Crop Straw Burning Research Articles

Molecular Characterization of Gaseous Organic Acids and Nitrogen‐Containing Compounds From Crop Straw and Wood Burning

AbstractBiomass burning serves as important sources of volatile organic compounds (VOCs), yet our understanding of the molecular characteristics of oxygenated volatile organic compounds (OVOCs) from fresh emissions remains limited. In this study, gaseous organic compounds in fresh smokes from burning typical Chinese crop straws and woods are measured using an iodide time‐of‐flight chemical ionization mass spectrometer. Approximately 750 molecular formulas are identified, with CHO compounds containing carbon, hydrogen and oxygen atoms accounting for 77%–95% of the total. C1–C3 organic acids and dicarboxylic acids dominate the total CHO signal intensities by 27%–48%, while well‐known molecular markers of biomass burning, such as monosaccharide, guaiacol and syringol derivatives, contribute 7%–17%. Notably, crop straw and wood burning emit a higher abundance of guaiacol than syringol derivatives by a factor of 5. Additionally, a variety of nitrogen‐containing compounds (mainly in the CHON group) is identified, including isocyanate, amide, amino acids, and pyridine. The mass spectral profiles of organic compounds are largely similar between crop straw and wood burning fuels, although wood burning produces higher contributions of compounds with carbon atoms numbers >10. The saturation concentrations of organic compounds are estimated using molecular formula‐based volatility parameterization, revealing that semi‐volatile and intermediate VOCs (S/intermediate volatility organic compounds (IVOCs)) predominate smoke releases by 35%–60% and 20%–43%, respectively, with only a small fraction of low‐volatility compounds. Given the widespread nature of biomass burning in winter China, our results may have significant implications for interpreting secondary organic aerosol formation through gas‐particle partitioning or aqueous‐phase reactions.

Agricultural expansion dominates rapid increases in cropland fires in Asia

Asia contains 58 % of the global population and approximately 39 % of the world’s cropland, making evaluation of the spatiotemporal variability patterns in cropland fire critical for understanding the interplay between crop residue burning and human activity in Asia. Although agricultural expansion and intensification have contributed to an overall decline in vegetation fires worldwide since the late 1990s, burned area by cropland fires in Asia has expanded by more than 19 % over the past two decades. India accounts for about 32 % of cropland fires in Asia, and the burned area has increased by more than two-thirds since 2003, particularly increased around 80 % during the two major cereal harvest seasons of March-May and October-November. In comparison, cropland fires have increased by <6 % in China since 2003, and there has been a marked downward trend in burned area in June due to the intensive implementation of the nationwide bans on open-land crop straw burning. The expansion of agricultural harvests is primarily responsible for the rapid increase in cropland fires in Asia, notably in India, where agricultural intensification is occurring with population growth and economic development in recent years, and crop straw burning should be strictly controlled in the future.

Fresh organic and soot particles from crop straw burning: Morphology, composition and size distribution

Particulate matter from biomass burning is considered to be one of the major sources of air pollution in China. To examine the characteristics of the particles emitted from the burning of crop straw, an open burning experiment is designed. Individual particles are collected in the flaming and smouldering stages, and analysed by individual particle analyses represented by high‐resolution transmission electron microscopy equipped with the energy‐dispersive X‐ray spectrometer. Five types of particles are identified, namely, pure organic particle, organic particle‐K (OP‐K), tar ball, K‐rich and soot particles. Of these, the OP‐K particles have the highest relative number percentage in all analysed particles in both the flaming and smouldering stages. Interestingly, the microscopic morphology of organic particles is completely different in the flaming and smouldering stages, being near‐spherical in the flaming stage and gel‐like in the smouldering stage. According to the elemental compositions, most of OP‐K particles contained potassium compounds in the form of KCl and K2SO4. High combustion efficiency and temperature promote the formation of crystal structure, resulting in the onion‐like microstructure of soot particles. Apparently, the soot microstructure is a fingerprint feature that helps identify combustion sources. In addition, the particles emitted in the flaming stage are smaller than those in the smouldering stage, implying that high temperature combustion tends to be associated with high combustion efficiency. The relationship between burning temperatures and particle sizes can help to understand the emission of particles from crop straw burning and find new ways to solve the problems caused by straw burning. The results of this study can provide more detailed ‘fingerprint’ characteristics of the particulate matter emitted from biomass‐burning sources, and an understanding of their potential impact on the atmospheric environment.

Enhanced open biomass burning detection: The BranTNet approach using UAV aerial imagery and deep learning for environmental protection and health preservation

Open biomass burning (OBB) in agriculture presents a significant and well-documented challenge, posing severe consequences for both environmental and human health. OBB releases air pollutants that degrade air quality and contribute to climate change, leading to premature deaths in regions with high concentrations of open crop straw burning (OCSB) emissions. Although policies aimed at prohibiting OBB are in place, the efficacy of these regulations in mitigating OCSB emissions remains ambiguous. Consequently, early prevention and monitoring of open biomass combustion are imperative for environmental preservation. Traditional monitoring techniques, reliant on fixed-position cameras, are constrained by their location and monitoring intensity, making concealed fire recognition a complex problem. To address this limitation and monitor the human living environment more flexibly and accurately, we propose a new method to identify straw fires in UAV Aerial Image Using CNN Branch Reinforce Transformer which named BranTNet, enabling early detection and rapid response to crop straw fires. By integrating computer vision technology and deep learning algorithms, straw fires in UAV-acquired aerial survey images can be detected and categorized. In the realm of artificial intelligence algorithms, we skillfully merge convolution and attention mechanisms, harnessing the full potential of both methodologies. Moreover, we seamlessly incorporate transfer learning, skillfully unifying self-training convolution modules with pre-trained transformer modules. This strategic amalgamation not only minimizes time costs but also ensures optimal experimental outcomes. Regarding data, we meticulously collected a substantial number of authentic samples, ensuring the sufficiency of our experimental dataset. The experimental results demonstrate that our proposed method exhibits exceptional accuracy and robustness in detecting and identifying straw fires in UAV aerial survey images. Our approach outperforms the use of convolution or attention mechanisms alone. By integrating this approach with drone technology, we unlock the potential for developing more versatile and precise monitoring solutions, expanding the application of drones to diverse domains. This progress contributes significantly to the early detection and prevention of crop straw fires, fundamentally reducing environmental pollution, curbing carbon emissions, and advancing the cause of carbon neutrality. This innovative technique for monitoring and preventing OBB holds substantial promise in mitigating the adverse effects of OBB on the environment and human health.

The evolution of open biomass burning during summer crop harvest in the North China Plain

Open biomass burning (OBB) negatively impacts air quality by discharging abundant fine particulate matter (PM2.5, aerodynamic diameter ≤2.5 µm) and trace gases. The statistical methods and numerical simulations have been used to estimate emissions from OBB. The former is poor in producing reliable distributions and transport of emissions, while studies with the latter have focused on cases analysis over short periods. This study investigates the multi-year evaluation of OBB and its contribution to PM2.5 and black carbon (BC) based on satellite observations and numerical modeling over the North China Plain. The number of fires increased by 206% from 2008 to 2012, and decreased by 84% from 2012 to 2016, indicating that the implementation of straw burning ban policy had achieved significant positive effects. The simulation from Weather Research and Forecasting model coupled with chemistry showed that the surface concentrations of PM2.5 and BC emitted by OBB in the burning source area increased from 22 and 3.22 μg/m3, respectively, in 2008 to 45.77 and 6.47 μg/m3, respectively, in 2012, and then decreased to 1.41 and 0.22 μg/m3, respectively, in 2016. The differentiated impacts on air quality of policies across provinces are also investigated. Open crop straw burning was banned early in Shandong and Henan provinces, but they suffer from poor air quality due to open straw burning until the effective straw burning ban in Anhui and Jiangsu provinces, which suggests the need for interregional collaboration for pollution control.

Effect of freeze-thaw cycles and biochar coupling on the soil water-soil environment, nitrogen adsorption and N2O emissions in seasonally frozen regions

Freeze-thaw cycles (FTCs) usually occur in the nongrowing season of crops, and the temporal mismatch between soil nitrogen (N) supply and crop N utilization increases the risk of N loss. Crop straw burning is a seasonal air pollution source, and biochar provides new alternatives for waste biomass recycling and soil pollution remediation. To investigate the effect of biochar on N loss and N2O emissions under frequent FTCs, different biochar content treatments (0 %, 1 %, 2 %) were set, and laboratory simulated soil column FTC tests were conducted. Based on the Langmuir and Freundlich models, the surface microstructure evolution and N adsorption mechanism of biochar before and after FTCs were analyzed, and the change characteristics of the soil water-soil environment, available N and N2O emissions under the interactive effect of FTCs and biochar were studied. The results showed that FTCs increased the oxygen (O) content by 19.69 % and the N content by 17.75 % and decreased the carbon (C) content by 12.39 % of biochar. The increase in the N adsorption capacity of biochar after FTCs was related to changes in surface structure and chemical properties. Biochar can improve the soil water-soil environment, adsorb available nutrients, and reduce N2O emissions by 35.89 %–46.31 %. The water-filled pore space (WFPS) and urease activity (S-UE) were the main environmental factors determining N2O emissions. Ammonium nitrogen (NH4+-N) and microbial biomass nitrogen (MBN), as substrates of N biochemical reactions, significantly affected N2O emissions. The interaction of biochar content and FTCs in different treatments had significant effects on available N (p < 0.05). The application of biochar is an effective way to reduce N loss and N2O emissions under the action of frequent FTCs. These research results can provide a reference for the rational application of biochar and efficient utilization of soil hydrothermal resources in seasonally frozen soil areas.

Assessing the contribution of open crop straw burning to ground-level ozone and associated health impacts in China and the effectiveness of straw burning bans

In recent years, ozone pollution in China has been shown to increase in frequency and persistence despite the concentrations of fine particulate matter (PM2.5) decreasing steadily. Open crop straw burning (OCSB) activities are extensive in China and emit large amounts of trace gases during a short period that could lead to elevated ozone concentrations. This study addresses the impacts of OCSB emissions on ground-level ozone concentration and the associated health impact in China. Total VOCs and NOx emissions from OCSB in 2018 were 798.8 Gg and 80.6 Gg, respectively, with high emissions in Northeast China (31.7%) and North China (23.7%). Based on simulations conducted for 2018, OCSB emissions are estimated to contribute up to 0.95 µg/m3 increase in annual averaged maximum daily 8-hour (MDA8) ozone and up to 1.35 µg/m3 for the ozone season average. The significant impact of OCSB emissions on ozone is mainly characterized by localized and episodic (e.g., daily) changes in ozone concentration, up to 20 µg/m3 in North China and Yangtze River Delta region and even more in Northeast China during the burning season. With the implementation of straw burning bans, VOCs and NOx emissions from OCSB dropped substantially by 46.9%, particularly over YRD (76%) and North China (60%). Consequently, reduced OCSB emissions result in an overall decrease in annual averaged MDA8 ozone, and reductions in monthly MDA8 ozone could be over 10 µg/m3 in North China. The number of avoided premature death due to reduced OCSB emissions (considering both PM2.5 and ozone) is estimated to be 6120 (95% Confidence Interval: 5320–6800), with most health benefits gained over east and central China. Our results illustrate the effectiveness of straw burning bans in reducing ozone concentrations at annual and national scales and the substantial ozone impacts from OCSB events at localized and episodic scales.

Online detection and source tracing of crop straw burning

The carbon dioxide, sulfur dioxide, and metal ions produced by straw burning can severely pollute the atmosphere; thus, online detection and traceability for straw burning is very important. However, to our best knowledge, there is no comprehensive system that can satisfy online detection, classification, and traceability due to the challenging online detection and traceability of straw burning. In this paper, a new system based on laser-induced breakdown spectroscopy (LIBS) and machine learning is developed, and this developed system is employed for the first time in online detection and traceability of straw combustion. Four different types of straw are selected and the straw burning smoke is monitored online using this developed system. The analysis of straw smoke spectra shows that there are Fe, Mn, and Ba heavy metal spectra in the smoke spectra. By comparing the smoke spectra of different types of straw, the characteristic spectral lines with large differences are selected and dimensionality reduction is performed by linear discriminant analysis algorithm. Then, combined with random forest to achieve classification, the final smoke recognition accuracy reaches 87.0%. Straw ash is then used as a reference analysis and the same operation is performed on it. Mn, Ba, and Li heavy metal spectral lines are found in the spectra of ash, and the final recognition accuracy is 92.6%. The innovative and developed system based on LIBS and machine learning is fast, online, and in situ and has far-reaching application prospects in the environment.

Marked rebound of agricultural fire emissions in Asia after the outbreak of COVID-19

East and South Asia are major hotspots of crop straw burning worldwide, with profound impacts on air quality and climate change. The Northeast China Plain (NECP) and Punjab, India, are two of the most fertile areas for crop production, which have large-scale agricultural fires during post-harvest seasons. Leveraging established fire-emission databases and satellite-retrieved agricultural fire spots, we show that, while the years 2018 and 2019 recorded low agricultural fire emissions in both the NECP and Punjab, probably due to the implementation of crop straw sustainable management, fire emissions markedly rebounded in 2020, reaching about 190% and 150% of 2019 levels, respectively. The COVID-19 lockdown measures somewhat disrupted eco-friendly crop straw management through restrictions on labor and transportation availability, such that farmers may have had to burn off crop wastes to clear up the land. We further demonstrate that the increased fire emissions in the NECP resulted in serious particulate matter pollution during the fire season in spring 2020, as opposed to considerable decreases in particles from fossil fuel emissions caused by the COVID-19 lockdown. This study suggests the unintended impacts of the COVID-19 pandemic on the agricultural sector and human health.

Emission Factors and Inventories of Carbonaceous Aerosols from Residential Biomass Burning in Guizhou Province, China

Biomass combustion results in the emission of substantial amounts of carbonaceous aerosols. Here, we report the emission characteristics of organic carbon (OC) and elemental carbon (EC) from biofuel combustion according to field measurements in rural households in Guizhou Province, China. The average emission factor of OC was 0.57 ± 0.16 g kg−1 for firewood burning, which was lower than that for crop straw burning. The average emission factor of EC was 1.1 ± 0.63 g kg−1 for firewood burning, which was higher than most crop straw burning, including corn (0.68 ± 0.29 g kg−1), rice (0.48 ± 0.40 g kg−1), and soybean (0.17 ± 0.21 g kg−1). The average OC/EC ratios from crop straw burning were high, 14.2 for rice straw burning, 11.7 for soybean straw burning, 5.1 for corn straw burning, and 2.8 for pepper straw burning. The average OC/EC ratio of firewood was the lowest at 0.54. In 2019, the estimated emissions of OC and EC from residential biomass fuel combustion in Guizhou Province were 3.6 and 5.6 Gg, respectively. Firewood burning was the primary contributor to total residential biofuel OC (≈81%) and EC (≈97%) emissions. High-emission areas included Tongren, Qiandongnan, and Qiannan.

Contributions of Open Biomass Burning and Crop Straw Burning to Air Quality: Current Research Paradigm and Future Outlooks

Since open biomass burning (OBB) and open crop straw burning (OCSB) could pose a great risk to human health via altering the air quality, these practices have grabbed considerable attention from the scientific community and policymakers in recent years. In order to have a greater and deeper understanding of the contributions of both OBB and OCSB on air quality, a bibliometric analysis was performed using the Web of Science core collection to understand the research developments and future perspectives of these issues between 1991 and 2021. VOSviewer software 1.6.15 and R version 4.0.3 were employed to determine the annual scientific production trend and the role of countries, institutions, authors, and journal metrics network analysis. The findings showed that the interest in the study of OBB and OCSB pollution related to air quality has increased significantly over the last decade. A total of 1,021 publications were retrieved, with English as the most preferably used language. Among all documents, research articles were the most commonly appearing document type, and the researchers mainly emphasized environmental science, meteorology, atmospheric sciences, energy fuels, and environmental engineering fields. In terms of article analysis, Atmospheric Chemistry Physics, followed by Atmospheric Environment, was found to be the leading journal in this research domain, whereas the most frequently utilized keywords in the documents were biomass, biomass burning, and PM2.5. In terms of countries, the United States emerged as the leader with the highest publication rate, followed by China and India. The Chinese Academy of Sciences was ranked first in the list of most productive institutions, followed by the University of Montana and the US Forest Service. Based on the analysis, the finer spatial and temporal resolution and the characterization and understanding of the complex processes that are occurring in the atmosphere, such as clustering, oxidation, surface chemistry, and their impact on air quality, need to be explored in depth. Our research analysis can provide a baseline for future studies in air quality.

Overview of the performance of satellite fire products in China: Uncertainties and challenges

Satellite fire observations provide an essential constraint for the estimation of global biomass burning emissions. In this study, we present a comprehensive insight into the performance of the common satellite fire products in eastern China. Despite consistent spatial patterns, both polar-orbiting and geostationary satellite observations have large omission errors for the agricultural burning fires. Owing to a coarse resolution of 2 km, approximately 90% of the concurrent 375 m Visible infrared Imaging Radiometer (VIIRS) fires are not detected in Himawari-8 products. Nevertheless, the total amount of daily Himawari-8 fires is much higher than those of VIIRS and 1 km Moderate resolution imaging spectroradiometer (MODIS). The peak time of diurnal fire counts in eastern China has obvious seasonal variations, some of which are missed by polar-orbiting satellite detection. Validation by 3 m PlanetScope images shows that VIIRS and MODIS have a very high accuracy in detecting crop straw burning fires. However, Himawari-8 fires have obvious false alarms due largely to their algorithm defects. Also, the coarse resolution of Himawari-8 tends to make fire detection more likely to be obscured by dense smoke. The unmanned aerial vehicle (UAV) supervisions reveal prevalent small agricultural fires (<0.5 × 104 m2) in the extensive croplands that are not detected in the common satellite fires. As control measures get more stringent, spatial-temporal patterns as well as the scales of biomass burning activities in China have undergone dramatic changes. Considering the crucial role of satellite fires in estimating biomass burning emissions, it is necessary to improve satellite fire detection with more advanced observations and retrieval methods.

Assessment of the effects of straw burning bans in China: Emissions, air quality, and health impacts

Open biomass burning (OBB) plays an important role in air pollution and climate change by releasing short-term but intensive amounts of particulate matter and gaseous air pollutants. During past years, policies with respect to prohibition on open straw burning have been issued in China in order to mitigate the air pollution problems and the effectiveness of these straw burning bans in different regions remains to be evaluated. In this study, open crop straw burning (OCSB) emissions during 2010–2018 were analyzed based on a commonly used emission inventory with high spatial and temporal resolution. High emissions concentrated over Northeast China (31.8% of national total PM2.5 emissions in 2018), East China (24.0%), and North China (16.6%). Simulations based on an integrated meteorology-air quality modeling system and an exposure-response function show that OCSB emissions could increase monthly PM2.5 concentration by as much as 10 μg/m3 during burning seasons in Northeast China and were associated with 4741 premature deaths in 2018. Spatial heterogeneities were observed with respect to the trends of OCSB emissions during 2010–2018. In East China, North China, and Central China, OCSB emissions showed a general declining trend since 2013 while an opposing increasing trend was observed in Northeast China with peak emissions in 2017. Comparing 2013 (before intensive implementation of straw burning bans) and 2018 (after), national total PM2.5 emissions from OCSB activities decreased by 46.9%, ranging from −14.1% to +70% depending on the specific regions. Northeast China is the only region that showed higher OCSB emissions in 2018 compared to 2013, probably associated with the relatively delayed implementation of the straw burning bans. Avoided number of premature deaths due to reduced OCSB emissions was estimated to be 4256 on a national scale, with most health benefits gained in East and Central China. Results from this study demonstrate the importance of OCSB contribution to PM2.5 concentrations and spatial heterogeneities exist in terms of the effectiveness of the straw burning bans in reducing OCSB emissions and gained health benefits.

Comprehensive characterizations of HULIS in fresh and secondary emissions of crop straw burning

The humic-like substances (HULIS) in PM2.5 in fresh and secondary emissions of crop straw burning will result in strong light absorption of atmospheric aerosols in the near-ultraviolet and visible light region. Herein, the relative carbon contents, light absorption properties, fluorescence characteristics, FTIR and 1H NMR spectra of fresh and secondary HULIS in crop straws (wheat, rice, and corn) burning were comprehensively characterized. The results showed that the ratios of carbon contents in HULIS to water-soluble organic carbon and organic carbon (HULIS-C/WSOC and HULIS/OC) of HULIS in secondary emissions of crop straw burning were higher than that in fresh emissions. The MAE365 (mass absorption efficiencies at 365 nm) of secondary HULIS in crop straws burning were larger than that in fresh emissions. Excitation-emission matrix (EEM) spectra indicated that fresh HULIS contained phenol-like substances, which can form light-absorbing substances through secondary conversion. The spectrum of FTIR and 1H-nuclear magnetic resonance (1H NMR) showed that chemical structures of secondary HULIS in crop straws combustion were more complicated and contained more absorbing aromatic groups (e.g. aromatic rings, carbonyl groups, and aliphatic chains). Therefore, the secondary aerosol conversion may cause more aromatic structures in HULIS from crop straws burning, resulting in stronger light absorption abilities.

The moving of high emission for biomass burning in China: View from multi-year emission estimation and human-driven forces

Biomass burning (BB) has significant impacts on air quality, climate and human health. In China, the BB emission has changed substantially over the past decades while the multi-year variation held high uncertainty and the driving forces have addressed little attention. Here, this research aimed to conduct a comprehensive and systematic analysis of BB variation in China and provided precise and targeted BB emission reduction suggestions. The moving of high emission for BB from 2003 to 2014 was clearly identified, by the view of reliable emission estimation and anthropogenic impacts. Multiple satellite products, field survey, time varying biomass loading data and measured emission factors were adopted to better estimating BB emission and reducing the uncertainty. Social-economic analysis was added to assess the anthropogenic impacts on high emission variation quantitatively. Results showed that the cumulative BB emissions of OC, EC, CH4, NOX, NMVOC, SO2, NH3, CO, CO2, PM2.5 and PM10 during 2003-2014 were 1.6 × 104, 5.64 × 103, 3.57 × 104, 1.7 × 104, 5.44 × 104, 2.96 × 103, 6.77 × 103, 6.5 × 105, 1.15 × 107, 5.26 × 104 and 6.04 × 104 Gg, respectively. Crop straw burning (in-field and domestic) in northeast China plain (NEP), north China plain (NCP), northern arid and semiarid region and loess plateau were the key sources, averagely contributed 73% for all the pollutants emission. While domestic straw burning and firewood burning in Sichuan basin (SB), Yunnan-Guizhou plateau and southern China were main contributors, averagely accounting for 70% of all the pollutants emission. On regional level, high emissions were mainly found in SB, NCP and NEP. Temporally, high emissions were mainly found in crop sowing harvesting and heating seasons. From 2003 to 2014, the BB emission for different biomass species has changed significantly in different regions. High emission has gradually moved from SB to NCP and NEP. Firewood burning and domestic straw burning emission decreased by 47% and 14% in SB, respectively. In-field straw burning emission increased by 52% and 231% in NCP and NEP respectively and domestic straw burning emission increased by 62% in NEP. Emissions from heating season have decreased while emissions in corn harvest season were continuously increased. Analysis of Environmental kuznets curve, agricultural productivity level, human burning habits, rural energy structure and local control policies revealed the internal human driving strength of the variation for BB emission. The unbalanced development of social economy and the policy bias were primary drivers of limiting the BB management. BB emission will alleviate in NCP and aggravate in NEP. For the further emission reduction, effective measures for corn sources management, straw returning and rural energy utilization should be systematically considered. This research provides a clear evidence for the multi-year variation pattern of BB emissions, which is critical for pollution prediction, air quality modeling and targeted mitigation strategies for the key regions of China.

Relative effects of open biomass burning and open crop straw burning on haze formation over central and eastern China: modeling study driven by constrained emissions

Abstract. Open biomass burning (OBB) has a high potential to trigger local and regional severe haze with elevated fine particulate matter (PM2.5) concentrations and could thus deteriorate ambient air quality and threaten human health. Open crop straw burning (OCSB), as a critical part of OBB, emits abundant gaseous and particulate pollutants, especially in fields with intensive agriculture, such as in central and eastern China (CEC). This region includes nine provinces, i.e., Hubei, Anhui, Henan, Hunan, Jiangxi, Shandong, Jiangsu, Shanghai, and Fujian. The first four ones are located inland, while the others are on the eastern coast. However, uncertainties in current OCSB and other types of OBB emissions in chemical transport models (CTMs) lead to inaccuracies in evaluating their impacts on haze formations. Satellite retrievals provide an alternative that can be used to simultaneously quantify emissions of OCSB and other types of OBB, such as the Fire INventory from NCAR version 1.5 (FINNv1.5), which, nevertheless, generally underestimates their magnitudes due to unresolved small fires. In this study, we selected June 2014 as our study period, which exhibited a complete evolution process of OBB (from 1 to 19 June) over CEC. During this period, OBB was dominated by OCSB in terms of the number of fire hotspots and associated emissions (74 %–94 %), most of which were located at Henan and Anhui (&gt; 60 %) with intensive enhancements from 5 to 14 June (&gt; 80 %). OCSB generally exhibits a spatiotemporal correlation with regional haze over the central part of CEC (Henan, Anhui, Hubei, and Hunan), while other types of OBB emissions had influences on Jiangxi, Zhejiang, and Fujian. Based on these analyses, we establish a constraining method that integrates ground-level PM2.5 measurements with a state-of-art fully coupled regional meteorological and chemical transport model (the two-way coupled WRF-CMAQ) in order to derive optimal OBB emissions based on FINNv1.5. It is demonstrated that these emissions allow the model to reproduce meteorological and chemical fields over CEC during the study period, whereas the original FINNv1.5 underestimated OBB emissions by 2–7 times, depending on specific spatiotemporal scales. The results show that OBB had substantial impacts on surface PM2.5 concentrations over CEC. Most of the OBB contributions were dominated by OCSB, especially in Henan, Anhui, Hubei, and Hunan, while other types of OBB emissions also exerted an influence in Jiangxi, Zhejiang, and Fujian. With the concentration-weighted trajectory (CWT) method, potential OCSB sources leading to severe haze in Henan, Anhui, Hubei, and Hunan were pinpointed. The results show that the OCSB emissions in Henan and Anhui can cause haze not only locally but also regionally through regional transport. Combining with meteorological analyses, we can find that surface weather patterns played a cardinal role in reshaping spatial and temporal characteristics of PM2.5 concentrations. Stationary high-pressure systems over CEC enhanced local PM2.5 concentrations in Henan and Anhui. Then, with the evolution of meteorological patterns, Hubei and Hunan in the low-pressure system were impacted by areas (i.e., Henan and Anhui) enveloped in the high-pressure system. These results suggest that policymakers should strictly undertake interprovincial joint enforcement actions to prohibit irregular OBB, especially OCSB over CEC. Constrained OBB emissions can, to a large extent, supplement estimations derived from satellite retrievals as well as reduce overestimates of bottom-up methods.

The comprehensive utilization technology of crop straw

the development of agriculture in our country is related to the economic development of our country, and agricultural development will produce a lot of crop straw. Crop straw is the name for the remains left after the crops are collected. In the north, corn is the most common one. A large number of crop straw burning causes a lot of pollution every year in the autumn harvest season, and damages the soil structure of the land. However, effective and reasonable return of crop straw can greatly increase the fertility of the land and effectively reduce the use of chemical fertilizer. Therefore, the comprehensive utilization of straw is under rapid research in order to effectively use the advantages of straw.

Punishing and rewarding: How do policy measures affect crop straw use by farmers? An empirical analysis of Jiangsu Province of China

Crop straw is the most important source of domestic energy in rural areas of many developing countries. However, as household income grows, rural residents begin to disuse crop straw, leading to a serious pollution and waste of biomass resources. This paper empirically examines the effect of public policy on crop straw use in the case of Jiangsu Province of China. Policy measures, such as burning ban and incentive programs for comprehensive use of crop straw, have important implication for rural energy supply and sustainable development of agriculture. Our results show that the burning ban has reduced crop straw burning in open field dramatically and driven farmers to retain straw into soil in sample areas. Straw retention subsidy, however, seems to play an insignificant role as the subsidy was low and not directly delivered to farmers. Moreover, crop straw markets in Jiangsu are inactive due partially to high cost of collecting and transporting crop straw, which may impose a big chanellge for straw-based energy plants that require larger scale and stable supply of crop straw. Our findings provide critical knowledge on designing and reforming current programs for crop straw management.

Assessment of Air Pollution Aggravation during Straw Burning in Hubei, Central China.

Crop straw burning frequently occurs in Central China, where agriculture is highly productive. We carried out a two-month observation on straw burning in Hubei Province from September 1 to October 31, 2015 to track the variations of air pollutants and comprehensively quantify their influence on regional air quality. Results showed that the concentration of suspended particles (particles smaller than 2.5 or 10 µm, i.e., PM2.5/PM10) and gas pollutants including ozone (O3), sulfur dioxide (SO2), nitrogen dioxide (NO2), and carbon monoxide (CO) was significantly enhanced with the increasing number of fire spots. The average daily concentrations of PM10, PM2.5 and O3 during the intensive burning period (from October 12 to 25) exceeded the daily limits published by the World Health Organization (WHO) by 101.8, 72.7 and 59.1 μg/m3, respectively. In the hourly distribution of pollutant concentration, PM10, PM2.5, O3, SO2, NO2 and CO were 63.49%, 46.29%, 65.56%, 64.40%, 48.57% and 13.49% higher during burning periods than during non-burning periods. Statistical results based on the air quality index (AQI) indicated that biomass burning was the key factor for the deterioration of local air quality, with a contribution ratio exceeding 41%. Additionally, the pollutants were more spatially homogeneous during the burning period than during the non-burning period. Straw burning not only worsened the local air quality but also raised the pollution level of surrounding regions due to the transport of air mass.

Variations in FINN Emissions of Particulate Matters and Associated Carbonaceous Aerosols from Remote Sensing of Open Biomass Burning over Northeast China during 2002–2016

Various particulate matters (PM) and associated carbonaceous aerosols released from open biomass burning (including open straw burning, grass and forest fires) are major sources of atmospheric pollutants. Northeast China is a central region with high forest and grass coverage, as well as an intensive agricultural area. In this study, the FINN (Fire INventory from Ncar) emission data was used to analyze the spatiotemporal variations of PM and associated carbonaceous aerosol component (PM2.5, PM10, OC and BC) emissions from open biomass burning in Northeast China from 2002 to 2016. The results show that the total amount of annual PM2.5, PM10, OC and BC emissions was estimated to be 59.0, 70.6, 31.5, and 4.3 kilotons, respectively, from open biomass burning over Northeast China, averaged from 2002 to 2016, with significant inter-annual variations in amplitudes from 28.0 to 122.3, 33.7 to 144.1, 15.0 to 65.0, and 2.1 to 8.6 kilotons. The regional PM2.5, PM10, OC and BC emissions showed significant seasonal variations with highest emissions in spring (with a seasonal peak in April), followed by autumn (with a seasonal peak in October), summer, and winter in Northeast China; high emissions were concentrated in the forests and grasslands with natural fires, as well as over agricultural areas with crop straw burning from human activities. The PM2.5, PM10, OC and BC emissions over forest areas presented decreasing trends, while the emissions over farmlands showed increasing trends in Northeast China during 2002–2016; this reflects on the dominance of biomass burning that shifted from forestland with natural fires to farmlands with increasing human activities. Three key meteorological drivers—strong near-surface wind speed, high air temperature and low relative humidity—were identified as having significant positive impacts on the inter-annual variations of PM2.5, PM10, OC and BC emissions from open biomass burning in Northeast China.