the regression QSAR models precisely predicted the mutagenic activity of diverse chemicals yielding high correlations (R ²) between the experimental and model-predicted values in the respective training (>0.96) and test (>0.94) sets. The test set root mean squared error (RMSE) and mean absolute error (MAE) values emphasized the usefulness of the developed models for predicting new compounds. Relevant structural features of diverse chemicals that were responsible and influence the mutagenic activity were identified. The applicability domains of the developed models were defined. The developed models can be used as tools for screening new chemicals for their mutagenicity assessment for regulatory purpose.

     

Removal of hexavalent chromium upon interaction with biochar under acidic conditions: mechanistic insights and application

Environmental Science and Pollution Research - Chromium pollution of soil and water is a serious environmental concern due to potential carcinogenicity of hexavalent chromium [Cr(VI)] when...     

Utilization of waste product (tamarind seeds) for the removal of Cr(VI) from aqueous solutions: Equilibrium, kinetics, and regeneration studies

In the present study, an adsorbent was prepared from tamarind seeds and used after activation for the removal of Cr(VI) from aqueous solutions. The tamarind seeds were activated by treating them with concentrated sulfuric acid (98% w/w) at a temperature of 150 °C. The adsorption of Cr(VI) was found to be maximum at low values of initial pH in the range of 1–3. The adsorption process of Cr(VI) was tested with Langmuir, Freundlich, Redlich–Peterson, Koble–Corrigan, Tempkin, Dubinin–Radushkevich and Generalized isotherm models. Application of the Langmuir isotherm to the system yielded a maximum adsorption capacity of 29.7 mg/g at an equilibrium pH value ranging from 1.12 to 1.46. The adsorption process followed second-order kinetics and the corresponding rate constants obtained were 2.605 × 10⁻³, 0.818 × 10⁻³, 0.557 × 10⁻³ and 0.811 × 10⁻³ g/mg min⁻¹ for 50, 200, 300 and 400 mg/L of initial Cr(VI) concentration, respectively. The regenerated activated tamarind seeds showed more than 95% Cr(VI) removal of that obtained using the fresh activated tamarind seeds. A feasible solution is proposed for the disposal of the contaminants (acid and base solutions) containing high concentrations of Cr(VI) obtained during the regeneration (desorption) process.     

Decay profile and metabolic pathways of quinalphos in water, soil and plants

The widespread occurrence of pesticide residues in different agricultural and food commodities has raised concern among the environmentalists and food chemists. In order to keep a proper track of these materials, studies on their decay profiles in the various segments of ecosystem under varying environmental conditions are needed. In view of this, the metabolites of quinalphos in water and soil under controlled conditions and in plants, namely tomato and radish in field conditions have been analysed and possible pathways suggested. In order to follow the decay of the pesticide, an HPLC procedure has been developed. Studies conducted in water at different temperatures, pH and organic content reveal that the persistence of the pesticide decreases with the increase in all the three variables. In the three different types of soils studied, the effect of pH is more or less apparent on a similar line. On an average a faster decay is observed in the case of plants than in water and soil. The decay profiles in all these cases follow first order kinetics. The metabolites were identified by GC-MS. The investigations reflect that degradation occurs through hydrolysis, S-oxidation, dealkylation and thiono-thiol rearrangement. The pathways seem to be complex and different metabolites were observed with the change in the matrix. Quinalphos oxon, O-ethyl-O-quinoxalin-2-yl phosphoric acid, 2-hydroxy quinoxaline and quinoxaline-2-thiol were observed in all the matrices. Results further indicate that the metabolites, 2-hydroxy quinoxaline and oxon, which are more toxic than parent compound, persist for a longer time.     

Magnetic properties of biogenic selenium nanomaterials

Environmental Science and Pollution Research - Bioreduction of selenium oxyanions to elemental selenium is ubiquitous; elucidating the properties of this biogenic elemental selenium (BioSe) is thus...     

Role of UPP pathway in amelioration of diabetes-associated complications

Environmental Science and Pollution Research - Type 2 diabetes (T2D) is one of the most widely spread metabolic disorder also called as “life style” disease. Due to the alarming number...     

Superior photodecomposition of pyrene by metal ion-loaded TiO2 catalyst under UV light irradiation

Background

The photocatalytic degradation of pyrene under UV (125?W Hg-Arc, 10.4?mW/cm²) irradiation of TiO₂ aqueous suspension has been found to be highly improved with the dissolved transition metal ions like Cu²⁺, Fe³⁺, Ag⁺, and Au³⁺, etc. As the reduction potential of these metals lies below the conduction band (CB) position (?0.1?eV) of TiO₂, the photoexcited electron transfer occurs more readily and reduces electron?Chole recombination rate. Therefore, it has a beneficial influence on the photocatalytic ability of TiO₂ because of rapid Fermi energy equilibrium between the CB of TiO₂ and its surface adsorbed metal ions.

Results and discussion

The Fermi level is referred to as the electrochemical potential and plays an important role in the band theory of solids. When metal and semiconductor are in contact, electron migration from photoirradiated semiconductor to the deposited metal occurs at the interface until two Fermi levels equilibrate and enhanced the photocatalytic activity of semiconductor photocatalyst. Ni²⁺ having more negative reduction potential (?0.25?eV) than the CB of TiO₂ imparts negligible co-catalytic activity to TiO₂ photoreaction. It also revealed that loading of Au³⁺ ions displayed higher degradation rate of pyrene than Au photodeposition. Furthermore, when the amount of dissolved Fe⁺³ and Au³⁺ ions gradually increases from 0.1 to 2?wt.%, the pyrene photodecomposition rate also become faster.     

Isolation and characterization of novel phorate-degrading bacterial species from agricultural soil

Based upon 16S rDNA sequence homology, 15 phorate-degrading bacteria isolated from sugarcane field soils by selective enrichment were identified to be different species of Bacillus, Pseudomonas, Brevibacterium, and Staphylococcus. Relative phorate degradation in a mineral salt medium containing phorate (50 μg ml^?1) as sole carbon source established that all the bacterial species could actively degrade more than 97 % phorate during 21 days. Three of these species viz. Bacillus aerophilus strain IMBL 4.1, Brevibacterium frigoritolerans strain IMBL 2.1, and Pseudomonas fulva strain IMBL 5.1 were found to be most active phorate metabolizers, degrading more than 96 % phorate during 2 days and 100 % phorate during 13 days. Qualitative analysis of phorate residues by gas liquid chromatography revealed complete metabolization of phorate without detectable accumulation of any known phorate metabolites. Phorate degradation by these bacterial species did not follow the first-order kinetics except the P. fulva strain IMBL 5.1 with half-life period (t½) ranging between 0.40 and 5.47 days.     

Growing stock and woody biomass assessment in Asola-Bhatti Wildlife Sanctuary,Delhi, India

Biomass is an important entity to understand the capacity of an ecosystem to sequester and accumulate carbon over time. The present study, done in collaboration with the Delhi Forest Department, focused on the estimation of growing stock and the woody biomass in the so-called lungs of Delhi—the Asola-Bhatti Wildlife Sanctuary in northern Aravalli hills. The satellite-derived vegetation strata were field-inventoried using stratified random sampling procedure. Growing stock was calculated for the individual sample plots using field data and species-specific volume equations. Biomass was estimated from the growing stock and the specific gravity of the wood. Among the four vegetation types, viz. Prosopis juliflora, Anogeissus pendula, forest plantation and the scrub, the P. juliflora was found to be the dominant vegetation in the area, covering 23.43 km² of the total area. The study revealed that P. juliflora forest with moderate density had the highest (10.7 m³/ha) while A. pendula forest with moderate density had the lowest (3.6 m³/ha) mean volume. The mean woody biomass was also found to be maximum in P. juliflora forest with moderate density (10.3 t/ha) and lowest in A. pendula forest with moderate density (3.48 t/ha). The total growing stock was estimated to be 20,772.95 m³ while total biomass worked out to be 19,366.83 t. A strong correlation was noticed between the normalized difference vegetation index (NDVI) and the growing stock (R ²?=?0.84)/biomass (R ²?=?0.88). The study demonstrated that growing stock and the biomass of the woody vegetation in Asola-Bhatti Wildlife Sanctuary could be estimated with high accuracy using optical remote sensing data.