Indo-Gangetic Plain Region Research Articles

Assessment of nighttime air quality over an urban location in Indo-Gangetic plain using remote sensing observations

Nocturnal inversion can trap atmospheric pollutants in the lower atmosphere and can significantly impact human health and reduce visibility, particularly in mega-cities. Therefore, nighttime monitoring of atmospheric aerosols and gases is very important. In this paper, we have selected an urban location of Kanpur located in a highly polluted region of Indo-Gangetic Plains (IGP) to study the variability in nighttime aerosols in response to trace gases and meteorological parameters. For this purpose, we have analyzed all the available data of aerosol optical depth at 500 nm (AOD), Angstrom Exponent (440–870) (AE) from AERONET's newly developed direct moon algorithm. We also examined nighttime data of temperature, relative humidity, methane, ozone, and carbon monoxide from AIRS (Atmospheric Infrared Sounder). The average values of nighttime AOD, AE, and precipitable water (PW) were observed to be 0.65 ± 0.04, 1.06 ± 0.21, and 2.86 ± 1.71, respectively. The highest value (0.90 ± 0.05) of lunar AOD is found in November with a corresponding AE value of 1.28 representing the dominance of fine-mode aerosols in Kanpur. In summer, AOD exhibited a slight decreasing trend (slope = −0.008) while AE exhibited an increasing trend (slope = 0.029) indicating that the aerosol burden is decreasing but the contribution of fine mode aerosols is increasing. Urban aerosols were the most abundant type (62.75 %) in the atmosphere of Kanpur during nighttime. Average values of methane, carbon monoxide, and ozone were found to be 1876.30 ± 21.79 ppbv, 127.40 ± 15.12 ppbv, and 40.76 ± 4.55 ppbv, respectively. HYSPLIT cluster analysis on high AOD day indicate the transportation of desert dust and biomass burning aerosols from western and north western regions of India. WTC between AOD and temperature posits a positive correlation in the medium-term period. AOD and carbon monoxide showed an anti-phase association.

Model simulation of carbonaceous fine particulate matter using SAFAR emission inventory and comparison with EDGAR-HTAP simulations

In this study, the evaluation of carbonaceous fine particulate matter (C-PM) was conducted using the SAFAR-India regional model. Two emission inventories were utilized: the newly developed SAFAR inventory and the global EDGAR-HTAP inventory, both for the year 2018. The simulation aimed to capture the seasonal and spatial patterns of black carbon (BC) and organic carbon (OC) concentrations. To validate model results, surface meteorological parameters, and C-PM concentrations were compared with the MERRA reanalysis data for the Indian region. Model simulated surface C-PM concentration with SAFAR emission inventory is found to be slightly overestimated (1.10), whereas simulated results with EDGAR emission inventory is significantly underestimated as compared to MERRA data. Model-simulated meteorological parameters showed a better correlation with MERRA reanalysis. Simulated geographical patterns of seasonal mean C-PM with SAFAR emission inventory exhibit quite a better comparison with MERRA reanalysis as against EDGAR simulated results. However, some differences in the present results are visible, particularly over the IGP region, as compared to MERRA data, but they are mainly attributed to a significant difference in the special resolution of present results (much finer) as compared to coarser MERRA data. In the Indo-Gangetic Plain (IGP) region, the concentration of BCSF and OCSF (BC and OC with SAFAR emission, respectively) show the peak during the winter, followed by the post-monsoon season. Although the correlation coefficients of hourly time series of surface BCSF and OCSF concentrations with MERRA over India are high (0.92 and 0.88), the poor RMSE, is attributed mainly to different scales of resolution. The model simulated BC, and OC concentrations with SAFAR emission input capture the pattern of spatial distribution reasonably well. The present evolution of BC and OC will help to better quantify their impact on climate and atmospheric conditions over the Indian region.

Aging of biomass burning emissions in the Indo-Gangetic Plain outflow: Implications for black carbon light-absorption enhancement

Recent studies worldwide have demonstrated that coating on atmospheric black carbon (BC) aerosol enhances its absorption potential. However, studies quantifying the light-absorption enhancement (Eabs) of BC are extremely limited over the Indian region. The northwestern Indo-Gangetic Plain (IGP) region witnesses annual episodes of substantial crop-residue burning during the post-monsoon season (PoMS), which has been attracting wide attention due to its impact on regional air quality and aerosol characteristics. Chemical aging of these biomass burning (BB) emissions occurs during its long-range transport across the IGP by the weak westerlies, and such atmospheric processing affects their chemical, optical, and radiative properties over downwind locations. This study examines the impact of atmospheric aging of biomass burning emissions on BC light-absorption enhancement (Eabs) using extensive, simultaneous measurements of single particle refractory BC and near-real-time mass spectrometry measurements of non-refractory submicron aerosols from an IGP outflow site. It was observed that organics were the dominant submicron aerosol species, and positive matrix factorization analysis of the organics mass spectra suggested that a large fraction of organics (64%) was secondary in nature. The BC particles in the IGP outflow (mass median diameter ∼ 0.18 ± 0.01 μm) were found to be thickly coated with volume-weighted bulk relative coating thickness in the range of 1.3–1.8. The evolution of biomass-burning organic aerosols (BBOA) indicated the presence of significant amounts of aged BBOA during the PoMS. Further, the oxidation products from the evolution of BB emissions contributed to enhanced coatings (∼ 30–70%) on BC. Mie core-shell theory calculations were then used to assess the changes in BC light absorption characteristics due to the coating of non-refractory mass on its cores. It was found that thick coatings on BC led to significant light-absorption enhancement (Eabs) (bulk Eabs in the range of 1.14–1.94 at 550 nm, depending on the extent of coating). Increased Eabs values of ≥1.8 were seen when the coating on BC exceeded 60% of its core size. The modeled bulk Eabs at 550 nm depicted a better association with highly oxidized secondary organic aerosols (SOA) than sulfate among the secondary aerosol species, suggesting an SOA-dominant regime. The present findings suggest that the critical impact of the aging of BC and co-emitted species from widespread BB emissions in the IGP outflow should be considered when evaluating the regional radiative implications.

A satellite-observation based study on responses of clouds to aerosols over South Asia during IOD events of south-west monsoon season

The present study investigated the possible effects of aerosols on cloud properties during positive and negative Indian Ocean Dipole (IOD) months over South Asia using 20 years (2002–2021) of long-term satellite-based observations and reanalyses datasets. Positive aerosol optical depth (AOD) differences between the two IOD phases are found mainly over the land areas and some parts of the Indian Ocean, with the maximum value observed over Indonesia, Malaysia, Northern China, Western India, and the Northern Arabian Sea. The negative AOD differences are seen over the equatorial Indian Ocean, some regions of Indian land mass, the North Indian Ocean, and some parts of the South China Sea, with the highest dip over the central Indo-Gangetic Plain region. The highest increase (decrease) in rainfall is observed over the western (eastern) pole. The reduced rainfall is responsible for the increased AOD over Indonesia, Malaysia, and neighboring regions. The strong negative relationships of cloud fraction (CF) with cloud top pressure and cloud optical depth (COD) suggest persisting optically thick middle and high-level clouds during the IOD months. Twomey effect is noticed over the study region during both the IOD phases irrespective of the meteorological conditions. CF and COD both showed an upsurge with increased AOD in the presence of high relative humidity and stronger updrafts, suggesting the role of prevailing meteorology in forming thicker clouds. However, the height of the cloud tops is getting lowered in polluted conditions. The aerosol-cloud relationships observed during IOD scenarios could be attributed to the prevailing meteorology.

Growth, yield, water productivity and economics of okra (Abelmoschus esculentus L.) in response to gravity drip irrigation under mulch and without-mulch conditions

Optimization of water by the drip irrigation system and soil water conservation through appropriate mulching is a prerequisite for sustainable crop production in water resource-scarce areas. A three seasons of field experiment was conducted to investigate the crop and water productivity of okra in relation to gravity drip irrigation use of mulch in combination with mulch under the environmental condition of the Indo-Gangetic plains of eastern India. Four levels of irrigation viz., surface irrigation at 1.0 IW/CPE (I1), drip irrigation at 0.6 (I2), 0.8 (I3) and 1.0 (I4) of crop evapotranspiration (ETc) and three mulches viz., no-mulch (M0), black polythene mulch (M1) and paddy straw mulch (M2) laid out in a split-plot design with three replications were investigated. Results showed that I3M1 produced the higher average growth, yield attributes, fruit yield (12.24 t ha−1), CWP, IWP, ECWP and EIWP and maximum economic returns, being almost identical to I4M1. Under severe water scarcity, I2M1 was an alternative. The highest BCR was accomplished in I4M0 followed by I3M0. Drip irrigation scheduling saved about 14–56% of water over surface irrigation, which could accommodate 11.1–48.6% of additional land area under the drip irrigation network. The optimal irrigation and ETarequirements were estimated at 86–136 mm and 142–168 mm, respectively for obtaining maximum yield (12.1–12.3 t ha−1). The water-yield production function model gives many options for allocating limited water resources under drip irrigation for a desirable yield. The crop yield response factor confirmed that moderate deficit irrigation management with a drip system across the growing period can be a feasible option for okra cultivators in the water-scarce regions of Indo-Gangetic plains or similar agro-climatic conditions.

Phytoremediation of heavy metals (Cr and Pb) from sewage irrigated soil of tropical sub-humid region of Indo-Gangetic plain using Amaranthus viridis

This study was conducted to find out the potential of Amaranthus viridis for the phytoremediation of heavy metals (Cr and Pb) grown on sewage irrigated site. The status of heavy metals in sewage irrigated soil was observed as Pb 4.91±0.96 mg/kg and Cr 3.48±0.51 mg/kg maximum in Buxibandh site and minimum concentration 2.11 0.19 mg/kg and Cr 1.82±0.19 mg/kg in Phaphamau sites. A. viridis grown on a sewage irrigated soils recorded maximum accumulation of Cr ranging from 4.23 0.28-4.11 0.15 mg/kg and minimum concentration 2.52±0.05–2.34±0.05 mg/kg in Buxibandh and Phaphamau respectively and maximum accumulation of Pb 4.4±10.52–4.27±0.39 mg/kg and minimum accumulation 2.89±0.04–2.43±0.06 mg/kg in root and shoot, respectively. The result shows the maximum potential of accumulation Pb 4.41±0.52 mg/kg followed by Cr 4.23±0.28 mg/kg in Buxibandh sewage irrigated site. The maximum dry biomass yield of A. viridis plants was recorded in Phaphamau sewage irrigated site of Cr and Pb sewage irrigated soils ranging 3.8±0.5–4.9±0.7 g/plant and 36±5–39±4.4 g/plant, respectively, while the minimum dry biomass yield as 2.5±0.4–2.8±0.4 g/plant and 26±1.2–28±3.9 g/plant in shoot and root, respectively, at Buxibandh sewage irrigated site. The accumulation of heavy metals hampered plant development and nutrients bioavailability. Furthermore, their bioconcentration factor (BCF) and translocation factor (TF) greater than 1.0 indicated the hyperaccumulation efficiency of plants ranges of Cr and Pb was recorded 1.33±0.04–1.06±0.05 mg/kg and 1.03±0.02–1.12±0.1 mg/kg, respectively. The result proved that the A. viridis had a great potential to remove heavy metals from sewage irrigated soils.

Quality, productivity and profitability of diversified fodder-based cropping systems for year-round fodder production in Indo-gangetic plains of India

An experiment was conducted during two consecutive years of 2017-18 and 2018-19 at National Dairy Research Institute, Karnal under randomized complete block design (RCBD) with three replications. This study aimed to evaluate the performance of eight fodder-based cropping systems (CS) in Indo-gangetic plain region (IGP) viz., sole napier bajra hybrid (CS ), sole guinea grass (CS ), napier bajra hybrid + cowpea (Kharif)/ 1 2 berseem (Rabi) (CS ), guinea grass + cowpea (Kharif)/ oats (Rabi) (CS ), multicut sorghum-berseem (Rabi) 3 4 (CS ), cowpea-maize-oats (CS ), baby corn-cowpea-chinese cabbage (Rabi) (CS ), summer moong–multicut 5 6 7 sorghum–ryegrass (Rabi) (CS ). The results revealed that selection of the crops in different cropping systems 8 significantly influenced green fodder yield and fodder quality. Among various fodder base cropping systems, NBH + cowpea/ berseem system was recorded with significantly higher green fodder (177 t/ha/year) and dry fodder (31.5 t/ha/year) yields and also fodder quality attributes. The highest crude protein yield (40.7 q/ha/year) was also recorded in NBH + cowpea/ berseem intercropping system. In terms of economics, the highest gross and net returns were obtained from baby corn-cowpea-chinese cabbage (Rs 3.15 and 2.40 lakh/ha/year, respectively), closely followed by NBH + cowpea/ berseem (Rs 2.74 and 2.15 lakh/ha/year, respectively). To ensure the year-round availability of quality fodder for dairy-based farmers, cultivation of the NBH + cowpea/ berseem cropping system proved to be a viable option.

Genotypic capacity of post-anthesis stem reserve mobilization in wheat for yield sustainability under drought and heat stress in the subtropical region.

Wheat productivity is severely affected by drought and heat stress conditions worldwide. Currently, stem reserve mobilization (SRM) is receiving increased attention as a trait that can sustain wheat yields under adverse environments. However, the significance of SRM in sustaining wheat yields under drought and heat stress conditions remains uncertain in the tropical climate of Indo-Gangetic Plain region. Therefore, this study aimed to investigate genotypic variations in SRM in wheat and their influence on yield sustainability under drought and heat stress environments. The experiment was designed in an alpha-lattice layout, accommodating 43 genotypes under four simulated environments [timely sown and well irrigated (non-stress); timely sown and water-deficit/drought stress; late-sown and well-irrigated crop facing terminally high temperature; and late-sown and water-deficit stress (both water-deficit and heat stress)]. The water-deficit stress significantly increased SRM (16%-68%, p < 0.01) compared to the non-stress environment, while the heat stress conditions reduced SRM (12%-18%). Both SRM and stem reserve mobilization efficiency exhibited positive correlations with grain weight (grain weight spike-1) under all three different stress treatments (p < 0.05). Strong positive correlations between stem weight (at 12days after anthesis) and grain weight were observed across the environments (p < 0.001); however, a significant positive correlation between stem weight and SRM was observed only with stress treatments. Results revealed that the SRM trait could effectively alleviate the impacts of water-deficit stress on yields. However, the SRM-mediated yield protection was uncertain under heat stress and combined water-deficit and heat stress treatments, possibly due to sink inefficiencies caused by high temperature during the reproductive period. Defoliated plants exhibited higher SRM than non-defoliated plants, with the highest increment observed in the non-stress treatment compared to all the stress treatments. Results revealed that wider genetic variability exists for the SRM trait, which could be used to improve wheat yield under drought stress conditions.

Chemical Characterization and Source Apportionment of PM10 Using Receptor Models over the Himalayan Region of India

This study presents the source apportionment of coarse-mode particulate matter (PM10) extracted by 3 receptor models (PCA/APCS, UNMIX, and PMF) at semi-urban sites of the Indian Himalayan region (IHR) during August 2018–December 2019. In this study, water-soluble inorganic ionic species (WSIIS), water-soluble organic carbon (WSOC), carbon fractions (organic carbon (OC) and elemental carbon (EC)), and trace elements of PM10 were analyzed over the IHR. Nainital (62 ± 39 µg m−3) had the highest annual average mass concentration of PM10 (average ± standard deviation at 1 σ), followed by Mohal Kullu (58 ± 32 µg m−3) and Darjeeling (54 ± 18 µg m−3). The annual total ∑WSIIS concentration order was as follows: Darjeeling (14.02 ± 10.01 µg m−3) &gt; Mohal-Kullu (13.75 ± 10.21 µg m−3) &gt; Nainital (10.20 ± 6.30 µg m−3), contributing to 15–30% of the PM10 mass. The dominant secondary ions (NH4+, SO42−, and NO3−) suggest that the study sites were strongly influenced by anthropogenic sources from regional and long-range transport. Principal component analysis (PCA) with an absolute principal component score (APCS), UNMIX, and Positive Matrix Factorization (PMF) were used for source identification of PM10 at the study sites of the IHR. All three models showed relatively similar results of source profiles for all study sites except their source number and percentage contribution. Overall, soil dust (SD), secondary aerosols (SAs), combustion (biomass burning (BB) + fossil fuel combustion (FFC): BB+FFC), and vehicular emissions (VEs) are the major sources of PM10 identified by these models at all study sites. Air mass backward trajectories illustrated that PM10, mainly attributed to dust-related aerosols, was transported from the Thar Desert, Indo-Gangetic Plain (IGP), and northwestern region of India (i.e., Punjab and Haryana) and Afghanistan to the IHR. Transported agricultural or residual burning plumes from the IGP and nearby areas significantly contribute to the concentration of carbonaceous aerosols (CAs) at study sites.

WiFEX: Walk into the Warm Fog over Indo-Gangetic Plain Region

Abstract The presence of persistent heavy fog in northern India during winter creates hazardous situations for transportation systems and disrupts the lives of about 400 million people. The meteorological factors responsible for its genesis and predictability are not yet completely understood in this region. Given its high potential for socioeconomic impact, there is a pressing need for extensive research that understands the inherently complex nature of the phenomena through field observations and modeling exercises. WiFEX is a first-of-its-kind multi-institutional initiative dealing with intensive ground-based measurement campaigns for developing a suitable fog forecasting capability under the aegis of the smart cities mission of India. Measuring campaigns were conducted during the 2015–20 winters at the Indira Gandhi International Airport, New Delhi, covering more than 90 dense fog events. The field experiments involved extensive suites of in situ instruments and gathered simultaneous observations of micrometeorological conditions, radiative fluxes, turbulence, droplet/aerosol microphysics, aerosol optical properties, fog water chemistry, and vertical thermodynamical structure to describe the environmental stability in which fog develops. An operational modeling framework, the WRF Model, was set up to provide fog predictions during the measurement campaign. These field observations helped to interpret the strengths and deficiencies in the numerical modeling framework. Four scientific objectives were pursued: (i) the life cycle of optically thin and thick fog, (ii) microphysical properties in the polluted boundary layer, (iii) fog water chemistry, gas–aerosol partitioning during the fog life cycle, and (iv) numerical prediction of fog. This paper presents an overview of WiFEX and a synthesis of selected observational and modeling analyses/findings related to the abovementioned scientific topics.

Productivity and profitability improvement of fodder maize under combined application of indigenously prepared panchagavya with organic and inorganic sources of nutrient

Irrational use of chemical fertilizers creates harmful effects on soil health and thus, led to a drop in crop productivity in the Indo-Gangetic Plains region (IGPR) of India. Organic nutrient sources such as Panchagavya and PGPR can be used to replace some proportion of chemical fertilizers to sustain productivity and soil health in the IGPR belt. This study was undertaken to determine the effect of integrated use of chemical fertilizers, organic manures and bio-fertilizers such as Panchagavya and PGPR on the productivity and economic feasibility of different maize cultivars. Results indicated that the J-1006 cultivar showed significantly higher fodder yield, nutrient use efficiencies and profitability than P-3396 and African Tall during both years. Though, nutrient content and accumulation were statistically at par with J-1006 and P-3396, but superior over African Tall. Among nutrient management, the maize fertilized with 75% RDF + PGPR +Panchagavya spray showed significantly higher fodder yield, nutrient content, accumulation, nutrient use efficiencies and net returns compared to control and 100% RDF. Overall, the growing of maize cv. J-1006 with the application of 75% RDF + PGPR + Panchagavya spray can be recommended to enhance fodder productivity, nutrient accumulation and profitability in the IGPR belt of India.

Impact of Lockdown on Column and Surface Aerosol Content over Ahmedabad and a Comparison with the Indo-Gangetic Plain

Changes in vertical column concentration, size distribution, and surface concentration of aerosol associated with the lockdown imposed by the COVID-19 pandemic in 2020 over the Ahmedabad region in Gujarat State, India, were analyzed. The results are compared with changes over selected Indo-Gangetic Plain (IGP) regions. On 25 March 2020, the prime minister of India declared a complete lockdown throughout the country and later lifted restrictions in a phased manner. Aerosol optical depth (AOD) over the Ahmedabad region on 29 March dropped to as low as 0.11, and in the first two weeks of lockdown, the weekly average AOD was only 0.18. On almost all days of the lockdown period, AOD over the Ahmedabad region was lower than the decadal mean. It was found that the Ahmedabad region responded differently to lockdown conditions compared to the IGP regions. During the first lockdown phase, AOD decreased by about 29% compared to the pre-lockdown period over the Ahmedabad region. However, the average reduction over the IGP was much more, about 50%. The average Angstrom exponent (AE) of 0.96 during the pre-lockdown period over the Ahmedabad region increased phase-wise to 1.36 during the L3 lockdown phase, indicating dominance of fine-mode particles during the lockdown period. It suggests a reduction in anthropogenically produced coarse-mode particles, typically dust produced by vehicular movement, construction, and industrial activities. However, on the other hand, over the IGP region, the high dominance of fine-mode particles during the pre-lockdown period had changed to a high dominance of coarse-mode particles, especially over the Delhi region. This indicates a reduction in anthropogenically produced fine-mode particles, which are mainly generated by fossil and biofuels/biomass combustion, over the IGP region by lockdown conditions. Within a few days of lockdown, PM2.5 was reduced by 64% and 76% over the Ahmedabad and Delhi regions, respectively. The lockdown imposed by the pandemic provided an excellent opportunity to ascertain background aerosol conditions in the atmosphere.

Influence of stubble burning on air quality of Northern India: a case study of Indo-Gangetic plains of India

Stubble burning is an emerging environmental issue in Northern India, which has severe implications for the air quality of the region. Although stubble burning occurs twice during a year, first during April-May and again in October-November due to paddy burning, the effects are severe during October-November months. This is exacerbated by the role of meteorological parameters and presence of inversion conditions in the atmosphere. The deterioration in the atmospheric quality can be attributed to the emissions from stubble burning which can be perceived from the changes observed in land use land cover (LULC) pattern, fire events, and sources of aerosol and gaseous pollutants. In addition, wind speed and wind direction also play a role in changing the concentration of pollutants and particulate matter over a specified area. The present study has been carried out for the states of Punjab, Haryana, Delhi, and western Uttar Pradesh to study the influence of stubble burning on the aerosol load of this region of Indo-Gangetic Plains (IGP). In this study, the aerosol level, smoke plume characteristics, long-range transport of pollutants, and affected areas during October-November from year 2016 to 2020 were examined over the Indo-Gangetic Plains (Northern India) region by the satellite observations. By MODIS-FIRMS (Moderate Resolution Imaging Spectroradiometer-Fire Information for Resource Management System) observations, it was revealed that there was an increase in stubble burning events with the highest number of events being observed during the year 2016 and then a decrease in the number of events in subsequent years from 2017 to 2020. MODIS observations revealed a strong AOD gradient from west to east. The prevailing north-westerly winds assist the spread of smoke plumes over Northern India during the peak burning season of October to November. The findings of this study might be used to expand on the atmospheric processes that occur over northern India during the post-monsoon season. The pollutant, smoke plume features, and impacted regions of biomass-burning aerosols in this region are critical for weather and climate research, especially given the rising trend in agricultural burning over the previous two decades.

Food insecurity in the Eastern Indo-Gangetic plain: Taking a closer look.

Food security is an important policy issue in India. As India recently ranked 107th out of 121 countries in the 2022 Global Hunger Index, there is an urgent need to dissect, and gain insights into, such a major decline at the national level. However, the existing surveys, due to small sample sizes, cannot be used directly to produce reliable estimates at local administrative levels such as districts. The latest round of available data from the Household Consumer Expenditure Survey (HCES 2011-12) done by the National Sample Survey Office of India used stratified multi-stage random sampling with districts as strata, villages as first stage and households as second stage units. Our Small Area Estimation approach estimated food insecurity prevalence, gap, and severity of each rural district of the Eastern Indo-Gangetic Plain (EIGP) region by modeling the HCES data, guided by local covariates from the 2011 Indian Population Census. In HCES, 5915 (34429), 3310 (17534) and 3566 (15223) households (persons) were surveyed from the 71, 38 and 18 districts of the EIGP states of Uttar Pradesh, Bihar and West Bengal respectively. We estimated the district-specific food insecurity indicators, and mapped their local disparities over the EIGP region. By comparing food insecurity with indicators of climate vulnerability, poverty and crop diversity, we shortlisted the vulnerable districts in EIGP. Our district-level estimates and maps can be effective for informed policy-making to build local resiliency and address systemic vulnerabilities where they matter most in the post-pandemic era. Our study computed, for the Indian states in the EIGP region, the first area-level small area estimates of food insecurity as well as poverty over the past decade, and generated a ranked list of districts upon combining these data with measures of crop diversity and climatic vulnerability.

High black carbon episodes over a polluted metropolis near the land-sea boundary and their impact on associated atmospheric dynamics.

The present investigation outlines the crucial factors that influence the black carbon (BC) concentrations over a polluted metropolis, Kolkata (22.57°N, 88.37°E), India. Located in the eastern part of the Indo Gangetic Plain (IGP) outflow region and close to the land-ocean boundary, Kolkata is subject to contrasting seasonal maritime airflow from the Bay of Bengal and continental air mass from the IGP and Tibetan plateau region, which modulates the local concentration of BC. The origin of aerosol transport and associated atmospheric dynamics with high and low BC activities over Kolkata are examined during 2012-2015 using data from multi-technique sources which include measurements of ground-based instruments of aethalometer and multi-frequency microwave radiometer, reanalysis data from ERA-5 and MEERA-2, and model outputs from HYPSLIT back trajectory model simulations. The study highlights the control of IGP wind inflow on the occurrence of anomalous enhancements in BC concentration during weekends and holidays when local emissions are low. High BC events are associated with enhanced atmospheric heating below the boundary layer (2000m) and significant negative surface radiative forcing. The response of the boundary layer to high and low BC episodes, shown in the diurnal variation in comparison with the seasonal mean, is investigated. Dominant suppression of morning and night-time boundary layer height is observed on high BC days. During the daytime in pre-monsoon, post-monsoon, and winter seasons, boundary layer height peaks are found to be strongly controlled by high BC episode occurrences as obtained from the hourly data of ERA-5.

Morphological and molecular analyses of grain traits in aromatic rice landrace accessions from indo-gangetic plain region of India

Morphological and molecular analyses of grain traits in aromatic rice landrace accessions from indo-gangetic plain region of India

Climatology and landscape determinants of AOD, SO2 and NO2 over Indo-Gangetic Plain

Indo-Gangetic Plains (IGP) experiences high loading of particulate and gaseous pollutants all year around and is considered to be the most polluted regions of India. Understanding the effect of landscape determinants on air pollution in IGP regions is crucial to make its environment sustainable. We examined satellite retrievals of OMI NO2 and SO2, and MODIS AOD to analyse the long-term trend, spatio-seasonal pattern and dynamics of aerosols, NO2 and SO2 over three IGP regions, namely Upper Indo-Gangetic plain (UIGP), Middle Indo-Gangetic plain (MIGP) and Lower Indo-Gangetic plain (LIGP) over the period 2005–2019. IGP experienced an overall increment in AOD (R2 = 0.63) and SO2 (R2 = 0.67) values, with LIGP (AOD, R2 = 0.8 & SO2, R2 = 0.8) experiencing the largest rate of enhancement. The levels of NO2 (R2 = 0.2) experienced a decrement after 2012 (owing to implementation of vehicle emission policy) except in MIGP, with UIGP (R2 = 0.23) exhibiting the largest rate of decrement. Seasonal heterogeneity in the nature of sources was observed over IGP regions. AOD (0.61 ± 0.1) and NO2 value (3.82 ± 0.98 × 1015 molecules/cm2) were found highest during post-monsoon in UIGP owing to crop residue burning activity. The value of NO2 (3.8 ± 1.4 × 1015 molecules/cm2) in MIGP was found highest during pre-monsoon due to high consumption of coal in power plants for summer cooling demand. The highest SO2 level (0.09 ± 0.06 DU) was observed during post-monsoon in UIGP, as a large number of brick kilns are fired during this period. Correlations among landscape determinants and pollutants revealed that topography is the dominant variable that affect the spatial pattern of AOD compared to vegetation and land use. Lower elevation tends to have high AOD values compared to higher elevation. Vegetation-AOD relationship showed an inverse association in IGP regions and is influenced by factors such as seasonal meteorology and size of the airborne particles. Vegetation possesses positive relationship with SO2 and NO2, implying no pollution abatement effect on SO2 and NO2 pollutants. Built-up change has deteriorating effect as well as quenching effect on pollutants. Increase in built terrain have deteriorated the air quality in UIGP whereas it favored in suppressing the aerosol level in LIGP.

Global trends in the aerosol optical, physical, and morphological properties obtained using multi-sensor measurements

Numerous studies have been carried out to examine the trends in the rapidly changing aerosol loading through the total Aerosol Optical Depth (AOD) but very few investigations have acknowledged its long-term implications through the combined optical, physical, and morphological properties of the aerosols. Using a multivariate linear regression trend analysis model on nearly two decades (i.e., 2001–2020) of multi-source global datasets, we tried to relate the contribution of each of the varying aerosol properties such as scattering, absorption, size, and shape, to the changing total AOD trends of that sensor. Region-wise analysis has shown that the decrease (increase) in the total AOD trends observed over North-Eastern America, South America, Europe, North-Western Africa, and Eastern and Central China (Indian) regions are mainly in connection with the decrease (increase) in the fine-mode and scattering aerosols. However, the major increase over the South African region is from the increase in absorbing and scattering aerosols. Interestingly, the Indo-Gangetic Plain region of India, where high total AOD trends are observed, has seen a plausible slight decrease in its absorbing, non-spherical, and coarse-mode aerosols in recent years. This study also details the region-wise response accompanying the implementation of stringent mitigation strategies to ensure accurate quantification of the changing aerosol patterns in the atmosphere.

Boron fractions and its availability in soils of the Indo-Gangetic plains

We studied relationships between available B and different fractions of B in soils, and how soil properties, climatic parameters, and cropping systems influenced their contents in soils of the Indo-Gangetic Plains (IGP). Available B in soils was assessed by four methods viz., hot-calcium chloride (HCC), mannitol-calcium chloride (MCC), hydrochloric acid (HCl) and salicylic acid (SA). Soil B was also separated into five fractions viz., readily soluble B (RSB), specifically adsorbed B (SAB), organically bound B (OrB), oxides bound B (OxB) and residual B (RB). On average, a higher amount of available B was found in soils of the upper and trans region of IGP dominated by illitic minerals compared with a lower amount in the lower region dominated by kaolinitic one. Among the fractions, RB constituted ∼ 89 % of the total, followed by OxB(6.11 %) > OrgB (5.32 %) ≫ SAB (0.46 %) > RSB (0.26 %). Variations in the amount of available B, and its fractions in soils were explained on the basis of variations in soil properties and climatic parameters. For example, most of the fractions of B (SAB, OrgB and OxB) along with its available amount decreased with increasing soil depth due to declining contents of organic C and amorphous Fe- and Al-oxides. Soil properties explained 51–76 % variability in available B, and 27–65 % in different B fractions. Rice-based cropping systems mobilized RB to available (RSB and SAB) and potentially available (OxB and OrgB) fractions. Among the methods used, HCC and MCC were found suitable for assessing available B status in the soils. The study thus explained variations in B availability in rice and non-rice-based cropping systems, predicted its availability, and also identified suitable method(s) for its estimation in soils of the IGP for a better B management.

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.