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NO 2 column mass density in different seasons using the TROPOMI data for the period 2018-2021. The cities marked on the map are Delhi (DEL), Singrauli (SIN), Korba (KOR), Talcher (TAL), Durgapur (DUR), Kolkata (KOL), Mumbai (MUM), Mundra (MUN), Chandrapur (CHA), Hyderabad (HYD), Bangalore (BAN) and Chennai (CHE).
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India is a country with more than 67% of its population (947 million) residing in rural areas and 33% in urban areas (472 million) as of 2020. Therefore, health of the people living in rural India is very important for its future development plans, economy and growth. Here, we analyse the rural air quality using satellite measurements of NO2 in Ind...
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... in NO 2 is observed over rural and urban NEI due to the less population and vehicular load in both urban and rural regions there. The merged data also show changes similar to the TROPOMI NO 2 over all rural and urban regions of India, attesting that the analysis presented here is robust, as also illustrated in Fig. S2. † Among the seasons (Fig. 4), winter shows highest NO 2 due to the shallow boundary layer, low temperature (lower rate of the oxidation process) and reduced wind speed, which limit the dispersal of pollutants. Rural areas make up 37.5%, but urban areas account for 62.5% of the total NO 2 pollution in India for the period ...
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... thermal power plants (e.g. the Vindhyachal TPS and Parichha TPS) also contributed to the high NO x over urban regions, with pollutant transport to adjoining rural regions causing a similar increase in NO 2 emissions there, except in NEI and HR due to limited air mass transport to these regions owing to their high-terrain topography, as shown in Fig. S4. † Aer the nationwide implementation of BSIII in 2010 (it was implemented only in 14 major cities in 2005), no major change is observed in the highly polluted regions, but a slight reduction is observed in rural and urban PI, rural NWI, rural CI and rural HR, indicating the direct impact of vehicular emissions on rural air quality. ...
Citations
... Both datasets indicate that emissions in China follow a parabolic trend, consistent with records from local monitoring systems and satellite measurements [13,84]. India demonstrated a sustained increase in emissions, aligning with studies based on ground-and satellite-based data [85][86][87], while Japan experienced a notable and sustained reduction in emissions during the same period [3]. The direct and strong relationships between REASv3.2.1 and satellite information corroborate these temporal similarities. ...
... In this sense, a set of trend patterns from SAM classification is comparable to that reported in North America, Europe, and Japan, aligning with global downward trends [4,49,65,111]. Some classes are also in accordance with trends reported for several regions in India, where a sustained increase in NO 2 has persisted since at least 2005, in accordance with regional studies and inventories [72,85,87]. A higher set of classes led us to describe the trend patterns in the eastern and southeastern regions of China, a pattern previously characterized by a parabolic curve (concealed trend) [11,47,112]. ...
... Specifically, the model corresponds to studies that indicate a general decrease in tropospheric NO 2 levels over industrialized and highly populated regions of the Western world, such as the US, the Netherlands, the UK, Italy, Japan, Germany, and France [3,65,121]. Conversely, the classification from SAM 100(nn48) also indicated that developing regions, such as China and India, have experienced increased tropospheric NO 2 levels at different stages in the last decades [13,72,[84][85][86][87]122]. ...
Nitrogen dioxide (NO2) is a critical air pollutant that has significant health and environmental impacts. Tropospheric NO2 refers specifically to the vertical column density of NO2, which is measured by satellites and serves as an indicator of anthropogenic NO2 sources. This pollutant is frequently assessed using satellite data owing to limitations in local monitoring. This investigation employs the Spectral Angle Mapper (SAM), a geometric machine-learning model, given its advantages in simplicity and computational efficiency, and OMI satellite measurements to carry out spatially supervised classification of tropospheric NO2 global patterns from 2005 to 2021. This study identifies four typical trends across developed urban centers, examining correlations with population growth, economic factors, and air quality policies. The results demonstrated regional variations, with a general downward trend in North America, Europe, and parts of Asia, underscoring the efficacy of stricter emission controls. However, upward trends persist in some Asian regions, reflecting varying policy implementations. This study revealed a pivotal inflection point around 2013, marking a shift in global NO2 dynamics. Although policies have led to improved air quality in some regions, achieving absolute decoupling of economic growth from NO2 emissions remains challenging. The COVID-19 pandemic has also exerted a significant influence, temporarily reducing emissions due to economic slowdowns. Overall, the SAM model effectively delineated NO2 patterns and provided insights for future policy and emission control strategies.
... Nevertheless, recent studies report increasing ozone precursors in India. For instance, Singh et al. (2023a) and Pathak and Kuttippurath (2022) studied the changes in NO 2 in rural and urban regions of India using satellite data and found its trend of 2×10 15 molec cm − 2 yr − 1 for the period of 2005-2019. The major sources of NO 2 are motor vehicles, power plants and waste disposal systems (Seinfeld & Pandis, 2016;Gopikrishnan et al., 2022). ...
There is a significant increase in ozone at the surface and troposphere due to growing population, industrialization and urbanization. The initiation of National Clean Air Programme (NCAP) in 2019 marked a turning point in addressing air pollution in Indian cities. The Central Pollution Control Board (CPCB) ground-based measurements show a reduction in number of days with continuous exposure to 8 h surface ozone (MDA-8) exceeding 100 ppb since the implementation of NCAP. For instance, cities such as Visakhapatnam and Tirupati reported zero days of MDA-8 ozone surpassing 100 ppb in 2022. Also, a substantial reduction is observed in the frequency of MDA-8 ozone exceeding the 100 ppb threshold at other stations. The NO2 and PM2.5 measurements from CPCB show a decreasing trend at most stations, whereas satellite-based HCHO and NO2 measurements show negative (0–0.004 mol m−2 month−1) and positive (0–0.02 m−2 month−1) trends, respectively, during the period of 2019–2022. Therefore, although the implementation of NCAP is oriented towards reducing PM10 concentrations, it is also proven to be effective in curbing ozone pollution in most cities of India. This study, therefore, suggests to continue the efforts of NCAP and to implement tailored regulations for reducing ozone pollution in cities with high pollution.
... These conditions during monsoon season led to a lower ozone concentration in India, mainly because of the reduction in net chemical production and stronger upward transport. However, the northern IGP and North West still have high TPO due to the anthropogenic sources of HCHO and NO x there (Ghude et al., 2008;Kuttippurath et al., 2022a;Pathak and Kuttippurath, 2022). ...
At higher concentrations, tropospheric ozone can cause respiratory difficulties, premature human mortality and can harm vegetation by reducing photosynthesis and its growth. It is an oxidant and also an important green- house gas with positive feedback to temperature. It is produced as a byproduct of chemical reactions involving nitrogen oxides (NO ) and volatile organic compounds (VOCs) in the presence of sunlight, rather than being emitted directly to the atmosphere. Here, we analyse the seasonal and inter-annual variability, long-term trends and radiative forcing of the tropospheric column ozone (TPO) in India for the period of 2005–2020 using satellite and ground-based data. The analysis shows very high annual averaged TPO in the Indo-Gangetic Plain (IGP) and North West India, about 45–50 DU. Our findings reveal a significant increase of TPO in India, with the highest trend in the peninsular region (0.295 ± 0.0617 DU/year) and the lowest in North West (0.179 ± 0.048 DU/ year). The increase in tropospheric ozone reveals a warming of about 0.5 °C in the troposphere as there is an as- sociated radiative forcing of about 0.2–0.5 W/m 2 at the tropopause (125 hPa); indicating that the increasing tropospheric ozone is a great concern for regional warming, public health and ecosystem dynamics.
... 6 Wet deposition and photolysis are the processes that act as sinks of NO 2 in the atmosphere. 3,7 NO x plays an important role in the formation of secondary aerosols, particulate matter (PM) and different trace gases including surface ozone and indirectly affect the regional and global climate. 8,9 The Third Pole (TP) is one of the remote and pristine regions on Earth that encompasses the Hindukush Himalaya (HKH) and Tien Shan Mountains. ...
The Third Pole, Hindu Kush Himalaya (HKH) and Tien Shan mountains, has been closely monitored for the past few decades because of its deteriorating environmental condition. Here, we analyse the spatio-temporal changes in tropospheric NO2 over TP using satellite observations from 2005 to 2020. The highest NO¬2 concentrations (i.e. ≥ 1 × 1015 molec. cm-2) are found in the boundaries close to Indo-Gangetic Plain (IGP), and Yellow and Yangtze River basins (YYRB). The analysis of Emissions Database for Global Atmospheric Research (EDGAR v6.1) shows that the main contribution to NO2 in the region is from the road transport (81%) and then power sector (7%). The Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) analyses illustrate that the major regions from which air mass reach TP is from IGP, Southeast Asia, YYRB, Central Asia and Middle East. Our analysis reveals a positive trend in NO2 over most regions of TP (up to 0.05 ± 0.01 × 1015 molec. cm-2 year-1) in the yearly averaged data for the period 2005–2020, which suggest that the pollution is spreading even to the inner regions of TP. Therefore, this study reveals that the inner TP, one of the most pristine regions on the earth, is getting polluted because of high anthropogenic activities within and nearby areas/cities; indicating the impact of regional development activities and socioeconomic changes in recent years.
The Indo-Gangetic Plain of South Asia, is one of the major urban air pollution hotspots in the world. Rapid urbanisation, associated with heavy dependency on industrial, agricultural, vehicular and household activities has contributed to a rise in air pollutants in the recent past. Among air pollutants, fine and coarse particulate matter (PM2.5 and PM10) and black carbon aerosols, are of great concern in the lower-middle countries of the globe. The particulate matter and trace gases (NOx and SO2) has affected 18.6 million people of Delhi with dense haze and smog. Acute and chronic exposure to air pollution has been linked to a variety of severe lung and heart disease, as well as other health issues. It is responsible for the 24% cases of strokes, 25% case of ischemic heart disease, 28% cases of lung cancer, and 43% cases of chronic obstructive pulmonary diseases in the world. India, itself has witnessed around 1.24 million fatalities due to air pollution, with ambient particulate matter accounting for 54% of these deaths. The megacities and semiurban region of the Indo-Gangetic Plains accounted for approximately 62% and 49% of the overall black carbon attributable cardiovascular disease mortality (CVM) burden respectively. Therefore, the chapter will attempt to review the work carried out on outdoor air pollutants, and its detrimental health effects in the Indo-Gangetic Plains.
The direct effect of pandemic induced lockdown (LD) on environment is widely explored, but its secondary impacts remain largely unexplored. Therefore, we assess the response of surface greenness and photosynthetic activity to the LD-induced improvement of air quality in India. Our analysis reveals a significant improvement in air quality marked by reduced levels of aerosols (AOD, -19.27%) and Particulate Matter (PM 2.5, -23%) during LD (2020) LD (2020) from pre-LD (March-September months for the period 2017-2019). The vegetation exhibit positive response reflected by increase in surface greenness [Enhanced Vegetation Index (EVI, +10.4%)] and photosynthetic activity [Solar Induced Florescence (SiF, +11%)] during LD from pre-LD that coincides with two major agricultural seasons of India; Zaid (March-May) and Kharif (June-September). In addition, the croplands show a higher response [two-fold in EVI (14.45%) and four-fold in SiF (17.7%)] than that of forests. The prolonged growing period (phenology) and high rate of photosynthesis (intensification) led to the enhanced greening during LD owing to reduced pollution. This study, therefore, provides new insights into the response of vegetation to the improved air quality, which would give ideas to counter the challenges of food security in the context of climate pollution, and combat global warming by more greening.
