Straw burning has emerged as a persistent and multifaceted challenge within global agricultural systems,particularly across Asia,Africa,and Latin America.This review reframes straw burning not as an isolated behaviora...Straw burning has emerged as a persistent and multifaceted challenge within global agricultural systems,particularly across Asia,Africa,and Latin America.This review reframes straw burning not as an isolated behavioral issue,but as the outcome of interlinked structural,technological,and socio-cultural constraints embedded in modern agricultural transitions.Drawing on a synthesis of recent empirical studies,we identify four conceptual turning points that reshape the understanding of straw burning:the structural consequences of mechanization,the trade-offs between high-and low-tech solutions,the cultural legitimacy of burning practices,and the need for systems-based,climate-aligned management paradigms.The analysis reveals that interventions focusing solely on technical innovation often overlook the deeper institutional and cultural factors that sustain burning as a rational choice under constrained conditions.We advocate for hybrid,place-based strategies that combine accessible agronomic practices with long-term investments in infrastructure,policy alignment,and community engagement.Moving beyond fragmented solutions and adopting an integrated systems lens enables this study to contribute a forward-looking framework for sustainable straw management that is environmentally just,socially legitimate,and economically viable.展开更多
We present a theoretical study of four-wave mixing(FWM)in a degenerate two-level atomic system subject to a magnetic field whose Zeeman sublevels constitute a tripod-type atomic system,which is driven by a linearly po...We present a theoretical study of four-wave mixing(FWM)in a degenerate two-level atomic system subject to a magnetic field whose Zeeman sublevels constitute a tripod-type atomic system,which is driven by a linearly polarized field,and coupled and probed by two sets of left and right circularly polarized fields.The optical effects of coherent hole burning(CHB)and electromagnetically induced transparency(EIT)are involved in the coherent system,among which the CHB has much larger response for the FWM than the EITs.Three situations of CHB are involved,and they are the solitary CHB,overlapped CHBs,and an overlap between CHB and EIT.The overlapped CHBs have the greatest magnitude of FWM signal among the three situations.Whereas,for the overlapped CHB and EIT,it has the smallest FWM magnitude,which is no more than one tenth of the former.While for the single CHB,the FWM magnitude is half of that of the overlapped CHBs.It is noted that,in the overlap between CHB and EIT,dual EIAs can be obtained,whose FWM signal also has an enhancement in comparison to no EIA.展开更多
Fire is a major type of disturbance that has important influences on ecosystem dynamics and carbon cycles.Yet our understanding of ecosystem fires and their carbon cycle consequences is still limited,largely due to th...Fire is a major type of disturbance that has important influences on ecosystem dynamics and carbon cycles.Yet our understanding of ecosystem fires and their carbon cycle consequences is still limited,largely due to the difficulty of large-scale fire monitoring and the complex interactions between fire,vegetation,climate,and anthropogenic factors.Here,using data from satellite-derived fire observations and ecosystem model simulations,we performed a comprehensive investigation of the spatial and temporal dynamics of China’s ecosystem fire disturbances and their carbon emissions over the past two decades(1997–2016).Satellite-derived results showed that on average about 3.47-4.53×10^(4) km^(2) of the land was burned annually during the past two decades,among which annual burned forest area was about 0.81-1.25×10^(4) km^(2),accounting for 0.33-0.51%of the forest area in China.Biomass burning emitted about 23.02 TgC per year.Compared to satellite products,simulations from the Energy Exascale Earth System Land Model(ELM)strongly overestimated China’s burned area and fire-induced carbon emissions.Annual burned area and fire-induced carbon emissions were high for boreal forest in Northeast China’s Daxing’anling region and subtropical dry forest in South Yunnan,as revealed by both the satellite product and the model simulations.Our results suggest that climate and anthropogenic factors play critical roles in controlling the spatial and seasonal distribution of China’s ecosystem fire disturbances.Our findings highlight the importance of multiple complementary approaches in assessing ecosystem fire disturbance and its carbon consequences.Further studies are required to improve the methods of observing and modelling China’s ecosystem fire disturbances,which will provide valuable information for fire management and ecosystem sustainability in an era when both human activities and the natural environment are rapidly changing.展开更多
Nowadays,people still rely on traditional heating methods in rural areas of northern China,such as Kang(bed-stoves) and burning caves in cold winter.Field measurements of indoor environment were carried out in several...Nowadays,people still rely on traditional heating methods in rural areas of northern China,such as Kang(bed-stoves) and burning caves in cold winter.Field measurements of indoor environment were carried out in several rural houses with burning-cave-coil-Kang coupling heating system in northern China.The results show that this system is able to realize the graded use of internal energy of burning cave.The temperature of supply pipe water ranged from 30 ℃ to 50 ℃ which met the demands in 74.7% of time.The surface temperature of Kang maintained at above 25 ℃.Compared with traditional burning cave,using burning-cave-coil-Kang coupled with heating system has a higher thermal efficiency of 48.9%,which is 8.32% higher than the traditional one.展开更多
Prescribed burning and tree thinning are commonly used restoration practices for US forests management to increase forest productivity and enhance plant and animal diversity. The impact of these practices in Alabama’...Prescribed burning and tree thinning are commonly used restoration practices for US forests management to increase forest productivity and enhance plant and animal diversity. The impact of these practices in Alabama’s Bankhead National Forest (BNF) to soil microbial components and overall forest soil health are unknown. We hypothesized that microbial assemblages and enzyme activities are continuously changing in forest ecosystems especially due to management selections. Therefore, the objective of this study was to assess changes in microbial community compositions (fungal vs bacterial populations) via fatty acid methyl ester (FAME) profiling and several enzyme activities (β-glucosaminidase, acid phosphatase, arylsulfatase, β-glucosidase, xylanase, laccase, and manganese peroxidase) critical to soil organic matter (SOM) dynamics and biogeochemical cycling. In this forest, heavily-thinned plots without burning or less frequent burning treatments seemed to provide more favorable conditions (higher pH and lower C:N ratios) for C and N mineralization. This may explain a slight increase (by 12%) detected in fungi:bacteria (F:B) ratio in the heavily-thinned plots relative to the control. Thinned (lightly and heavily) plots showed greater ligninolytic (laccase and MnP) activities and lower β-glucosidase and β-glucosaminidase activities compared to the no-thinned plots probably due to increase depositions of woody recalcitrant C materials. We observed significant but negative correlations between the ligninolytic laccase and manganese peroxidase (Lac and MnP) enzymes respectively, with MBC (?0.45* and ?0.68** respectively) and MBN (?0.43* and ?0.65** respectively). Prescribed burning treatment reduced microbial biomass C and N of the 9-yr burned plot/lightly thinned plotsprobably due to depletion of labile C sources with the high temperatures, leaving mostly recalcitrant C sources as available soil substrates. Gram-positive bacteria (i15:0, a15:0, i17:0, and a17:0), actinomycetes (10-Me17:0, 10-Me18:0), AMF (16:1ω5c), and saprophytic fungi (18:1ω9c), largely contributed to the microbial compositions. This study bridges knowledge gaps in our understanding of microbial community compositions and enzyme-mediated processes in repeatedly burned and thinned forest ecosystems.展开更多
Rice straw,which is produced after the harvest of rice,is a major agricultural waste in the world.Rice straw has a high carbon/nitrogen ratio and is more resistant to microbial degradation than other straws because it...Rice straw,which is produced after the harvest of rice,is a major agricultural waste in the world.Rice straw has a high carbon/nitrogen ratio and is more resistant to microbial degradation than other straws because its main constituents are cellulose and hemicelluloses encrusted by lignin.When rice straw is burned,hazardous substances such as carbon dioxide,methane,carbon monoxide,and nitrogen monoxide are released into the air as smoke(less than 10μm-sized particles).The rise in the burning of rice straw has contributed to too many accidents and health issues in the general population residing in Haryana,Punjab,and Uttar Pradesh of India.These states are being urged by the National Green Tribunal to generate money instead of burning rice straw.Even though these lignocellulosic materials might be beneficial,not much has been carried out with them.This overview covers the properties of rice straw and husks,the numerous procedures used to create valuable products,and various applications that may be made for them.These include energy sources,environmental adsorbents,building supplies,and specialist commodities.展开更多
China’s endeavors to mitigate recurrent crop residue burning(CRB)and improve air quality have yielded positive results owing to recent pollution prevention policies.Nonetheless,persistent challenges remain,particular...China’s endeavors to mitigate recurrent crop residue burning(CRB)and improve air quality have yielded positive results owing to recent pollution prevention policies.Nonetheless,persistent challenges remain,particularly in the Northeast China(NEC),where low temperature complicates crop residue management.Here,we examined the effects of cropping pattern adjustment on variations of CRB patterns in NEC during 2001-2021,utilizing the Moderate-resolution Imaging Spectroradiometer(MODIS)burned area dataset,the Visible Infrared Imaging Radiometer Suite(VIIRS)active fire dataset,and the high-accuracy crop planting area maps.Our results revealed an overall upward trend of 805.96 km^(2)/yr in NEC CRB from 2001 to 2021.The corn CRB area accounted for more than 50%of the total CRB area in each CRB-intensive year(2013-2021),and the increasing corn CRB generally aligns with the growing corn cultivation fields.A seasonal shift in CRB was found around 2017,with intensive CRB activities transitioning from both autumn and spring to primarily spring,particularly in the Songnen Plain and Sanjiang Plain.The changing trend of PM2.5 concentration aligned spatially with the shift.Moreover,the CRBs in spring of 2020 and 2021 were more severe than the major burning seasons in previous years,likely due to the disruptions during COVID-19 lockdowns.In certain years,the explanatory power of spring CRB on PM2.5 concentration was comparable to that of other natural factors,such as precipitation.This study underscores the critical need for sustained and region-specific strategies to tackle the challenges posed by CRBs.展开更多
Prescribed burning is commonly used to maintain forest ecosystem functions and reduce the risk of future wildfires.Although many studies have investigated the response of microbial community to wildfires in forest eco...Prescribed burning is commonly used to maintain forest ecosystem functions and reduce the risk of future wildfires.Although many studies have investigated the response of microbial community to wildfires in forest ecosystems,the effects of prescribed burnings on soil microbial community structure are less studied.It is also unclear that how post-fire soil physiochemical properties changes affected soil microbial communities.Here,we studied the impacts of prescribed burning on soil microbiome in three typical temperate forests of northern China by collecting soil physicochemical and high-throughput sequencing for 16S rRNA and 18S rRNA was applied to analyze the diversity and community composition of soil microbes(bacteria and fungi).Compared with pre-fire condition,prescribed burning significantly decreased Chaol index and altered soil bacterial communities(P<0.05),whereas it had no significant effect on fungal diversity and community structure of the(P>0.05).Planctomycetes and Actinobacteria made the greatest contributions to the bacterial community dissimilarity between the pre-fire and post-fire conditions.The main variables influencing the post-fire soil microbial community structure are soil pH,available phosphorus,total nitrogen,and the ratio of soil total carbon to soil total nitrogen,which could account for 73.5% of the variation in the microbial community structure in these stands.Our findings demonstrated a great discrepancy in the responses of bacteria and fungi to prescribed burning.Prescribed burning altered the soil microbial structure by modifying the physicochemical properties.Our results pointed that it is essential to evaluate the impact of prescribed burnings on forest ecosystem functions.These findings provide an important baseline for assessing post-fire microbial recovery in the region and offer critical guidance for restoration efforts.展开更多
Over the past decade,biomass burning has emerged as one of the main polluting events in northern India.It is one of the major sources of brown carbon(Br C),the light-absorbing organic carbon component of PM_(2.5).Most...Over the past decade,biomass burning has emerged as one of the main polluting events in northern India.It is one of the major sources of brown carbon(Br C),the light-absorbing organic carbon component of PM_(2.5).Most studies on the impact of biomass burning in India are based on source locations or urban areas;very little is known about its effects on a regional background location.We examine the effect of biomass burning on regional air quality and co-occurring meteorological factors.Year-long PM_(2.5)levels and light absorption by carbonaceous aerosols at 880 nm and 370 nm were measured at Rohtak,a regional background location.Results showed that post-harvest biomass burning in the Punjab-Haryana region affects the regional air quality with a lead of one to two days.A comparison of dispersionnormalized concentrations showed that open-field biomass burning not only affects regional air quality in the post-monsoon season(kharif crops)but is also a dominant source of PM_(2.5)in the post-harvest summer season(rabi crop).A significant(p<0.05)difference is observed in PM_(2.5),b_(abs-880),and b_(abs-370)between biomass burning days and non-biomass burning days during the kharif and rabi harvest seasons.Regression analyses confirm that in summer,regional PM_(2.5)and light absorption by aerosols are influenced more strongly by post-harvest burning of rabi crops.However,adverse meteorology plays a more dominant role in the post-monsoon season than biomass burning.These findings underscore the need for better policy interventions to curb biomass burning and improve air quality during both harvest seasons.展开更多
Rice straw,a by-product of rice cultivation,is commonly disposed of through open-field burning,which contributes to air pollution and environmental degradation.This study aims to identify the key factors influencing f...Rice straw,a by-product of rice cultivation,is commonly disposed of through open-field burning,which contributes to air pollution and environmental degradation.This study aims to identify the key factors influencing farmers’decisions on rice straw management and to develop policy recommendations that encourage the sustainable utilization of rice straw within the supply chain.A mixed-methods approach was adopted,combining qualitative interviews with nine key informants and a quantitative survey of 585 rice farmers across Thailand.Multinomial Logit Regression(MLR)was employed to analyze farmers’preferences among four management options:burning,composting,animal feeding,and selling.The results reveal that membership in farmer groups,ownership of livestock,access to baling machinery,knowledge,and skills related to straw utilization,ease of field access,availability of storage facilities,engagement in integrated farming,and year-round access to baling services significantly increased the likelihood of choosing sustainable alternatives over the burning straw.These findings underscore the importance of both capacity-building and infrastructure in enabling sustainable practices.Based on these insights,the study proposes a multi-level policy framework to enhance the value creation of rice straw.National policies should focus on expanding access to machinery and supporting innovation,while local governments should facilitate farmer training and improve straw logistics.Strengthening farmer organizations and market connections is also crucial for scaling adoption.Overall,structural integration and stakeholder coordination are key to reducing straw burning and promoting sustainable resource use in rice-producing regions.展开更多
Biomass burning(BB)emits carbonaceous aerosols that significantly influence air quality in Southwest China during spring.To further understand the characteristics of spring BB and its original contribution to organic ...Biomass burning(BB)emits carbonaceous aerosols that significantly influence air quality in Southwest China during spring.To further understand the characteristics of spring BB and its original contribution to organic carbon(OC),daily fine particulate matter(PM_(2.5))samples were collected from March to May 2022 in Pu'er,Southwest China.The concentrations of OC,elemental carbon(EC),levoglucosan(Lev),and potassium from BB(K+BB)during the study period ranged from 5.3 to 31.2μg/m^(3),0.86-13.1μg/m^(3),0.06-0.82μg/m^(3),and 0.05-2.88μg/m^(3),respectively.To eliminate the effects of Lev degradation,this study uses the Aging of Air Mass(AAM)index to correct the atmospheric concentration of Lev and combines Bayesian mixture modeling with a molecular tracer method to assess the original contribution of BB to OC.The results indicated that the AAM index was 0.18±0.05,indicating that the degradation of Lev reached 82%.When considering the degradation of levoglucosan in the atmosphere,the primary source of BB aerosols was crop-straw combustion(71.1%),followed by the combustion of certain hardwoods and softwoods(24.9%)and grasses(4.0%).The original contribution of BB to OC was 62.4%,which was much greater than the contribution when levoglucosan degradation(23.7%)was ignored.The air mass inverse trajectories and Moderate Resolution Imaging Spectroradiometer(MODIS)fire hotspots indicated that the BB plume from Southeast Asia during spring could influence PM_(2.5)long-range transport in remote locations,and the contribution could reach 82%in Southwest China.展开更多
Accurate characterization of three-dimensional burning crack propagation remains pivotal yet challenging for energetic material safety,as conventional diagnostics and models inadequately resolve coupled crack-pressure...Accurate characterization of three-dimensional burning crack propagation remains pivotal yet challenging for energetic material safety,as conventional diagnostics and models inadequately resolve coupled crack-pressure dynamics in confined explosives.This study combines a novel spherical confinement system(with/without sapphire windows)with synchronized high-speed imaging and 3D reconstruction to overcome optical limitations in opaque explosives.Experimental analysis of centrally ignited HMX-based PBX-1 reveals:(1)burning cracks propagate radially with equatorial acceleration and polar deceleration,(2)systematic formation of 3–4 dominant crack branches across geometries,and(3)pressure evolution exhibiting gradual accumulation(subsurface cracking)followed by exponential growth(surface burn-through),with decay governed by cavity expansion.Building on Hill's framework,we develop a model incorporating cavity volume and fracture toughness criteria,validated against PBX explosive(95%HMX-based)experiments.The model demonstrates improved prediction of pressure trends compared to prior approaches,particularly in resolving laminar-phase accumulation and crackinduced surge transitions.Results establish structural cavity volume as a critical modulator of measured pressure and reveal direction-dependent crack kinematics as fundamental features of constrained combustion.This work provides experimentally validated insights into mechanisms of reaction pressure development and burning cracks pathways during constrained PBX explosive combustion.展开更多
We present a theoretical investigation of the electromagnetically induced absorption(EIA)due to transfer of population(TOP)in the double two-level system(TLS).It shows that one TLS is responsible for the sub-natural a...We present a theoretical investigation of the electromagnetically induced absorption(EIA)due to transfer of population(TOP)in the double two-level system(TLS).It shows that one TLS is responsible for the sub-natural absorption part of EIA,and the other TLS is responsible for the natural absorption part of EIA.We propose a scheme in which the sub-natural absorption part of EIA is governed by the effect of coherent hole burning(CHB)and achieves an enhancement of at least two orders of magnitude with the detuned coupling field,while the natural absorption part is dominated by the effect of Mollow absorption(MA)and does not change with the detuned coupling field.Due to the effects of CHB and MA,the magnitude of four-wave mixing(FWM)achieves a significant increase for double TLS.We show in detail the evolution of the magnitude of the FWM signal with coupling detuning and Rabi frequency.It is demonstrated that strong resonances occur in the FWM profile at frequencies symmetrically displaced from the frequency of the coupling field by coupling detuning.展开更多
Based on field survey and measurement, and the simulated field burning test by indoor burning bed, a multiple linear regression model was established with factors of fuel load（x1）, temperature（x2）, fuel moisture c...Based on field survey and measurement, and the simulated field burning test by indoor burning bed, a multiple linear regression model was established with factors of fuel load（x1）, temperature（x2）, fuel moisture content（x3）, wind velocity（x4）, aspect（xs）, slope（x6）, forest height（x7）, propagation velocity（x8）, fire line intensity（xg） and prescribed burning width of fire isolated belt（y）. The results showed that the multivari- ate linear model was y=-12.371 ＋4.182x1 ＋0.435x2 ＋0.013x3＋0.083x4＋0.017x5＋0.916x6＋ 0.540x7, and the influences of the factors on the prescribed burning width of fire isolated belt were in the order of x6, x7, x1, x4, x3, x2, x5. This model make it easier to establish fire isolated belt by using fuel characteristics, topographic factors, meteorological factors, and forest stand factors, providing basis for the development of prescribed burning and forest management fire.展开更多
To explore the efficiency and safety of hyaluronic acid for burn victims, we searched for all the relative references, selected the references according to the inclusion criterion, assessed them critically and conduct...To explore the efficiency and safety of hyaluronic acid for burn victims, we searched for all the relative references, selected the references according to the inclusion criterion, assessed them critically and conducted Meta-analysis. The experimental group and the control groups have statistically significant difference in the average time for wound healing. If we make subgroup analysis according to the origin, the outcomes of both foreign study and Chinese study have statistical significance. No statistically significant difference is revealed in the incidence of adverse reaction. In terms of the healing time for diverse burn wounds, statistically significant difference exists in the superficial second-degree burn. There is no statistically significant difference in deep second-degree burn, skin-grafting sites and donor sites. It revealed that hyaluronic acid can accelerate the healing of burn on skin, especially for superficial second-degree burn. And its adverse reaction by external use is negligible.展开更多
Foliar uptake of airborne metal(loid)s plays a crucial role in metal(loid)accumulation in plant organs and is influ-enced by the size and emission sources of aerosols.Given the high enrichment of toxic metal(loid)s in...Foliar uptake of airborne metal(loid)s plays a crucial role in metal(loid)accumulation in plant organs and is influ-enced by the size and emission sources of aerosols.Given the high enrichment of toxic metal(loid)s in submicron-scale particulates(PM1),this study established a PM1 exposure system to examine airborne metal(loid)accu-mulation and foliar physiological responses in Oryza sativa L.The results showed that the concentrations of Cu,Zn,As,Pb,and Cd in the leaves and grains were influenced not only by the airborne metal(loid)levels but also by the specific nature of the PM1 particles.The quantitative model for PM1-associated Pb entry into leaf tissue indicated that foliar Pb accumulation was primarily driven by particle adhesion,followed by hydrophilic pene-tration and trans-stomatal liquid film migration,accounting for 87%–89%of the total accumulation.The strong hygroscopicity and high Pb activity of PM1 emitted from waste incineration(WI)increased the Pb absorption coefficient via the hydrophilic and liquid film migration pathway.In contrast,the high hydrophobicity of PM1 from coal burning(CB)led to greater retention of Pb on leaf surfaces.Both foliar reactive oxygen metabolism and photosynthesis indices were sensitive to air pollution.Foliar metal(loid)accumulation and airborne PM1 concentration accounted for the variance in physiological responses in rice leaves.Our results also indicated that Pb was the key element in PM1 emissions from both coal burning(CB)and waste incineration(WI)responsible for significant physiological changes in rice leaves.展开更多
Annual haze in Northern Thailand has become increasingly severe,impacting health and the environment.How-ever,the sources of the haze remain poorly quantified due to limited observational data on aerosol molecular tra...Annual haze in Northern Thailand has become increasingly severe,impacting health and the environment.How-ever,the sources of the haze remain poorly quantified due to limited observational data on aerosol molecular tracers.This study comprehensively investigates chemical composition of PM_(2.5),including both inorganic and organic compounds throughout haze and post-haze periods in 2019 at a rural site of Northern Thailand.Average PM_(2.5) concentrations during haze and post-haze period were 87±36 and 21±11μg/m^(3),respectively.Organic matter was the dominant contributor in PM_(2.5) mass,followed by water soluble inorganic ions and mineral dust.Molecular markers,including levoglucosan,dehydroabietic acid,and 4-nitrocatechol,and ions(Cl^(-),and K^(+)),were used to characterize low haze(PM_(2.5)<100μg/m^(3))and episodic haze(PM_(2.5)>100μg/m^(3)).Low haze is associated with local aerosols from agricultural waste burning,while episodic haze is linked to aged aerosols from mixed agricultural waste,softwood,and hardwood burning.Source apportionment incorporating these molecular markers in receptor modelling(Positive matrix factorization),identified three distinct biomass burning sources:mixed,local,and aged biomass burnings,contributing 31,19 and 13%of PM_(2.5) during haze period.During post-haze period,contributions shifted,with local biomass burning(32%)comparable to secondary sulfate(34%)and mixed dust and traffic sources(26%).These findings demonstrate that both regional and local sources con-tribute to severe haze,highlighting the need for integrated policies for cross-border cooperation as well as stricter regulations to reduce biomass burning in Northern Thailand and Southeast Asia.展开更多
Cereal straw is one of the most abundant biomass burned in China but its contribution to fine particulates is not adequately understood. In this study, three main kinds of cereal straws were collected from five grain ...Cereal straw is one of the most abundant biomass burned in China but its contribution to fine particulates is not adequately understood. In this study, three main kinds of cereal straws were collected from five grain producing areas in China. Fine particulate matters （PMzs） from the cereal straws subjected to control burnings, both under smoldering and flaming status, were sampled by using a custom made dilution chamber and sampling system in the laboratory. Element carbon （EC） and organic carbon （OC） was analyzed. 141 compounds of organic matters were measured by gas chromatography-mass spectrum （GC-MS）. Source profiles of particulate organic matters emitted from cereal straw burnings were obtained. The results indicated that organic matters contribute a large fraction in fine particulate matters. Levoglucosan had the highest contributions with averagely 4.5% in mass of fine particulates and can be considered as the tracer of biomass burnings. Methyloxylated phenols from lignin degradation also had high concentrations in PM2.5, and contained approximately equal amounts of guaiacyl and syringyl compounds. 13-Sitostrol also made up relatively a large fraction of PMz5 compared with the other sterols （0.18%-0.63% of the total fine particle mass）. Normal alkanes, PAHs, fatty acids, as well as normal alkanols had relatively lower concentrations compared with the compounds mentioned above. Carbon preference index （CPI） of normal alkanes and alkanoic acids showed characteristics of biogenic fuel burnings. Burning status significantly influenced the formations of EC and PAHs. The differences between the emission profiles of straw and wood combustions were displayed by the fingerprint compounds, which may be used to identify the contributions between wood and straw burnings in source apportionment researches.展开更多
Soil organic carbon （C） and total nitrogen （N） pools of a Chinese fir （Cunninghamia lanceolata （Lamb.） Hook.） （CF） forest, and an evergreen broadleaf （EB） forest located in mid-subtropical, southeastern Ch...Soil organic carbon （C） and total nitrogen （N） pools of a Chinese fir （Cunninghamia lanceolata （Lamb.） Hook.） （CF） forest, and an evergreen broadleaf （EB） forest located in mid-subtropical, southeastern China, were compared before clearcutting, with the effect of slash burning on organic C and total N in the top 10 cm of soil before and after burning also being evaluated. Prior to clearcutting CF forest had significantly lower （P 〈0.05） organic C and total N in the soil （0-100 cm） compared to EB forest with approximately 60% of the C and N at the two forest sites stored at the 0 to 40 cm soil. In post-burn samples of the 0-10 cm depth at 5 days, 1 year, and 5 years for CF and EB forests, significantly lower levels （P 〈0.05） of organic C and total N than those in the pre-burn samples were observed. Compared to the pre-burn levels, at post-burn year 5, surface soil organic C storage was only 85% in CF forest and 72% in EB forest, while total N storage was 77% for CF forest and 73% for EB forest. Slash burning caused marked long-term changes in surface soil C and N in the two forest types.展开更多
文摘Straw burning has emerged as a persistent and multifaceted challenge within global agricultural systems,particularly across Asia,Africa,and Latin America.This review reframes straw burning not as an isolated behavioral issue,but as the outcome of interlinked structural,technological,and socio-cultural constraints embedded in modern agricultural transitions.Drawing on a synthesis of recent empirical studies,we identify four conceptual turning points that reshape the understanding of straw burning:the structural consequences of mechanization,the trade-offs between high-and low-tech solutions,the cultural legitimacy of burning practices,and the need for systems-based,climate-aligned management paradigms.The analysis reveals that interventions focusing solely on technical innovation often overlook the deeper institutional and cultural factors that sustain burning as a rational choice under constrained conditions.We advocate for hybrid,place-based strategies that combine accessible agronomic practices with long-term investments in infrastructure,policy alignment,and community engagement.Moving beyond fragmented solutions and adopting an integrated systems lens enables this study to contribute a forward-looking framework for sustainable straw management that is environmentally just,socially legitimate,and economically viable.
基金supported by the Open Subject of the State Key Laboratory of Quantum Optics and Quantum Optics Devices(Grant No.KF202209).
文摘We present a theoretical study of four-wave mixing(FWM)in a degenerate two-level atomic system subject to a magnetic field whose Zeeman sublevels constitute a tripod-type atomic system,which is driven by a linearly polarized field,and coupled and probed by two sets of left and right circularly polarized fields.The optical effects of coherent hole burning(CHB)and electromagnetically induced transparency(EIT)are involved in the coherent system,among which the CHB has much larger response for the FWM than the EITs.Three situations of CHB are involved,and they are the solitary CHB,overlapped CHBs,and an overlap between CHB and EIT.The overlapped CHBs have the greatest magnitude of FWM signal among the three situations.Whereas,for the overlapped CHB and EIT,it has the smallest FWM magnitude,which is no more than one tenth of the former.While for the single CHB,the FWM magnitude is half of that of the overlapped CHBs.It is noted that,in the overlap between CHB and EIT,dual EIAs can be obtained,whose FWM signal also has an enhancement in comparison to no EIA.
基金funding was provided by the Carbon Mitigation Initiative(CMI)of the Princeton Environmental Institute,and by an Oak Ridge National Lab research subcontract to A.C.C.Y.and P.C.were supported by the fire_cci project(http://www.esa-fire-cci.org/)funded by the European Space AgencyS.R.was supported by a Graduate Research Fellowship from the U.S.National Science Foundation+1 种基金R.T.,J.M.,X.S.and D.R.were supported by the Terrestrial Ecosystem Science Scientific Focus Area(TES SFA)project and the Reducing Uncertainties in Biogeochemical Interactions through Synthesis and Computing Scientific Focus Area(RUBISCO SFA)project funded by the US Department of Energy,Office of Science,Office of Biological and Environmental ResearchOak Ridge National Laboratory is supported by the Office of Science of the US Department of Energy under Contract No.DE-AC05-00OR22725.
文摘Fire is a major type of disturbance that has important influences on ecosystem dynamics and carbon cycles.Yet our understanding of ecosystem fires and their carbon cycle consequences is still limited,largely due to the difficulty of large-scale fire monitoring and the complex interactions between fire,vegetation,climate,and anthropogenic factors.Here,using data from satellite-derived fire observations and ecosystem model simulations,we performed a comprehensive investigation of the spatial and temporal dynamics of China’s ecosystem fire disturbances and their carbon emissions over the past two decades(1997–2016).Satellite-derived results showed that on average about 3.47-4.53×10^(4) km^(2) of the land was burned annually during the past two decades,among which annual burned forest area was about 0.81-1.25×10^(4) km^(2),accounting for 0.33-0.51%of the forest area in China.Biomass burning emitted about 23.02 TgC per year.Compared to satellite products,simulations from the Energy Exascale Earth System Land Model(ELM)strongly overestimated China’s burned area and fire-induced carbon emissions.Annual burned area and fire-induced carbon emissions were high for boreal forest in Northeast China’s Daxing’anling region and subtropical dry forest in South Yunnan,as revealed by both the satellite product and the model simulations.Our results suggest that climate and anthropogenic factors play critical roles in controlling the spatial and seasonal distribution of China’s ecosystem fire disturbances.Our findings highlight the importance of multiple complementary approaches in assessing ecosystem fire disturbance and its carbon consequences.Further studies are required to improve the methods of observing and modelling China’s ecosystem fire disturbances,which will provide valuable information for fire management and ecosystem sustainability in an era when both human activities and the natural environment are rapidly changing.
基金Sponsored by the National Natural Science Foundation of China(Grant No.51178075)the Fundamental Research Funds for the Central Universities(Grant No.DUT17RW118)
文摘Nowadays,people still rely on traditional heating methods in rural areas of northern China,such as Kang(bed-stoves) and burning caves in cold winter.Field measurements of indoor environment were carried out in several rural houses with burning-cave-coil-Kang coupling heating system in northern China.The results show that this system is able to realize the graded use of internal energy of burning cave.The temperature of supply pipe water ranged from 30 ℃ to 50 ℃ which met the demands in 74.7% of time.The surface temperature of Kang maintained at above 25 ℃.Compared with traditional burning cave,using burning-cave-coil-Kang coupled with heating system has a higher thermal efficiency of 48.9%,which is 8.32% higher than the traditional one.
文摘Prescribed burning and tree thinning are commonly used restoration practices for US forests management to increase forest productivity and enhance plant and animal diversity. The impact of these practices in Alabama’s Bankhead National Forest (BNF) to soil microbial components and overall forest soil health are unknown. We hypothesized that microbial assemblages and enzyme activities are continuously changing in forest ecosystems especially due to management selections. Therefore, the objective of this study was to assess changes in microbial community compositions (fungal vs bacterial populations) via fatty acid methyl ester (FAME) profiling and several enzyme activities (β-glucosaminidase, acid phosphatase, arylsulfatase, β-glucosidase, xylanase, laccase, and manganese peroxidase) critical to soil organic matter (SOM) dynamics and biogeochemical cycling. In this forest, heavily-thinned plots without burning or less frequent burning treatments seemed to provide more favorable conditions (higher pH and lower C:N ratios) for C and N mineralization. This may explain a slight increase (by 12%) detected in fungi:bacteria (F:B) ratio in the heavily-thinned plots relative to the control. Thinned (lightly and heavily) plots showed greater ligninolytic (laccase and MnP) activities and lower β-glucosidase and β-glucosaminidase activities compared to the no-thinned plots probably due to increase depositions of woody recalcitrant C materials. We observed significant but negative correlations between the ligninolytic laccase and manganese peroxidase (Lac and MnP) enzymes respectively, with MBC (?0.45* and ?0.68** respectively) and MBN (?0.43* and ?0.65** respectively). Prescribed burning treatment reduced microbial biomass C and N of the 9-yr burned plot/lightly thinned plotsprobably due to depletion of labile C sources with the high temperatures, leaving mostly recalcitrant C sources as available soil substrates. Gram-positive bacteria (i15:0, a15:0, i17:0, and a17:0), actinomycetes (10-Me17:0, 10-Me18:0), AMF (16:1ω5c), and saprophytic fungi (18:1ω9c), largely contributed to the microbial compositions. This study bridges knowledge gaps in our understanding of microbial community compositions and enzyme-mediated processes in repeatedly burned and thinned forest ecosystems.
文摘Rice straw,which is produced after the harvest of rice,is a major agricultural waste in the world.Rice straw has a high carbon/nitrogen ratio and is more resistant to microbial degradation than other straws because its main constituents are cellulose and hemicelluloses encrusted by lignin.When rice straw is burned,hazardous substances such as carbon dioxide,methane,carbon monoxide,and nitrogen monoxide are released into the air as smoke(less than 10μm-sized particles).The rise in the burning of rice straw has contributed to too many accidents and health issues in the general population residing in Haryana,Punjab,and Uttar Pradesh of India.These states are being urged by the National Green Tribunal to generate money instead of burning rice straw.Even though these lignocellulosic materials might be beneficial,not much has been carried out with them.This overview covers the properties of rice straw and husks,the numerous procedures used to create valuable products,and various applications that may be made for them.These include energy sources,environmental adsorbents,building supplies,and specialist commodities.
基金supported by the National Key Research and Devel-opment Program of China(Grant No.2023YFD1500200)the funding project of Northeast Geological S&T Innovation Center of China Geologi-cal Survey(Grant No.QCJJ2022-9)+3 种基金the Strategic Priority Research Pro-gram of the Chinese Academy of Sciences(Grant No.XDA28060100)the Youth Interdisciplinary Team Project of the Chinese Academy of Sciences(JCTD-2021-04)the Informatization Plan of the Chinese Academy of Sciences(Grant No.CAS-WX2021PY-0109)the National Natural Science Foundation of China(Grants No.41971078,42271375,72221002,42001378).
文摘China’s endeavors to mitigate recurrent crop residue burning(CRB)and improve air quality have yielded positive results owing to recent pollution prevention policies.Nonetheless,persistent challenges remain,particularly in the Northeast China(NEC),where low temperature complicates crop residue management.Here,we examined the effects of cropping pattern adjustment on variations of CRB patterns in NEC during 2001-2021,utilizing the Moderate-resolution Imaging Spectroradiometer(MODIS)burned area dataset,the Visible Infrared Imaging Radiometer Suite(VIIRS)active fire dataset,and the high-accuracy crop planting area maps.Our results revealed an overall upward trend of 805.96 km^(2)/yr in NEC CRB from 2001 to 2021.The corn CRB area accounted for more than 50%of the total CRB area in each CRB-intensive year(2013-2021),and the increasing corn CRB generally aligns with the growing corn cultivation fields.A seasonal shift in CRB was found around 2017,with intensive CRB activities transitioning from both autumn and spring to primarily spring,particularly in the Songnen Plain and Sanjiang Plain.The changing trend of PM2.5 concentration aligned spatially with the shift.Moreover,the CRBs in spring of 2020 and 2021 were more severe than the major burning seasons in previous years,likely due to the disruptions during COVID-19 lockdowns.In certain years,the explanatory power of spring CRB on PM2.5 concentration was comparable to that of other natural factors,such as precipitation.This study underscores the critical need for sustained and region-specific strategies to tackle the challenges posed by CRBs.
基金financially supported by the National Natural Science Foundation(No.32471868,No.32001324)Youth Lift Project of China Association for Science and Technology(No.YESS20210370)+1 种基金Fundamental Research Funds for the Central Universities(2572023CT01)We thank the Grassland Bureau and the National Innovation Alliance of Wildland Fire Prevention and Control Technology of China for supporting this research.
文摘Prescribed burning is commonly used to maintain forest ecosystem functions and reduce the risk of future wildfires.Although many studies have investigated the response of microbial community to wildfires in forest ecosystems,the effects of prescribed burnings on soil microbial community structure are less studied.It is also unclear that how post-fire soil physiochemical properties changes affected soil microbial communities.Here,we studied the impacts of prescribed burning on soil microbiome in three typical temperate forests of northern China by collecting soil physicochemical and high-throughput sequencing for 16S rRNA and 18S rRNA was applied to analyze the diversity and community composition of soil microbes(bacteria and fungi).Compared with pre-fire condition,prescribed burning significantly decreased Chaol index and altered soil bacterial communities(P<0.05),whereas it had no significant effect on fungal diversity and community structure of the(P>0.05).Planctomycetes and Actinobacteria made the greatest contributions to the bacterial community dissimilarity between the pre-fire and post-fire conditions.The main variables influencing the post-fire soil microbial community structure are soil pH,available phosphorus,total nitrogen,and the ratio of soil total carbon to soil total nitrogen,which could account for 73.5% of the variation in the microbial community structure in these stands.Our findings demonstrated a great discrepancy in the responses of bacteria and fungi to prescribed burning.Prescribed burning altered the soil microbial structure by modifying the physicochemical properties.Our results pointed that it is essential to evaluate the impact of prescribed burnings on forest ecosystem functions.These findings provide an important baseline for assessing post-fire microbial recovery in the region and offer critical guidance for restoration efforts.
基金supported by the Ministry of Environment,Forest and Climate Change(Mo Fand CC),Government of India,under the NCAP-COALESCE project(No.14/10/2014-CC(Vol.II))。
文摘Over the past decade,biomass burning has emerged as one of the main polluting events in northern India.It is one of the major sources of brown carbon(Br C),the light-absorbing organic carbon component of PM_(2.5).Most studies on the impact of biomass burning in India are based on source locations or urban areas;very little is known about its effects on a regional background location.We examine the effect of biomass burning on regional air quality and co-occurring meteorological factors.Year-long PM_(2.5)levels and light absorption by carbonaceous aerosols at 880 nm and 370 nm were measured at Rohtak,a regional background location.Results showed that post-harvest biomass burning in the Punjab-Haryana region affects the regional air quality with a lead of one to two days.A comparison of dispersionnormalized concentrations showed that open-field biomass burning not only affects regional air quality in the post-monsoon season(kharif crops)but is also a dominant source of PM_(2.5)in the post-harvest summer season(rabi crop).A significant(p<0.05)difference is observed in PM_(2.5),b_(abs-880),and b_(abs-370)between biomass burning days and non-biomass burning days during the kharif and rabi harvest seasons.Regression analyses confirm that in summer,regional PM_(2.5)and light absorption by aerosols are influenced more strongly by post-harvest burning of rabi crops.However,adverse meteorology plays a more dominant role in the post-monsoon season than biomass burning.These findings underscore the need for better policy interventions to curb biomass burning and improve air quality during both harvest seasons.
文摘Rice straw,a by-product of rice cultivation,is commonly disposed of through open-field burning,which contributes to air pollution and environmental degradation.This study aims to identify the key factors influencing farmers’decisions on rice straw management and to develop policy recommendations that encourage the sustainable utilization of rice straw within the supply chain.A mixed-methods approach was adopted,combining qualitative interviews with nine key informants and a quantitative survey of 585 rice farmers across Thailand.Multinomial Logit Regression(MLR)was employed to analyze farmers’preferences among four management options:burning,composting,animal feeding,and selling.The results reveal that membership in farmer groups,ownership of livestock,access to baling machinery,knowledge,and skills related to straw utilization,ease of field access,availability of storage facilities,engagement in integrated farming,and year-round access to baling services significantly increased the likelihood of choosing sustainable alternatives over the burning straw.These findings underscore the importance of both capacity-building and infrastructure in enabling sustainable practices.Based on these insights,the study proposes a multi-level policy framework to enhance the value creation of rice straw.National policies should focus on expanding access to machinery and supporting innovation,while local governments should facilitate farmer training and improve straw logistics.Strengthening farmer organizations and market connections is also crucial for scaling adoption.Overall,structural integration and stakeholder coordination are key to reducing straw burning and promoting sustainable resource use in rice-producing regions.
基金supported by the Basic Research Key Project of Science and Technology Department of Yunnan Province(No.202401AS070116)the National Natural Science Foundation of China(No.21966016)。
文摘Biomass burning(BB)emits carbonaceous aerosols that significantly influence air quality in Southwest China during spring.To further understand the characteristics of spring BB and its original contribution to organic carbon(OC),daily fine particulate matter(PM_(2.5))samples were collected from March to May 2022 in Pu'er,Southwest China.The concentrations of OC,elemental carbon(EC),levoglucosan(Lev),and potassium from BB(K+BB)during the study period ranged from 5.3 to 31.2μg/m^(3),0.86-13.1μg/m^(3),0.06-0.82μg/m^(3),and 0.05-2.88μg/m^(3),respectively.To eliminate the effects of Lev degradation,this study uses the Aging of Air Mass(AAM)index to correct the atmospheric concentration of Lev and combines Bayesian mixture modeling with a molecular tracer method to assess the original contribution of BB to OC.The results indicated that the AAM index was 0.18±0.05,indicating that the degradation of Lev reached 82%.When considering the degradation of levoglucosan in the atmosphere,the primary source of BB aerosols was crop-straw combustion(71.1%),followed by the combustion of certain hardwoods and softwoods(24.9%)and grasses(4.0%).The original contribution of BB to OC was 62.4%,which was much greater than the contribution when levoglucosan degradation(23.7%)was ignored.The air mass inverse trajectories and Moderate Resolution Imaging Spectroradiometer(MODIS)fire hotspots indicated that the BB plume from Southeast Asia during spring could influence PM_(2.5)long-range transport in remote locations,and the contribution could reach 82%in Southwest China.
基金supported by the National Natural Science Foundation of China(Grant No.12402445)the National Defense Foundation Stabilization Support Program(Grant No.JCKYS2024212108)the National Key Laboratory of Shock Wave Physics and Detonation Physics Foundation(Grant No.2024CXPTGFJJ06404)。
文摘Accurate characterization of three-dimensional burning crack propagation remains pivotal yet challenging for energetic material safety,as conventional diagnostics and models inadequately resolve coupled crack-pressure dynamics in confined explosives.This study combines a novel spherical confinement system(with/without sapphire windows)with synchronized high-speed imaging and 3D reconstruction to overcome optical limitations in opaque explosives.Experimental analysis of centrally ignited HMX-based PBX-1 reveals:(1)burning cracks propagate radially with equatorial acceleration and polar deceleration,(2)systematic formation of 3–4 dominant crack branches across geometries,and(3)pressure evolution exhibiting gradual accumulation(subsurface cracking)followed by exponential growth(surface burn-through),with decay governed by cavity expansion.Building on Hill's framework,we develop a model incorporating cavity volume and fracture toughness criteria,validated against PBX explosive(95%HMX-based)experiments.The model demonstrates improved prediction of pressure trends compared to prior approaches,particularly in resolving laminar-phase accumulation and crackinduced surge transitions.Results establish structural cavity volume as a critical modulator of measured pressure and reveal direction-dependent crack kinematics as fundamental features of constrained combustion.This work provides experimentally validated insights into mechanisms of reaction pressure development and burning cracks pathways during constrained PBX explosive combustion.
基金supported by the Open Subject of the State Key Laboratory of Quantum Optics Technologies and Devices(Grant No.KF202209)。
文摘We present a theoretical investigation of the electromagnetically induced absorption(EIA)due to transfer of population(TOP)in the double two-level system(TLS).It shows that one TLS is responsible for the sub-natural absorption part of EIA,and the other TLS is responsible for the natural absorption part of EIA.We propose a scheme in which the sub-natural absorption part of EIA is governed by the effect of coherent hole burning(CHB)and achieves an enhancement of at least two orders of magnitude with the detuned coupling field,while the natural absorption part is dominated by the effect of Mollow absorption(MA)and does not change with the detuned coupling field.Due to the effects of CHB and MA,the magnitude of four-wave mixing(FWM)achieves a significant increase for double TLS.We show in detail the evolution of the magnitude of the FWM signal with coupling detuning and Rabi frequency.It is demonstrated that strong resonances occur in the FWM profile at frequencies symmetrically displaced from the frequency of the coupling field by coupling detuning.
基金Supported by the Scientific Research Fund of the Education Bureau of Yunnan Province,China (2011C113)the Science and Technology Innovation Program for Undergraduates,Southwest Forestry University,China (1031)the "Forest Protection"Key Discipline of Yunnan Province,China (XKZ200905)~~
文摘Based on field survey and measurement, and the simulated field burning test by indoor burning bed, a multiple linear regression model was established with factors of fuel load（x1）, temperature（x2）, fuel moisture content（x3）, wind velocity（x4）, aspect（xs）, slope（x6）, forest height（x7）, propagation velocity（x8）, fire line intensity（xg） and prescribed burning width of fire isolated belt（y）. The results showed that the multivari- ate linear model was y=-12.371 ＋4.182x1 ＋0.435x2 ＋0.013x3＋0.083x4＋0.017x5＋0.916x6＋ 0.540x7, and the influences of the factors on the prescribed burning width of fire isolated belt were in the order of x6, x7, x1, x4, x3, x2, x5. This model make it easier to establish fire isolated belt by using fuel characteristics, topographic factors, meteorological factors, and forest stand factors, providing basis for the development of prescribed burning and forest management fire.
文摘To explore the efficiency and safety of hyaluronic acid for burn victims, we searched for all the relative references, selected the references according to the inclusion criterion, assessed them critically and conducted Meta-analysis. The experimental group and the control groups have statistically significant difference in the average time for wound healing. If we make subgroup analysis according to the origin, the outcomes of both foreign study and Chinese study have statistical significance. No statistically significant difference is revealed in the incidence of adverse reaction. In terms of the healing time for diverse burn wounds, statistically significant difference exists in the superficial second-degree burn. There is no statistically significant difference in deep second-degree burn, skin-grafting sites and donor sites. It revealed that hyaluronic acid can accelerate the healing of burn on skin, especially for superficial second-degree burn. And its adverse reaction by external use is negligible.
基金supported by the National Natural Science Foundation of China(Nos.42077367 and 21677123).
文摘Foliar uptake of airborne metal(loid)s plays a crucial role in metal(loid)accumulation in plant organs and is influ-enced by the size and emission sources of aerosols.Given the high enrichment of toxic metal(loid)s in submicron-scale particulates(PM1),this study established a PM1 exposure system to examine airborne metal(loid)accu-mulation and foliar physiological responses in Oryza sativa L.The results showed that the concentrations of Cu,Zn,As,Pb,and Cd in the leaves and grains were influenced not only by the airborne metal(loid)levels but also by the specific nature of the PM1 particles.The quantitative model for PM1-associated Pb entry into leaf tissue indicated that foliar Pb accumulation was primarily driven by particle adhesion,followed by hydrophilic pene-tration and trans-stomatal liquid film migration,accounting for 87%–89%of the total accumulation.The strong hygroscopicity and high Pb activity of PM1 emitted from waste incineration(WI)increased the Pb absorption coefficient via the hydrophilic and liquid film migration pathway.In contrast,the high hydrophobicity of PM1 from coal burning(CB)led to greater retention of Pb on leaf surfaces.Both foliar reactive oxygen metabolism and photosynthesis indices were sensitive to air pollution.Foliar metal(loid)accumulation and airborne PM1 concentration accounted for the variance in physiological responses in rice leaves.Our results also indicated that Pb was the key element in PM1 emissions from both coal burning(CB)and waste incineration(WI)responsible for significant physiological changes in rice leaves.
文摘Annual haze in Northern Thailand has become increasingly severe,impacting health and the environment.How-ever,the sources of the haze remain poorly quantified due to limited observational data on aerosol molecular tracers.This study comprehensively investigates chemical composition of PM_(2.5),including both inorganic and organic compounds throughout haze and post-haze periods in 2019 at a rural site of Northern Thailand.Average PM_(2.5) concentrations during haze and post-haze period were 87±36 and 21±11μg/m^(3),respectively.Organic matter was the dominant contributor in PM_(2.5) mass,followed by water soluble inorganic ions and mineral dust.Molecular markers,including levoglucosan,dehydroabietic acid,and 4-nitrocatechol,and ions(Cl^(-),and K^(+)),were used to characterize low haze(PM_(2.5)<100μg/m^(3))and episodic haze(PM_(2.5)>100μg/m^(3)).Low haze is associated with local aerosols from agricultural waste burning,while episodic haze is linked to aged aerosols from mixed agricultural waste,softwood,and hardwood burning.Source apportionment incorporating these molecular markers in receptor modelling(Positive matrix factorization),identified three distinct biomass burning sources:mixed,local,and aged biomass burnings,contributing 31,19 and 13%of PM_(2.5) during haze period.During post-haze period,contributions shifted,with local biomass burning(32%)comparable to secondary sulfate(34%)and mixed dust and traffic sources(26%).These findings demonstrate that both regional and local sources con-tribute to severe haze,highlighting the need for integrated policies for cross-border cooperation as well as stricter regulations to reduce biomass burning in Northern Thailand and Southeast Asia.
基金Project supported by the Hi-Tech Research and Development Program (863) of China (No. 2001AA641060 2003AA641040)the National Basic Research Program (973) of China (No. 2002CB410801).
文摘Cereal straw is one of the most abundant biomass burned in China but its contribution to fine particulates is not adequately understood. In this study, three main kinds of cereal straws were collected from five grain producing areas in China. Fine particulate matters （PMzs） from the cereal straws subjected to control burnings, both under smoldering and flaming status, were sampled by using a custom made dilution chamber and sampling system in the laboratory. Element carbon （EC） and organic carbon （OC） was analyzed. 141 compounds of organic matters were measured by gas chromatography-mass spectrum （GC-MS）. Source profiles of particulate organic matters emitted from cereal straw burnings were obtained. The results indicated that organic matters contribute a large fraction in fine particulate matters. Levoglucosan had the highest contributions with averagely 4.5% in mass of fine particulates and can be considered as the tracer of biomass burnings. Methyloxylated phenols from lignin degradation also had high concentrations in PM2.5, and contained approximately equal amounts of guaiacyl and syringyl compounds. 13-Sitostrol also made up relatively a large fraction of PMz5 compared with the other sterols （0.18%-0.63% of the total fine particle mass）. Normal alkanes, PAHs, fatty acids, as well as normal alkanols had relatively lower concentrations compared with the compounds mentioned above. Carbon preference index （CPI） of normal alkanes and alkanoic acids showed characteristics of biogenic fuel burnings. Burning status significantly influenced the formations of EC and PAHs. The differences between the emission profiles of straw and wood combustions were displayed by the fingerprint compounds, which may be used to identify the contributions between wood and straw burnings in source apportionment researches.
基金Project supported by the National Natural Science Foundation of China (No. 30170770).
文摘Soil organic carbon （C） and total nitrogen （N） pools of a Chinese fir （Cunninghamia lanceolata （Lamb.） Hook.） （CF） forest, and an evergreen broadleaf （EB） forest located in mid-subtropical, southeastern China, were compared before clearcutting, with the effect of slash burning on organic C and total N in the top 10 cm of soil before and after burning also being evaluated. Prior to clearcutting CF forest had significantly lower （P 〈0.05） organic C and total N in the soil （0-100 cm） compared to EB forest with approximately 60% of the C and N at the two forest sites stored at the 0 to 40 cm soil. In post-burn samples of the 0-10 cm depth at 5 days, 1 year, and 5 years for CF and EB forests, significantly lower levels （P 〈0.05） of organic C and total N than those in the pre-burn samples were observed. Compared to the pre-burn levels, at post-burn year 5, surface soil organic C storage was only 85% in CF forest and 72% in EB forest, while total N storage was 77% for CF forest and 73% for EB forest. Slash burning caused marked long-term changes in surface soil C and N in the two forest types.
