Size-distribution and driving factors of aerosol oxidative potential in rural kitchen microenvironments of northeastern India.

This study reports size-resolved dithiothreitol (DTT)-based oxidative potential (OP: total and water-soluble) in rural kitchens using liquefied petroleum gas (LPG), firewood (FW), and mixed biomass (MB) fuels in northeastern (NE) India. In comparison to LPG, volume-normalized total OP (OPtotal(v)DTT) was enhanced by a factor of ∼5 in biomass-using kitchens (74 ± 35 to 78 ± 42 nmol min-1 m-3); however, mass-normalized total OP (OPtotal(m)DTT) was similar between LPG and FW users and higher by a factor of 2 in MB-using kitchens. The water-insoluble OP (OPwi(v, m)DTT) fraction in OPtotal(v, m)DTT was greater than 50% across kitchens. Size distributions across kitchens and OPDTT categories ranged from unimodal to trimodal. OPws(v)DTT was driven by metals as well as organics across size fractions while OPwi(v)DTT was majorly constrained by metals with an increasing importance of organics in fine particles of biomass-using kitchens. Multiple linear regression analysis revealed that Cu and Ba explained 71% of the OPtotal(v)DTT variability in LPG-using kitchens, while water-soluble organic carbon (WSOC) and Ba were responsible for 44% variability in FW-using kitchens. Finally, the high internal dose of OPtotal(v)DTT (28-31 nmol min-1 m-3) in biomass-using kitchens established the severity of oxidative stress on the exposed population.

Optical source apportionment of aqueous brown carbon (BrC) on a daytime and nighttime basis in the eastern Indo-Gangetic Plain (IGP) and insights from 13C and 15N isotopic signatures.

This study reports day-night and seasonal variations of aqueous brown carbon (BrCaq) and constituent humic-like substances (HULIS) (neutral and acidic HULIS: HULIS-n and HULIS-a) from the eastern Indo-Gangetic Plain (IGP) of India during 2019-2020. This is followed by the application of the receptor model positive matrix factorization (PMF) for optical source apportionment of BrCaq and the use of stable isotopic ratios (δ13C and δ15N) to understand atmospheric processing. Nighttime BrCaq absorption and mass absorption efficiencies (MAE) were enhanced by 40-150 % and 50-190 %, respectively, compared to the daytime across seasons, possibly as a combined effect from daytime photobleaching, dark-phase secondary formation, and increased nighttime emissions. MAE250 nm/MAE365 nm (i.e., E2/E3) ratios and Angstrom Exponents revealed that BrCaq and HULIS-n were relatively more aromatic and conjugated during the biomass burning-dominated periods while BrCaq and HULIS-a were comprised mostly of non-conjugated aliphatic structures from secondary processes during the photochemistry-dominated summer. The relative radiative forcing of BrCaq with respect to elemental carbon (EC) was 10-12 % in the post-monsoon and winter in the 300-400 nm range. Optical source apportionment using PMF revealed that BrCaq absorption at 300, 365 and 420 nm wavelengths in the eastern IGP is mostly from biomass burning (60-75 %), followed by combined marine and fossil fuel-derived sources (24-31 %), and secondary processes (up to 10 %). Source-specific MAEs at 365 nm were estimated to be the highest for the combined marine and fossil fuel source (1.34 m2 g-1) followed by biomass burning (0.78 m2 g-1) and secondary processing (0.13 m2 g-1). Finally, δ13C and δ15N isotopic analysis confirmed the importance of summertime photochemistry and wintertime NO3--dominated chemistry in constraining BrC characteristics. Overall, the quantitative apportionment of BrCaq sources and processing reported here can be expected to lead to targeted source-specific measurements and a better understanding of BrC climate forcing in the future.

Insights into seasonal-variability of SVOCs, morpho-elemental and spectral characteristics of PM2.5 collected at a dense industrial site: Faridabad, Haryana, India.

The development-oriented anthropogenic activities have led to intensive increase in emission of various organic pollutants, which contribute considerably to human health risk. In the present study, chemical, physical and spectral characterisation of fine particulate matter (PM2.5), collected at Faridabad city, in northern India, were examined. Seasonal variation of organic compounds [n-alkanes, polyaromatic hydrocarbons (PAHs) and phthalic acid esters (PAEs)], and potential health risk of Polyaromatic hydrocarbons (PAHs) exposure using toxic equivalency potential (TEQ) approach had been assessed. These showed seasonal average values ranging from 156.4 ± 57.0 ng/m3 to 217.6 ± 72.9 ng/m3, 98.0 ± 21.4 ng/m3 to 177.8 ± 72.8 ng/m3, and 30.9 ± 11.9 ng/m3 to 82.5 ± 29.2 ng/m3, respectively, with the highest value for winter. It is noteworthy that unlike, n-alkanes and PAEs, PAHs were least during spring. The high molecular weight PAHs (BaP, BkF, DahA and IcdP) were found to exhibit higher TEQ values (ranging from 0.7 to 9.7) despite of their lower concentrations. The PAH diagnostic ratio, carbon preference index and total index revealed the enhanced impact of biogenic sources of emissions in comparison to diesel emission sources during winter.

The role of particulate matter in reduced visibility and anionic composition of winter fog: a case study for Amritsar city.

Severe fog events during winter months in India are a serious concern due to the higher incidence of road accidents, flight delays and increased occurrence of respiratory diseases. The present paper is an attempt to study the twenty fog samples collected from the rooftop of an academic building of Guru Nanak Dev University, Amritsar, India from November 2017 to January 2018. Fog samples were analysed for various parameters viz. pH, electrical conductivity (EC), chloride (Cl-), nitrate (NO3 -) and sulphate (SO4 2-) levels. The pH, EC, and Cl-, NO3 - and SO4 2- levels in the fog samples were estimated as 6.3-7.9, 240-790 µS cm-1, 108-2025 µeq L-1, 105-836 µeq L-1 and 822-5642 µeq L-1, respectively. It was noticed that sulphate was the dominant anion in fog samples. The SO4 2- to NO3 - molar ratio in the fog was estimated as 7.6 which suggests the burning of fossil fuel as the major pollutant from vehicular exhausts. Multiple regression analysis was performed to evaluate the effect of PM2.5/PM10 ratio and relative humidity (RH) on visibility. A box-cox plot of power transformation produced better model fitting, employing a square root transformation of the visibility which indicated that the PM2.5/PM10 and RH have an exponential effect on visibility.

Evidence of the presence of SARS-CoV-2 virus in atmospheric air and surfaces of a dedicated COVID hospital.

The present study was conducted from July 1, 2020 to September 25, 2020 in a dedicated coronavirus disease 2019 (COVID-19) hospital in Delhi, India to provide evidence for the presence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus in atmospheric air and surfaces of the hospital wards. Swabs from hospital surfaces (patient's bed, ward floor, and nursing stations area) and suspended particulate matter in ambient air were collected by a portable air sampler from the medicine ward, intensive care unit, and emergency ward admitting COVID-19 patients. By performing reverse-transcriptase polymerase chain reaction (RT-PCR) for E-gene and RdRp gene, SARS-CoV-2 virus was detected from hospital surfaces and particulate matters from the ambient air of various wards collected at 1 and 3-m distance from active COVID-19 patients. The presence of the virus in the air beyond a 1-m distance from the patients and surfaces of the hospital indicates that the SARS-CoV-2 virus has the potential to be transmitted by airborne and surface routes from COVID-19 patients to health-care workers working in COVID-19 dedicated hospital. This warrants that precautions against airborne and surface transmission of COVID-19 in the community should be taken when markets, industries, educational institutions, and so on, reopen for normal activities.

Hierarchically Porous Calcium Carbonate Scaffolds for Bone Tissue Engineering.

Hierarchically porous CaCO3 scaffolds comprised of micro- (diameter = 2.0 ± 0.3 µm) and nano-sized (diameter = 50.4 ± 14.4 nm) pores were fabricated on silicon substrates using a supercritical CO2-based process. Differentiated human THP-1 monocytes exposed to the CaCO3 scaffolds produced negligible levels of the inflammatory cytokine tumor necrosis factor-alpha (TNF-α), confirming the lack of immunogenicity of the scaffolds. Extracellular matrix (ECM) proteins, vitronectin and fibronectin, displayed enhanced adsorption to the scaffolds compared to the silicon controls. ECM protein-coated CaCO3 scaffolds promoted adhesion, growth, and proliferation of osteoblast MC3T3 cells. MC3T3 cells grown on the CaCO3 scaffolds produced substantially higher levels of transforming growth factor-beta and vascular endothelial growth factor A, which regulate osteoblast differentiation, and exhibited markedly increased alkaline phosphatase activity, a marker of early osteoblast differentiation, compared to controls. Moreover, the CaCO3 scaffolds stimulated matrix mineralization (calcium deposition), an end point of advanced osteoblast differentiation and an important biomarker for bone tissue formation. Taken together, these results demonstrate the significant potential of the hierarchically porous CaCO3 scaffolds for bone tissue engineering applications.

Microwave-assisted three-component domino reaction: Synthesis of indolodiazepinotriazoles.

A microwave-assisted three-component protocol involving N-1 alkylation of 2-alkynylindoles with epichlorohydrin, ring opening of the epoxide with sodium azide, and an intramolecular Huisgen azide-internal alkyne 1,3-dipolar cycloaddition domino sequence has been described. The efficacy of the methodology has been demonstrated by treating various 2-alkynylindoles (aromatic/aliphatic) with epichlorohydrin and sodium azide furnishing annulated tetracyclic indolodiazepinotriazoles in satisfactory yields.

Cascade intermolecular Michael addition-intramolecular azide/internal alkyne 1,3-dipolar cycloaddition reaction in one pot.

A rapid one-pot protocol for the synthesis of indole-based polyheterocycles via a sequential Lewis acid catalyzed intermolecular Michael addition and an intramolecular azide/internal alkyne 1,3-dipolar cycloaddition reaction has been described. The generality of the method has been demonstrated by treating a series of aromatic/aliphatic 2-alkynyl indoles with substituted (E)-1-azido-2-(2-nitrovinyl)benzenes to furnish annulated tetracyclic indolo[2,3-c][1,2,3]triazolo[1,5-a][1]benzazepines in good yields.

Synthesis of iodo-indoloazepinones in an iodine-mediated three-component domino reaction via a regioselective 7-endo-dig iodo-cyclization pathway.

An efficient and rapid synthetic strategy for the naturally occurring indoloazepinone scaffold via a three-component reaction of indole-2-carboxamides, 1,3-disubstituted propargyl alcohols, and I(2) is described. The strategy involves a C-H functionalization-alkyne activation-intramolecular hydroamidation-deprotonation domino sequence. The salient feature of this sequence is regioselective electrophilic 7-endo-dig iodo-cyclization during the intramolecular hydroamidation to afford a seven-membered azepinone ring annulated to the indole.

Unprecedented Cu-catalyzed coupling of internal 1,3-diynes with azides: one-pot tandem cyclizations involving 1,3-dipolar cycloaddition and carbocyclization furnishing naphthotriazoles.

A one-pot protocol for the synthesis of triazole-annulated polyheterocycles via metal-catalyzed coupling of internal 1,4-disubstituted 1,3-diynes and organic azides has been described. The mechanistic rationale for the reaction suggests tandem cyclizations involving copper-catalyzed cycloaddition and 6-endo carbocyclization reactions. The cascade cyclization leads to an increase in molecular complexity to furnish naphtho[1,2-d]triazoles in satisfactory yields. The generality of the method has been demonstrated by using a series of aromatic/aliphatic azides and symmetrical internal 1,3-diynes.