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Building an effective clean air action plan for a city's air pollution problem requires an extensive network of monitoring stations to represent spatial and temporal patterns and an understanding of the sources contributing to the problem. In India, the National Clean Air Programme (NCAP) was launched in 2019 to develop clean air action plans for 131 non-attainment cities, which includes conducting source apportionment studies and establishing emission baselines. As of February 2023, only 39 cities have completed the apportionment studies. In this paper, we present the essential resources needed to strengthen the ambient air monitoring networks, for designing a representative airshed size, sampling size, and sampling frequency, to effectively track the progress made in the cities for better air quality. The NCAP cities were grouped into 104 airsheds (5.3% of the national area), collectively representing a total of 164 cities and a total population of 295 million (21% of the national total). Of these airsheds, 73 contain only one city; 18 contain two cities, and nine contain three cities. Four airsheds – Delhi, Mumbai, Indore, and Chandigarh contain 10, 8, 5, and 5 cities respectively. To measure and analyse particulate matter pollution, a total of 2118 sampling sites are recommended for the 104 airsheds. Cities could consider hybrid monitoring networks by complementing existing regulatory monitoring network with a high-density network of low-cost/sensor-grade monitors. An airshed level air quality management plan, an enhanced monitoring network, and consolidation of information on emission sources, are crucial for optimizing the clean air efforts under NCAP. [Display omitted] • Defined 104 airsheds to represent 131 non-attainment cities under NCAP. • Defined the minimum number of monitors required in the airsheds. • Conducted high-resolution meteorological modelling to determine minimum filter sampling frequency per airshed. • Examples of hybrid networks to reduce monitoring costs. [ABSTRACT FROM AUTHOR]

This paper presents the long – term observational studies on aerosol optical properties measured at Sri Krishnadevaraya University (SKU) campus (14° 62′ N, 77° 65′ E, 331m asl), Anantapur, in southern India during 2007–2013 using a ground based Multi – Wavelength solar Radiometer (MWR). Seasonal mean values of Aerosol Optical Depth (AOD) for the whole study period were observed to be 0.34 ± 0.03, 0.45 ± 0.04, 0.24 ± 0.04, and 0.31 ± 0.03 during the winter, summer, monsoon and post – monsoon, respectively. Annual mean values of Ångström exponent (α) (turbidity coefficient (β)) varied from 0.68 ± 0.25 (0.18 ± 0.03) to 1.1 ± 0.12 (0.32 ± 0.12) during 2007–2013. However, high values of α in the range of 0.8–1.1 were observed during the winter, while low values in the range 0.3–0.7 were noticed during the monsoon. The frequency distribution of AODs during winter in the range of 0.2–0.4 is about 78%, while summer these were shifted from 0.3 to 0.6 around ∼70%, which indicated the dust strongly affects this region. The accumulated frequencies of Ångström exponent (α) less than 1.0 and greater than 1.0 were about 69% and 31%, respectively, occurred in the summer months indicates the dominance of coarse particles. Columnar size distributions, retrieved from the spectral optical depths, in general, show a bimodal log normal distribution in the optically active size range. The seasonal mean effective radius (R eff ) was found to be high in monsoon (∼0.61 μm) and low in winter (∼0.38 μm). The highest mean mass loading values are lies between 475 ± 36 to 769 ± 49 mg m −2 during the summer, whereas the lowest value in the range 204 ± 19 to 278 ± 23 mg m −2 during the monsoon. The difference between α and curvature effect have been studied as a function of AOD on seasonal basis. Finally, to understand the contribution of long range transported aerosols, we have investigated this analysis making use of back trajectories obtained from the HYSPLIT model for different seasons. [ABSTRACT FROM AUTHOR]

This paper presents a new inventory of NMVOC emissions from anthropogenic sources in India for the year 2010. The main new element of this inventory, compared to previous work for India, is the use of new and more detailed data on solvent use sectors and oil production and distribution system. The results are presented at the national and state level for major sectors and VOC species. Finally, the annual emissions were spatially distributed at a fine resolution of 36 × 36 km 2 using detailed spatial information. The total anthropogenic NMVOC emissions in India in 2010 were estimated at 9.81 Tg which is in the range of the estimates made in most other studies. The majority of emissions (60%) originated from residential combustion of biomass for cooking. Solvent use sectors and oil production and distribution contributed about 20% followed by transport (12%) and open burning of agricultural residues (7%). Specie-wise distribution shows highest contribution from alkenes and alkynes (38%), followed by alkanes (22%), and aromatics (16%). [ABSTRACT FROM AUTHOR]

India has more than 100,000 brick kilns producing around 250 billion bricks annually. Indian brick industry is often a small scale industry and third largest consumer of coal in the country. With the growing demand for building materials and characterised by lack of pollution control measures the brick industry has a potential to cause adverse effects on the environment. This paper presents assessment of five brick making technologies based on the measurements carried out at seventeen individual brick kilns. Emissions of PM, SO 2 , CO and CO 2 were measured and these emissions were used to estimate the emission factors for comparing the emissions across different fuel or operating conditions. Estimated emission from brick kilns in South Asia are about 0.94 million tonnes of PM; 3.9 million tonnes of CO and 127 million tonnes of CO 2 per year. Among various technologies that are widely used in India, Zig zag and vertical shaft brick kilns showed better performance in terms of emissions over the traditional fixed chimney Bull's trench kilns. This suggests that the replacement of traditional technologies with Zig zag, vertical shaft brick kilns or other cleaner kiln technologies will contribute towards improvements in the environmental performance of brick kiln industry in the country. Zig zag kilns appear to be the logical replacement because of low capital investment, easy integration with the existing production process, and the possibility of retrofitting fixed chimney Bull's trench kilns into Zig zag firing. [ABSTRACT FROM AUTHOR]

The global burden of disease study estimated 695,000 premature deaths in 2010 due to continued exposure to outdoor particulate matter and ozone pollution for India. By 2030, the expected growth in many of the sectors (industries, residential, transportation, power generation, and construction) will result in an increase in pollution related health impacts for most cities. The available information on urban air pollution, their sources, and the potential of various interventions to control pollution, should help us propose a cleaner path to 2030. In this paper, we present an overview of the emission sources and control options for better air quality in Indian cities, with a particular focus on interventions like urban public transportation facilities; travel demand management; emission regulations for power plants; clean technology for brick kilns; management of road dust; and waste management to control open waste burning. Also included is a broader discussion on key institutional measures, like public awareness and scientific studies, necessary for building an effective air quality management plan in Indian cities. [ABSTRACT FROM AUTHOR]

Since the past two decades, high aerosol loading is being observed over the Indian mainland. It becomes necessary to continuously monitor and understand the distribution of aerosol loading over the Indian landmass, as it might have serious health and climatic implications. Whereas there have been extensive studies reporting seasonal distribution and trends of columnar aerosol amounts over the Indian region using data from ground based as well as space borne measurements, in-depth studies on the aerosol vertical profile distribution and in particular, seasonal trends are still lacking. This paper demonstrates the seasonal variability of aerosol vertical structure over the Indian mainland using decadal daily datasets (2009–2018) from CALIOP Lidar (onboard NASA-CNES's CALIPSO satellite) augmented by the variability in columnar AOD from MODIS (onboard NASA's AQUA and TERRA platforms). The changing aerosol amounts in both vertical and total column levels have also been presented. Over Indian landmass, we could find statistically significant increasing trends in aerosol extinction within lower altitude levels during all the seasons. The trends in the vertical distribution of aerosols are also compared with respect to trends in AOD derived from MODIS (Aqua/Terra). Additionally, we have also examined the seasonal variability and trends of aerosol extinction over five selected cities (based on pollution and population levels) of the country. • Decadal-scale seasonal variability of aerosol extinction profiles over India. • Increasing vertical and columnar trends of aerosols during all seasons. • Small and spherical particles more dominant during October–February. [ABSTRACT FROM AUTHOR]

Current ozone (O 3) concentration levels entail significant damages in crop yields around the world. The reaction of the emitted precursors (mostly methane and nitrogen oxides) with solar radiation contribute to O 3 levels that exceed established thresholds for crop damage. This paper shows current and projected (up to 2080) relative yield losses (RYLs) driven by O 3 exposure for different crops and the associated economic damages applying dynamic crop production and prices that are calculated per region and period. We adjust future crop yields in the Global Change Assessment Model (GCAM) to reflect the RYLs and analyze the effects on agricultural markets. We find that the changes (generally reductions) in O 3 precursor emissions in a reference scenario would reduce the agricultural damages, compared to present, for most of the regions, with a few exceptions including India, where higher future O 3 concentrations have large negative impacts on crop yields. The annual economic impact of O 3 driven losses from 2010 to 2080 are, in billion US dollars at 2015 prices ($B), 5.0–6.0, 9.8–18.8, 6.7–10.6 and 10.4–12.5 for corn, soybeans, rice and wheat, respectively, with the large losses for wheat and soybeans driven by their comparatively high responses to O 3. When O 3 effects are explicitly modelled as exogenous yield shocks in future periods, there is a direct impact in future agricultural markets. Therefore, the aggregated net present value (NPV) of crop production would be reduced around by $90.8 B at a global level. However, these changes are not distributed evenly across regions, and the net present market value of the crops would increase by up to $118.2 B (India) or decrease by up to $59.2 B (China). • Future ozone concentration levels will exceed established thresholds. • Annual economic damages of O 3 -related yield losses range from $34 B to $45 B. • USA, the European Union, India and China bear the majority of the economic damages. • Considering O 3 effects, cumulative NPV of crop production decreases around $90.8 B. [ABSTRACT FROM AUTHOR]

This paper deals with the temporal changes in the altitude distribution of tropospheric ozone (O 3) based on the measurements by balloon-borne O 3 -sondes during 2011–2014, conducted at the tropical, coastal site Thiruvananthapuram on the south west coast of India. This is the first study from this region addressing the highly dynamic nature of tropospheric O 3 profiles (in terms of their vertical structure and short-term changes) and attempting to categorise them based on 121 in-situ measured O 3 profiles. The tropospheric O 3 profiles could be categorised into four major groups namely (i) those with steady O 3 mixing ratio (ii) with increasing mixing ratio, (iii) with mid-tropospheric enhancement and (iv) with multiple layers/laminar nature. The causative mechanisms of these different categories were examined. The observed differences in the tropospheric O 3 distribution are attributed to meteorological conditions in particular the synoptic scale systems, long range transport, intrusion from stratosphere and photochemistry, most importantly, the effect of water vapour content. Water vapour and O 3 showed complex dependence with positive and negative association depending on the precursor levels and availability of water vapour. The altitudinal changes in O 3 also exhibited close association with those of potential temperature and equivalent potential temperature. An analysis of the seasonal characteristics of vertical distribution of tropospheric O 3 also carried out along with the altitude-dependent seasonal behaviour. In general, the total column O 3 estimated by the integration of O 3 -sonde retrieved profiles differed by about ±10% with those retrieved by satellite-based measurements. The TCO contributes to about 16% (34 DU) of the total column O 3 , with minimum of 9% in October and maximum of 27% on March. In general, the OMI retrievals under-estimates the O 3 -sonde derived TCO by 5–10 DU in all the seasons. • Dynamic nature of tropospheric O 3 profiles observations based on O 3 -sonde. • Dependence of O 3 on water vapour shows positive and negative correlation. • Amount of water vapour and precursors decide nature of water vapour dependence of O 3. • The seasonal variation of tropospheric O 3 is altitude-dependent. • Tropospheric column O 3 contributes about 16% of the total column O 3. [ABSTRACT FROM AUTHOR]