Investigation of fire regime dynamics and modeling of burn area over India for the twenty-first century.

The characteristics of the vegetation fire (VF) regime are strongly influenced by geographical variables such as regional physiographic settings, location, and climate. Understanding the VF regime is extremely important for managing and mitigating the impacts of fires on ecosystems, communities, and human activities in forest fire-prone regions. The present study thereby aimed to explore the potential effects of the confounding factors on VF in India to offer actionable and achievable solutions for mitigating this concurring environmental issue sustainably. A global burn area (250 m) data (Fire-CCIv5.1) and fire radiative power (FRP) were used to investigate the dynamics of VF across seven different divisions in India. The study also used the maximum and minimum temperatures, precipitation, population density, and intensity of human modification to model forest burn areas (including grassland). The Coupled Model Intercomparison Project-6 (CMIP6) was used to predict the burn area for 2030 and 2050 future climate scenarios. The present study accounted for a sizable increasing trend of VF during 2001-2019 period. The highest increasing trend was found in central India (513 and 343 km2 year-1 in the forest and crop fire, respectively), followed by southern India (364 km2 year-1 in forest fire), and upper Indo-Gangetic plain (128 km2 year-1 in crop fire). The FRP has varied significantly across the divisions, with the north-eastern Himalayas exhibiting the highest FRP hotspot. The maximum and minimum temperatures have the greatest influence on forest fires, according to Random Forest (RF) modeling. The estimated pre-monsoonal burn area for 2050 and 2050 future scenarios suggested a more frequent forest fire occurrence across India, particularly in southern and central India. A comprehensive forest fire control policy is therefore essential to safeguard and conserve forest cover in the regions, affected by forest fire periodically.

Energy inequality and air pollution nexus in India.

Energy usage, inequality, and their impacts are deeply intertwined, especially in India. Every year, cooking using biomass-based solid fuel usage causes death to tens of thousands of Indians, specifically, economically unprivileged people. Solid fuel burning has been known as one of the prominent sources of ambient PM2.5 (particulate matter with an aerodynamic diameter of <2.5 µm) concentration in the atmosphere. Thus, limiting the PM2.5 emission from biomass-based cooking fuel through the transition to LPG has gained priority. The government report in India indicates that nearly 8 million households became beneficiaries of the LPG connection through the PMUY scheme till 2019. The transition to clean cooking fuel may have an influence on the ambient PM2.5 concentration. In this study, to explore the nexus between energy inequality and air pollution, we investigated the present status of clean fuel usage in India and its drivers, including the impact of such a massive transition to cleaner fuel on ambient air quality, with a specific focus on PM2.5. The results show an improvement of 15 % in LPG usage from 2015 to 2019 in India., Yet the majority of poorer (>60 %) and poorest communities (>90 %) still use solid biomass as the cooking fuel. No significant correlation (r = 0.036; p-value â‰« 0.05) was obtained between LPG usage and ambient PM2.5 concentration suggesting the influence of other confounding factors which might subdue the anticipated effect of the usage of clean fuel. The analysis suggests, despite the successful launching of the PMUY, the low LPG usage pattern among the poor, because of the lack of an effective subsidy policy, might jeopardize the effort to fix the standard of ambient air as per WHO.

Revisiting the levels of Aerosol Optical Depth in south-southeast Asia, Europe and USA amid the COVID-19 pandemic using satellite observations.

The countries around the world are dealing with air quality issues for decades due to their mode of production and energy usages. The outbreak of COVID-19 as a pandemic and consequent global economic shutdown, for the first time, provided a base for the real-time experiment of the effect of reduced emissions across the globe in abetting the air pollution issue. The present study dealt with the changes in Aerosol Optical Depth (AOD), a marker of air pollution, because of global economic shutdown due to the coronavirus pandemic. The study considered the countries in south and south-east Asia (SSEA), Europe and the USA for their extended period of lockdown due to coronavirus pandemic. Daily Aerosol Optical Depth (AOD) from Moderate-resolution imaging spectroradiometer (MODIS) and tropospheric column density of NO2 and SO2 from Ozone monitoring instrument (OMI) sensors, including meteorological data such as wind speed (WS) and relative humidity (RH) were analyzed during the pre-lockdown (2017-2019) and lockdown periods (2020). The average AOD, NO2 and SO2 during the lockdown period were statistically compared with their pre-lockdown average using Wilcoxon-signed-paired-rank test. The accuracy of the MODIS-derived AOD, including the changing pattern of AOD due to lockdown was estimated using AERONET data. The weekly anomaly of AOD, NO2 and SO2 was used for analyzing the space-time variation of aerosol load as restrictions were imposed by the concerned countries at the different points of time. Additionally, a random forest-based regression (RF) model was used to examine the effects of meteorological and emission parameters on the spatial variation of AOD. A significant reduction of AOD (-20%) was obtained for majority of the areas in SSEA, Europe and USA during the lockdown period. Yet, the clusters of increased AOD (30-60%) was obtained in the south-east part of SSEA, the western part of Europe and US regions. NO2 reductions were measured up to 20-40%, while SO2 emission increased up to 30% for a majority of areas in these regions. A notable space-time variation was observed in weekly anomaly. We found the evidence of the formation of new particles for causing high AOD under high RH and low WS, aided by the downward vertical wind flow. The RF model showed a distinguishable relative importance of emission and meteorological factors among these regions to account for the spatial variability of AOD. Our findings suggest that the continued lockdown might provide a temporary solution to air pollution; however, to combat persistent air quality issues, it needs switching over to the cleaner mode of production and energy. The findings of this study, thus, advocated for alternative energy policy at the global scale.

Characterisation of emission from open-field burning of crop residue during harvesting period in north-west India.

Open-field crop residue burning is one of the important sources of atmospheric pollution in north-west India during the harvesting period. In this work, we studied NO2 and SO2 concentrations and physical and chemical properties of aerosols from open-field combustion of rice and wheat residue. NO2 and SO2 were analysed using UV-spectrophotometer and ion chromatography (IC) respectively. The aerosol particles were analysed by scan electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM-EDX) for their physical dimension (size distribution) and elemental composition, and by IC for their ionic content. The measured concentrations of gases during burning showed rice straw burning spews more NO2 and SO2 than wheat straw burning. The calculated size of the particles ranged from 0.26 to 151.09 µm with high standard deviation. The median diameter of 1.64 µm (± 6.9) represented the central tendency of the particles emitted due to this combustion process. Comparative content analysis revealed that rice-borne particles are richer in Na, K, Al, Si and Zn, whereas, wheat-borne particles are more abundant in C, Mg, Fe, P and Cl. The results from IC and SEM-EDX evidenced the presence of fluoride, sulphate, carbonate, chloride, oxides and silicate compounds in particles. The emission of greenhouse gases (GHGs) and aerosols with this particle chemistry increases the atmospheric opacity through the absorption and scattering of incoming radiation at a significant amount in the UV-IR range causing high aerosol optical depth (AOD).