BTEX in ambient air of India: a scoping review of their concentrations, sources, and impact

Toxic gaseous organic air pollutants such as benzene, toluene, ethylbenzene, and xylene isomers (m, p, and o-x) (BTEX) are considered hazardous due to its adverse impacts on human health and on climate change. This review identifies the major research questions addressed so far and the research gap in research articles, published between 2001 and 2022, focusing on the ambient BTEX concentrations in different locations in India along with its sources, ozone formation potential (OFP), and associated health risks. The ambient levels of BTEX were also compared with those of other Asian countries. A comparison of ambient BTEX levels with different microenvironments in India is also presented. BTEX concentrations were found in the range of 30.95 to 317.18 µg m−3 and multi-fold higher in urban environments than those measured in the rural air. In most reported studies, the order of occurrence of BTEX compounds was toluene > benzene > xylene isomers > ethylbenzene and winter had higher concentrations than in other seasons, including summer. As far as BTEX levels in classified areas of urban environments are concerned, traffic locations have shown the highest BTEX concentrations, followed by residential, commercial, and industrial locations. OFP indicated that xylene isomers and toluene contributed to ozone formation. The major gaps in reported studies on BTEX measurement are (1) source apportionment; (2) impact on lower tropospheric chemistry, human health, and climate change; and (3) removal techniques from air.publishe

Hydrolytic cleavage of paraoxon and parathion by oximate and functionalized oximate ions: A comparative study

560-565<span style="font-size:11.0pt;font-family: " times="" new="" roman";mso-fareast-font-family:"times="" roman";mso-bidi-font-family:="" mangal;letter-spacing:-.1pt;mso-ansi-language:en-gb;mso-fareast-language:en-us;="" mso-bidi-language:hi"="" lang="EN-GB">Bimolecular reactions of O,O-diethyl-O-p-nitrophenylphosphate (paraoxon) and O,O-diethyl-O-p-nitrophenyl phosphorothioate (parathion) with oximate (pyridinealdoxime 2-PyOx- and 4-PyOx-) and its functionalized oximate, 4-(hydroxyimino)methyl)-1-alkylpyridinium bromide ions (alkyl = C10H21 (4-C10PyOx-); alkyl = C12H25 (4-C12PyOx-)) have been investigated in aqueous and cationic micellar media of cetylpyridinium bromide, cetyltrimethyl-ammonium bromide and cetyltetradecyltrimethylammonium bromide at pH 9.5 and 27 oC. Under the micellized condition, a 1.2×103 fold and 9.0×106 fold rate enhancement over the aqueous reaction of paraoxon (ko = 7.5×10-8 s-1) and parathion (ko = 9.5×10-11) is observed.</span

Interaction of thiolated amino acids and peptide onto the gold nanoparticle surface: Radical scavenging activity

1206-1214The interaction of gold nanoparticles (AuNPs) with thiolated amino acid, L-cysteine, and peptide, glutathione, is reported. Additionally, thioglycolic acid has also been employed to study the effect of other functional groups such as amine on interparticle interaction mechanism. The functionalized AuNPs have been characterized through UV-visible spectroscopy, FTIR analysis and transmission electron microscopy. The plasmon-plasmon interactions amongst the functionalized AuNPs are found to be dependent on ligand concentration, pH and salt environment. The assembly of AuNPs mediated by L-Cys and GSH has been monitored by the evolution of the surface plasmon resonance absorption. The optical spectra of AuNPs is shifted to the red region, indicating dipole-dipole interactions in the AuNPs assembly. The self-assembly is more pronounced in the case of amino acid and tripeptide, due to the zwitterion-type electrostatic interactions between amino acid groups of L-Cys/GSH bound to different NPs. Furthermore, the scavenging behavior of the studied thiolated ligands and the corresponding AuNPs has been studied by using 1,1-diphenyl 2-picryl hydrazil radical. AuNPs significantly reduces the radical scavenging ability of thiolated antioxidants

Kinetic study of hydrolytic decomposition of organophosphates and thiophosphate by N-hydroxyamides in cationic micellar media<b></b>

726-730The nucleophilic hydrolytic reactions of p-nitrophenyl diphenyl phosphate (PNPDPP), p-nitrophenyl diethyl phosphate (Paraoxon) and p-nitrophenyl diethyl phosphorothioate (Parathion) with N-hydroxyamides have been investigated at 27 °C. With cationic micelles, rate enhancement has been observed on the nucleophilic attack at P center. All the rate surfactant profiles show typical micelle assisted bimolecular reactions. The interfacial ion exchange, control of the interfacial nucleophile concentration and the reactivity at the micellar interface has been explained

β‑Cyclodextrin Stabilized Nanoceria for Hydrolytic Cleavage of Paraoxon in Aqueous and Cationic Micellar Media

Beta-cyclodextrin (β-CD) stabilized cerium oxide nanoparticles (β-CD@CeO2 NPs) were synthesized through a hydrothermal route. The electronic properties, surface functional group, surface composition, size, and morphologies of the as-synthesized β-CD@CeO2 NPs were characterized using UV–visible spectroscopy, FTIR analysis, high resolution X-ray photoelectron spectroscopy (HRXPS), high resolution transmission electron microscopy (HRTEM), and field emission scanning electron microscopy (FESEM). The pH-dependent variation of the ζ-potential of β-CD@CeO2 NPs and the catalytic activity of the NPs for the hydrolysis of paraoxon were investigated. The observed pseudo-first-order rate constant (kobs) for the hydrolysis of paraoxon is increased with increasing pH and the ζ-potential of β-CD@CeO2 NPs. The kinetics and mechanism of hydrolysis of paraoxon in the aqueous and cationic micellar media have been discussed

Physicochemical Properties and Supernucleophilicity of Oxime-Functionalized Surfactants: Hydrolytic Catalysts toward Dephosphorylation of Di- and Triphosphate Esters

Aggregation and kinetic studies have been performed to understand the hydrolytic potencies of the series of oxime-functionalized surfactants, viz., 3- hydroxyiminomethyl-1-alkylpyridinium bromide (alkyl = C_<i>n</i>H_2<i>n</i>+1, <i>n</i> = 10, 12, 14, 16, 18) in the cleavage of phosphate esters, <i>p</i>-nitrophenyl diphenyl phosphate (PNPDPP) and bis­(2,4-dinitrophenyl) phosphate (BNDPP), in mixed micelles with cetylpyridinium bromide (CPB). Micellization and surface properties of mixed micelles functional surfactants with CPB were studied by conductivity and surface tension measurements. Acid dissociation constants (p<i>K</i>_a) were determined, the effect of functional surfactant alkyl chain length and pH on the observed rate constant (<i>k</i>_obs) for phosphate ester cleavage has been discussed, and the effect of substrate on the supernucleophilicities of the studied oximes was monitored. Functionalized oxime-based surfactants were proved to be supernucleophiles to attack on the PO center of tri- and diphosphate esters. Oximes with hexadecyl alkyl chain length (3-C₁₆) showed maximum micellar effect on the rate constants toward PNPDPP. Micellar effects were analyzed in terms of the pseudophase model

Nitrogen and Sulphur co-doped Graphene: A Robust Material for Methylene Blue Removal

N, S co-doped graphene (NSG) has been synthesized by using graphene oxide, cyanamide and sodium sulphide as a source of C, N and S respectively. Due to its excellent electronic properties and stability, NSG has been used as an adsorbent for methylene blue (MB) removal from aqueous solution. Adsorption efficiencies of Graphene, N-doped graphene, S-doped graphene and NSG were compared during the study and it was found that NSG was the most efficient material for the adsorption of MB. The study was carried out in the UV-visible region by observing the changes in absorbance. NSG has excellent properties to adsorb the MB dye with a removal efficiency of 93.76±0.2%. Additionally, desorption studies were also carried out using 0.1 M cetylpyridinium chloride as cationic surfactant and the desorption% was found to be 50.28±0.1%, signifying its reusability as an adsorbent. This indicates that NSG opens a new window for the design of heteroatom-doped carbon material as well as its application in the adsorption studies. Accordingly, the synthesized material will be employed for wastewater treatment as a reusable adsorbent of MB in the near future with high efficiency and appreciable stability. In addition, the material has several other future applications such as electrode material for supercapacitor battery, sensor, adsorbent for metal ions and biomolecules, etc

Chemical fractionation of particulate-bound metal(loid)s to evaluate their bioavailability, sources and associated cancer risk in India

Eleven potentially toxic metal(loid)s (Al, As, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, and Zn), proven source markers of mineral based coal-fired industrial emissions and vehicular exhausts, were analysed using the four steps sequential extraction method to evaluate metal(loid)s concentration, in total and fractions of bioavailable and non-bioavailable for fine (PM2.5) and coarse (PM10–2.5) particulate modes. A total of 26-day-wise samples with three replications (total number of samples = 78) were collected in January–December 2019 for each PM10 and PM2.5 at an urban-residential site in India. In both the coarse and fine particulate modes, Pb and Cr have respectively shown the highest and lowest total concentrations of the measured metal(loid)s, indicating the presence of coal-fired power plants and heavy vehicular activities near to study area. In addition, Mn has shown highest bioavailable fraction for both coarse and fine particulate modes. More than 50 % of metal(loid)s concentration, in total to a bioavailable fraction (BAF) were observed in case of As, Cd, Cr, Co, Mn, Ni, and Pb of PM2.5. Mn and Zn have shown similar behaviour in the case of coarse particulate mode. Source apportionment of metal(loid)s bioavailable fractions using positive matrix factorization (PMF 5.0) has found three significant sources: crustal and natural dust (30.04 and 39 %), road traffic (49.57 and 20 %), and industrial emission (20.39 and 41 %) for coarse and fine particulate mode, respectively. Cancer risk through the inhalation pathway was high in total concentration but lower in BAF concentration in both age groups (children and adults).publishe