In this study, we integrated a remote-sensing fire product (MOD14A1) and land-use product (MCD12Q1) to extract the number of crop-residue burning (CRB) spots and the fire radiative power (FRP) in China from 2001 to 2018. Moreover, we conducted three trend analyses and two geographic distribution analyses to quantify the interannual variations and summarize the spatial characteristics of CRB on grid (0.25° × 0.25°) and regional scales. The results indicated that CRB presents distinctive seasonal patterns with each sub-region. All trend analyses suggested that the annual number of CRB spots in China increased significantly from 2001 to 2018; the linear trend reached 2615 spots/year, the Theil-Sen slope was slightly lower at 2557 spots/year, and the Mann-Kendal τ was 0.75. By dividing the study period into two sub-periods, we found that the five sub-regions presented different trends in the first and second sub-periods; e.g., the Theil-Sen slope of eastern China in the first sub-period (2001–2009) was 1021 spots/year but was −1599 spots/year in the second period (2010–2018). This suggests that summer CRB has been effectively mitigated in eastern China since 2010. Further, the average FRP of CRB spots presented a decreasing trend from 27.5 MW/spot in 2001 to only 15.8 MW/spot in 2018; this may be attributable to more scattered CRB rather than aggregated CRB. Collectively, the fire spots, FRP, and average FRP indicated that spring, summer, and autumn CRB had dropped dramatically over previous levels by 2018 due to strict mitigation measures by local governments.

Biomass burning as fuel in the traditional grass-roofed rural households of Western Province of Kenya in open fire places, in poorly ventilated conditions, lead to accumulation of soot under the roofs. This study characterized and quantified the polycyclic aromatic hydrocarbons (PAHs) in accumulated soot in these households and determined the variation in PAHs concentrations with fuel biomass type. Soot samples collected from the households were extracted, cleaned and analysed by gas chromatography. The PAHs were identified using retention times, verified by gas chromatographic mass spectral analysis and quantified from peak area responses using the internal standard method. The PAHs levels significantly varied (P≤0.05) with biomass type in the order: dung≥indigenous trees≥exotic trees≥shrubs and crop residues. Use of dung and wood from indigenous trees as fuel should be discouraged since they are higher emitters (P≤0.05) of carcinogenic PAHs.

Carbon sequestration in agricultural soils is controlled by the balance of added organic residues and microbial oxidation of both residues and native organic matter (OM) as moderated by management and tillage. The PC-based model CQESTR predicts decomposition of residues, organic amendments and soil OM, based on cropping practices. CQESTR uses RUSLE (Revised Universal Soil Loss Equation) crop rotation and management practice, crop production, and operation databases. These data are supplemented with residue nitrogen and soil OM, bulk density, and layer thickness. CQESTR was calibrated with soil carbon data from 70-year-long experiments at the Research Center at Pendleton, OR. The calibrated model provides estimates with a 95% confidence interval of 0.33% OM. Validation at 11 independent sites resulted in a matching of observed with calculated OM with a 95% confidence interval of 0.55% OM. A 12th site, with a history of severe erosion, provided a poor match.

Worship activities like burning joss paper during the Chinese Hanyi festival is a common, traditional custom in northwest China. However, the pollutants of e.g., soot particles, released from joss paper burning and the corresponding impacts on urban air quality were poorly investigated, which can be a particular concern since these activities are conducted in an uncontrolled manner. In this study, a long time-of-flight (LToF) soot particle aerosol mass spectrometry (SP-AMS) was deployed to characterize the refractory black carbon (rBC) emitted from the joss paper burning, as well as crop residue, coal combustion, and traffic during the Hanyi Festival in mid-November 2020 in the northwestern city of Xi'an in China. Large difference (from <5% to >100%) in the fragmentation patterns (Cₙ⁺) for the measured rBC from different source emissions were found when compared to the reference Regal Black. Using the receptor model of positive matrix factorization (PMF) with the multilinear engine (ME-2) algorithm, the obtained rBC mass spectra were used as the anchoring profiles to evaluate the emission strengths of different source types to the atmospheric rBC. Our results show that the burning of joss paper accounted for up to 42% of the atmospheric rBC mass, higher than traffic (14–17%), crop residue (10–17%), coal (18–20%) during the Hanyi festival in northwest China. Moreover, we show that the overall air quality can be worsened due to the practice of uncontrolled burning of joss paper during the festival, which is not just confined to the people who do the burning. Although worship activities occur mainly during festival periods, the pollution events contributed by joss paper burning may pose an acute exposure risk for public health. This is particularly important since burning joss paper during worship activities is common in China and most Asian countries with similar traditions.

As a promising amendment, biochar has excellent characteristics and can be used as a remediation agent for diverse types of soil pollution. Biochar is mostly made from agricultural wastes, forestry wastes, and biosolids (eg, sewage sludge), but not all the biochar has the same performance in the improvement of soil quality. There is a lack of guidelines devoted to the selection of biochar to be used for different types of soil pollution, and this can undermine the remediation efficiency. To shed light on this sensitive issue, this review focus on the following aspects, (i) how feedstocks affect biochar properties, (ii) the effects of biochar on heavy metals and organic pollutants in soil, and (iii) the impact on greenhouse gas emissions from soil. Generally, the biochars produced from crop residue and woody biomass which are composed of lignin, cellulose, and hemicellulose are more suitable for organic pollution remediation and greenhouse gas emission reduction, while biochar with high ash content are more suitable for cationic organic pollutant and heavy metal pollution (manure and sludge, etc.). Additionally, the effect of biochar on soil microorganisms shows that gram-negative bacteria in soil tend to use WB biochar with high lignin content, while biochar from OW (rich in P, K, Mg, and other nutrients) is more able to promote enzyme activity. Finally, our recommendations on feedstocks selection are presented in the form of a flow diagram, which is precisely intended to be used as a support for decisions on the crucial proportioning conditions to be selected for the preparation of biochar having specific properties and to maximize its efficiency in pollution control.

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 × ∼10 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.

Although crop residue return increases upland soil emissions of nitrous oxide (N₂O), a potent greenhouse gas, the mechanisms responsible for the increase remain unclear. Here, we investigate N₂O emission pathways, gross nitrogen (N)-cycling rates, and associated N-cycling gene abundances in an upland soil following the addition of various organic material under aerobic incubation using a combination of ¹⁵N tracing technique, acetylene (C₂H₂) inhibition, and real-time PCR (qPCR) methods. Increased total N₂O emissions following organic material amendment was attributed to both increased nitrification-derived N₂O emissions, following increased ammonia-oxidizing bacteria (AOB)-amoA abundance, and denitrification-derived N₂O emissions, following increased nirS and decreased nosZ abundance. Increasing plant residue carbon (C)/N ratio decreased total N₂O emissions by decreasing the contribution of denitrification to N₂O emissions, potentially due to higher proportions of denitrified N emitted as N₂O than nitrified N emitted as N₂O. We further propose a novel conceptual framework for organic material input effects on denitrification-derived N₂O emissions based on the decomposable characteristics of the added organic material. For slowly decomposing organic materials (e.g., plant residue) with insufficient available C, NO₃⁻-N immobilization surpassed denitrification, resulting in gradual decrease in denitrification-derived N₂O emissions with an increase in mineralization of plant residue C losses. In contrast, available C provided by readily available C sources (e.g., glucose) seemed sufficient to support the co-occurrence of NO₃⁻-N immobilization and denitrification. Overall, for the first time, we offer a microbial process perspective of N₂O emissions following organic material input. The findings could facilitate the improvement of process-orientated models of N₂O emissions and the formulation of appropriate N₂O mitigation strategies for crop residue-amended soils.

Chromium (Cr) poses serious consequences on human and animal health due to its potential carcinogenicity. The present study aims at preparing a novel biochar derived from Chenopodium quinoa crop residues (QBC), its activation with magnetite nanoparticles (QBC/MNPs) and strong acid HNO₃ (QBC/Acid) to evaluate their batch and column scale potential to remove Cr (VI) from polluted water. The QBC, QBC/MNPs and QBC/Acid were characterized with SEM, FTIR, EDX, XRD as well as point of zero charge (PZC) to get an insight into their adsorption mechanism. The impact of different process parameters including dose of the adsorbent (1–4 g/L), contact time (0–180 min), initial concentration of Cr (25–200 mg/L) as well as solution pH (2–8) was evaluated on the Cr (VI) removal from contaminated water. The results revealed that QBC/MNPs proved more effective (73.35–93.62-%) for the Cr (VI) removal with 77.35 mg/g adsorption capacity as compared with QBC/Acid (55.85–79.8%) and QBC (48.85–75.28-%) when Cr concentration was changed from 200 to 25 mg/L. The isothermal experimental results follow the Freundlich adsorption model rather than Langmuir, Temkin and Dubinin-Radushkevich adsorption isotherm models. While kinetic adsorption results were well demonstrated by pseudo second order kinetic model. Column scale experiments conducted at steady state exhibited excellent retention of Cr (VI) by QBC, QBC/MNPs and QBC/Acid at 50 and 100 mg Cr/L. The results showed that this novel biochar (QBC) and its modified forms (QBC/Acid and QBC/MNPs) are applicable with excellent reusability and stability under acidic conditions for the practical treatment of Cr (VI) contaminated water.

Biomass integrated gasification combined cycle (IGCC) is attracting increased interest because it can achieve high system energy efficiency (>50%), which is predicted to increase with the increase in the solar share in biomass IGCC. This study evaluated the potential of crop residues numerically for the co-production of power and bio-fertilizer using ASPEN Plus® simulation software. The results showed that the gas yield increases with increasing temperature and decreasing pressure while the yield of bio-fertilizer is dependent on the biomass composition. The biomass with a low ash content produces high bio-fertilizer at the designated gasification temperature. The IGCC configuration conserves more energy than a directly-fired biomass power plant. In addition, the solar-assisted IGCC attains a higher net electricity output per unit of crop residue feed and achieves net thermal efficiencies of around 53%. The use of such hybrid systems offer the potential to produce 0.55 MW of electricity per unit of solar-thermal energy at a relatively low cost. The ASPEN Plus model predicted that the solar biomass-based IGCC set up is more efficient in increasing the power generation capacity than any other conversion system. The results showed that a solar to electricity efficiency of approximately 55% is achievable with potential improvements. This work will contribute for the sustainable bioenergy production as the relationship between energy production and biomass supplies very important to ensure the food security and environmental sustainability.

Continuous measurements of Black Carbon (BC) aerosol mass concentrations were carried at Dehradun (30.33°N, 78.04°E, 700 m amsl), a semi-urban site in the foothills of north-westHimalayas, India during January 2011–December 2017. We reported both the BC seasonal variations as well as mass concentrations from fossil fuel combustion (BCff) and biomass burning (BCbb) sources. Annual mean BC exhibited a strong seasonal variability with maxima during winter (4.86 ± 0.78 μg m⁻³) followed by autumn (4.18 ± 0.54 μg m⁻³), spring (3.93 ± 0.75 μg m⁻³) and minima during summer (2.41 ± 0.66 μg m⁻³). Annual averaged BC mass concentrations were 3.85 ± 1.16 μg m⁻³ varying from 3.29 to 4.37 μg m⁻³ whereas BCff and BCbb ranged from 0.11 to 7.12 μg m⁻³ and 0.13–3.6 μg m⁻³. The percentage contributions from BCff and BCbb to total BC are 66% and 34% respectively, indicating relatively higher contribution from biomass burning as compared to other locations in India. This is explained using potential source contribution function (PSCF) and concentration weighted trajectories (CWT) analysis which reveals the potential sources of BC originating from the north-west and eastern parts of IGP and the western part of the Himalayas that are mostly crop residue burning and forest fire regions in India. The annual mean ARF at top-of-atmosphere (TOA), at surface (SUR), and within the atmosphere (ATM) were found to be −14.84 Wm⁻², −43.41 Wm⁻², and +28.57 Wm⁻² respectively. To understand the impact of columnar aerosol burden on ARF, the radiative forcing efficiency (ARFE) was estimated and averaged values were −31.81, −91.63 and 59.82 Wm⁻² τ⁻¹ for TOA, SUR and ATM respectively. The high ARFE within the atmosphere indicates the dominance of absorbing aerosol (BC and dust) over Northwest Himalayas.