Influence of anthropogenic emissions on tropospheric ozone and its precursors over the Indian tropical region during a monsoon

An emission inventory of ozone precursors developed for the year 1991 and 2001 is used in a Chemistry-Transport Model (MOZART) to examine the tropospheric changes in ozone and its precursors that have occurred during the 1990s in the geographical region of India in response to enhanced human activities. The maximum variation in ozone concentration near the surface is found to be around 5-10 ppbv. It reaches 5-7% in the lower part of the free troposphere and 3-5% in the upper troposphere. The maximum decadal increase in CO and NOx is about 50-70 ppbv (10-18%) and 0.5-1.5 ppbv (20-50%), respectively in the boundary layer. However, in most of the troposphere, the relative magnitude reduces with height and becomes less then 5% above 10 km. The variation in some of the volatile organic compounds is found to be significant

Is ultraviolet Radiation a Confounding Variable for COVID-19 in India?

The current global Coronavirus disease (COVID-19) became a pandemic due to its contagion nature and rapid spread throughout the world. The pandemic caused a lockdown resulting in a large decline in the level of anthropogenic emissions of tiny aerosol particles that altered the solar irradiance and decreased the quantity of aerosol, which opposes global warming. This study first demonstrates that surface ultraviolet radiation (UV) increased significantly during the lockdown period in four major Indian mega cities, whose magnitude varies based on city demography. Results shows that the correlation between the high rate of increase in Ultraviolet irradiance (UV-irradiance) on mortality and morbidity. Although there are numerous confounding factors for the pandemic, UV-irradiance could be one of the factors supporting the hypothesis that increased solar UV dose may increase rate of disinfection as radiation warps the structure of genetic material of the virus and deactivates it. Another factor which also have potential to add up increase of Vitamin D3 production per minute of exposure due to UV-irradiance resulting in an increased human immune system to fight COVID-19 more effectively. However, it is cautioned here that a high dose of direct UV exposure to humans may be fatal leading to skin damage and melanoma cancer. Hence, the harmful impact of UV-Irradiance on the human body and its application to possible disinfectant to virus deactivation should be understood in a proper perspective

Process-based Diagnostics of Extreme Pollution Trail using Numerical Modelling during Fatal Second COVID-19 wave in the Indian Capital

The world's worst outbreak, the second COVID-19 wave, not only unleashed unprecedented devastation of human life, but also made an impact of lockdown in the Indian capital, New Delhi, in particulate matter (PM: PM2.5 and PM10) virtually ineffective during April to May 2021. The air quality remained not only unabated but also was marred by some unusual extreme pollution events. SAFAR-framework model simulations with different sensitivity experiments were conducted using the newly developed lockdown emission inventory to understand various processes responsible for these anomalies in PM. Model results well captured the magnitude and variations of the observed PM before and after the lockdown but significantly underestimated their levels in the initial period of lockdown followed by the first high pollution event when the mortality counts were at their peak (∼400 deaths/day). It is believed that an unaccounted emission source was playing a leading role after balancing off the impact of curtailed lockdown emissions. The model suggests that the unprecedented surge in PM10 (690 μg/m3) on May 23, 2021, though Delhi was still under lockdown, was associated with large-scale dust transport originating from the north west part of India combined with the thunderstorm. The rainfall and local dust lifting played decisive roles in other unusual events. Obtained results and the proposed interpretation are likely to enhance our understanding and envisaged to help policymakers to frame suitable strategies in such kinds of emergencies in the future

Overview of the Temperature Response in the Mesosphere and Lower Thermosphere to Solar Activity

The natural variability in the terrestrial mesosphere needs to be known to correctly quantify global change. The response of the thermal structure to solar activity variations is an important factor. Some of the earlier studies highly overestimated the mesospheric solar response. Modeling of the mesospheric temperature response to solar activity has evolved in recent years, and measurement techniques as well as the amount of data have improved. Recent investigations revealed much smaller solar signatures and in some case no significant solar signal at all. However, not much effort has been made to synthesize the results available so far. This article presents an overview of the energy budget of the mesosphere and lower thermosphere (MLT) and an up-to-date status of solar response in temperature structure based on recently available observational data. An objective evaluation of the data sets is attempted and important factors of uncertainty are discussed

Air Quality, National Standards and Human Health in India (NIAS Policy Brief No. NIAS/NSE/EEC/U/PB/25/2021)

A clean air environment is prudent to healthy living. Studies related to the impact of ambient air pollution on public health are limited in India. Studies conducted by researchers at NIAS indicate that the natural baseline levels for Particulate Matter pollution in 10 megacities (with different climatological conditions) are significantly higher than the WHO’s Air Quality Guidelines levels. The exposure-response function cannot be universal due to the adaptive power of human beings. Therefore, coordinated national effort between MoES, MOEFCC, and ICMR is required to conduct scientific studies to determine the "exposure-response function" for Indians

Decadal growth in emission load of major air pollutants in Delhi

The Indian capital megacity of Delhi is reeling under deteriorating air quality, and control measures are not yielding any significant changes, mainly due to a poor understanding of sources of emissions; hence, priority option in mitigation planning is lacking. In this paper, we have made an attempt to develop a spatially resolved technological high-resolution gridded () emission inventory for eight major pollutants of the Delhi region where high-resolution activity data of all possible major and unattended minor sources are generated by organizing a mega-campaign involving hundreds of volunteers. It is for the first time that we are able to estimate the decadal growth in emissions of various pollutants by comparing newly developed 2020 emissions with SAFAR (System of Air Quality and Weather Forecasting and Research) emissions of 2010 using the identical methodology and quantum of activity data. The estimated annual emissions for PM2.5, PM10, CO, NOx, VOC, SO2, BC, and OC over the Delhi National Capital Region (NCR) are estimated to be 123.8, 243.6, 799.0, 488.9, 730.0, 425.8, 33.6, and 20.3 Gg yr−1, respectively, for the year 2020. The decadal growth (2010–2020) in PM2.5 and PM10 is found to be marginal at 31 % and 3 %, respectively. The maximum growth is found to be in the transport sector followed by the industrial and other sectors. Maximum decadal growth found for the pollutants BC, OC, and NOx is 57 %, 34 %, and 91 %, respectively. The decadal shift of sectorial emissions with changing policies is examined. The complete dataset is available on Zenodo at https://doi.org/10.5281/zenodo.7715595 (Sahu et al., 2023)

A comprehensive high‑resolution gridded emission inventory of anthropogenic sources of air pollutants in Indian megacity Kolkata

In this study, we present a first-ever effort made to develop an ultra-high-resolution gridded emission inventory (i.e. ~ 0.4 km × ~ 0.4 km) for the Indian megacity Kolkata. As the rising demand for fossil fuels based energy along with the spread of urban corridors have forced the anthropogenic activities to a mounting level, therefore determining the sources responsible is of paramount importance. This has worsened not only the regional air quality but also has an indirect effect on the global air quality. The spatial and temporal variation of the source requires an accurate estimation of the surface emission which is the most essential parameter to study the air quality, that positively has been fulfilled in this study. The annual emission for 2020 is calculated to be 37.2 Gg/yr of PM2.5, 61.4 Gg/yr of PM10, 222.6 Gg/yr of CO, 131.3 Gg/yr of NOx, 60.3 Gg/yr of SO2, 120.4 Gg/yr of VOC, 9.5 Gg/yr of BC and 16.8 Gg/yr of OC that prevails in the toxic air of megacity Kolkata. The present surface chemistry dataset will be the first line of detailed information regarding emission hotspots in the megacity that could be used as important tool for clean air mitigation strategies, input into the air quality modeling study to tackle environmental issues, and public health

Seasonal Variability in Fine Particulate Matter Water Content and Estimated pH over a Coastal Region in the Northeast Arabian Sea

The acidity of atmospheric particles can promote specific chemical processes that result in the production of extra condensed phases from lesser volatile species (secondary fine particulate matter), change the optical and water absorption characteristics of particles, and enhance trace metal solubility that can function as essential nutrients in nutrient-limited environments. In this study, we present an estimated pH of fine particulate matter (FPM) through a thermodynamic model and assess its temporal variability over a coastal location in the northeast Arabian Sea. Here, we have used the chemical composition of FPM (PM2.5) collected during the period between 2017–2019. Chemical composition data showed large variability in water-soluble ionic concentrations (WSIC; range: 2.3–39.9 μg m−3) with higher and lower average values during the winter and summer months, respectively. SO42− ions were predominant among anions, while NH4+ was a major contributor among cations throughout the season. The estimated pH of FPM from the forward and reverse modes exhibits a moderate correlation for winter and summer samples. The estimated pH of FPM is largely regulated by SO42− content and strongly depends on the relative ambient humidity, particularly in the forward mode. Major sources of FPM assessed based on Positive matrix factorization (PMF) and air-mass back trajectory analyses demonstrate the dominance of natural sources (sea salt and dust) during summer months, anthropogenic sources in winter months and mixed sources during the post-monsoon season

radiative forcing of carbonaceous aerosols over two urban environments in northern india

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