Extreme Concentrations of Nitric Oxide Control Daytime Oxidation and Quench Nocturnal Oxidation Chemistry in Delhi during Highly Polluted Episodes.

Delhi, India, suffers from periods of very poor air quality, but little is known about the chemical production of secondary pollutants in this highly polluted environment. During the postmonsoon period in 2018, extremely high nighttime concentrations of NOx (NO and NO2) and volatile organic compounds (VOCs) were observed, with median NOx mixing ratios of ∼200 ppbV (maximum of ∼700 ppbV). A detailed chemical box model constrained to a comprehensive suite of speciated VOC and NOx measurements revealed very low nighttime concentrations of oxidants, NO3, O3, and OH, driven by high nighttime NO concentrations. This results in an atypical NO3 diel profile, not previously reported in other highly polluted urban environments, significantly perturbing nighttime radical oxidation chemistry. Low concentrations of oxidants and high nocturnal primary emissions coupled with a shallow boundary layer led to enhanced early morning photo-oxidation chemistry. This results in a temporal shift in peak O3 concentrations when compared to the premonsoon period (12:00 and 15:00 local time, respectively). This shift will likely have important implications on local air quality, and effective urban air quality management should consider the impacts of nighttime emission sources during the postmonsoon period.

A new perspective of probing the level of pollution in the megacity Delhi affected by crop residue burning using the triple oxygen isotope technique in atmospheric CO2.

Air quality in the megacity Delhi is affected not only by local emissions but also by pollutants from crop residue burning in the surrounding areas of the city, particularly the rice straw burning in the post monsoon season. As a major burning product, gaseous CO2, which is rather inert in the polluted atmosphere, provides an alternative solution to characterize the impact of biomass burning from a new perspective that other common tracers such as particulate matters are limited because of their physical and chemical reactiveness. Here, we report conventional ([CO2], δ13C, and δ18O) and unconventional (Δ17O) isotope data for CO2 collected at Connaught Place (CP), a core area in the megacity Delhi, and two surrounding remote regions during a field campaign in October 18-20, 2017. We also measured the isotopic ratios near a rice straw burning site in Taiwan to constrain their end member isotopic compositions. Rice straw burning produces CO2 with δ13C, δ18O, and Δ17O values of -29.02 ± 0.65, 19.63 ± 1.16, and 0.05 ± 0.02‰, respectively. The first two isotopic tracers are less distinguishable from those emitted by fossil fuel combustion but the last one is significantly different. We then utilize these end member isotopic ratios, with emphasis on Δ17O for the reason given above, for partitioning sources that affect the CO2 level in Delhi. Anthropogenic fraction of CO2 at CP ranges from 4 to 40%. Further analysis done by employing a three-component (background, rice straw burning, and fuel combustion) mixing model with constraints from the Δ17O values yields that rice straw burning contributes as much as ∼70% of the total anthropogenic CO2, which is more than double of the fossil fuel contribution (∼30%), during the study days.

Purification and Characterization of 2S Albumin from Seeds of Wrightia tinctoria Exhibiting Antibacterial and DNase Activity.

2S albumin is a low-molecular-weight seed storage protein belonging to the prolamin superfamily. In the present work a small 2S albumin (WTA) protein of ~16 kDa has been purified from the seeds of Wrightia tinctoria. The WTA is a heterodimer protein with a small subunit of ~5 kDa and a larger subunit of ~11 kDa bridged together through disulphide bonds. The protein exhibits deoxyribonucleases activity against closed circular pBR322 plasmid DNA and linear BL21 genomic DNA. The protein also showed antibacterial activity against Morexalla catarrhalis. CD studies indicate a high α-helical content in the protein. The conserved disulphide bonds in the protein suggest that the WTA is highly stable under high pH and temperature like other 2S albumin.

Structural, Functional and Evolutionary Aspects of Seed Globulins.

Globulins are a major class of seed storage proteins which were thought to be enzymatically inactive. These proteins belong to the most ancient cupin superfamily. They can be graded into 11S legumin type and 7S vicilin type based on their sedimentation coefficients. Members from both classes share structural homology are thought to have evolved from either one-domain germin predecessor by duplication or by horizontal gene transfer of two-domain gene from bacteria to eukaryotes. Globulins are known to define the nutritional quality of the seeds, however, they are also involved in sucrose binding, desiccation, defense against microbes, hormone binding and oxidative stress etc. Major drawback with globulins is their tendency to bind to IgE. Studying structural-functional behavior of such protein can help in modifying proteins for enhanced functionality in food processing industries.

Role of meteorology in seasonality of air pollution in megacity Delhi, India.

The winters in megacity Delhi are harsh, smoggy, foggy, and highly polluted. The pollution levels are approximately two to three times those monitored in the summer months, and the severity is felt not only in the health department but also in the transportation department, with regular delays at airport operations and series of minor and major accidents across the road corridors. The impacts felt across the city are both manmade (due to the fuel burning) and natural (due to the meteorological setting), and it is hard to distinguish their respective proportions. Over the last decade, the city has gained from timely interventions to control pollution, and yet, the pollution levels are as bad as the previous year, especially for the fine particulates, the most harmful of the criteria pollutants, with a daily 2009 average of 80 to 100 µg/m(3). In this paper, the role of meteorology is studied using a Lagrangian model called Atmospheric Transport Modeling System in tracer mode to better understand the seasonality of pollution in Delhi. A clear conclusion is that irrespective of constant emissions over each month, the estimated tracer concentrations are invariably 40% to 80% higher in the winter months (November, December, and January) and 10% to 60% lower in the summer months (May, June, and July), when compared to annual average for that year. Along with monitoring and source apportionment studies, this paper presents a way to communicate complex physical characteristics of atmospheric modeling in simplistic manner and to further elaborate linkages between local meteorology and pollution.