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
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
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
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
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
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
Burning mouth syndrome is a debilitating medical condition affecting nearly 1.3 million of Americans.Its common features include a burning painful sensation in the mouth,often associated with dysgeusia and xerostomia,...Burning mouth syndrome is a debilitating medical condition affecting nearly 1.3 million of Americans.Its common features include a burning painful sensation in the mouth,often associated with dysgeusia and xerostomia,despite normal salivation.Classically, symptoms are better in the morning,worsen during the day and typically subside at night.Its etiology is largely multifactorial,and associated medical conditions may include gastrointestinal,urogenital,psychiatric,neurologic and metabolic disorders,as well as drug reactions.BMS has clear predisposition to peri-/post menopausal females.Its pathophysiology has not been fully elucidated and involves peripheral and central neuropathic pathways.Clinical diagnosis relies on careful history taking,physical examination and laboratory analysis.Treatment is often tedious and is aimed at correction of underlying medical conditions,supportive therapy,and behavioral feedback.Drug therapy with alpha lipoic acid,clonazepam,capsaicin,and antidepressants may provide symptom relief.Psychotherapy may be helpful.Short term follow up data is promising,however,long term prognosis with treatment is lacking.BMS remains an important medical condition which often places a recognizable burden on the patient and health care system and requires appropriate recognition and treatment.展开更多
To investigate the impact on urban air pollution by crop residual burning outside Nanjing, aerosol concentration, pollution gas concentration, mass concentration, and water-soluble ion size distribution were observed ...To investigate the impact on urban air pollution by crop residual burning outside Nanjing, aerosol concentration, pollution gas concentration, mass concentration, and water-soluble ion size distribution were observed during one event of November 4-9, 2010. Results show that the size distribution of aerosol concentration is bimodal on pollution days and normal days, with peak values at 60- 70 and 200-300 nm, respectively. Aerosol concentration is 104 cm-3.nm-1 on pollution days. The peak value of spectrum distribution of aerosol concentration on pollution days is 1.5-3.3 times higher than that on a normal day. Crop residual burning has a great impact on the concentration of fine particles. Diurnal variation of aerosol concentration is trimodal on pollution days and normal days, with peak values at 03：00, 09：00 and 19：00 local standard time. The first peak is impacted by meteorological elements, while the second and third peaks are due to human activities, such as rush hour traffic. Crop residual burning has the greatest impact on SO2 concentration, followed by NO2, 03 is hardly affected. The impact of crop residual burning on fine particles （〈 2.1 μm） is larger than on coarse particles （〉 2.1 μm）, thus ion concentration in fine particles is higher than that in coarse particles. Crop residual burning leads to similar increase in all ion components, thus it has a small impact on the water-soluble ions order. Crop residual burning has a strong impact on the size distribution of K^＋, Cl^-, Na^＋, and F- and has a weak impact on the size distributions of NH4^＋, Ca^2＋, NO3^- and SO4^2-.展开更多
The Sichuan Basin has experienced serious air pollution from fine particulate matter(PM2.5) in the past few years with biomass burning has been identified as a major source of PM2.5 in this region.We used single parti...The Sichuan Basin has experienced serious air pollution from fine particulate matter(PM2.5) in the past few years with biomass burning has been identified as a major source of PM2.5 in this region.We used single particle aerosol mass spectrometer to investigate the characteristics of biomass burning particles in three interacting cities representing different types of urban environment in the Sichuan Basin.A total of 739,794,279,610,and380,636 biomass burning particles were detected at Ya’an,Guang’an,and Chengdu,which represented 42%,69%,and 61%,respectively,of the total number of particles.We analyzed the chemical composition,transportation,and evolution of biomass burning particles.The contribution of K-elemental carbon and K-secondary inorganic particles was highest in Ya’an(36%) and Guang’an(47%),respectively,reflecting the important role of fresh biomass burning particles and long-distance transport in these two cities.Air masses originating from different directions corresponded to different levels of PM2.5 and the contributions of polluted clusters increased significantly on polluted days.Fresh and secondary inorganic biomass burning particles increased pollution at Ya’an and Guang’an,respectively,but dominated different stages of pollution in Chengdu.K-nitrate particles were formed by photochemical reactions,whereas K-sulfate particles were formed by both photochemical and liquid-phase reactions.Investigation of the degree of particle aging showed that there were more fresh particles at Ya’an and more aged particles at Guang’an.These results are useful in helping our understanding of the characteristics of biomass burning particles and evaluating their role in PM2.5 pollution in the Sichuan Basin.展开更多
Based on satellite image data and China＇s Statistical Yearbooks（2000 to 2014）, we estimated the total mass of crop residue burned, and the proportion of residue burned in the field vs.indoors as domestic fuel. The ...Based on satellite image data and China＇s Statistical Yearbooks（2000 to 2014）, we estimated the total mass of crop residue burned, and the proportion of residue burned in the field vs.indoors as domestic fuel. The total emissions of various pollutants from the burning of crop residue were estimated for 2000-2014 using the emission factor method. The results indicate that the total amount of crop residue and average burned mass were 8690.9 Tg and4914.6 Tg, respectively. The total amount of emitted pollutants including CO2, CO, NOx,VOCs, PM（2.5）, OC（organic carbon）, EC（element carbon） and TC（total carbon） were 4212.4–8440.9 Tg, 192.8–579.4 Tg, 4.8–19.4 Tg, 18.6–61.3 Tg, 18.8–49.7 Tg, 6.7–31.3 Tg, 2.3–4.7 Tg, and8.5–34.1 Tg, respectively. The emissions of pollutants released from crop residue burning were found to be spatially variable, with the burning of crop residue mainly occurring in Northeast, North and South China. In addition, pollutant emissions per unit area（10 km ×10 km） were mostly concentrated in the central and eastern regions of China. Emissions of CO2, NOx, VOCs, OC and TC were mainly from rice straw burning, while burning of corn and wheat residues contributed most to emissions of CO, PM（2.5） and EC. The increased ratio of PM（2.5） emissions from crop residue burning to the total emitted from industry during the study period is attributed to the implementation of strict emissions management policies in Chinese industry. This study also provides baseline data for assessment of the regional atmospheric environment.展开更多
In a quest of search for a new burning rate modifier for composite propellant, strontium titanate (SrTiO3), a perovskite oxide has been chosen for evaluation in a composite propellant formulation based on its other ca...In a quest of search for a new burning rate modifier for composite propellant, strontium titanate (SrTiO3), a perovskite oxide has been chosen for evaluation in a composite propellant formulation based on its other catalytic applications. Initially, SrTiO3 was characterized for particle size, morphology and material/ phase identification (using XRD). By varying SrTiO3 content in a standard composite propellant, different compositions were prepared and their performance and processing parameters like the end of mix (EOM) viscosity, mechanical properties, density, burning rate, pressure exponent (n-value), etc. were measured. The results reveal that 2% SrTiO3 causes more than 12% enhancement in propellant burning rate (at 70 ksc pressure) in comparison to the standard propellant composition. The pressure exponent also increases to 0.46, whereas the standard composition was having its value as 0.35.展开更多
Atmospheric particulate and polycyclic aromatic hydrocarbons （PAHs） size distribution were measured at Jhu-Shan （a rural site） and Sin-Gang （a town site） in central Taiwan during the rice straw burning and non-b...Atmospheric particulate and polycyclic aromatic hydrocarbons （PAHs） size distribution were measured at Jhu-Shan （a rural site） and Sin-Gang （a town site） in central Taiwan during the rice straw burning and non-burning periods. The concentrations of total PAHs accounting for a roughly 58% （34%） increment in the concentrations of total PAHs due to rice-straw burning. Combustion-related PAHs during burning periods were 1.54-2.57 times higher than those during non-burning periods. The mass median diameter （MMD） of 0.88-1.21 μm in the particulate phase suggested that rice-straw burning generated the increase in coarse particle number. Chemical mass balance （CMB） receptor model analyses showed that the primary pollution sources at the two sites were similar. However, ricestraw burning emission was specifically identified as a significant source of PAH during burning periods at the two sites. Open burning of rice straws was estimated to contribute approximately 6.3%-24.6% to total atmospheric PAHs at the two sites.展开更多
Emission factors （EFs） of parent polycyclic aromatic hydrocarbons （pPAHs）, nitrated PAHs （nPAHs）, and oxygenated PAHs （oPAHs） were measured for indoor corn straw burned in a brick cooking stove under different...Emission factors （EFs） of parent polycyclic aromatic hydrocarbons （pPAHs）, nitrated PAHs （nPAHs）, and oxygenated PAHs （oPAHs） were measured for indoor corn straw burned in a brick cooking stove under different burning conditions. The EFs of total 28 pPAHs, 6 nPAHs and 4 oPAHs were （7.9 ±3.4）, （6.5 ±1.6）×10^-3, and （6.1 ±1.4）×10^-1mg/kg, respectively. Fuel charge size had insignificant influence on the pollutant emissions. Measured EFs increased significantly in a fast burning due to the oxygen deficient atmosphere formed in the stove chamber. In both restricted and enhanced air supply conditions, the EFs of pPAHs, nPAHs and oPAHs were significantly higher than those measured in normal burning conditions. Though EFs varied among different burning conditions, the composition profiles and calculated isomer ratios were similar, without significant differences. The results from the stepwise regression model showed that fuel burning rate, air supply amount, and modified combustion efficiency were the three most significant influencing factors, explaining 72%-85% of the total variations.展开更多
Most clinicians dread seeing the patient presenting with a primary complaint of a burning pain on one or more oral mucosal surfaces. Unlike most other clinical conditions presenting in a dental office, burning mouth s...Most clinicians dread seeing the patient presenting with a primary complaint of a burning pain on one or more oral mucosal surfaces. Unlike most other clinical conditions presenting in a dental office, burning mouth syndrome is poorly understood with few evidence based remedies. More recently, advances have been made towards clarifying the possible etiology of the disorder and testing the possible therapeutic modalities available. This article attempts to summarize the ＂state of the art＂ today.展开更多
The burning of crop residues emits large quantities of atmospheric aerosols.Published studies have developed inventories of emissions from crop residue burning based on statistical data.In contrast,this study used sat...The burning of crop residues emits large quantities of atmospheric aerosols.Published studies have developed inventories of emissions from crop residue burning based on statistical data.In contrast,this study used satellite-retrieved land-cover data(1 km×1 km)as activity data to compile an inventory of atmospheric pollutants emitted from the burning of crop residues in China in 2015.The emissions of PM10,PM2.5,VOCs,NOx,SO2,CO,and NH3 from burning crop straw on nonirrigated farmland in China in 2015 were 610.5,598.4,584.4,230.6,35.4,3329.3,and 36.1 Gg(1 Gg=109 g),respectively;the corresponding emissions from burning paddy rice residues were 234.1,229.7,342.3,57.5,57.5,1122.1,and 21.5 Gg,respectively.The emissions from crop residue burning showed large spatial and temporal variations.The emissions of particulate matter and gaseous pollutants from crop residue burning in nonirrigated farmland were highest in east China,particularly in Shandong,Henan,Anhui,and Sichuan provinces.Emissions from burning paddy rice residue were highest in east and central China,with particularly high levels in Shandong,Jiangsu,Zhejiang,and Hunan provinces.The monthly variations in atmospheric pollutant emissions were similar among different regions,with the highest levels observed in October in north,northeast,northwest,east,and southwest China and in June and July in central and south China.The developed inventory of emissions from crop residue burning is expected to help improve air quality models by providing high-resolution spatial and temporal data.展开更多
The effect of forests clear felling and associated burning on the population of soil nitrogen transforming bacteria and actinomycetes are reported at three pair sites of Chittagong University campus, Bangla- desh in m...The effect of forests clear felling and associated burning on the population of soil nitrogen transforming bacteria and actinomycetes are reported at three pair sites of Chittagong University campus, Bangla- desh in monsoon tropical climate. Clear felled area or burnt site and 15-21 year mixed plantation of native and exotic species, situated side by side on low hill having Typic Dystrochrepts soil was represented at each pair site. At all the three pair sites, clear felled area or burnt site showed very significantly （p~_0.001） lower population of actinomycetes, Rhizobium, Nitrosomonas, Nitrobacter and ammonifying as well as deni- trifying bacteria compared to their adjacent mixed plantation. From en- vironmental consideration, this finding has implication in managing natural ecosystem.展开更多
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.
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.
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 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.
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.
文摘Burning mouth syndrome is a debilitating medical condition affecting nearly 1.3 million of Americans.Its common features include a burning painful sensation in the mouth,often associated with dysgeusia and xerostomia,despite normal salivation.Classically, symptoms are better in the morning,worsen during the day and typically subside at night.Its etiology is largely multifactorial,and associated medical conditions may include gastrointestinal,urogenital,psychiatric,neurologic and metabolic disorders,as well as drug reactions.BMS has clear predisposition to peri-/post menopausal females.Its pathophysiology has not been fully elucidated and involves peripheral and central neuropathic pathways.Clinical diagnosis relies on careful history taking,physical examination and laboratory analysis.Treatment is often tedious and is aimed at correction of underlying medical conditions,supportive therapy,and behavioral feedback.Drug therapy with alpha lipoic acid,clonazepam,capsaicin,and antidepressants may provide symptom relief.Psychotherapy may be helpful.Short term follow up data is promising,however,long term prognosis with treatment is lacking.BMS remains an important medical condition which often places a recognizable burden on the patient and health care system and requires appropriate recognition and treatment.
基金supported by the National Basic Research Program (973) of China (No. 2010CB428505)the National Natural Science Foundation of China (No. 41030962,40875078)+2 种基金the Research Fund for the Doctoral Program of Higher Education of China (No. 20093228110003)the Priority Academic Program Development of Jiangsu Higher Education Institutionsthe Jiangsu Provinc eGraduate Cultivation Innovative Project (No. CXZZ11-0616)
文摘To investigate the impact on urban air pollution by crop residual burning outside Nanjing, aerosol concentration, pollution gas concentration, mass concentration, and water-soluble ion size distribution were observed during one event of November 4-9, 2010. Results show that the size distribution of aerosol concentration is bimodal on pollution days and normal days, with peak values at 60- 70 and 200-300 nm, respectively. Aerosol concentration is 104 cm-3.nm-1 on pollution days. The peak value of spectrum distribution of aerosol concentration on pollution days is 1.5-3.3 times higher than that on a normal day. Crop residual burning has a great impact on the concentration of fine particles. Diurnal variation of aerosol concentration is trimodal on pollution days and normal days, with peak values at 03：00, 09：00 and 19：00 local standard time. The first peak is impacted by meteorological elements, while the second and third peaks are due to human activities, such as rush hour traffic. Crop residual burning has the greatest impact on SO2 concentration, followed by NO2, 03 is hardly affected. The impact of crop residual burning on fine particles （〈 2.1 μm） is larger than on coarse particles （〉 2.1 μm）, thus ion concentration in fine particles is higher than that in coarse particles. Crop residual burning leads to similar increase in all ion components, thus it has a small impact on the water-soluble ions order. Crop residual burning has a strong impact on the size distribution of K^＋, Cl^-, Na^＋, and F- and has a weak impact on the size distributions of NH4^＋, Ca^2＋, NO3^- and SO4^2-.
基金supported by the National Natural Science Foundation of China (No.41805095)the Sichuan Science and Technology Program (Nos.2018SZ0288 and2019YFS0476)the Fundamental Research Funds for the Central Universities (2682017CX080).
文摘The Sichuan Basin has experienced serious air pollution from fine particulate matter(PM2.5) in the past few years with biomass burning has been identified as a major source of PM2.5 in this region.We used single particle aerosol mass spectrometer to investigate the characteristics of biomass burning particles in three interacting cities representing different types of urban environment in the Sichuan Basin.A total of 739,794,279,610,and380,636 biomass burning particles were detected at Ya’an,Guang’an,and Chengdu,which represented 42%,69%,and 61%,respectively,of the total number of particles.We analyzed the chemical composition,transportation,and evolution of biomass burning particles.The contribution of K-elemental carbon and K-secondary inorganic particles was highest in Ya’an(36%) and Guang’an(47%),respectively,reflecting the important role of fresh biomass burning particles and long-distance transport in these two cities.Air masses originating from different directions corresponded to different levels of PM2.5 and the contributions of polluted clusters increased significantly on polluted days.Fresh and secondary inorganic biomass burning particles increased pollution at Ya’an and Guang’an,respectively,but dominated different stages of pollution in Chengdu.K-nitrate particles were formed by photochemical reactions,whereas K-sulfate particles were formed by both photochemical and liquid-phase reactions.Investigation of the degree of particle aging showed that there were more fresh particles at Ya’an and more aged particles at Guang’an.These results are useful in helping our understanding of the characteristics of biomass burning particles and evaluating their role in PM2.5 pollution in the Sichuan Basin.
基金supported by the Fujian Agriculture and Forestry University Funds for Distinguished Young Scholar(No.xjq201613)the National Natural Science Foundation of China(No.31400552)+1 种基金the International Science and Technology Cooperation Program of Fujian Agriculture and Forestry University(No.KXB16008A)the Asia-Pacific Network for Sustainable Forest Management and Rehabilitation(APFnet/2010/FPF/001)Phase II
文摘Based on satellite image data and China＇s Statistical Yearbooks（2000 to 2014）, we estimated the total mass of crop residue burned, and the proportion of residue burned in the field vs.indoors as domestic fuel. The total emissions of various pollutants from the burning of crop residue were estimated for 2000-2014 using the emission factor method. The results indicate that the total amount of crop residue and average burned mass were 8690.9 Tg and4914.6 Tg, respectively. The total amount of emitted pollutants including CO2, CO, NOx,VOCs, PM（2.5）, OC（organic carbon）, EC（element carbon） and TC（total carbon） were 4212.4–8440.9 Tg, 192.8–579.4 Tg, 4.8–19.4 Tg, 18.6–61.3 Tg, 18.8–49.7 Tg, 6.7–31.3 Tg, 2.3–4.7 Tg, and8.5–34.1 Tg, respectively. The emissions of pollutants released from crop residue burning were found to be spatially variable, with the burning of crop residue mainly occurring in Northeast, North and South China. In addition, pollutant emissions per unit area（10 km ×10 km） were mostly concentrated in the central and eastern regions of China. Emissions of CO2, NOx, VOCs, OC and TC were mainly from rice straw burning, while burning of corn and wheat residues contributed most to emissions of CO, PM（2.5） and EC. The increased ratio of PM（2.5） emissions from crop residue burning to the total emitted from industry during the study period is attributed to the implementation of strict emissions management policies in Chinese industry. This study also provides baseline data for assessment of the regional atmospheric environment.
文摘In a quest of search for a new burning rate modifier for composite propellant, strontium titanate (SrTiO3), a perovskite oxide has been chosen for evaluation in a composite propellant formulation based on its other catalytic applications. Initially, SrTiO3 was characterized for particle size, morphology and material/ phase identification (using XRD). By varying SrTiO3 content in a standard composite propellant, different compositions were prepared and their performance and processing parameters like the end of mix (EOM) viscosity, mechanical properties, density, burning rate, pressure exponent (n-value), etc. were measured. The results reveal that 2% SrTiO3 causes more than 12% enhancement in propellant burning rate (at 70 ksc pressure) in comparison to the standard propellant composition. The pressure exponent also increases to 0.46, whereas the standard composition was having its value as 0.35.
基金The Central Taiwan University of Science and Technology supported this work under the grant 94-INS-024
文摘Atmospheric particulate and polycyclic aromatic hydrocarbons （PAHs） size distribution were measured at Jhu-Shan （a rural site） and Sin-Gang （a town site） in central Taiwan during the rice straw burning and non-burning periods. The concentrations of total PAHs accounting for a roughly 58% （34%） increment in the concentrations of total PAHs due to rice-straw burning. Combustion-related PAHs during burning periods were 1.54-2.57 times higher than those during non-burning periods. The mass median diameter （MMD） of 0.88-1.21 μm in the particulate phase suggested that rice-straw burning generated the increase in coarse particle number. Chemical mass balance （CMB） receptor model analyses showed that the primary pollution sources at the two sites were similar. However, ricestraw burning emission was specifically identified as a significant source of PAH during burning periods at the two sites. Open burning of rice straws was estimated to contribute approximately 6.3%-24.6% to total atmospheric PAHs at the two sites.
基金supported by the National Natural Science Foundation of China (No.41130754,41001343)the Beijing Municipal Government (No.YB20101000101)+2 种基金Ministry of Environmental Protection (No.201209018)NIEHS (No.P42 ES016465)Guofeng Shen’s work in was supported by Jiangsu EPDProject (combined air pollution in Nanjing and surrounding area)
文摘Emission factors （EFs） of parent polycyclic aromatic hydrocarbons （pPAHs）, nitrated PAHs （nPAHs）, and oxygenated PAHs （oPAHs） were measured for indoor corn straw burned in a brick cooking stove under different burning conditions. The EFs of total 28 pPAHs, 6 nPAHs and 4 oPAHs were （7.9 ±3.4）, （6.5 ±1.6）×10^-3, and （6.1 ±1.4）×10^-1mg/kg, respectively. Fuel charge size had insignificant influence on the pollutant emissions. Measured EFs increased significantly in a fast burning due to the oxygen deficient atmosphere formed in the stove chamber. In both restricted and enhanced air supply conditions, the EFs of pPAHs, nPAHs and oPAHs were significantly higher than those measured in normal burning conditions. Though EFs varied among different burning conditions, the composition profiles and calculated isomer ratios were similar, without significant differences. The results from the stepwise regression model showed that fuel burning rate, air supply amount, and modified combustion efficiency were the three most significant influencing factors, explaining 72%-85% of the total variations.
文摘Most clinicians dread seeing the patient presenting with a primary complaint of a burning pain on one or more oral mucosal surfaces. Unlike most other clinical conditions presenting in a dental office, burning mouth syndrome is poorly understood with few evidence based remedies. More recently, advances have been made towards clarifying the possible etiology of the disorder and testing the possible therapeutic modalities available. This article attempts to summarize the ＂state of the art＂ today.
基金Under the auspices of National Key R&D Program of China(No.2017YFC0212303,2017YFC0212304)Key Research Program of Frontier Sciences,Chinese Academy of Sciences(No.QYZDB-SSW-DQC045)+1 种基金National Natural Science Foundation of China(No.41775116)Youth Innovation Promotion Association of Chinese Academy of Sciences(No.2017275).
文摘The burning of crop residues emits large quantities of atmospheric aerosols.Published studies have developed inventories of emissions from crop residue burning based on statistical data.In contrast,this study used satellite-retrieved land-cover data(1 km×1 km)as activity data to compile an inventory of atmospheric pollutants emitted from the burning of crop residues in China in 2015.The emissions of PM10,PM2.5,VOCs,NOx,SO2,CO,and NH3 from burning crop straw on nonirrigated farmland in China in 2015 were 610.5,598.4,584.4,230.6,35.4,3329.3,and 36.1 Gg(1 Gg=109 g),respectively;the corresponding emissions from burning paddy rice residues were 234.1,229.7,342.3,57.5,57.5,1122.1,and 21.5 Gg,respectively.The emissions from crop residue burning showed large spatial and temporal variations.The emissions of particulate matter and gaseous pollutants from crop residue burning in nonirrigated farmland were highest in east China,particularly in Shandong,Henan,Anhui,and Sichuan provinces.Emissions from burning paddy rice residue were highest in east and central China,with particularly high levels in Shandong,Jiangsu,Zhejiang,and Hunan provinces.The monthly variations in atmospheric pollutant emissions were similar among different regions,with the highest levels observed in October in north,northeast,northwest,east,and southwest China and in June and July in central and south China.The developed inventory of emissions from crop residue burning is expected to help improve air quality models by providing high-resolution spatial and temporal data.
文摘The effect of forests clear felling and associated burning on the population of soil nitrogen transforming bacteria and actinomycetes are reported at three pair sites of Chittagong University campus, Bangla- desh in monsoon tropical climate. Clear felled area or burnt site and 15-21 year mixed plantation of native and exotic species, situated side by side on low hill having Typic Dystrochrepts soil was represented at each pair site. At all the three pair sites, clear felled area or burnt site showed very significantly （p~_0.001） lower population of actinomycetes, Rhizobium, Nitrosomonas, Nitrobacter and ammonifying as well as deni- trifying bacteria compared to their adjacent mixed plantation. From en- vironmental consideration, this finding has implication in managing natural ecosystem.
