Temperature projections and heatwave attribution scenarios over India: A systematic review.

The average global temperature is rising due to anthropogenic emissions. Hence, a systematic approach was used to examine the projected impacts of rising global temperatures on heatwaves in India and provide insights into mitigation and adaptation strategies. With over 24,000 deaths attributed to heatwaves from 1992 to 2015, there is an urgent need to understand India's vulnerabilities and prepare adaptive strategies under various emission scenarios.This situation is predicted to worsen as heatwaves become more frequent, intense, and long-lasting. Severe heatwaves can exacerbate chronic health conditions, vector-borne diseases, air pollution, droughts and other socio-economic pressures causing higher mortality and morbidity. Heatwaves with severe consequences have increased and are expected to become more frequent in Indian climatic and geographical conditions. As per the future projection studies, the temperature could rise ±1.2° C to ±3.5° C and will start reducing by the end of 2050. The study also provides data from the research that employs climatic models and statistical approaches for a more precise characterization of heat extremes and improved projections. Also, the study appraises the past, present and future heatwave trend projections. Most of these studies compute future projections using the Coupled Model Intercomparison Project (CMIP5) models and Representative Concentration Pathway (RCP). Limited systematic reports have been found using CMIP6, whereas the best-suited and widely used method was the RCP8.5. The study findings will aid in identifying the zones most susceptible to heatwave risk and provide actionable projections for policymakers to examine the existing evidence for developing proper planning and policy formulation, considering the future climate and temperature projections.

Health risk assessment of aerosol particles (PM2.5 and PM10) during winter crop at the agricultural site of Delhi, India.

For the last few decades, air pollution in developing country like India is increasing, and it is a matter of huge concern due to its associated human health impacts. In this region, the burgeoning population, escalating urbanization and industrialization, has been cited as the major reason for such a high air pollution. The present study was carried out for health risk assessment of aerosol particles (PM10 and PM2.5) and its associated heavy metals of an agriculture farm site at Indian Agricultural Research Institute (IARI) considered to be green urban area in Delhi, India. The concentrations of both PM10 and PM2.5 varied significantly from 136 to 177 µg/m3 and 56 to 162 µg/m3, respectively at the site. In the present case, the highest PM10 and PM2.5 levels were reported in January, followed by December. The levels of ambient PM10 and PM2.5 are influenced by wind prevailing meteorology. These levels of PM10 and PM2.5 are more than the permissible limits of WHO guidelines of 15 and 5 µg/m3, respectively, thereby leading to high aerosol loadings specifically in winters. The PM concentration of the atmosphere was found to be negatively correlated with temperature during the sampling period. The concentrations of surface ozone O3 and NOx in the present study were observed to be high in February and March, respectively. The increasing air pollution in the city of Delhi poses a great risk to the human health, as the particulate matter loaded with heavy metals can enter humans via different pathways, viz., ingestion, inhalation, and absorption through skin. The mean hazard index for metals (Zn, Pb, Cd, As, Cr, and Ni) was observed within the acceptable limit (HI < 1), thereby indicating negligible non-carcinogenic effects to residing population. The carcinogenic risk assessment was conducted for Cd, Pb, and As only, as the concentrations for other metals were found to be quite low. The carcinogenic risk values were also within the limits of USEPA standards, indicating no carcinogenic risks to the health of children and adults residing near the site. This information about the PM pollution at the agricultural site and health risk assessment will serve as a baseline data in assessment of human health impacts due to air pollution at the local scale and can be used for development of mitigation strategies for tackling air pollution.

Environmental impacts of Indian coal thermal power plants and associated human health risk to the nearby residential communities: A potential review.

Worldwide, harmful emissions from coal power plants cause many illnesses contribute to premature deaths burden. Despite its high impact on human health and being a major source of toxic pollutants, coal has been considered a component of global energy for decades. Hence, this work was envisaged to understand the rising environmental and multiple health issues from coal power plants. Studies on the adverse impacts of coal power plants on the environment, including soil, surface water, groundwater and air, were critically evaluated. The health risk from exposure to different pollutants and toxic metals released from the power plant was also demonstrated. The study also highlighted the government initiatives and policies regarding coal power operation and generation. Lastly, the study focused on guiding coal power plant owners and policymakers in identifying the essential cues for the risk assessment and management. The current study found an association between environmental and human health risks due to power generation, which needs intervention from the scientific and medical fields to jointly address public concerns. It is also suggested that future research should concentrate on exposure assessment techniques by integrating source-identification and geographic information systems to assess the health effects of different contaminants from power plants and to mitigate their adverse impact.

Very high particulate pollution over northwest India captured by a high-density in situ sensor network.

Exposure to particulate matter less than 2.5 µm in diameter (PM2.5) is a cause of concern in cities and major emission regions of northern India. An intensive field campaign involving the states of Punjab, Haryana and Delhi national capital region (NCR) was conducted in 2022 using 29 Compact and Useful PM2.5 Instrument with Gas sensors (CUPI-Gs). Continuous observations show that the PM2.5 in the region increased gradually from < 60 µg m-3 in 6-10 October to up to 500 µg m-3 on 5-9 November, which subsequently decreased to about 100 µg m-3 in 20-30 November. Two distinct plumes of PM2.5 over 500 µg m-3 are tracked from crop residue burning in Punjab to Delhi NCR on 2-3 November and 10-11 November with delays of 1 and 3 days, respectively. Experimental campaign demonstrates the advantages of source region observations to link agricultural waste burning and air pollution at local to regional scales.

The concentration of potentially toxic elements (PTEs) in drinking water from Shiraz, Iran: a health risk assessment of samples.

The existence of potentially toxic elements (PTEs) in water bodies has posed a menace to human health. Thus, water resources should be protected from PTEs, and their effect on the exposed population should be investigated. In the present investigation, the concentrations of PTEs such as lead (Pb), mercury (Hg), manganese (Mn), and iron(Fe) in the drinking water of Shiraz, Iran, were determined for the first time. In addition, hazard quotient, hazard index, cancer risk, and sensitivity analysis were applied to estimate the noncarcinogenic and carcinogenic impacts of Pb, Hg, Mn, and Fe on exposed children and adults through ingestion. The mean concentrations (µg/L) of Pb, Hg, Mn, and Fe were 0.36, 0.32, 2.28, and 8.72, respectively, in winter and 0.50, 0.20, 0.55, and 10.36, respectively, in summer. The results displayed that Fe concentration was more than the other PTEs. PTE concentrations were lower than the standard values of the Environment Protection Agency and World Health Organization. Values of the degree of contamination and heavy metal pollution index for lead, mercury, manganese, and iron were significantly low (< 1) and excellent (< 50), respectively. Based on the Spearman rank correlation analysis, positive and negative relationships were observed in the present study. The observations of the health risk assessment demonstrated that mercury, lead, iron, and manganese had an acceptable level of noncarcinogenic harmful health risk in exposed children and adults (hazard quotients < 1 and hazard index < 1). The carcinogenic risk of lead was low (< E - 06), which can be neglected. Monte Carlo simulation showed that water intake rate and mercury concentration were the most critical parameters in the hazard index for children and adults. Lead concentration was also the most crucial factor in the cancer risk analysis. The results of the present study proved that the drinking water of Shiraz is safe and healthy and can be confidently consumed by people.

Application of machine learning approaches to predict the impact of ambient air pollution on outpatient visits for acute respiratory infections.

With a remarkable increase in industrialization among fast-developing countries, air pollution is rising at an alarming rate and has become a public health concern. The study aims to examine the effect of air pollution on patient's hospital visits for respiratory diseases, particularly Acute Respiratory Infections (ARI). Outpatient hospital visits, air pollution and meteorological parameters were collected from March 2018 to October 2021. Eight machine learning algorithms (Random Forest model, K-Nearest Neighbors regression model, Linear regression model, LASSO regression model, Decision Tree Regressor, Support Vector Regression, X.G. Boost and Deep Neural Network with 5-layers) were applied for the analysis of daily air pollutants and outpatient visits for ARI. The evaluation was done by using 5-cross-fold confirmations. The data was randomly divided into test and training data sets at a scale of 1:2, respectively. Results show that among the studied eight machine learning models, the Random Forest model has given the best performance with R2 = 0.606, 0.608 without lag and 1-day lag respectively on ARI patients and R2 = 0.872, 0.871 without lag and 1-day lag respectively on total patients. All eight models did not perform well with the lag effect on the ARI patient dataset but performed better on the total patient dataset. Thus, the study did not find any significant association between ARI patients and ambient air pollution due to the intermittent availability of data during the COVID-19 period. This study gives insight into developing machine learning programs for risk prediction that can be used to predict analytics for several other diseases apart from ARI, such as heart disease and other respiratory diseases.

Understanding the influence of summer biomass burning on air quality in North India: Eight cities field campaign study.

Near real-time monitoring of major air pollutants, i.e., particulate matter (PM10, PM2.5, PM1), trace gases (O3, CO, NO, NO2, NOx, NH3, CO2, SO2) and Volatile Organic Compounds (VOCs: benzene, ethylbenzene, m-, p-xylene, o-xylene and toluene) along with climatological parameters was done in eight-cities field campaigns during the rabi (wheat) crop residue burning period in the northwest of Indo-Gangetic Plain (IGP) region. The phase-wise monitoring was done at eight locations representing rural, semi-urban and urban backgrounds. During the whole campaign, the semi-urban site (Sirsa) observed the highest average concentration of PM10 (226 ± 111 µg m-3) and PM2.5 (91 ± 67 µg m-3). The urban site (Chandigarh) reported the minimum concentrations of all the three size fractions of particulate matter with PM10 as 89 ± 54 µg m-3, PM2.5 as 42 ± 22 µg m-3 and PM1 as 20 ± 13 µg m-3 where the monitoring was done in the early phase of the campaign. The highest VOC concentration was recorded at the semi-urban (Sirsa) site, whereas the lowest was at a rural location (Fatehgarh Sahib). NH3 concentration was observed highest in rural sites (31.7 ± 29.8 ppbv), which can be due to the application of fertilizers in agricultural activities. Visible Infrared Imaging Radiometer Suite (VIIRS) based fire and thermal anomalies, along with HYSPLIT back trajectory analysis, show that major air masses over monitoring sites (22 %-70 %) were from the rabi crop residue burning regions. The characteristic ratios and Principal component analysis (PCA) results show that diverse sources, i.e., emissions from crop residue burning, solid biomass fuels, vehicles and industries, majorly degrade the regional air quality. This multi-city study observed that semi-urban regions have the most compromised air quality during the rabi crop residue burning and need attention to address the air quality issues in the IGP region.

Evaluation of groundwater for drinking and irrigation applications concerning physicochemical and ionic parameters through multiple indexing approach: a case study around the industrial zone, Punjab, India.

The seasonal quality of groundwater and its appropriateness for drinking and irrigation were assessed using a multiple indexing approach in this study. Physicochemical and ionic parameters were examined in groundwater samples near the industrial zone of Rupnagar, Punjab. To assess groundwater quality, water quality index (WQI) and pollution index were used. The Durov's, piper, wilcox and stiff diagrams were plotted to understand the hydro-chemistry. Similarly, the irrigation indices, i.e., salinity hazard, sodium adsorption ratio, soluble sodium percentage (Na%), magnesium adsorption ratio, residual sodium carbonate, permeability index and Kelley's ratio were applied to ascertain the water quality for agricultural purposes. As a result, total hardness, calcium (Ca2+), magnesium (Mg2+) and fluoride (F-) were found above the standard permissible limits. WQI analysis showed 12% samples of pre-monsoon (PRE-M) and 28% samples of post-monsoon (POS-M) were of poor quality, which may pose health risks. Hydrochemistry revealed the predominance of Ca2+, Na+, Mg2+ and HCO3- ions in the groundwater attributed to natural and anthropogenic sources. Piper diagram revealed Ca2+-Mg2+-Cl-, Na+-Cl-, Ca2+-Na+- HCO3-, Ca2+- HCO3- and Ca2+-Cl, Ca2+-HCO3- water types exist in the study area. USSL diagram showed that the samples from both seasons come under the low salinity hazard. In addition, total dissolved solids and electrical conductivity showed a strong positive association, indicating the saline nature of groundwater. Furthermore, hierarchical clustering classified groundwater into three groups (I, II and III), revealing that groundwater quality varies due to natural and anthropogenic effects. Based on the findings, the groundwater was found marginally suitable for drinking and irrigation purposes. It is therefore recommended that the groundwater is examined on a regular basis in order to maintain its quality.

Identification of prominent airborne pollen in a city situated in foot-hills of Himalayas, Chandigarh, India.

Pollen allergy is considered one of the important critical thrust areas, as 20-30% of the world population suffers from allergic rhinitis. The increase in global surface temperature directly affects pollen physiological (e.g., pollen production) and morphological parameters and indirectly affects the distribution pattern, the allergenic potential of pollen, and plant species. Therefore, periodic sampling and pollen studies of a region have become necessary to assess the status of change in species and its morphological characteristics of different taxa. The current study is conducted to identify the airborne pollen based on studying their unique and distinctive morphological characters to serve as a reference pollen guide for future research. The airborne pollens were trapped using the Burkard volumetric sampler at three different locations in Chandigarh from 2018 to 2020 and analyzed under Leica DM5500B-Automated Upright Microscope System. The study investigated various pollen features such as shape, size, aperture type, and exine/surface pattern for taxonomic classification of plant groups. The majority of LM-analyzed pollen grains were prolate-spheroidal or oblate, whereas the aperture types were 3-zonocolporate, 3-colpate, and 3-zonocolporate. Exine patterns were predominantly psilate, reticulate, and straite and were easily discernible. Nonetheless, the vast majority of airborne pollen belonging to both arboreal and non-arboreal was quite small and fall into small pollen size classes, i.e., 10-24 µm. The exine pattern was readily apparent and were predominantly psilate, reticulate, and straight. The current study improved the knowledge on airborne pollen biodiversity, which will help to understand the regional distribution, long-range transport, and construct the current status of morphological features of species/taxa.

The multiple value characteristics of fly ash from Indian coal thermal power plants: a review.

Coal-powered thermal plants are the primary source of energy production around the globe. More than half (56.89%) of the Indian power plants use coal for power production. Coal burning in power plants results in coal combustion residuals, which contain coal fly ash (CFA) that is recognized as principle by-product. CFA is difficult to characterize due to its broad compositional variation. Hence, the present article summarizes the various physical, chemical, mineralogical, and petrological characterizations of CFA to its use in different applications. Indian coal thermal power plants are found to release two types of CFA: F (fine) and C (coarse). CFA particles are identified as unburned carbon particles with a large fraction of silica oxides, alumina oxides, and iron oxides with a small fraction of calcium oxide (CaO). Morphologically, CFA particles are spherical, with large carbon molecules and a smooth texture surface. In terms of mineralogy; quartz, mullite, magnetite, and hematite are the dominant mineral phases of CFA and tend to be non-plastic, with permeability levels ranging from 8 × 10-6 to 1.87 × 10-4 cms-1. Petrographically, CFA is enriched in inertinite and liptinites as well as collotelinite, collodetrinite, and vitrodetrinite particles. Moreover, CFA is found to be composed of various organic and inorganic particles. By virtue of multiple characterizations, it has been utilized in several applications for decades, which is still quite limited. Therefore, current study aim to provide helpful insights into the potential use of CFA-derived products in different ways to increase sustainability.

Occupational exposure to airborne pollen and associated health risks among gardeners: a perception-based survey.

Airborne pollen are considered a major trigger of respiratory diseases that causes morbidity and subsequently affects a person's quality of life (QOL). Outdoor workers, such as gardeners, florists, etc., are at greater risk of allergies due to continuous exposure to the high concentration of allergens. The current study aims to assess the associated health risks among gardeners due to occupational exposure to airborne pollen. A semi-structured questionnaire-based survey was conducted among gardeners (496) in Chandigarh, covering their socio-demographic status, occupational and environmental history, and respiratory and other health-related problems. Out of 496 respondents from 26 gardens in the city, 72.58% fall under the category of plantsman (mali), followed by 15.72% of grass cutters and 3.02% of headmali/supervisor. The majority of gardeners were males (95.76%) and a maximum number of respondents were in the age group of 29-38 years (27.41%). Among all, 4.2%, 3.6%, and 3.2% of respondents perceived the problem of shortness of breath and breathing problems. At the same time, 3.2% of respondents perceived that their breathing is never wholly satisfactory and surprisingly, all of them are plantsman (mali). Moreover, 18.9% of the respondents covered their faces with a cloth and only 0.5% of the respondents wore both spectacles and covered their faces with a cloth. Out of all respondents, 6.5% reported irritation in the eyes without wearing any personal protective device. The results show that a large proportion of gardeners are illiterate and unaware of occupational hazards and pollen allergies in their workplaces. Moreover, the regulatory authorities conduct no formal health awareness and training/education sessions to minimize the exposure and associate risk. The findings of the study will aid in a better understanding of the working conditions and health status of occupational gardeners, as well as the development of appropriate methods to improve their working conditions.

Preventable mortality attributable to exposure to air pollution at the rural district of Punjab, India.

Air pollution has emerged as a leading global health risk in recent decades, where its health impacts are primarily focused on urban areas. In India, semi-urban and rural areas are also emerging as air pollution hotspots. As these regions are out of focus, the current study monitored air pollution (PM2.5) at a rural district of Punjab in North India and attempted to study the associated health impacts. Hospital data of outpatient department (OPD), inpatient department (IPD) and all-cause mortality was correlated with change in PM2.5 concentrations. PM2.5 concentrations showed seasonal variations having relatively higher concentrations during post-monsoon and winter seasons. This rise in air pollution (annual average 92 µg/m3) was found to be mainly due to crop residue burning, including local meteorology. In comparison, hospital data shows that hospital visits and admissions were higher during monsoon. This shows that hospital admissions could not be directly linked to air pollution in rural areas as other factors such as short days during winters and self-medication, socio-economic factors and dependency on local unauthorised traditional healers may influence. The application of the AirQ + model for short-term health effects reveals that out of 2582 total deaths, preventable deaths ranging from 246 (WHO guidelines value - 10 µg/m3) to 159 (Indian NAAQS - 40 µg/m3) could be ascribed to air pollution exposure and specifically PM2.5. However, these deaths are avoidable by developing strategies to minimise air pollution in rural areas. Hence, a comprehensive approach is needed to plan air pollution reduction strategies, including urban, semi-urban and rural areas.

Pollen allergy: Developing multi-sectorial strategies for its prevention and control in lower and middle-income countries.

Pollen allergy is considered a major public health problem that causes morbidity and subsequently affects a patient's quality of life. Pollen due to their large size cannot enter the thoracic regions of the respiratory tract but can affect the nasopharyngeal mucous membrane. At the same time, the submicronic-pollen particles can act as respirable particles reaching deeper into the upper airways leading to exacerbation of asthma, chronic obstructive pulmonary disease (COPD) and other allergic reactions. Based on the existing literature, expanding evidence shows that climate change and air pollutants could affect the pollen number, morphology, season, allergen content, and distribution pattern. Hence, this will influence the prevalence and occurrence of allergies linked to pollen exposure. Being a part of biogenic pollutants, pollen allergens are not expected to diminish in the foreseeable future. Therefore, it is imperative that steps need to be strengthened to improve and optimize preventive/adaptive strategies. This paper aims to review the major causes of widespread allergy, identify the major gaps, and suggest key preventive/adaptive measures to address the onset and exacerbation of pollen-related allergic diseases with a major focus on lower and middle-income countries. The study also discusses how-to implement the prevention and control measures at the individual, health care communities and organizations, Local Governments, National/International Governments levels to decrease the risk of illnesses associated with pollen allergy.

Distribution of heavy metals in surface soil near a coal power production unit: potential risk to ecology and human health.

Coal thermal power plants are the dominant factor in producing various hazardous elements in surrounding surface soil, resulting in a significant human health hazard. In the current study, the seasonal (pre- and post-monsoon) concentration of As, Cd, Co, Cr, Cu, Fe, Li, Mg, Mn, Ni, Pb, and Zn in surface soil around coal power production unit was analyzed using inductively coupled plasma-mass spectrometry (ICP-MS). The possible health risks throughout multiple exposure routes, i.e., ingestion, dermal, and inhalation were estimated for adult and children. Furthermore, geo-accumulation index (Igeo), enrichment factor (EF), pollution factor (CF), ecological risk index, and pollution load index (PLI) were applied to interpret the environmental pollution in the study area. The geospatial distribution pattern was computed to understand the trace and hazardous element distribution in the surface soil. As a result, the concentration of Fe (mg/kg) in pre-monsoon (15,620) and post-monsoon (27,180), Ni (mg/kg) in pre-monsoon (19.8), and post-monsoon (81.7) was found above the standard limits of soil prescribed by the WHO and FAO. Enrichment factor was observed between 0.95-6948 (pre-monsoon) and 0.53-116.09 (post-monsoon). The ecological risk index was found moderate to considerable for As and Cd metals during both seasons. In addition, the average PLI value was observed high for both seasons indicating the contamination of the study area with heavy metals. Moreover, Igeo values for Fe, Mg, and As were found relatively high. Conversely, health risks to the human population were found within the USEPA acceptable limits.

COVID-19 pandemic: What can we learn for better air quality and human health?

The COVID-19 lockdown resulted in improved air quality in many cities across the world. With the objective of what could be the new learning from the COVID-19 pandemic and subsequent lockdowns for better air quality and human health, a critical synthesis of the available evidence concerning air pollution reduction, the population at risk and natural versus anthropogenic emissions was conducted. Can the new societal norms adopted during pandemics, such as the use of face cover, awareness regarding respiratory hand hygiene, and physical distancing, help in reducing disease burden in the future? The use of masks will be more socially acceptable during the high air pollution episodes in lower and middle-income countries, which could help to reduce air pollution exposure. Although post-pandemic, some air pollution reduction strategies may be affected, such as car-pooling and the use of mass transit systems for commuting to avoid exposure to airborne infections like coronavirus. However, promoting non-motorized modes of transportation such as cycling and walking within cities as currently being enabled in Europe and other countries could overshadow such losses. This demand focus on increasing walkability in a town for all ages and populations, including for a differently-abled community. The study highlighted that for better health and sustainability there. is also a need to promote other measures such as work-from-home, technological infrastructure, the extension of smart cities, and the use of information technology.

Understanding seasonal variation in ambient air quality and its relationship with crop residue burning activities in an agrarian state of India.

In India, Indo-Gangetic Plains (IGP) is becoming the hotspot of air pollution due to increasing anthropogenic activities such as rapid industrial growth, infrastructure development, transportation activities, and seasonal practice of crop residue burning. In the current study, seasonal variation in ambient air quality for 14 parameters, i.e., particulate matter (PM), trace gases, and volatile organic compounds (VOCs), along with meteorological parameters, was studied in 21 districts of the Haryana state for year 2019, situated in IGP. To analyze spatial variation of pollutants, ambient air quality data of 23 continuous ambient air quality monitoring stations were divided into three zones based on ecology and cropping pattern. All the zones showed annual mean PM10 and PM2.5 concentrations much higher than national ambient air quality standards. Annual mean PM10 concentration (±standard deviation) in Zones-1, 2, and 3 was 156±86, 174±93, and 143±74 µg m-3, whereas for PM2.5 was 71±44, 85±54, and 78±47 µg m-3. The results showed a considerable seasonal variation in the concentration of all pollutants. Most of the pollutants peak in the post-monsoon season, followed by winters in which crop residue burning predominates in many parts of the Haryana. PM10 concentrations increased by 65-112% and PM2.5 concentrations increased by 131-147% in the post-monsoon season compared to monsoons. The post-monsoon season showed the highest concentration of PM10, NO, and toluene (Zone-1); and PM2.5, NH3, CO, and benzene (Zone-2); whereas in winters, SO2 (Zone-1); ethylbenzene, m,p-xylene, and xylene (Zone-2); and NO2 and NOx (Zone-3) showed the maximum pollution levels. The O3 concentration was highest in the pre-monsoon season (Zone-1). The satellite-based fire counts and PCA results show a significant influence of crop residue burning in the post-monsoon season and solid biomass burning in winters on Haryana's air quality. The study could help to understand seasonal variation in ambient air quality and the influence of factors such as crop residue burning in the IGP region, which could help to formulate season-specific control measures to improve regional air quality.

Seasonal variations in carbonaceous species of PM2.5 aerosols at an urban location situated in Indo-Gangetic Plain and its relationship with transport pathways, including the potential sources.

The study examines the variation in organic carbon (OC) and elemental carbon (EC) in PM2.5 concentration at an urban location of Indo-Gangetic Plains (IGP) to understand the impact of seasonality and regional crop residue burning activities. Seasonal cluster analysis of backward air masses and concentration-weighted trajectory (CWT) analysis was performed to identify seasonal transport pathways and potential source regions of carbonaceous aerosols. The mean PM2.5 level during the study period was 57 ± 41.6 µgm-3 (5.0-187.3 µgm-3), whereas OC and EC concentration ranges from 2.8 µgm-3 to 28.2 µgm-3 and 1.3 µgm-3 to 15.5 µgm-3 with a mean value of 8.4 ± 5.5 µgm-3 and 5.1 ± 3.3 µgm-3 respectively. The highest mean PM2.5 concentration was found during the winter season (111.3 ± 25.5 µgm-3), which rises 3.6 times compared to the monsoon season. OC and EC also follow a similar trend having the highest levels in winter. Total carbonaceous aerosols contribute ∼38% of PM2.5 composition. The positive linear trend between OC and EC identified the key sources. HYSPLIT cluster analysis of backward air mass trajectories revealed that during the post-monsoon, winters, pre-monsoon, and monsoon, 71%, 81%, 60%, and 43% of air masses originate within the 500 km radius of IGP. CWT analysis and abundance of OC in post-monsoon and winters season establish a linkage between regional solid-biomass fuel use and crop residue burning activities, including meteorology. Moreover, the low annual average OC/EC ratio (1.75) indicates the overall influence of vehicular emissions. The current dataset of carbonaceous aerosols collated with other Indian studies could be used to validate the global aerosol models on a regional scale and aid in evidence-based air pollution reduction strategies.

COVID-19 pandemic and sudden rise in crop residue burning in India: issues and prospects for sustainable crop residue management.

The seasonal burning of crop residue significantly affects the environment, leading to poor air quality over Indo-Gangetic Plain (IGP) in India. Hence, there have been significant efforts to minimize crop residue burning through policy, innovations, and awareness measures. However, an abrupt increase in paddy residue burning was observed over IGP during 2020. Hence, the study explores the factors leading to this sharp rise. The business as usual trends analysis revealed that paddy crop residue burning activities increased significantly (60%) in 2020 compared to the previous year. The massive increase in crop residue burning consequently seems to be linked with the COVID-19 pandemic, which affected the farmer's income, including the poor compliance by the regulatory authorities. The study also highlights the issues and prospects for sustainable crop residue management and explores the solutions to minimize crop residue burning. There are few crops in India that have guaranteed minimum sale price and are also subsidized. These provisions encourage farmers to grow those particular crops, resulting in the generation of large amounts of crop residue from these specific crops. There have been several efforts by the Indian government, including based on recent court intervention. Still, there is no respite from burning activities and the occurrence of Delhi winter smog every year. Hence, the study emphasizes a need to adopt integrated approaches having in situ eco-friendly solutions, which enhances the farmer's income and focuses on employability, capacity building, awareness generation, and in situ economically viable solutions.