Indo-Gangetic Plains Research Articles

Statistical and geospatial assessment of trace and toxic elements distribution in ground and surface water of northern parts of the Indo-Gangetic plains: Source identification and health risk assessment

This study focusses on ground and surface water resources in the northern parts of the Indo-Gangetic Plains. The study aims to identify potential contaminants, analyse their distribution, trace their origins, and evaluate associated health risk. Samples from 80 locations; groundwater (n = 69) and surface water (n = 11) were analysed for nineteen trace and toxic elements using ICP-MS. Eight elements in groundwater (Mn, Fe, Ni, Zn, As, Tl, U and Se) and six in surface water (Al, Mn, Fe, Ni, Zn, and Tl) exceeded WHO (2011) and BIS (2012) limits in certain areas. The geospatial analysis reveals hotspots of trace and toxic element concentration, with higher levels detected in the southeast and western regions of the study area. Correlation matrices revealed a robust correlation (∼>0.75–0.99, p < 0.01) among all trace and toxic elements (excluding Li, Be, As, Ag, and U) in surface water samples when compared to groundwater samples. Cluster analysis and principal component analysis (PCA) (explains 70.09 cumulative percent for total 6 of factors) of groundwater chemistry indicates that Zn, Ni and Tl contamination may originate from industrial activities (metallurgical processes and manufacturing). The potential sources of Mn may be both geological and human-induced, while Fe, Se, As and U can originate from specific geological formations or human-related activities like over-extraction and leaching of excess fertilizers into aquifers. For surface water, PCA (explains 92.92 cumulative percent for total 5 of factors) identifies industrial activities as the main source of Mn, Fe, Tl, Ni, and Zn, while Al originates from both geological and anthropogenic sources. The water quality index indicated poor to very poor water quality in the western and central regions, whereas the northern and eastern regions exhibited excellent water quality. Health risk assessment reveals HI values for groundwater water: 3.85 (adults), 7.70 (children); surface water: 1.52 (adults), 3.05 (children), emphasizing the urgent need for remediation measures.

Contrasting nature of aerosols over South Asian cities and its surrounding environment

Cross-country assessment of aerosol loading was made over several South Asian megacities using multiple high-resolution remote-sensing database to assess how aerosols vary within the city and its suburbs. Parameters sensitive to aerosol optical and microphysical properties were processed over city-core and its surrounding, separated by a buffer. Cities across the Indo-Gangetic Plain (IGP; AOD:0.52–0.72) along with Mumbai (0.47) and Bangalore (0.46) denote comparatively high aerosol loading against non-IGP cities. City-core specific AOD was invariably high compared to surrounding, however with varying gradient having robust geographical signature. Exceptions to this general trend were in Kathmandu (ΔAOD: 0.07) and Dhaka (ΔAOD: 0.01) while strong positive AOD gradient was noted in Bangalore (+0.11), Colombo (+0.08) and in Mumbai (+0.07). While all mainland cities exhibited robust intraannual variability, distinction between city-core and its surrounding AOD exhibited varying seasonality. City-specific geometric coefficient of variation indicated insignificant association with mean AOD as opposed to European and American cities. Both pixel-based and city-specific analysis revealed a strong increasing trend in AOD with highest magnitude in Varanasi and Bangalore. Aerosol sub-types based on aerosols’ sensitivity to UV-absorption and particle size denotes higher relative abundance of carbonaceous smoke aerosols within city-core, without having significant distinction for mineral dusts and urban aerosols.

Significance of anthropogenic black carbon in modulating atmospheric and cloud properties through aerosol-radiation interaction during a winter-time fog-haze

The present study investigated the aerosol-radiation-cloud interaction of anthropogenic black carbon (BC) during a severe fog-haze event by utilizing WRF-Chem, multi-satellite and in-situ observations, reanalyses datasets, and HYSPLIT model. The WRF-Chem model adequately captured the regional distribution of aerosol, cloud, and meteorological variables over the study domain. The maximum BC surface concentration (≥7 μg m−3) was predominantly evident over densely populated central and lower Indo-Gangetic Plain (IGP) regions. Although smoke aerosols usually persisted within 4 km above the surface at daylight hours, they reached as high as 6 km during nighttime, specifically over the central IGP regions. The heavily influenced areas by BC aerosols expanded to almost the entire landmass and the continental outflow region upon doubling the anthropogenic emission. The geographical distribution of maximum perturbations in net shortwave radiation flux at the surface closely matched the spatial patterns of the highest BC concentration, indicating a crucial role of BC in directly preventing the incoming sunlight from reaching the surface. Consequently, the reduced solar radiation at the ground might result in substantial surface cooling (between −0.3 and −0.5 °C), eventually prohibiting surface evapotranspiration and diminishing the outgoing sensible and latent heat fluxes. Also, more amplified cooling in the polluted atmosphere can prevent further development of the planetary boundary layer (PBL), increasing particle entrapment near the surface via an ‘aerosol-radiation-PBL’ feedback loop. However, the most striking contrast between the two scenarios (typical and polluted) was the prolonged and intensified warming (0.5–0.8 °C) in the mid-troposphere, causing a remarkable drop in moisture (more than two to three times) and hence burn-off of liquid cloud droplets due to the semi-direct effect of increased BC aerosols. The intense mid-tropospheric heating could remarkably enhance the updraft velocity, supporting the vertical transport of the additional moisture to higher altitudes, forming more ice clouds at night. Therefore, the current study highlighted the urgency of mitigating anthropogenic BC emissions in highly polluted regions since increased emissions could considerably worsen severe fog-haze conditions and influence both liquid water and ice clouds, depending on the atmospheric conditions.

Estimation of Particulate Matter (PM10) Over Middle Indo-Gangetic Plain (Patna) of India: Seasonal Variation and Source Apportionment

Despite extensive research on particulate matter (PM) pollution in India’s Indo-Gangetic Plain (IGP), source apportionment remains challenging. This study investigates the effect of particulate matter (PM10)-associated water soluble inorganic ions (WSIIs) on ambient air concentration across the middle IGP from January to December 2018. Moreover, the seasonal fluctuation and chemical characterization of PM10 were assessed for the year 2018. The results revealed a high concentration of PM10 (156 µg/m3), exceeding the WHO and National Ambient Air Quality Standard (NAAQS) limits. The highest PM10 levels were observed during autumn, winter, summer, and the rainy season. The study identified SO42− and NH4+ as the most common WSIIs, constituting 46% and 23% of the total WSIIs. Source apportionment analysis indicated that street dust, biomass burning, and vehicle and industrial emissions together with secondary formation significantly contributed to IGP’s PM pollution. Additionally, the investigation of air mass back trajectory suggests that air quality in IGP is largely influenced by eastern and western Maritime air masses originated from the Arabian Sea, the Bay of Bengal, Gujarat, Afghanistan, Pakistan, and Bangladesh.

Various presowing treatments for enhancing Melia dubia (Cav.) seed germination, seedling development, and vigor index

Melia dubia (Cav.) is one of the most promising agroforestry multipurpose tree species. However, there is a shortage of this quality planting material due to its low germination ability. Our study assessed six different presowing treatments, namely, soaking in tap water for 24 h, soaking in a cow dung slurry for 7 days (CDS), scarification with 50 % H2SO4 for 5 min, soaking in 200 ppm gibberellic acid (GA3) for 24 h, and soaking in CDS + H2SO4, GA3 + H2SO4 or the control (no application), for enhancing seed germination and growth in Melia dubia during 2019–20 in the Indo-Gangetic Plains region. STAR version 2.0.1 was used to analyze the observed data using one-way ANOVA. The results of this study showed that different treatments substantially impacted the germination and growth of Melia dubia. Compared with those of untreated seeds (control), the germination percentage of seeds treated with cow dung slurry significantly increased by 49 %, the biomass percentage significantly increased by 25 %, and the vigor index significantly increased by 79 %. In conclusion, our study revealed that treating Melia dubia seeds with cow dung slurry for a period of 7 days enhances germination and seedling growth and is also cost-effective for nursery managers and farmers due to the absence of associated costs.

A Comprehensive Review of Surface Ozone Variations in Several Indian Hotspots

Ozone at ground level (O3) is an air pollutant that is formed from primary precursor gases like nitrogen oxides (NOx) and volatile organic compounds (VOCs). It plays a significant role as a precursor to highly reactive hydroxyl (OH) radicals, which ultimately influence the lifespan of various gases in the atmosphere. The elevated surface O3 levels resulting from anthropogenic activities have detrimental effects on both human health and agricultural productivity. This paper provides a comprehensive analysis of the variations in surface O3 levels across various regions in the Indian subcontinent, focusing on both spatial and temporal changes. The study is based on an in-depth review of literature spanning the last thirty years in India. Based on the findings of the latest study, the spatial distribution of surface O3 indicates a rise of approximately 50–70 ppbv during the summer and pre-monsoon periods in the northern region and Indo-Gangetic Plain. Moreover, elevated levels of surface O3 (40–70 ppbv) are observed during the pre-monsoon/summer season in the western, southern, and peninsular Indian regions. The investigation also underscores the ground-based observations of diurnal and seasonal alterations in surface O3 levels at two separate sites (rural and urban) in Kannur district, located in southern India, over a duration of nine years starting from January 2016. The O3 concentration exhibits an increasing trend of 7.91% (rural site) and 5.41% (urban site), ascribed to the rise in vehicular and industrial operations. This review also presents a succinct summary of O3 fluctuations during solar eclipses and nocturnal firework displays in the subcontinent.

Unveiling Superabsorbent Hydrogels Efficacy Through Modified Agronomic Practices in Soybean–Wheat System Under Semi‐Arid Regions of South Asia

ABSTRACTThe sustainability of global agriculture at higher productivity level is a concern owing to climate change, serious environmental footprints, dipping factor productivity and shrinking availability of natural resources, especially. The situation is worsening in the ‘Food Bowl of India’—Indo‐Gangetic plains (IGP) by several amalgamated factors, such as declining groundwater, unpredictable precipitation owing to climate change and cultivation of heavy water duty crops. To neutralise these issues, a field experiment was executed for the period 2019–2021 to assess the efficacy of indigenous hydrogels (P‐hydrogel and Superabsorbent polymer hydrogel‐1118) and their application methods viz., seed treatment, slurry application and soil application on crop yield and water productivity, soil moisture dynamics and profitability in a soybean–wheat cropping system under irrigation and rainfed conditions. In both study years (2019–2020 and 2020–2021), due to higher seed germination percentage, irrigation application together with seed treatment and slurry application of superabsorbent polymer hydrogel‐1118 improved system productivity by 8.1%–26.7% and system water productivity by 17.6%–33.8% over control. Wheat grain yield was enhanced by 8.0% (2019–2020) to 32.2% (2020–2021) due to superabsorbent polymer hydrogel‐1118 hydrogel with 10 cm lesser use of irrigation water compared with control (no‐hydrogel). Soil moisture content in 0–15 cm soil layer was also found higher by 1.8%–2.4% in superabsorbent polymer hydrogel‐1118 and P‐hydrogel slurry‐applied plots. Therefore, higher gross profitability (31.8%), net profitability (89.8%) and B:C (26.9%) in wheat could be attributed to increased crop yields when seeds were treated with superabsorbent polymer hydrogel‐1118. Therefore, the utilisation of modified hydrogel application, in the form of seed treatment (seed coating) and slurry application has demonstrated improvement in seed germination, crop yield and water productivity and made soybean–wheat cultivation more economical. This approach presents a feasible solution to achieving a viable production system of soybean and wheat crops by reducing irrigation amounts in the IGP of India, as well as other comparable ecological places worldwide.

Long-Term Consequences of Tillage and Residue Management on the Performance of Rice-Wheat Cropping System in Indo-Gangetic Plains of India

ABSTRACT A field experiment was carried out to evaluate the effect of tillage and residue management practices on grain yield, economics, and soil fertility in a RWCS. The results inferred that wheat sown with happy seeder (full residue retained)-ZWW recorded 11.5% higher grain yield as compared to zero tillage sowing (residue removed)-ZWWO and 10.9% higher than farmer’s practice (TRWO-CWWO, residue removed and sowing with seed cum fertilizer drill after preparatory tillage). Retention or incorporation of paddy residues produced 16.0% higher grain yield than its removal or burning simultaneously improving soil health. Puddled transplanted rice (PTR) with or without wheat stubble recorded a 33.2% significantly higher yield than zero tillage direct seeded rice (ZTDSR) without wheat stubble. System productivity in TRW-ZWW treatment was 15 and 6.8% higher than zero residue treatments and only rice residue retained/incorporated treatments, respectively, and resulted in additional returns of Rs. 28,871 ha−1 as compared with conventional RWCS. There was a significant (p < .05) improvement in soil organic carbon in residue retained/incorporated plots.

Five years of conservation tillage and weed management in a rice-chickpea rotation of northern Gangetic Plains of India: Weed growth, yield benefits and economic profitability

Cropping system diversification of cereal-cereal systems with alternative systems preferably with pulses/legumes is demand of time across the globe for sustenance of natural resources and climate resilience. Rice-chickpea has been advocated as a futuristic cropping system in rice ecologies of South Asia for diversification of dominating rice-wheat system. However, the long-term sustainability of this system with respect to weed severity/growth, crop/system productivity, profitability, and yield stability under variable tillage, crop residues, and weed management practices has not been studied elaborately. Hence, present study was undertaken for five consecutive years in split-plot design with four tillage and residue management practices in main plot (conventional and zero tillage with and without residues), and three weed control practices (pre + post emergence herbicides and manual weeding) in sub-plot. Conservation tillage system comprising zero-tilled (ZT) direct seeded rice (ZTDSR) - ZT chickpea with rice residue retention (ZTDSR-ZTC+RR) led to the lower weed density in chickpea (by 10 %) and system (by 7 %) than conventional-tilled (CT) puddled transplanted rice - CT chickpea without residues (PTR-CTC-R; farmer practice). Among weed management practices, pendimethalin 1 kg a.i. ha−1 – metsulfuron-methyl + chlorimuron ethyl (ready-mix) 4 g a.i. ha−1 in rice and oxyfluorfen 150 g a.i. ha−1 – propaquizafop 100 g a.i. ha−1 in chickpea decreased the weed density in system by 14–22 % (p < 0.05) than pendimethalin + one hand weeding. The best weed management practice (pendimethalin – metsulfuron-methyl + chlorimuron ethyl) had significantly total weed density rice (by 7 %) and system (by 10 %) than current recommendation of the Indo-Gangetic Plains region (pendimethalin - bispyribac-sodium). It suggested that rotation of bispyribac-sodium with metsulfuron-methyl+chlorimuron ethyl (mixture herbicide) could reduce weed density and increase yield over time. Mean of five years indicated a non-significant yield difference among conservation and conventional tillage systems in rice. However, conservation tillage practice (ZTDSR-ZTC+RR) had 10 % higher chickpea yield and 4 % higher system yield (five years mean) over the PTR-CTC-R (p < 0.05). Further, conservation tillage comprising ZT in both crops in system with added residues (ZTDSR-ZTC+RR) resulted in an economic benefit of INR 22,000 than the conventional tillage in both crops without residues (PTR-CTC-R). Moreover, five years sustainable yield index was 16 % higher in ZTDSR-ZTC+RR system than conventional-tilled rice-chickpea system. Thus, conservation tillage with suitable pre- + post- emergence herbicides such as pendimethalin – metsulfuron-methyl + chlorimuron ethyl in rice and oxyfluorfen – propaquizafop in chickpea can reduce the weed density and enhance the crop and system productivity over time than conventional tillage. This system can also sustain the yields of component crops and system in long-run with higher yield stability over conventional tillage without residues. This system can be adopted in the cereal-cereal based cropping system of rice ecologies to diversify the system and to reverse the weed infestation and yield decline.

Groundwater Arsenic Contamination in the Indo-Gangetic Plain of Bihar: The Psychological Well-being and Quality of Life of its Diseased Inhabitants

The health impacts of groundwater arsenic contamination are only partially known until the arsenic menace is deciphered from a psychological standpoint. Arsenic toxicity’s psychological health and well-being perspective is warranted to attain sustainable development goal 3 of the United Nations towards good health and well-being for all. This study assesses psychological well-being and its substantial effect on the quality of life of the arsenic-affected diseased inhabitants of Bihar who reside in the middle Indo-Gangetic plain. Cross-sectional correlational survey research was done on a sample of 382 inhabitants drawn through purposive sampling. T-test, correlation, and regression analysis were employed for the purpose. The psychological well-being of the arsenic-affected diseased inhabitants was poor compared to that of their healthy counterparts. Further, the quality of life of this population is strongly associated with and affected by their psychological well-being. Findings call for immediate attention and intervention from mental health professionals and policymakers. Knowledge generation about the psychological health impacts of groundwater arsenic contamination paves a path to improved human resources and well-being for sustainable development.

An Annotated Checklist of Earthworms (Annelida: Clitellata: Oligochaeta) of Indo-Gangetic Plains of India

A checklist of earthworm species hitherto known from Indo–Gangetic Plains of India is presented. In total, 98 species and subspecies are recorded, belonging to 33 genera spread over 9 families. Of these, 38 species are recognized as endemics and 34 as exotics. For every species and subspecies, the checklist comprises state-wise distributional information, all important synonyms, type locality and citations to the original description found in the literature.

Long-Term Impact of Crop Diversification and Nutrient Management on Soil Phosphorus Pools in Indo-Gangetic Plain

ABSTRACT Understanding the dynamics of soil phosphorus (P) over extended periods of soil and crop management practices is essential for sustainable P management. This study assessed the impact of four crop rotations [maize-wheat (M-W), maize-wheat-mungbean (M-W-Mb), maize-wheat-maize-chickpea (M-W-M-C), and pigeonpea-wheat (P-W)] each with three levels of nutrient management [control (CT), integrated nutrient management (suboptimal fertilizer+ farmyard manure + crop residue + bio-fertilizers; INM), and sole-chemical fertilizers (CF)] on soil inorganic and organic P (Pi and Po) pools and crop–soil relationships at the end of 15-year cropping. Legume-inclusive rotations resulted in higher labile-P pools, being higher with M-W-M-C and P-W. M-W-M-C rotation had higher moderately labile organic P (Po) in both surface (+23%) and subsurface (+18%) depths over M-W. Di-calcium P (Ca2-P) (+6%) and microbial biomass P (MBP) (+46%) increased in M-W-Mb over M-W, while iron-P (Fe-P) was reduced (−12%) in subsurface soil. INM enhanced bioavailable-P [soluble-P (+17%), labile-Pi (+15%) labile-Po (+12%), MBP (+96%), moderately labile-Po (+22%)] over CF in surface soil, while CF had a higher Fe-P (+16%). Legumes in rotation caused notable changes in the surface-to-subsurface ratio (SSBR) of Ca2-P (1.18–1.50) and occluded-P (1.64–2.78). INM had a higher SSBR of labile-P pools but had a lower SSBR of occluded-P facilitating mobilization of the later in the surface. Hence, in tropical soils, legume-inclusive diversification (particularly with chickpea) and INM involving crop residue recycling could be a sustainable option to improve P use efficiency, crop productivity, and save fertilizer resources.

Productivity, nutrient uptake and nitrogen economy of wheat (Triticum aestivum) in a conservation agriculture-based cotton (Gossypium herbaceum)–wheat system

Conservation agriculture (CA) practices like zero-till and residue retention along with nitrogen management is vital for improving degraded soil health and optimizing the yield potential of wheat (Triticum aestivum L.) crop. Present study was carried out during winter (rabi) seasons of 2021–22 and 2022–23 at ICAR-Indian Agricultural Research Institute, New Delhi for optimizing wheat productivity in a conservation agriculture-based cotton (Gossypium herbaceum L.)-wheat system. The experiment was laid out in a randomized complete block design (RCBD) with three replications consisting of combination of 3 different crop establishment methods, viz. permanent broad bed (PBB), permanent narrow bed (PNB) and zero-till flatbed (ZTFB) with residue (R) and without residue along with 2 doses of nitrogen (75N, 100N) and conventional tillage (CT). The CA-based practices showed overall superior response in terms of growth, yield and nutrients uptake of wheat than CT. Among them, the PBBR100N resulted in significantly higher plant height, leaf area index, dry-matter accumulation, crop growth rate, and relative growth rate compared to PNB, PBB, ZTFB and CT. This treatment led to significantly higher grain (16.2–19.4%) and straw (9.6–11.6%) yields than CT. The net returns and benefit cost ratio (23.4% and 27.9%) were also higher than that in CT. Again, in this treatment, N uptake by wheat crop was higher by 85%, P uptake by 53.1%, and K uptake by 40.1%, and available soil N, P and K by 16.1, 25.3 and 43.7%, respectively than CT. Therefore, the study suggests that the adoption of CA-based practices with broad bed in Indo-Gangetic Plains will not only enhance the productivity of wheat but also result in improved soil health by restoring soil fertility.

Effect of Different Levels of Integrated Nutrient Management in Mustard (Brassica juncea L.)

A field experiment was conducted during the Rabi session of 2020-21 in Jaunpur district which lies Indo-Gangetic plains of Central Uttar Pradesh to study the effect of integrated nutrient management in mustard (Brassica juncea L.). The trial was laid down in randomized block design (RBD) with three replications and twelve treatments viz, T1 100% RDF, T2 100% RDF + Azotobacter, T3 100% RDF + Azotobacter + PSB, T4 75% RDF + 25% N from FYM, T5 75% RDF + 25% N from FYM + Azotobacter, T6 75% RDF + 25% N from FYM + Azotobacter + PSB, T7 50% RDF + 50% N from FYM, T8 50% RDF + 50% N from FYM + Azotobacter, T9 50% RDF + 50% N from FYM + Azotobacter + PSB, T10 25% RDF + 75% N from FYM, T11 25% RDF + 75% N from FYM + Azotobacter, T12 25% RDF + 75% N from FYM + Azotobacter + PSB. Result of this study revealed that there was significant effect on growth and yield parameters. Plant height, number of branches, number of siliques, length of silique, number of seed per siliqua, test weight, seed and stover yield in T6 which was statistically at par with T9, T8, T7, T3. Maximum yield (1807 kg/ha) was recorded in T6. It may be concluded that RDF with organic Manure (FYM) and Biofertilizer (Azotobacter + PSB) is possible to produce more yield in mustard crops cultivated without much soil productivity under Indo-Gangetic plains of central Uttar Pradesh.

On-farm evidence on breaking yield barriers through optimizing wheat cropping system in Indo Gangetic Plain

The wheat production in the food basket of South Asia has plateaued with threats of environmental sustainability and posing a serious challenge to future food security. For sustainable wheat production in conventional rice-wheat (CTRW) systems under changing climatic scenario, atwo-year on-farm study was conducted. We evaluated system optimization practices (SOP) of legume inclusion with CTR-zero-tillage (ZT) wheat-mungbean (CTR-ZTWMb) and direct seeded rice-ZT wheat-mungbean (DSR-ZTWMb) and triple ZT (raised bed) based futuristic systems of maize-wheat-mungbean (ZTMWMb) and soybean-wheat-mungbean (ZTSWMb). The global warming potential (GWP) of wheat production was significantly reduced by 811 kg CO2 eq/ha (783−861) in the SOP compared to CTRW. Moreover, the water usein wheat reduced by 85.9 and 85.2 ha-mm/ha in CTR-ZTWMb and DSR-ZTWMb with higher reduction in ZTMWMb and ZTSWMb by128.7 and 118.0 ha-mm/ha, respectively over CTRW. Similarly, the total weed density was reduced at 60 (39 and 52 %) and 90 (38 and 49 %) days after sowing with CTR-ZTWMb and DSR-ZTWMb over CTRW. However, the weed density reduction was lesser with ZTSWMb and ZTMWMb at 60 (3.0 and 23.6 %), and 90 (9.8 and 31.0 %) days after sowingcompared to the CTRW.The partial factor productivity (PFP) of NPK applied was 8.5–19.0 % higher under SOP over the CTRW. The use of non-renewable energy in wheat cultivation was reduced by 24.4–28.9 % with SOP over CTRW. The enhancement in wheat grain yield (7.4–11.8 %) and net returns (98–169 US$/ha) was also recorded with CTR-ZTWMb and DSR-ZTWMb and this gain in futuristic systems (ZTMWMb and ZTSWMb) was much higher in grain yield (17.2–21.0 %) as well as in net returns (283 and 362 US$/ha) over CTRW. The adoption of these SOPs on 1 million ha could produce 0.37–1.05 million t additional wheat over CTRW. The on-farm study evidenced thatwheat production with system optimization practices of legume inclusion and zero tillage are better alternatives to achieve higher productivity and profitability with a lesserenvironmental footprint in Indo-Gangetic Plains and similar agroecological regions.

Assessment of the impact of observations at Nainital (India) and Comilla (Bangladesh) on the CH4 flux inversion

Methane emission in South Asia is poorly understood due to a lack of observations, despite being a major contributor to methane emissions globally. We present the first results of atmospheric CH4 inversions using air samples collected weekly at Nainital, India (NTL), and Comilla, Bangladesh (CLA), in addition to surface background flask measurements by NOAA, CSIRO and AGAGE using the MIROC4-ACTM. Our simulations span from 2000 to 2020 (considering the fixed “edge” effect), but the main analysis period is 2013–2020, when both the NTL and CLA datasets are available. An additional flux uncertainty reduction of up to 40% was obtained (mainly in the northern part of the Indian subcontinent), which enhanced our confidence in flux estimation and reaffirmed the significance of observations at the NTL and CLA sites. Our estimated regional flux was 64.0 ± 4.7 Tg-CH4 yr−1 in South Asia for the period 2013–2020. We considered two combinations of a priori fluxes that represented different approaches for CH4 emission from rice fields and wetlands. By the inversion, the difference in emissions between these combinations was notably reduced due to the adjustment of the CH4 emission from the agriculture, oil and gas, and waste sectors. At the same time, the discrepancy in wetland emissions, approximately 8 Tg-CH4 yr−1, remained unchanged. In addition to adjusting the annual totals, the inclusion of NTL/CLA observations in the inversion analysis modified the seasonal cycle of total fluxes, possibly due to the agricultural sector. While the a priori fluxes consisted of a single peak in August, the a posteriori values indicated double peaks in May and September. These peaks are highly likely associated with field preparation for summer crops and emissions from rice fields during the heading stage (panicle formation). The newly incorporated sites primarily exhibit sensitivity to the Indo-Gangetic Plain subregion, while coverage in southern India remains limited. Expanding the observation network is necessary, with careful analysis of potential locations using back-trajectory methods for footprint evaluation.

Long‐Term Trend in Black Carbon Mass Concentration Over Central Indo‐Gangetic Plain Location: Understanding the Implied Change in Radiative Forcing

AbstractFor the first‐time, analysis of a decade long measurement of Black Carbon mass concentration (BC) was carried out at a representative central Indo‐Gangetic Plain (IGP) location, Varanasi (25.30°N, 83.03°E, 79 m asl), from 2009 to 2021 to understand its physical, optical, and radiative impacts. During the 13‐year study period, the daily BC mass concentration was found to vary between 0.07 and 46.23 μg m−3 (mean 9.18 ± 6.53 μg m−3) and showed a strong inter‐annual and intra‐annual variations. The inter‐annual variability of BC showed a significant decreasing trend (−0.47 μg m−3 yr−1), with a maximum during the post‐monsoon (−1.86 μg m−3 yr−1) and minimum during the pre‐monsoon season (−0.31 μg m−3 yr−1). The Black Carbon Aerosol Radiative Forcing (BC‐ARF) at the top of the atmosphere (BC‐ARFT), surface (BC‐ARFS), and within the atmosphere (BC‐ARFA) was found to be 10.3 ± 6.4, −30.1 ± 18.9, and 40.5 ± 25.2 W m−2, respectively. BC‐ARF also showed a strong inter‐annual variability with a decreasing trend for BC‐ARFT (−0.47 W m−2 yr−1) and BC‐ARFA (−1.94 W m−2 yr−1), while it showed an increasing trend for BC‐ARFS (1.33 W m−2 yr−1). Concentrated weighted trajectories (CWT) and potential source contribution function (PSCF) analyses were performed at the station to determine the potential source sectors and transport routes of BC aerosols. These analyses revealed that the long‐range source of BC at Varanasi originates from the upper and lower IGP, central highlands, southern peninsular region, Pakistan, and even from the Central East Asia region.

Enhancing productivity, soil health, and reducing global warming potential through diverse conservation agriculture cropping systems in India's Western Indo-Gangetic Plains

ContextThe rice-wheat (RW) system, spanning 13.5 million hectares in South Asia, is crucial for food security and livelihoods. However, intensive conventional tillage-based practices have harmed soil and environmental health, decreased productivity trends and increased greenhouse gas emissions. ObjectiveThis study aims to develop resilient, climate-smart cropping systems within the RW system, focusing on soil and crop productivity, economic viability, and reduced greenhouse gas (GHG) emissions. MethodsOver eight years, the study evaluated diverse parameters compared to farmer practices (FP) in seven scenarios (Sc), including one representing FP (Sc1) and six based on conservation agriculture (CA) principles. The study assessed system crop productivity, economic returns, soil quality (organic carbon; OC, nitrogen; N, phosphorus; P, potassium; K contents, bulk density; BD, soil aggregation, infiltration rates, microbial counts, and earthworm density), and GHG emissions. ResultsCA-based scenarios (Sc2 to Sc7) showed improved soil quality, lower bulk density, enhanced soil aggregation, and increased infiltration rates compared to Sc1. In the 0–15 cm layer, surface soil organic carbon (OC) and C stock were 63.7 % and 49.6 % higher, respectively, in CA-based scenarios. Additionally, available N, P and K contents in the surface layer increased by 10.2 %, 28.6 %, and 21.8 % under CA-based scenarios. Adoption of CA in intensified maize-based scenarios (Sc4 and Sc5) led to the increased system and economic yields, higher soil quality index (SQI), reduced GHG emissions and increased C stock compared to Sc1. ImplicationsThe study highlights that Conservation Agriculture (CA) practices and diversified crop rotations can address issues like falling crop productivity, reduced economic returns, soil degradation, and increasing environmental impacts in northwestern India's traditional rice-wheat system. However, widespread adoption requires government policies, including C credit payments and guaranteed markets with supportive pricing.

Groundwater irrigation is critical for adapting wheat systems to warming temperatures in the Eastern Indo-Gangetic Plains in India

Warming temperatures are reducing wheat yields in India, and one way to reduce negative impacts is to sow wheat earlier. Yet farmers in Northeast India commonly sow wheat past the optimum time window. Previous studies have suggested this delay is driven by delays in the preceding rice growing season, which have cascading impacts on wheat sow date. It, however, remains unclear which specific rice management decisions are the most consequential for wheat sow date and what potential strategies may help advance the overall crop calendar. We used household survey data from 356 farmers in Bihar, India and structural equation modeling to identify the specific time points in the rice growing season that most impact wheat sow date. Our results suggest that late rice nursery establishment and rice harvest were associated with subsequent delays in the crop calendar. We also found that increasing groundwater irrigation access prior to the start of monsoon rains may be the most effective way to advance rice and wheat sowing. Our results provide insights into the specific time points in the crop calendar when interventions may be the most consequential, which is critical for developing interventions to help farmers adapt wheat systems to warming temperatures.

Source apportionment of fine particulate matter in middle Indo-Gangetic Plain by coupled radiocarbon –molecular organic tracer method

Despite significant emissions of fine particulate matter (FPM) from the Indo-Gangetic Plain (IGP) that affect the climate and air quality in the region, the sources of these emissions are not adequately addressed. This research uses a combined radiocarbon-molecular organic tracer technique to investigate the degree of contamination, seasonal fluctuations, and contribution of FPM in the middle IGP (Patna), India. The findings indicated levoglucosan (L) as the single primary BB tracer chemical, ranging from 149 ng/m3 to 490 ng/m3 (median 282 ng/m3). Winter (median 462 ng/m3) showed a 2–3 times higher level of L than the monsoon season (median 180 ng/m3). A significant association of L with other organic tracers such as galactosan (G), mannosan (M), vallinic acid, syringic acid, p-hydroxybenzoic acid (pHA) and dehydroabietic acid (DHAA)(r = 0.53 to 0.89, p < 0.05), and moderate connection with Cl− (r = 0.21, p < 0.05), SO42− (r = 0.29, p < 0.05), and NO3- (r = 0.22, p < 0.05) indicated significant BB contribution. However, non-sea salt (nss-K+) was not related to L. Based on seven days of air mass back trajectories and MODIS active fire counts analysis, we conclude that OAs composition is not the local origin but is also impacted by long-range atmospheric transport from Pakistan/Afghanistan, followed by the Bay of Bengal and the Arabian Sea. Chemical analysis of organic tracers and positive matrix factorization (PMF) modeling study identified three unique sources, i.e., biomass burning, secondary aerosols formation, and mixed type (fossil fuels and construction dust) as the primary source of FPM in Patna, accounted for 46.1 %, 28.9 %, and 24.9 %, of total emissions, respectively. The radiocarbon (14 C) analysis of total carbon (TC) samples further supported this conclusion. The results of the 14 C study indicated that emissions from BB, such as wood and stubble, were responsible for 57% of the TC concentration.