Source attribution of carbon monoxide over Northern India during crop residue burning period over Punjab.

National Capital Territory of Delhi and its satellite cities suffer from poor air quality during the post-monsoon months of October-November. In this study, a novel attempt is made to estimate the contribution of different emission sources (industrial, residential, power generation, transportation, biomass burning, photochemical production, lateral transport, etc.) towards the criteria air pollutant carbon monoxide (CO) concentration over North India. Multiple simulations of the WRF-Chem model with a tagged tracer approach with different inputs (6 anthropogenic emission inventories and 3 biomass burning emission inventories) were used. The model performance was evaluated against the MOPITT retrieved CO surface concentration. Analysis of model simulated CO over North India suggests that anthropogenic emissions contribute around 32-49% to surface CO concentration while crop residue burning contributes 27-44% of which 80% originates from Punjab. For Delhi, the contribution from anthropogenic sources is dominant (53-77%) of which 10-28% is from the domestic sector and 14-55% is from the transport sector. Agricultural waste burning contributes about 15-30% to Delhi's surface CO concentration (of which 75% originates from Punjab). Crop residue burning emission is a chief source of CO over Punjab with a contribution of about 56-76%. The results suggest that industrial, transport, and domestic sector activities are more responsible for increased CO levels over New Delhi and surrounding regions than crop residue burning over Punjab. Furthermore, critical meteorological parameters like 10 m wind speed, boundary layer height, 2 m temperature, total precipitation, and relative humidity were evaluated against CO concentration to understand their impact on CO distribution. Results conclude that deteriorating air quality over the North Indian region is caused by a combination of prevailing meteorological factors (such as slow winds, shallow mixing layer, and cold temperatures) and man-made emissions.

Source contribution of black carbon aerosol during 2020-2022 at an urban site in Indo-Gangetic Plain.

The extensive emissions of black carbon (BC) from the Indo-Gangetic Plain (IGP) region of India have been well recognized. Particularly, biomass emissions from month-specific crop-residue burning (April, May, October, November) and heating activities (December-February) are considered substantial contributors to BC emissions in the IGP. However, their precise contribution to ambient BC aerosol has not been quantified yet and remains an issue of debate. Therefore, this study aims to fill this gap by quantifying the contribution of these month-specific biomass emissions to ambient BC at an urban site in IGP. This study presents the analysis of BC mass concentrations (MBC) measured for 3 years (2020-2022) in Delhi using an optical photometer i.e., continuous soot monitoring system (COSMOS). A statistical analysis of monthly mean MBC and factors affecting the MBC (ventilation coefficients, air mass back trajectories, fire counts) is performed to derive month-wise contribution due to background concentration, conventional emission, regional transport, crop-residue burning, and heating activities. The yearly mean MBC (5.3 ± 4.7, 5.6 ± 5.0, and 5.3 ± 3.5 µg m-3 during 2020, 2021, and 2022, respectively) remained relatively consistent with repetitive monthly patterns in each year. The peak concentrations were observed from November to January and low concentrations from June to September. Anthropogenic activities contributed significantly to MBC over Delhi with background concentration contributing only 30 % of observed MBC. The percentage contribution of emissions from crop-residue burning varied from 15 % (May) to 37 % (November), while the contribution from heating activities ranged from 25 % (December) to 39 % (January). This source quantification study highlights the significant impact of month-specific biomass emissions in the IGP and can play a vital role in better management and control of these emissions in the region.

Hotspot driven air pollution during crop residue burning season in the Indo-Gangetic Plain, India.

Intensive crop residue burning (CRB) in northern India triggers severe air pollution episodes over the Indo-Gangetic Plain (IGP) each year during October and November. We have quantified the contribution of hotspot districts (HSDs) and total CRB to poor air quality over the IGP. Initially, we investigated the spatiotemporal distribution of CRB fire within the domain and pinpointed five HSD in each Punjab and Haryana. Furthermore, we have simulated air quality and quantified the impact of CRB using the Weather Research and Forecasting model coupled with Chemistry (WRF-Chem), incorporating recent anthropogenic emissions (EDGAR v5) and biomass burning emissions (FINN v2.4) inventories, along with MOZART-MOSAIC chemistry. The key finding is that HSDs contributed ∼80% and ∼50% of the total fire counts in Haryana and Punjab, respectively. The model effectively captured observed PM2.5 concentrations, with a normalized mean bias (NMB) below 0.2 and R-squared (R2) exceeding 0.65 at the majority of validation sites. However, some discrepancies were observed at a few sites in Delhi, Punjab, Haryana, and West Bengal. The National Capital Region experienced the highest PM2.5 concentrations, followed by Punjab, Haryana, Uttar Pradesh, Bihar, and West Bengal. Moreover, HSDs were responsible for about 70% of the total increase in CRB-induced PM2.5 in the western, central, and eastern cities, and around 50% in the northern cities. By eliminating CRB emissions across the domain, we could potentially save approximately 18,000 lives annually. Policymakers, scientists, and institutions can leverage the framework to address air pollution at national and global scales by targeting source-specific hotspots. This approach, coupled with appropriate technological and financial solutions, can contribute to achieving climate change and sustainable development goals.

Crop residue burning increased during the COVID-19 lockdown: A case study of rural India.

The customary practice of crop residue burning (CRB) is a major policy concern across several developing economies because of the associated increase in air pollution and reduction in soil quality. CRB poses a hazard to public health and sustainable farmland management. We collected original survey data from a panel of 400 wheat farmers on CRB choices during April-May of 2019 and 2020 - with the latter coinciding with India's COVID-19 nationwide lockdown. This timeline of events facilitated a unique identification of changes in CRB that are attributable to the lockdown. Several studies find that lockdowns during 2020 had beneficial effects on the environment owing to reduced economic activity. However, our findings indicate that CRB may have unintentionally increased during the lockdown. A binary variable regression framework analyzes the determinants of CRB choices of farmers over two years. We control for farmers' opinions on various socioeconomic aspects of the pandemic lockdown to examine its effects on their CRB decisions. The lockdown significantly increased the likelihood of CRB by up to 12%. Furthermore, farmers who lost agricultural income and those compelled to sell assets during the lockdown were 22% and 19% more inclined, respectively, to choose CRB. Labor mobility ceased during the lockdown and increased the cost of environmentally friendly farmland management; this increased the likelihood of CRB by 6%. This study contributes to a growing literature on the unintentional consequences of pandemic lockdowns.

Crop residue burning in China (2019-2021): Spatiotemporal patterns, environmental impact, and emission dynamics.

Crop residue burning (CRB) is a major contributor to air pollution in China. Current fire detection methods, however, are limited by either temporal resolution or accuracy, hindering the analysis of CRB's diurnal characteristics. Here we explore the diurnal spatiotemporal patterns and environmental impacts of CRB in China from 2019 to 2021 using the recently released NSMC-Himawari-8 hourly fire product. Our analysis identifies a decreasing directionality in CRB distribution in the Northeast and a notable southward shift of the CRB center, especially in winter, averaging an annual southward movement of 7.5°. Additionally, we observe a pronounced skewed distribution in daily CRB, predominantly between 17:00 and 20:00. Notably, nighttime CRB in China for the years 2019, 2020, and 2021 accounted for 51.9%, 48.5%, and 38.0% respectively, underscoring its significant environmental impact. The study further quantifies the hourly emissions from CRB in China over this period, with total emissions of CO, PM10, and PM2.5 amounting to 12,236, 2,530, and 2,258 Gg, respectively. Our findings also reveal variable lag effects of CRB on regional air quality and pollutants across different seasons, with the strongest impacts in spring and more immediate effects in late autumn. This research provides valuable insights for the regulation and control of diurnal CRB before and after large-scale agricultural activities in China, as well as the associated haze and other pollution weather conditions it causes.

Predicting opinion using deep learning: From burning to sustainable management of organic waste in Indian State of Punjab.

In winter season, the burning of crop residues for ease of sowing the next crop, along with industrial emissions and vehicular pollution leads to settling of a thick layer of smog in northern part of India. Therefore, to understand the opinion of farmers regarding sustainable management of organic waste, the present study was conducted in Ludhiana district of Indian state of Punjab. An ex post facto research design was used and a total of 800 dairy farmers having significant crop area were selected randomly for the study, grouped equally as small and large dairy farmers. Results revealed that majority of farmers had a highly favourable opinion regarding organic waste management due to the fact that they were aware of the ill-effects of undesirable practices like crop residue burning. Further, to predict the farmers' opinion and the effect of independent variables on farmers' opinion, a multi-layer perceptron feed-forward deep neural network was developed with mean squared error of 0.036 and 0.137 for validation and training data sets respectively, marking a novel approach of analysing farmers' behaviour. The neural network highlighted that with increase in the magnitude of input variables, namely, education, experience in dairying, information source utilisation, knowledge regarding organic waste management, etc., the farmers' opinion regarding sustainable waste management increases. The study concluded with the impression that cognitive processes like education, information and knowledge play a significant role in forming the opinion of the farmers. Therefore, efforts focusing on enhancing cognition should be made for sustainable management of organic waste.

Greenhouse gas emissions from agricultural residue burning have increased by 75 % since 2011 across India.

Quantifying crop residue burning across India is imperative, owing to its adverse impacts on public health, the environment, and agricultural productivity. Specific information about the extent and characteristics of agricultural crop burning can verify the emission potential of agricultural systems and thereby facilitate targeted dissemination of agricultural innovations and support policymakers in mitigating the harmful effects. With a focus on district-level burning estimates, our study provides a comprehensive seasonal analysis of agricultural burning in India, including burned area, dry matter burned, and gaseous emissions for seven major crops from 2011 to 2020. To quantify the actual residues burned, we developed a remote sensing-based approach that incorporates the monitoring of agricultural burned area to quantify the actual residues burned. Including this satellite measure of the burned area greatly improves emissions estimates and minimizes error compared to typical approaches, which instead use an assumed fraction of total residues that are burned for each crop type. We estimated that emissions have increased by approximately 75 % for CO and Greenhouse gasses - CO2, CH4 and N2O - from 2011 to 2020. Total CO2e emissions increased from ~19,340 Gg.yr-1 in 2011 to ~33,834 Gg.yr-1 in 2020. Most emissions occurred during end of the Kharif season, followed by Rabi, caused by the burning of rice and wheat residues. Among the Indian states, Punjab has the highest burning activity, with 27 % (2.0 million hectares) of its total cultivated area burned in 2020. Interestingly, Madhya Pradesh has emerged as the second-largest contributor, accounting for 30 % of the total burned area across India in 2020. Our study demonstrates how satellite data can be used to map agricultural residue burning at scale, and this information can provide crucial insights for policy framing, targeting, and interventions to manage agricultural residues without compromising air quality and climate.

A rapid assessment of stubble burning and air pollutants from satellite observations.

For the last several years, the air quality of India's capital Delhi and surrounding region (NCR) has been degrading to a very poor and severe category during the autumn season. In addition to the various sources of air pollutants within the NCR region, the stubble burning in Punjab and Haryana states contributes to the poor air quality in this region. The current study employs the Moderate Resolution Imaging Spectroradiometer (MODIS) active fire products and TROPOspheric Monitoring Instrument (TROPOMI) products on carbon monoxide (CO) and nitrogen dioxide (NO2) concentrations for spatio-temporal assessment of stubble burning and associated emissions. The analysis performed in the Google Earth Engine (GEE) platform indicated a nearly threefold rise in crop residue burning in November than in October, with 92.58% and 7.42% reported from Punjab and the Haryana states in November, respectively. The study highlights the availability of near-real-time remote sensing observations and the utility of the GEE platform for rapid assessment of stubble burning and emissions thereof, having the potential for developing mitigation strategies.

Estimation of agricultural burned affected area using NDVI and dNBR satellite-based empirical models.

One of the major crucial issues that need worldwide attention is open stubble burning, which imposes a variety of adverse impacts on nature and human society, destroying the world's biodiversity. Many earth observation satellites render information to monitor and assess agricultural burning activities. In this study, different remotely sensed data (Sentinel-2A, VIIRS) has been employed to estimate the quantitative measurements of agricultural burned areas of the Purba Bardhaman district from October-December 2018. The multi-temporal image differencing techniques and indices (NDVI, NBR, and dNBR) and VIIRS active fires data (VNP14IMGT) have been utilized to spot agricultural burned areas. In the case of the NDVI technique, a prominent area, 184.82 km2 of agricultural burned area (7.85% of the total agriculture), was observed. The highest (23.04 km2) burned area was observed in the Bhatar block, located in the middle part of the district, and the lowest (0.11 km2) burned area was observed in the Purbasthali-II block, which is located in the eastern part of the district. On the other hand, the dNBR technique revealed that the agricultural burned areas enwrap 8.18% of the total agricultural area, which is 192.45 km2. As per the earlier NDVI technique, the highest agricultural burned areas (24.82 km2) were observed in the Bhatar block, and the lowest (0.13 km2) burn area occurred in the Purbashthali-II block. In both cases, it is observed that agricultural residue burning is high in the western part of the Satgachia block and the adjacent areas of the Bhatar block, which is in the middle part of Purba Bardhaman. The agricultural burned area was extracted using different spectral separability analyses, and the performance of dNBR was the most effective in spectral discrimination of burned and unburned surfaces. This study manifested that agricultural residue burning started in the central part of Purba Bardhaman. Later it spread all over the district due to the trend of early harvesting rice crops in this region. The performance of different indices for mapping the burned areas was evaluated and compared, revealing a strong correlation (R2) = 0.98. To estimate the campaign's effectiveness against the dangerous practice and plan the control of the menace, regular monitoring of crop stubble burning using satellite data is required.

Bio-energy potential of available livestock waste and surplus agriculture crop residue: An analysis of 602 rural districts of India.

The majority of households in rural India use cow dung and crop residue for cooking, which contributes to both indoor and outdoor air pollution. After being used for cooking and other agricultural purposes, surplus crop residue left uncollected and burned openly accountable for notorious air pollution episodes in India. Air pollution and clean energy are critical challenges in India. Utilizing locally available biomass waste can be a sustainable solution to reducing air pollution and energy poverty. However, formulating any such policy and its practical implementation requires a clear understanding of currently available resources. The current study presents the first district-scale analysis of the cooking energy potential of locally available biomass (livestock and crop waste) if converted to energy by anaerobic digestion processes for 602 rural districts. The analysis indicates that rural India needs 1927TJ/day (2.75 MJ/capita-day) energy to meet the cooking energy demand. Utilizing locally available livestock waste can generate 715 TJ/day (1.02 MJ/capita-day) of energy, equivalent to 37 % of the demand. Only 2.15 % of districts have 100 % potential for cooking energy demand by utilizing locally produced livestock waste. Using surplus crop residue for energy can provide 2296 TJ/day(3.27 MJ/capita-day) of energy. If locally utilized, surplus residue can meet 100 % of energy demand in 39 % of districts. Combining livestock waste and surplus residue can produce 3011 TJ/day(4.29 MJ/capita-day) of energy, fulfilling >100 % of energy demand in 55.6 % of rural districts. Furthermore, converting agricultural waste into clean energy has the potential to reduce PM2.5 emissions by 33 % to 85 % in different scenarios.

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.

Quantification and evaluation of atmospheric emissions from crop residue burning constrained by satellite observations in China during 2016-2020.

In rural regions of China, crop residue burning (CRB) is the major biomass burning activity, which can result in massive emissions of atmospheric particulate, greenhouse gas, and trace gas pollutants. Based on Himawari-8 satellite fire radiative power and agricultural statistics data, we implemented a daily inventory of agricultural fire emissions in 2016-2020 with a 2-km spatial resolution, including atmospheric pollutants such as CO2, CH4, CO, N2O, NOX, NH3, SO2, PM10, PM2.5, Hg, OC, EC, and NMVOCs. Our inventory constrained by geostationary satellite monitoring is more consistent with the actual CRB emissions in China, as many flaring events occur surreptitiously in the early morning and late evening to avoid regulation, which may be overlooked by polar-orbiting satellites. The spatiotemporal characterizations of various CRB emissions are found to be consistent with multiple satellite trace gas retrievals. We also assessed the effectiveness of field burning bans in China. Combined with other relevant datasets, it was found that although China has been advocating for a long time not to burn straw in the open field, CRB emissions was not successfully controlled nationwide until 2016. We estimated that the cumulative reduction of CO2 CRB emissions alone amounts to 809 ± 651 (2σ) teragram (Tg) during the 13th Five-Year Plan period (2016-2020), with an average value equivalent to 1.2 times the total annual territorial CO2 emissions by fossil fuels from Germany in 2021 (675 Tg, ranked 1st in EU27 and 7th in the world). Our inventory also suggests that continuous, long-term controls are necessary. Otherwise, CRB emissions may only be delayed on a seasonal scale, rather than reduced.

Characterization of paddy-residue burning derived carbonaceous aerosols using dual carbon isotopes.

A large scale paddy-residue burning (PRB) happens every year in the northwest Indo-Gangetic Plain (IGP) during the post-monsoon season, and winds transport pollutants from the source region up to the northern Indian Ocean affecting air quality of the IGP and marine region. In this study, day-night pairs of fine aerosol samples (n = 69) were collected during October-November over Patiala (30.2°N, 76.3°E, 250 m amsl), a site located in the source region of PRB. Carbonaceous aerosols (CA) were characterised using chemical species and dual carbon isotopes (13C and 14C) to estimate bio vs non-bio contributions and understand their characteristics. Percentage of bio fraction (fbio, estimated using 14C) in CA varied from 74 % to 87 % (avg: 80 ± 3) during days and 71 % to 96 % (avg: 85 ± 7 %) during nights. Further, the fbio was found to be better correlated with aerosol mass spectrometer derived f60 compare to levoglucosan (LG) or nssK+, suggesting f60 a useful proxy for PRB. The δ13C varied from -27.7 ‰ to -26.0 ‰ (avg: -27.0 ± 0.4 ‰) and - 28.7 ‰ to -26.4 ‰ (avg: -27.5 ± 0.7 ‰) during day and night, respectively. Measured δ13C of the samples was found to be more enriched than expected by 0.3 to 2.0 ‰, indicating the presence of aged CA also in Patiala even during PRB period. From fbio versus δ13C correlation, and from Miller-Trans plot, δ13C of PRB is found to be -28.9 ± 1.1 ‰, which also infers that Miller-Trans plot can be used to understand source isotopic signature in the absence of radiocarbon measurements in aerosols. Further, the characteristics ratios of organic carbon (OC) to elemental carbon (EC) (11.9 ± 4.1), LG to potassium (K+) (0.84 ± 0.15), OC/LG (19.7 ± 2.0) and K+/EC (0.75 ± 0.27) were calculated by considering samples with fbio higher than 0.90, which can be used for source apportionment studies. Such studies are crucial in assessing the effects of PRB on regional air quality and climate.

Drivers of air pollution variability during second wave of COVID-19 in Delhi, India.

To curb the 2nd wave of COVID-19 disease in April-May 2021, a night curfew followed by full lockdown was imposed over the National Capital Territory, Delhi. We have analyzed the observed variation in pollutants and meteorology, and role of local and transboundary emission sources during night-curfew and lockdown, as compared to pre-lockdown period and identical periods of 2020 lockdown as well as of 2018 and 2019. In 2021, concentration of pollutants (except O3, SO2, and toluene) declined by 4-16% during night-curfew as compared to the pre-lockdown period but these changes are not statistically significant. During lockdown in 2021, various pollutants decreased by 1-28% as compared to the night-curfew (except O3 and PM2.5), but increased by 31-129% compared to the identical period of 2020 lockdown except O3. Advection of pollutants from the region of moderate lockdown restrictions and an abrupt increase in crop-residue burning activity (120-587%) over Haryana and Punjab increased the air pollution levels over NCT during the lockdown period of 2021 as compared to 2020 in addition to a significant contribution of long-range transport. The increase in PM2.5 during the lockdown period of 2021 compared to 2020 might led to 5-29 additional premature mortalities.

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.

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.

Environmental and political implications of underestimated cropland burning in Ukraine.

Open burning is illegal in Ukraine, yet Ukraine has, on average, 300 times more fire activity per year (2001-2019) than most European countries. In 2016 and 2017, 47% of Ukraine was identified as cultivated area, with a total of 70% of land area dedicated to agricultural use. Over 57% of all active fires in Ukraine detected using space-borne Visible Infrared Imaging Radiometer Suite (VIIRS) during 2016 and 2017 were associated with pre-planting field clearing and post-harvest crop residue removal, meaning that the majority of these fires are preventable. Due to the small size and transient nature of cropland burns, satellite-based burned area (BA) estimates are often underestimated. Moreover, traditional spectral-based BA algorithms are not suitable for distinguishing burned from plowed fields, especially in the black soil regions of Ukraine. Therefore, we developed a method to estimate agricultural BA by calibrating VIIRS active fire data with exhaustively mapped cropland reference areas (42 958 fields). Our study found that cropland BA was significantly underestimated (by 30%-63%) in the widely used Moderate Resolution Imaging Spectroradiometer-based MCD64A1 BA product, and by 95%-99.9% in Ukraine's National Greenhouse Gas Inventory. Although crop residue burns are smaller and emit far less emissions than larger wildfires, reliable monitoring of crop residue burning has a number of important benefits, including (a) improving regional air quality models and the subsequent understanding of human health impacts due to the proximity of crop residue burns to urban locations, (b) ensuring an accurate representation of predominantly smaller fires in regional emission inventories, and (c) increasing awareness of often illegal managed open burning to provide improved decision-making support for policy and resource managers.

Influence of agricultural activities on atmospheric pollution during post-monsoon harvesting seasons at a rural location of Indo-Gangetic Plain.

The emissions from agricultural activities significantly impact the air quality at local (rural) and regional scales. The study monitored the near real-time concentrations of emission from agrarian activities, i.e., particulate matter (PM10, PM2.5, PM1), traces gases and VOCs, along with meteorological parameters in a rural area of Indo-Gangetic Plains (IGP). As different agricultural activities take place simultaneously in the region, sampling period was divided into three phases based on regional agricultural activities as HB (harvesting-burning) period, BTS (burning-tillage-sowing) period and PFS (pesticide-fertilizer spray) period. The highest mean concentration (± standard deviation) of particulate matter, i.e., PM10, PM2.5, PM1 was observed during HB period as 151.0 ± 52.3, 94.7 ± 32.9 and 41.0 ± 16.3 µgm-3 followed by PFS as 121.7 ± 49.1, 87.8 ± 35.5 and 39.7 ± 15.7 µgm-3 and BTS period as 92.5 ± 38.8, 63.5 ± 28.4, 26.6 ± 10.9 µgm-3 respectively. The mean concentration of NO (8.4 ± 3.4 ppb), SO2 (5.8 ± 1.2 ppb), CO (0.9 ± 0.3 ppm), O3 (12.5 ± 3.3 ppb) was also highest during harvesting-burning period. In the burning-tillage-sowing period, the mean concentration of NO2 (31.0 ± 2.9 ppb), benzene (2.8 ± 0.6 µgm-3) and o-xylene (2.1 ± 0.3 µgm-3) were highest. The data of crop residue burning fires showed that during HB period, around 34,683 active fires were there in the region (state of Punjab), whereas, in studied district, the number of fire counts were 635. During the HB period, around 70% of the air masses were originated within a 500 km area, whereas during the BTS and PFS period, 75% and 86% of air masses were originated from 500 km region, respectively. The ratio of PM2.5/PM10 during study period ranged from 0.63 to 0.72 and was observed highest during PFS period. The current study investigated the influence of agricultural activities on air quality during post-monsoon season in a rural area of Indo-Gangetic Plains to understand the impact of these activities on air quality in the region and plan mitigation strategies.

Quantifying the high resolution seasonal emission of air pollutants from crop residue burning in India.

Biomass burning, a recurring global phenomenon is also considered an environmental menace, making headlines every year in India with onset of autumn months. Agriculture is demographically the broadest economic sector and plays a significant role in the overall socio-economic fabric of India. Hence, disposal of crop residue is done mainly by burning leading to deterioration of air quality. Residue burning in parts of India is blamed for changing air quality in nearby cities. The spatial distribution of these emissions has always been a challenge due to various data constraints. We hereby present a comprehensive spatially resolved seasonal high resolution gridded (∼10 km × âˆ¼10 km) emission inventory of major pollutants from crop residue burning source in India for the latest year 2018. The winter months contributes almost around ∼50% of total emission followed by summer (∼48%), which is the prime cause of changing air quality in nearby cities. Among all the crops; rice, wheat, maize and sugarcane accounts ∼90% of total PM10 load in the country. The estimated emission for PM2.5, PM10, BC and OC, CO, NOx, SO2, VOC, CH4 and CO2 are found to 990.68 Gg/yr, 1231.26 Gg/yr, 123.33 Gg/yr, 410.99 Gg/yr, 11208.18 Gg/yr, 484.55 Gg/yr, 144.66 Gg/yr, 1282.95 Gg/yr, 785.56 Gg/yr and 262051.06 Gg/yr respectively. The cropping pattern and its role in different geographic regions are analysed to identify all potential emission hotspots regions scattered across the country. The developed gridded emissions inventory is envisaged to serve as an important input to regional atmospheric chemistry transport model to better quantify its contribution in deteriorating air quality in various regions of India, paving the way to policy makers to better plan the mitigation and control strategies. The developed fundamental tool is likely to be useful for air quality management.

In situ decomposition of crop residues using lignocellulolytic microbial consortia: a viable alternative to residue burning.

Open field burning of crop residue causes severe air pollution and greenhouse gas emission contributing to global warming. In order to seek an alternative, the current study was initiated to explore the prospective of lignocellulolytic microbes to expedite in situ decomposition of crop residues. Field trials on farmers' field were conducted in the state of Haryana and Maharashtra, to target the burning of rice and wheat residue and sugarcane trash, respectively. A comparative study among crop residue removal (CRR), crop residue burning (CRB) and in situ decomposition of crop residues (IND) revealed that IND of rice and wheat residues took 30 days whereas IND of sugarcane trash took 45 days. The decomposition status was assessed by determining the initial and final lignin to cellulose ratio which increased significantly from 0.23 to 0.25, 0.21 to 0.23 and 0.24 to 0.27 for rice, wheat residues and sugarcane trash, respectively. No yield loss was noticed in IND for both rice-wheat system and sugarcane-based system; rather IND showed relatively better crop yield as well as soil health parameters than CRB and CRR. Furthermore, the environmental impact assessment of residue burning indicated a substantial loss of nutrients (28-31, 23-25 and 51-77 kg ha-1 of N+P2O5+K2O for rice, wheat and sugarcane residue) as well as the emission of pollutants to the atmosphere. However, more field trials, as well as refinement of the technology, are warranted to validate and establish the positive potential of in situ decomposition of crop residue to make it a successful solution against the crop residue burning.