At present, the use of furnaces in the northern rural areas of China is very common, due to the insufficient burning of fuel (coal, wood, etc.), carbon monoxide (CO) and other toxic gases are produced, CO colorless an...At present, the use of furnaces in the northern rural areas of China is very common, due to the insufficient burning of fuel (coal, wood, etc.), carbon monoxide (CO) and other toxic gases are produced, CO colorless and odorless, difficult to find in time, and bring huge safety risks to the life and health of residents. Based on the above problems, we developed a gas monitoring and removal device which could reduce the effect of extinction coefficient. The device was composed of ash settling area, gas disturbance area, spectral absorption identification area and gas removal area. After the air entered the device, the large-size particles were first settled to purify the solid particles in the gas, the gas was disturbed through the multi-layer separator to achieve the turbulent production of the gas, and then the gas was identified through the optical element of the direct absorption spectrum technology. When the toxic gas component reached the threshold, the spray device would automatically start for chemical removal to achieve the role of purifying the gas. At the same time, the device’s alarm could be alerted by buzzer and flash to remind users to evacuate in time. By improving the optical device, the effect of extinction coefficient on measurement was reduced and the monitoring accuracy was improved.展开更多
[Objective] The aim was to study the dynamic variation of extinction coefficient of corn population, so as to improve the accuracy of assessment on net primary productivity （NPP） or yield. [Method] Based on the data...[Objective] The aim was to study the dynamic variation of extinction coefficient of corn population, so as to improve the accuracy of assessment on net primary productivity （NPP） or yield. [Method] Based on the data of photosynthetic active radiation and leaf area index during corn growing season （from May to September） in 2006, observed in Jinzhou observation station of corn farmland ecosystem, China Meteorological Administration, the dynamic variation of extinction coefficient of corn population was analyzed. [Result] There was a great daily variation in the extinction coefficient of corn population during growing season, and the maximum value appeared from 7：00 to 9：00 and from 15：00 to 17：00, while the minimum could be found around 12：00, but the amplitude of variation decreased in tasseling stage. On a large time scale （5 d）, there was a parabolic relationship between extinction coefficient （K） and leaf area index （LAI）, with determination coefficient R2 of 0.960 7. The simulation equation of extinction coefficient, based on the sun elevation angle or leaf area index, had poor accuracy at various time during growing season, so a new dynamic model of extinction coefficient was established, namely K=λ（0.784 8-0.001 6θ）（0.154 8LAI2-0.558 6LAI＋0.654）. [Conclusion] The effect of sun elevation angle and leaf area index on extinction coefficient during corn growing season was considered in the new dynamic model of extinction coefficient, and its simulated result was superior to that of single-factor model.展开更多
The objective of this study was to reconstruct light extinction coefficients （b ext ） according to chemical composition components of particulate matter up to 2.5 μm in size （PM 2.5 ）. PM 2.5 samples were collect...The objective of this study was to reconstruct light extinction coefficients （b ext ） according to chemical composition components of particulate matter up to 2.5 μm in size （PM 2.5 ）. PM 2.5 samples were collected at the monitoring station of the South China of Institute of Environmental Science （SCIES, Guangzhou, China） during January 2010, and the online absorbing and scattering coefficients were obtained using an aethalometer and a nephelometer. The measured values of light absorption coefficient by particle （b ap ） and light scattering coefficient by particle （b sp ） significantly correlated （R 2 0.95） with values of b ap and b sp that were reconstructed using the Interagency Monitoring of Protected Visual Environments （IMPROVE） formula when RH was 70%. The measured b ext had a good correlation （R 2 0.83） with the calculated b ext under ambient RH conditions. The result of source apportionment of b ext showed that ammonium sulfate [（NH 4 ） 2 SO 4 ] was the largest contributor （35.0%） to b ext , followed by ammonium nitrate （NH 4 NO 3 , 22.9%）, organic matter （16.1%）, elemental carbon （11.8%）, sea salt （4.7%）, and nitrogen dioxide （NO 2 , 9.6%）. To improve visibility in Guangzhou, the effective control of secondary particles like sulfates, nitrates, and ammonia should be given more attention in urban environmental management.展开更多
With the method of differential optical absorption spectroscopy （DOAS）, average concentrations of aerosol particles along light path were measured with a flashlight source in Chiba area during the period of one mont...With the method of differential optical absorption spectroscopy （DOAS）, average concentrations of aerosol particles along light path were measured with a flashlight source in Chiba area during the period of one month. The optical thickness at 550 nm is compared with the concentration of ground-measured suspended particulate matter （SPM）. Good correlations are found between the DOAS and SPM data, leading to the determination of the aerosol mass extinction efficiency （MEE） to be possible in the lower troposphere. The average MEE value is about 7.6m^2.g^-1 , and the parameter exhibits a good correlation with the particle size as determined from the wavelength dependence of the DOAS signal intensity.展开更多
The canopy light extinction coefficient （K） is a key factor in affecting ecosystem carbon, water, and energy processes. However, K is assumed as a constant in most biogeochemical models owing to lack of in-site meas...The canopy light extinction coefficient （K） is a key factor in affecting ecosystem carbon, water, and energy processes. However, K is assumed as a constant in most biogeochemical models owing to lack of in-site measurements at diverse terrestrial ecosystems. In this study, by compiling data of K measured at 88 terrestrial ecosystems, we investigated the spatiotemporal variations of this index across main ecosystem types, including grassland, cropland, shrubland, broadleaf forest, and needleleaf forest. Our results indicated that the average K of all biome types during whole growing season was 0.56. However, this value in the peak growing season was 0.49, indicating a certain degree of seasonal variation. In addition, large variations in K exist within and among the plant functional types. Cropland had the highest value of K （0.62）, followed by broadleaf forest （0.59）, shrubland （0.56）, grassland （0.50）, and needleleaf forest （0.45）. No significant spatial correlation was found between K and the major environmental factors, i.e., mean annual precipitation, mean annual temperature, and leaf area index （LAI）. Intra-annually, significant negative correlations between K and seasonal changes in LAI were found in the natural {K=2/π[cosαcosθsina^-1（tanθtanα）＋（1＋cos^2a-cos^2θ^1/2）],a＋θ〉π/2 K=cosαcosθ,α＋θ≤π/2 k K is usually calculated with the Beer Lambert Law （Monsi and Sakei, 1953）：K = - In （Ii/Io） cosθ/（LAIΩ）,（2）ecosystems. In cropland, however, the temporal relation- ship was site-specific. The ecosystem type specific values of K and its temporal relationship with LAI observed in this study may contribute to improved modeling of global biogeochemical cycles.展开更多
The extinction coefficient of semiconductor nanocrystals is a key parameter for understanding both the quantum confinement and applications of the nanocrystals. The existing extinction coefficients of CdE （E = Se, S...The extinction coefficient of semiconductor nanocrystals is a key parameter for understanding both the quantum confinement and applications of the nanocrystals. The existing extinction coefficients of CdE （E = Se, S） nanocrystals were found to have an unacceptable deviation for the zinc-blende CdE quantum dots （QDs）. The analysis reveals that, in addition to the interference of impurities, the commonly applied extinction coefficient per CdE nanocrystal is sensitive to the size, shape, and density of the surface ligands of nanocrystals. The extinction coefficient per CdE unit does not depend on accurate information of the size, shape, and number of surface ligands of the nanocrystals. A new three-step purification scheme was developed to investigate three classes of possible impurities for accurate determination of the extinction coefficient per CdE unit, including CdE clusters not considered previously. Given that the sole ligands of zinc-blende CdE nanocrystals are cadmium fatty acid salts （CdFa2）, a universal formula for the nanocrystals can be written as （CdE）,（CdFa2）,. The n：rn ratio was accurately determined for purified nanocrystals. The resulting extinction coefficients per unit for both CdSe and CdS QDs were found to decrease exponentially as the size of the QDs increases, with the corresponding bulk value as the large-size limit.展开更多
Based on daily visibility data obtained from 1980-2002 and air pollution index data from 2001-2004 in Xi＇an, long-term variations and relationships for daily horizontal extinction coefficient and mass concentration o...Based on daily visibility data obtained from 1980-2002 and air pollution index data from 2001-2004 in Xi＇an, long-term variations and relationships for daily horizontal extinction coefficient and mass concentration of PM10 have been evaluated. A decreasing trend was found in horizontal extinction coefficient during the past 23 years, with higher values observed in 1980s relative to 1990s, and the highest and lowest values in winter and summer, respectively. Significant correlation and similar seasonal variations existed between horizontal extinction coefficient and PM10 concentration, suggesting the high influence of PM10 to the visibility drop at a site in the Guanzhong Plain of central China during the past two decades.展开更多
Determining the optical properties of media remains an important part of scientific research. Knowledge of these optical properties, particularly absorption and diffusion coefficients, has direct applications in biome...Determining the optical properties of media remains an important part of scientific research. Knowledge of these optical properties, particularly absorption and diffusion coefficients, has direct applications in biomedical therapeutic diagnostics. The determination of these coefficients was previously reserved for optically dilute media. Recently, a technique called Structured Laser Illumination Planar Imaging (SLIPI) has been developed for measuring extinction coefficients in dense media. For such a medium and technique, no study has reported the determination of absorption and scattering coefficients. In this study, we have developed a simple calculation method based on the combination of Kubelka-Munk relations and extinction, both functions of the medium’s absorption and diffusion coefficients. The equations thus developed enable absorption and diffusion coefficients to be easily calculated from extinction coefficient measurements alone, using the SLIPI technique. The analysis method thus developed was applied to ten (10) milk solutions of different concentrations considered to be predominantly diffusive, and to ten (10) coffee solutions of different concentrations considered to be predominantly absorbent. The coefficient values obtained have been analysed and compared to the literature ones and they would be satisfactory.展开更多
This research directly supported the author’s thesis work in partial fulfilment of Master of Science in biology from the University of North Texas(United States)from August 1996 to September 1997.Two sites at Lake Ra...This research directly supported the author’s thesis work in partial fulfilment of Master of Science in biology from the University of North Texas(United States)from August 1996 to September 1997.Two sites at Lake Ray Roberts,Denton County,Texas(United States)were examined and contrasted for productivity.The site located in the pelagic zone exhibited a slight,thermal gradient with no stratification,and a slightly stratified clinograde oxygen profile which is typical for summer-stratified eutrophic lakes.The site located in the shallow,littoral zone exhibited high,increasing turbidity with depth,marked by shallow light attenuation through the water column.Temperature was constant at every depth in the littoral site,with a slight,clinograde oxygen profile,typical for shallow,littoral areas subject to wind-induced mixing.Volume estimations of chlorophyll-α shows a strong presence in the euphotic zone,indicating photosynthesis occurs until approximately 2.2 m below the surface.The shallow,littoral site showed the basic signs of higher productivity than the open,pelagic site.展开更多
The current paper introduces an empirical method for estimating the vertical distribution of background stratospheric aerosol extinction profiles covering the latitude bands of 50±5°N,40±5°N,30...The current paper introduces an empirical method for estimating the vertical distribution of background stratospheric aerosol extinction profiles covering the latitude bands of 50±5°N,40±5°N,30±5°N,and 20±5°N and the longitude range of 75 135°E based on Stratospheric Aerosol and Gas Experiment (SAGE) II aerosol extinction measurements at wavelengths of 1020 nm,525 nm,452 nm,and 386 nm for the volcanically calm years between 1998 2004.With this method,the vertical distribution of stratospheric aerosol extinction coefficients can be estimated according to latitude and wavelength.Comparisons of the empirically calculated aerosol extinction profiles and the SAGE II aerosol measurements show that the empirically calculated aerosol extinction coefficients are consistent with SAGE II values,with relative differences within 10% from 2 km above the tropopause to 33 km,and within 22% from 33 km to 35 km.The empirically calculated aerosol stratospheric optical depths (vertically integrated aerosol extinction coefficient) at the four wavelengths are also consistent with the corresponding SAGE II optical depth measurements,with differences within 2.2% in the altitude range from 2 km above the tropopause to 35 km.展开更多
This paper presents an empirical model for estimating the zonal mean aerosol extinction profiles in the stratosphere over 10°-wide latitude bands between 60°S and 60°N, on the basis of Stratospheric Aer...This paper presents an empirical model for estimating the zonal mean aerosol extinction profiles in the stratosphere over 10°-wide latitude bands between 60°S and 60°N, on the basis of Stratospheric Aerosol and Gas Experiment(SAGE) II aerosol extinction measurements at 1.02, 0.525, and 0.452 μm during the volcanically quiescent period between 1998–2004. First, an empirical model is developed for calculating the stratospheric aerosol extinction profiles at 1.02 μm. Then, starting from the 1.02 μm extinction profile and an exponential spectral dependence, an empirical algorithm is developed that allows the aerosol extinction profiles at other wavelengths to be calculated. Comparisons of the model-calculated aerosol extinction profiles at the wavelengths of 1.02, 0.525, and 0.452 μm and the SAGE II measurements show that the model-calculated aerosol extinction coefficients conform well with the SAGE II values, with the relative differences generally being within 15% from 2 km above the tropopause to 40 km. The model-calculated stratospheric aerosol optical depths at the three wavelengths are also in good agreement with the corresponding optical depths derived from the SAGE II measurements, with the relative differences being within 0.9% for all latitude bands. This paper provides a useful tool in simulating zonal mean aerosol extinction profiles, which can be used as representative background stratospheric aerosols in view of atmospheric modeling and remote sensing retrievals.展开更多
On the Loess Plateau, water is the main limiting factors for vegetation growth. Root distribution characters have special ecological meaning as it reflected the utilizations of trees to the environments. Even-aged sta...On the Loess Plateau, water is the main limiting factors for vegetation growth. Root distribution characters have special ecological meaning as it reflected the utilizations of trees to the environments. Even-aged stands ofRobinia pseudoacacia on slope lands facing south and north were selected as sampling plots for root distribution investigation. Investigatiing results showed that indicated that on all sites, root biomass decreased with depth, and the distribution depth of fine root was deeper than that of coarser root. The results of variance analysis indicated that there were great differences in root biomass among different diameter classes, and coarser root was the main sources of variance, and the root biomass, especially fine root (?<3mm) biomass on northern exposition sites was bigger than that on southern exposition sites. Analysis of the vertical root distribution parameters, root extinction coefficient, β indicated that the value of β on northern exposition was more than 0.982, while the value of β on southern exposition was less than 0.982, which indicated that the vertical root distribution depth ofRobinia pseudoacacia on southern exposition was deeper than that on southern exposition. And the distribution depth of fine roots (Φ<1mm) was deeper than that of thicker roots(Φ<3mm), which was in favor of the uptake of water and nutrients from deeper layers, helped the trees to adapt the arid environment, and promoted the growth of the upper parts of the tree. Keywords Root diameter classes - Variance analysis - Root extinction coefficient - Vertical distribution characters - Site conditions - Loess Plateau CLC number S792.27.01 Document code A Foundation Item: This research was supported by National Natural Science Foundation of China (30371150 and 40371075).Biography: LI Peng (1974-) male, post: Ph. D. in Northwest Scientific & Technological University of Agriculture and Forestry, Yangling 712100, Shaanxi Province, P. R. China. Tel: 029-82312651.Responsible editor: Chai Ruihal展开更多
To know the annual water consumption of forest, it is necessary to acquire the annual transpiration value of stands. This paper is based on the data measured in the typical weather of the growth season, from 1998 to 2...To know the annual water consumption of forest, it is necessary to acquire the annual transpiration value of stands. This paper is based on the data measured in the typical weather of the growth season, from 1998 to 2000, with the LI 1600 Steady Porometer and the general weather information. The daily variation of transpiration in black locust forest ( Robinia pesudoacacia L.) is modeled by Penman Monteith equation. As a result of the model, a continuous daily transpiration in the growth season was calculated. The net radiation, intercepted by black locust forest canopy, was acquired from a semi empirical equation of measuring net radiation R n with the extinction coefficient k and leaf area index LAI . The canopy integral stomatic resistance is a mimesis with an empirical equation of measuring data. Compared with measuring data, the relative error of the modeled ones is less than 12% averagely. At last, the total transpiration of black locust forest during the period of 1998 and 2000 in the growth season of May to October, as an average transpiration of the different density stands, were 192 46, 187 07 and 195 59?mm respectively.展开更多
To better understand the potential causes of visibility impairment in autumn and winter in Chengdu,relative humidity(RH),visibility,the concentrations of PM2.5 and its chemical components were on-line measured continu...To better understand the potential causes of visibility impairment in autumn and winter in Chengdu,relative humidity(RH),visibility,the concentrations of PM2.5 and its chemical components were on-line measured continuously in Chengdu from Nov.2016 to Jan.2017.Six obvious haze episodes occurred in Chengdu,with the total time of haze episodes accounted for more than 90%of the total observation period,and higher NO2 concentrations and RH were related to the high particle concentrations in haze episodes.The visibility decreased in a non-linear tendency under different RH conditions with the increase of PM2.5 concentrations,which was more sensitive to RH under lower PM2.5 concentrations.The threshold concentration of PM2.5 got more smaller with the increase of RH.During the entire observation period,organic matter(OM)was the largest contributor(31.12%to extinction coefficient(bext)),followed by NH4NO3 and(NH4)2SO4 with 28.03%and 23.01%,respectively.However,with the visibility impairment from Type I(visibility>10 km)to Type IV(visibility≤2 km),the contribution of OM to bextdecreased from 38.12%to 26.77%,while the contribution of NH4NO3 and(NH4)2SO4 to bextincreased from 19.09%and 20.20%to 34.29%and 24.35%,respectively,and NH4NO3 became the largest contributor to bextat Type IV.The results showed that OM and NH4NO3 were the key components of PM2.5 for visibility impairment in Chengdu,indicating that the control of precursors emissions of carbonaceous species and NH4NO3 could effectively improve the visibility in Chengdu.展开更多
Improving radiation use efficiency （RUE） of the canopy is necessary to increase wheat （Triticum aesfivum） production. Tridimensional uniform sowing （U） technology has previously been used to construct a uniforml...Improving radiation use efficiency （RUE） of the canopy is necessary to increase wheat （Triticum aesfivum） production. Tridimensional uniform sowing （U） technology has previously been used to construct a uniformly distributed population structure that increases RUE. In this study, we used tridimensional uniform sowing to create a wheat canopy within which light was spread evenly to increase RUE. This study was done during 2014-2016 in the Shunyi District, Beijing, China. The soil type was sandy loam. Wheat was grown in two sowing patterns： （1） tridimensional uniform sowing （U）; （2） conventional drilling （D）. Four planting densities were used： 1.8, 2.7, 3.6, and 4.5 million plants ha-1. Several indices were measured to compare the wheat canopies： photosynthetic active radiation intercepted by the canopy （IPAR）, leaf area index （LAI）, leaf mass per unit area （LMA）, canopy extinction coefficient （K）, and RUE. In two sowing patterns, the K values decreased with increasing planting density, but the K values of U were lower than that of D. LMA and IPAR were higher for U than for D, whereas LAI was nearly the same for both sowing patterns. IPAR and LAI increased with increasing density under the same sowing pattern. However, the difference in IPAR and LAI between the 3.6 and 4.5 million plants ha-1 treatments was not significant for both sowing patterns. Therefore, LAI within the same planting density was not affected by sowing pattern. RUE was the largest for the U mode with a planting density of 3.6 million plants ha-1 treatment. For the D sowing pattern, the lowest planting density （1.8 million plants ha-1） resulted in the highest yield. Light radiation interception was minimal for the D mode with a planting density of 1.8 million plants ha-1 treatment, but the highest RUE and highest yield were observed under this condition. For the U sowing pattern, IPAR increased with increasing planting density, but yield and RUE were the highest with a planting density of 3.6 million plants ha-1. These results indicated that the optimal planting density for improving the canopy light environment differed between the sowing patterns. The effect of sowing patternxplanting density interaction on grain yield, yield components, RUE, IPAR, and LMA was significant （P〈0.05）. Correlation analysis indicated that there is a positive significant correlation between grain yield and RUE （t=0.880, P〈0.01）, LMA （r=0.613, P〈0.05）, andspike number （t=0.624, P〈0.05）. These results demonstrated that the tridimensional uniform sowing technique, particularly at a planting density of 3.6 million plants ha-0, can effectively increase light interception and utilization and unit leaf area. This leads to the production of more photosynthetic products that in turn lead to significantly increased spike number （P〈0.05）, kernel number, grain weight, and an overall increase in yield.展开更多
Black locust（Robinia pseudoacacia L.） and Chinese pine（Pinus tabulaeformis Carr.） are two woody plants that are widely planted on the Loess Plateau for controlling soil erosion and land desertification. In this st...Black locust（Robinia pseudoacacia L.） and Chinese pine（Pinus tabulaeformis Carr.） are two woody plants that are widely planted on the Loess Plateau for controlling soil erosion and land desertification. In this study, we conducted an excavation experiment in 2008 to investigate the overall vertical root distribution characteristics of black locust and Chinese pine. We also performed triaxial compression tests to evaluate the root cohesion（additional soil cohesion increased by roots） of black locust. Two types of root distribution, namely, vertical root（VR） and horizontal root（HR）, were used as samples and tested under four soil water content（SWC） conditions（12.7%, 15.0%, 18.0% and 20.0%, respectively）. Results showed that the root lengths of the two species were mainly concentrated in the root diameter of 5–20 mm. A comparison of root distribution between the two species indicated that the root length of black locust was significantly greater than that of Chinese pine in nearly all root diameters, although the black locust used in the comparison was 10 years younger than the Chinese pine. Root biomass was also significantly greater in black locust than in Chinese pine, particularly in the root diameters of 3–5 and 5–10 mm. These two species were both found to be deep-rooted. The triaxial compression tests showed that root cohesion was greater in the VR samples than in the HR samples. SWC was negatively related to both soil shear strength and root cohesion. These results could provide useful information on the architectural characteristics of woody root system and expand the knowledge on shallow slope stabilization and soil erosion control by plant roots on the Loess Plateau.展开更多
As a powerful tool to scan the atmosphere, the I idar can derive visibility values by directly collecting the backscattering laser light from the atmosphere. Simultaneous measurements of atmospheric visibility by Micr...As a powerful tool to scan the atmosphere, the I idar can derive visibility values by directly collecting the backscattering laser light from the atmosphere. Simultaneous measurements of atmospheric visibility by Micro-pulsed lidar （MPL） and a commercial visibility meter （VM） NQ-1 have been performed to evaluate the feasibility of the MPL system designed by the Ocean Remote Sensing Laboratory （ORSL） of the Ocean University of China （OUC） from October 21 2005 to November 21 2005 in the Shilaoren Sightseeing Garden on the Qingdao coast. All the 880 data samples obtained by the two instruments have high correlation coefficients （up to 0.86）, which indicates it is feasible to utilize MPL to measure atmospheric visibility.展开更多
In fall–winter, 2007–2013, visibility and light scattering coefficients（b sp） were measured along with PM_（2.5）mass concentrations and chemical compositions at a background site in the Pearl River Delta（PRD） r...In fall–winter, 2007–2013, visibility and light scattering coefficients（b sp） were measured along with PM_（2.5）mass concentrations and chemical compositions at a background site in the Pearl River Delta（PRD） region. The daily average visibility increased significantly（p 〈 0.01） at a rate of 1.1 km/year, yet its median stabilized at ~13 km. No haze days occurred when the 24-hr mean PM_（2.5）mass concentration was below 75 μg/m^3. By multiple linear regression on the chemical budget of particle scattering coefficient（b sp）, we obtained site-specific mass scattering efficiency（MSE） values of 6.5 ± 0.2, 2.6 ± 0.3, 2.4 ± 0.7 and 7.3 ± 1.2 m2/g,respectively, for organic matter（OM）, ammonium sulfate（AS）, ammonium nitrate（AN） and sea salt（SS）. The reconstructed light extinction coefficient（b ext） based on the Interagency Monitoring of Protected Visual Environments（IMPROVE） algorithm with our site-specific MSE revealed that OM, AS, AN, SS and light-absorbing carbon（LAC） on average contributed 45.9% ± 1.6%,25.6% ± 1.2%, 12.0% ± 0.7%, 11.2% ± 0.9% and 5.4% ± 0.3% to light extinction, respectively.Averaged b ext displayed a significant reduction rate of 14.1/Mm·year（p 〈 0.05）; this rate would be 82% higher if it were not counteracted by increasing relative humidity（RH） and hygroscopic growth factor（f（RH）） at rates of 2.5% and 0.16/year-1（p 〈 0.01）, respectively, during the fall–winter, 2007–2013. This growth of RH and f（RH） partly offsets the positive effects of lowered AS in improving visibility, and aggravated the negative effects of increasing AN to impair visibility.展开更多
Depending on various government policies,COVID-19(Corona Virus Disease-19) lockdowns have had diverse impacts on global aerosol concentrations.In 2022,Changchun a provincial capital city in Northeast China,suffered a ...Depending on various government policies,COVID-19(Corona Virus Disease-19) lockdowns have had diverse impacts on global aerosol concentrations.In 2022,Changchun a provincial capital city in Northeast China,suffered a severe COVID-19 outbreak and implemented a very strict lockdown that lasted for nearly two months.Using ground-based polarization Light Detection and Ranging(LiDAR),we detected real-time aerosol profile parameters(EC,extinction coefficient;DR,depolarization ratio;AOD,aerosol optical depth),as well as air-quality and meteorological indexes from 1 March to 30 April in 2021 and 2022 to quantify the effects of lockdown on aerosol concentrations.The period in 2022 was divided into three stages:pre-lockdown(1-10 March),strict lockdown(11 March to 10 April),and partial lockdown(11-30 April).The results showed that,during the strict lockdown period,compared with the pre-lockdown period,there were substantial reductions in aerosol parameters(EC and AOD),and this was consistent with the concentrations of the atmospheric pollutants PM_(2.5)(particulate matter with an aerodynamic diameter ≤2.5 μm) and PM_(2.5)(particulate matter with an aerodynamic diameter ≤10 μm),and the Oconcentration increased by 8.3%.During the strict lockdown,the values of EC within0-1 km and AOD decreased by 16.0% and 11.2%,respectively,as compared to the corresponding period in 2021.Lockdown reduced the conventional and organized emissions of air pollutants,and it clearly delayed the time of seasonal emissions from agricultural burning;however,it did not decrease the number of farmland fire points.Considering meteorological factors and eliminating the influence of wind-blown dust events,the results showed that reductions from conventional organized emission sources during the strict lockdown contributed to a 30% air-quality improvement and a 22% reduction in near-surface extinction(0-2 km).Aerosols produced by urban epidemic prevention and disinfection can also be identified using the EC.Regarding seasonal sources of agricultural straw burning,the concentrated burning induced by the epidemic led to the occurrence of heavy pollution from increased amounts of atmospheric aerosols,with a contribution rate of 62%.These results indicate that there is great potential to further improve air quality in the local area,and suggest that the comprehensive use of straw accompanied by reasonable planned burning is the best way to achieve this.展开更多
Lanthanum hexaboride nanopartieles, with high emission electrons in cathode materials and peculiar blocking near infrared wavelengths, were applied for many aspects. Based on the quasi-static approximation of Mie theo...Lanthanum hexaboride nanopartieles, with high emission electrons in cathode materials and peculiar blocking near infrared wavelengths, were applied for many aspects. Based on the quasi-static approximation of Mie theory, the size dependent optical prop- erties of LaB6 nanoparticles were researched, such as refractive index n（ω）, extinction coefficient k（ω）, reflectivity R（ω）, absorption coefficient a（ω）, and electron energy loss L（ω）. Due to the localized surface plasmon resonance （LSPR）, the extinction coefficient k（ω） and absorption coefficient a（ω） depended on the size, and the LSPR peaks red-shifted with sizes increased, which was different from that of bulk materials. In addition, electron energy-loss spectrum L（co） showed electrons oscillation reinforced, since electrons absorbed the photon energy and generated resonance. Further, reftectivity R（ω） and refractive index n（ω） indicated that the light in near infrared region could not be propagated on the surface of LaB6 materials, which exhibited metallic behaviors. So the resonance peak of LaB6 nanoparticle was located in near-infrared region, making use of this property for solar control glazing and heat-shielding application.展开更多
文摘At present, the use of furnaces in the northern rural areas of China is very common, due to the insufficient burning of fuel (coal, wood, etc.), carbon monoxide (CO) and other toxic gases are produced, CO colorless and odorless, difficult to find in time, and bring huge safety risks to the life and health of residents. Based on the above problems, we developed a gas monitoring and removal device which could reduce the effect of extinction coefficient. The device was composed of ash settling area, gas disturbance area, spectral absorption identification area and gas removal area. After the air entered the device, the large-size particles were first settled to purify the solid particles in the gas, the gas was disturbed through the multi-layer separator to achieve the turbulent production of the gas, and then the gas was identified through the optical element of the direct absorption spectrum technology. When the toxic gas component reached the threshold, the spray device would automatically start for chemical removal to achieve the role of purifying the gas. At the same time, the device’s alarm could be alerted by buzzer and flash to remind users to evacuate in time. By improving the optical device, the effect of extinction coefficient on measurement was reduced and the monitoring accuracy was improved.
基金Supported by Major Project of Chinese National Programs for Fundamental Research and Development(2006CB400502)National Natural Science Funds for Distinguished Young Scholar(40625015)~~
文摘[Objective] The aim was to study the dynamic variation of extinction coefficient of corn population, so as to improve the accuracy of assessment on net primary productivity （NPP） or yield. [Method] Based on the data of photosynthetic active radiation and leaf area index during corn growing season （from May to September） in 2006, observed in Jinzhou observation station of corn farmland ecosystem, China Meteorological Administration, the dynamic variation of extinction coefficient of corn population was analyzed. [Result] There was a great daily variation in the extinction coefficient of corn population during growing season, and the maximum value appeared from 7：00 to 9：00 and from 15：00 to 17：00, while the minimum could be found around 12：00, but the amplitude of variation decreased in tasseling stage. On a large time scale （5 d）, there was a parabolic relationship between extinction coefficient （K） and leaf area index （LAI）, with determination coefficient R2 of 0.960 7. The simulation equation of extinction coefficient, based on the sun elevation angle or leaf area index, had poor accuracy at various time during growing season, so a new dynamic model of extinction coefficient was established, namely K=λ（0.784 8-0.001 6θ）（0.154 8LAI2-0.558 6LAI＋0.654）. [Conclusion] The effect of sun elevation angle and leaf area index on extinction coefficient during corn growing season was considered in the new dynamic model of extinction coefficient, and its simulated result was superior to that of single-factor model.
基金supported by the Special Scientific Research Funds for Environment Protection Commonweal Section (Grant Nos 200809143 and 201009001)Knowledge Innovation Program of the Chinese Academy of Sciences (Grant No IAP09320)
文摘The objective of this study was to reconstruct light extinction coefficients （b ext ） according to chemical composition components of particulate matter up to 2.5 μm in size （PM 2.5 ）. PM 2.5 samples were collected at the monitoring station of the South China of Institute of Environmental Science （SCIES, Guangzhou, China） during January 2010, and the online absorbing and scattering coefficients were obtained using an aethalometer and a nephelometer. The measured values of light absorption coefficient by particle （b ap ） and light scattering coefficient by particle （b sp ） significantly correlated （R 2 0.95） with values of b ap and b sp that were reconstructed using the Interagency Monitoring of Protected Visual Environments （IMPROVE） formula when RH was 70%. The measured b ext had a good correlation （R 2 0.83） with the calculated b ext under ambient RH conditions. The result of source apportionment of b ext showed that ammonium sulfate [（NH 4 ） 2 SO 4 ] was the largest contributor （35.0%） to b ext , followed by ammonium nitrate （NH 4 NO 3 , 22.9%）, organic matter （16.1%）, elemental carbon （11.8%）, sea salt （4.7%）, and nitrogen dioxide （NO 2 , 9.6%）. To improve visibility in Guangzhou, the effective control of secondary particles like sulfates, nitrates, and ammonia should be given more attention in urban environmental management.
基金Project supported by National Natural Science Foundation of China （Grant No 10274080）.
文摘With the method of differential optical absorption spectroscopy （DOAS）, average concentrations of aerosol particles along light path were measured with a flashlight source in Chiba area during the period of one month. The optical thickness at 550 nm is compared with the concentration of ground-measured suspended particulate matter （SPM）. Good correlations are found between the DOAS and SPM data, leading to the determination of the aerosol mass extinction efficiency （MEE） to be possible in the lower troposphere. The average MEE value is about 7.6m^2.g^-1 , and the parameter exhibits a good correlation with the particle size as determined from the wavelength dependence of the DOAS signal intensity.
文摘The canopy light extinction coefficient （K） is a key factor in affecting ecosystem carbon, water, and energy processes. However, K is assumed as a constant in most biogeochemical models owing to lack of in-site measurements at diverse terrestrial ecosystems. In this study, by compiling data of K measured at 88 terrestrial ecosystems, we investigated the spatiotemporal variations of this index across main ecosystem types, including grassland, cropland, shrubland, broadleaf forest, and needleleaf forest. Our results indicated that the average K of all biome types during whole growing season was 0.56. However, this value in the peak growing season was 0.49, indicating a certain degree of seasonal variation. In addition, large variations in K exist within and among the plant functional types. Cropland had the highest value of K （0.62）, followed by broadleaf forest （0.59）, shrubland （0.56）, grassland （0.50）, and needleleaf forest （0.45）. No significant spatial correlation was found between K and the major environmental factors, i.e., mean annual precipitation, mean annual temperature, and leaf area index （LAI）. Intra-annually, significant negative correlations between K and seasonal changes in LAI were found in the natural {K=2/π[cosαcosθsina^-1（tanθtanα）＋（1＋cos^2a-cos^2θ^1/2）],a＋θ〉π/2 K=cosαcosθ,α＋θ≤π/2 k K is usually calculated with the Beer Lambert Law （Monsi and Sakei, 1953）：K = - In （Ii/Io） cosθ/（LAIΩ）,（2）ecosystems. In cropland, however, the temporal relation- ship was site-specific. The ecosystem type specific values of K and its temporal relationship with LAI observed in this study may contribute to improved modeling of global biogeochemical cycles.
文摘The extinction coefficient of semiconductor nanocrystals is a key parameter for understanding both the quantum confinement and applications of the nanocrystals. The existing extinction coefficients of CdE （E = Se, S） nanocrystals were found to have an unacceptable deviation for the zinc-blende CdE quantum dots （QDs）. The analysis reveals that, in addition to the interference of impurities, the commonly applied extinction coefficient per CdE nanocrystal is sensitive to the size, shape, and density of the surface ligands of nanocrystals. The extinction coefficient per CdE unit does not depend on accurate information of the size, shape, and number of surface ligands of the nanocrystals. A new three-step purification scheme was developed to investigate three classes of possible impurities for accurate determination of the extinction coefficient per CdE unit, including CdE clusters not considered previously. Given that the sole ligands of zinc-blende CdE nanocrystals are cadmium fatty acid salts （CdFa2）, a universal formula for the nanocrystals can be written as （CdE）,（CdFa2）,. The n：rn ratio was accurately determined for purified nanocrystals. The resulting extinction coefficients per unit for both CdSe and CdS QDs were found to decrease exponentially as the size of the QDs increases, with the corresponding bulk value as the large-size limit.
文摘Based on daily visibility data obtained from 1980-2002 and air pollution index data from 2001-2004 in Xi＇an, long-term variations and relationships for daily horizontal extinction coefficient and mass concentration of PM10 have been evaluated. A decreasing trend was found in horizontal extinction coefficient during the past 23 years, with higher values observed in 1980s relative to 1990s, and the highest and lowest values in winter and summer, respectively. Significant correlation and similar seasonal variations existed between horizontal extinction coefficient and PM10 concentration, suggesting the high influence of PM10 to the visibility drop at a site in the Guanzhong Plain of central China during the past two decades.
文摘Determining the optical properties of media remains an important part of scientific research. Knowledge of these optical properties, particularly absorption and diffusion coefficients, has direct applications in biomedical therapeutic diagnostics. The determination of these coefficients was previously reserved for optically dilute media. Recently, a technique called Structured Laser Illumination Planar Imaging (SLIPI) has been developed for measuring extinction coefficients in dense media. For such a medium and technique, no study has reported the determination of absorption and scattering coefficients. In this study, we have developed a simple calculation method based on the combination of Kubelka-Munk relations and extinction, both functions of the medium’s absorption and diffusion coefficients. The equations thus developed enable absorption and diffusion coefficients to be easily calculated from extinction coefficient measurements alone, using the SLIPI technique. The analysis method thus developed was applied to ten (10) milk solutions of different concentrations considered to be predominantly diffusive, and to ten (10) coffee solutions of different concentrations considered to be predominantly absorbent. The coefficient values obtained have been analysed and compared to the literature ones and they would be satisfactory.
文摘This research directly supported the author’s thesis work in partial fulfilment of Master of Science in biology from the University of North Texas(United States)from August 1996 to September 1997.Two sites at Lake Ray Roberts,Denton County,Texas(United States)were examined and contrasted for productivity.The site located in the pelagic zone exhibited a slight,thermal gradient with no stratification,and a slightly stratified clinograde oxygen profile which is typical for summer-stratified eutrophic lakes.The site located in the shallow,littoral zone exhibited high,increasing turbidity with depth,marked by shallow light attenuation through the water column.Temperature was constant at every depth in the littoral site,with a slight,clinograde oxygen profile,typical for shallow,littoral areas subject to wind-induced mixing.Volume estimations of chlorophyll-α shows a strong presence in the euphotic zone,indicating photosynthesis occurs until approximately 2.2 m below the surface.The shallow,littoral site showed the basic signs of higher productivity than the open,pelagic site.
基金supported by the National Basic Research Program of China(Grant No.2011CB403401)the National Natural Science Foundation of China(Grant No.40875084)
文摘The current paper introduces an empirical method for estimating the vertical distribution of background stratospheric aerosol extinction profiles covering the latitude bands of 50±5°N,40±5°N,30±5°N,and 20±5°N and the longitude range of 75 135°E based on Stratospheric Aerosol and Gas Experiment (SAGE) II aerosol extinction measurements at wavelengths of 1020 nm,525 nm,452 nm,and 386 nm for the volcanically calm years between 1998 2004.With this method,the vertical distribution of stratospheric aerosol extinction coefficients can be estimated according to latitude and wavelength.Comparisons of the empirically calculated aerosol extinction profiles and the SAGE II aerosol measurements show that the empirically calculated aerosol extinction coefficients are consistent with SAGE II values,with relative differences within 10% from 2 km above the tropopause to 33 km,and within 22% from 33 km to 35 km.The empirically calculated aerosol stratospheric optical depths (vertically integrated aerosol extinction coefficient) at the four wavelengths are also consistent with the corresponding SAGE II optical depth measurements,with differences within 2.2% in the altitude range from 2 km above the tropopause to 35 km.
基金supported by the National Natural Science Foundation of China (Grant No. 41275047)the National Basic Research Program of China (Grant No. 2013CB955801)the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant No. XDA05100300)
文摘This paper presents an empirical model for estimating the zonal mean aerosol extinction profiles in the stratosphere over 10°-wide latitude bands between 60°S and 60°N, on the basis of Stratospheric Aerosol and Gas Experiment(SAGE) II aerosol extinction measurements at 1.02, 0.525, and 0.452 μm during the volcanically quiescent period between 1998–2004. First, an empirical model is developed for calculating the stratospheric aerosol extinction profiles at 1.02 μm. Then, starting from the 1.02 μm extinction profile and an exponential spectral dependence, an empirical algorithm is developed that allows the aerosol extinction profiles at other wavelengths to be calculated. Comparisons of the model-calculated aerosol extinction profiles at the wavelengths of 1.02, 0.525, and 0.452 μm and the SAGE II measurements show that the model-calculated aerosol extinction coefficients conform well with the SAGE II values, with the relative differences generally being within 15% from 2 km above the tropopause to 40 km. The model-calculated stratospheric aerosol optical depths at the three wavelengths are also in good agreement with the corresponding optical depths derived from the SAGE II measurements, with the relative differences being within 0.9% for all latitude bands. This paper provides a useful tool in simulating zonal mean aerosol extinction profiles, which can be used as representative background stratospheric aerosols in view of atmospheric modeling and remote sensing retrievals.
基金This research was supported by National Natural Science Foundation of China (30371150 and 40371075).
文摘On the Loess Plateau, water is the main limiting factors for vegetation growth. Root distribution characters have special ecological meaning as it reflected the utilizations of trees to the environments. Even-aged stands ofRobinia pseudoacacia on slope lands facing south and north were selected as sampling plots for root distribution investigation. Investigatiing results showed that indicated that on all sites, root biomass decreased with depth, and the distribution depth of fine root was deeper than that of coarser root. The results of variance analysis indicated that there were great differences in root biomass among different diameter classes, and coarser root was the main sources of variance, and the root biomass, especially fine root (?<3mm) biomass on northern exposition sites was bigger than that on southern exposition sites. Analysis of the vertical root distribution parameters, root extinction coefficient, β indicated that the value of β on northern exposition was more than 0.982, while the value of β on southern exposition was less than 0.982, which indicated that the vertical root distribution depth ofRobinia pseudoacacia on southern exposition was deeper than that on southern exposition. And the distribution depth of fine roots (Φ<1mm) was deeper than that of thicker roots(Φ<3mm), which was in favor of the uptake of water and nutrients from deeper layers, helped the trees to adapt the arid environment, and promoted the growth of the upper parts of the tree. Keywords Root diameter classes - Variance analysis - Root extinction coefficient - Vertical distribution characters - Site conditions - Loess Plateau CLC number S792.27.01 Document code A Foundation Item: This research was supported by National Natural Science Foundation of China (30371150 and 40371075).Biography: LI Peng (1974-) male, post: Ph. D. in Northwest Scientific & Technological University of Agriculture and Forestry, Yangling 712100, Shaanxi Province, P. R. China. Tel: 029-82312651.Responsible editor: Chai Ruihal
基金SupportedbytheNationalNaturalScienceFoundationofChina(39970 6 2 2 )andtheTeachingandResearchAwardProgramforYongCadremanTeachersinHigherEducationInstitutionsofMOE P .R .China
文摘To know the annual water consumption of forest, it is necessary to acquire the annual transpiration value of stands. This paper is based on the data measured in the typical weather of the growth season, from 1998 to 2000, with the LI 1600 Steady Porometer and the general weather information. The daily variation of transpiration in black locust forest ( Robinia pesudoacacia L.) is modeled by Penman Monteith equation. As a result of the model, a continuous daily transpiration in the growth season was calculated. The net radiation, intercepted by black locust forest canopy, was acquired from a semi empirical equation of measuring net radiation R n with the extinction coefficient k and leaf area index LAI . The canopy integral stomatic resistance is a mimesis with an empirical equation of measuring data. Compared with measuring data, the relative error of the modeled ones is less than 12% averagely. At last, the total transpiration of black locust forest during the period of 1998 and 2000 in the growth season of May to October, as an average transpiration of the different density stands, were 192 46, 187 07 and 195 59?mm respectively.
基金supported by Sichuan Science and Technology Program (Nos. 2018SZ0316, 2018SZDZX0023)the Research on Forecasting Technology of Heavy Pollution Weather
文摘To better understand the potential causes of visibility impairment in autumn and winter in Chengdu,relative humidity(RH),visibility,the concentrations of PM2.5 and its chemical components were on-line measured continuously in Chengdu from Nov.2016 to Jan.2017.Six obvious haze episodes occurred in Chengdu,with the total time of haze episodes accounted for more than 90%of the total observation period,and higher NO2 concentrations and RH were related to the high particle concentrations in haze episodes.The visibility decreased in a non-linear tendency under different RH conditions with the increase of PM2.5 concentrations,which was more sensitive to RH under lower PM2.5 concentrations.The threshold concentration of PM2.5 got more smaller with the increase of RH.During the entire observation period,organic matter(OM)was the largest contributor(31.12%to extinction coefficient(bext)),followed by NH4NO3 and(NH4)2SO4 with 28.03%and 23.01%,respectively.However,with the visibility impairment from Type I(visibility>10 km)to Type IV(visibility≤2 km),the contribution of OM to bextdecreased from 38.12%to 26.77%,while the contribution of NH4NO3 and(NH4)2SO4 to bextincreased from 19.09%and 20.20%to 34.29%and 24.35%,respectively,and NH4NO3 became the largest contributor to bextat Type IV.The results showed that OM and NH4NO3 were the key components of PM2.5 for visibility impairment in Chengdu,indicating that the control of precursors emissions of carbonaceous species and NH4NO3 could effectively improve the visibility in Chengdu.
基金supported by the National Key Research and Development Program of China (2016YFD0300407)the earmarked fund for China Agriculture Research System (CARS-03)
文摘Improving radiation use efficiency （RUE） of the canopy is necessary to increase wheat （Triticum aesfivum） production. Tridimensional uniform sowing （U） technology has previously been used to construct a uniformly distributed population structure that increases RUE. In this study, we used tridimensional uniform sowing to create a wheat canopy within which light was spread evenly to increase RUE. This study was done during 2014-2016 in the Shunyi District, Beijing, China. The soil type was sandy loam. Wheat was grown in two sowing patterns： （1） tridimensional uniform sowing （U）; （2） conventional drilling （D）. Four planting densities were used： 1.8, 2.7, 3.6, and 4.5 million plants ha-1. Several indices were measured to compare the wheat canopies： photosynthetic active radiation intercepted by the canopy （IPAR）, leaf area index （LAI）, leaf mass per unit area （LMA）, canopy extinction coefficient （K）, and RUE. In two sowing patterns, the K values decreased with increasing planting density, but the K values of U were lower than that of D. LMA and IPAR were higher for U than for D, whereas LAI was nearly the same for both sowing patterns. IPAR and LAI increased with increasing density under the same sowing pattern. However, the difference in IPAR and LAI between the 3.6 and 4.5 million plants ha-1 treatments was not significant for both sowing patterns. Therefore, LAI within the same planting density was not affected by sowing pattern. RUE was the largest for the U mode with a planting density of 3.6 million plants ha-1 treatment. For the D sowing pattern, the lowest planting density （1.8 million plants ha-1） resulted in the highest yield. Light radiation interception was minimal for the D mode with a planting density of 1.8 million plants ha-1 treatment, but the highest RUE and highest yield were observed under this condition. For the U sowing pattern, IPAR increased with increasing planting density, but yield and RUE were the highest with a planting density of 3.6 million plants ha-1. These results indicated that the optimal planting density for improving the canopy light environment differed between the sowing patterns. The effect of sowing patternxplanting density interaction on grain yield, yield components, RUE, IPAR, and LMA was significant （P〈0.05）. Correlation analysis indicated that there is a positive significant correlation between grain yield and RUE （t=0.880, P〈0.01）, LMA （r=0.613, P〈0.05）, andspike number （t=0.624, P〈0.05）. These results demonstrated that the tridimensional uniform sowing technique, particularly at a planting density of 3.6 million plants ha-0, can effectively increase light interception and utilization and unit leaf area. This leads to the production of more photosynthetic products that in turn lead to significantly increased spike number （P〈0.05）, kernel number, grain weight, and an overall increase in yield.
基金funded by the National Natural Science Foundation of China (30872067)the Youth Foundation of Taiyuan University of Technology (2012L017, 2013T037)
文摘Black locust（Robinia pseudoacacia L.） and Chinese pine（Pinus tabulaeformis Carr.） are two woody plants that are widely planted on the Loess Plateau for controlling soil erosion and land desertification. In this study, we conducted an excavation experiment in 2008 to investigate the overall vertical root distribution characteristics of black locust and Chinese pine. We also performed triaxial compression tests to evaluate the root cohesion（additional soil cohesion increased by roots） of black locust. Two types of root distribution, namely, vertical root（VR） and horizontal root（HR）, were used as samples and tested under four soil water content（SWC） conditions（12.7%, 15.0%, 18.0% and 20.0%, respectively）. Results showed that the root lengths of the two species were mainly concentrated in the root diameter of 5–20 mm. A comparison of root distribution between the two species indicated that the root length of black locust was significantly greater than that of Chinese pine in nearly all root diameters, although the black locust used in the comparison was 10 years younger than the Chinese pine. Root biomass was also significantly greater in black locust than in Chinese pine, particularly in the root diameters of 3–5 and 5–10 mm. These two species were both found to be deep-rooted. The triaxial compression tests showed that root cohesion was greater in the VR samples than in the HR samples. SWC was negatively related to both soil shear strength and root cohesion. These results could provide useful information on the architectural characteristics of woody root system and expand the knowledge on shallow slope stabilization and soil erosion control by plant roots on the Loess Plateau.
基金supported by the National Natural Science Foundation of China(Nos.40275009 and 40405005).
文摘As a powerful tool to scan the atmosphere, the I idar can derive visibility values by directly collecting the backscattering laser light from the atmosphere. Simultaneous measurements of atmospheric visibility by Micro-pulsed lidar （MPL） and a commercial visibility meter （VM） NQ-1 have been performed to evaluate the feasibility of the MPL system designed by the Ocean Remote Sensing Laboratory （ORSL） of the Ocean University of China （OUC） from October 21 2005 to November 21 2005 in the Shilaoren Sightseeing Garden on the Qingdao coast. All the 880 data samples obtained by the two instruments have high correlation coefficients （up to 0.86）, which indicates it is feasible to utilize MPL to measure atmospheric visibility.
基金funded by Strategic Priority Research Program of the Chinese Academy of Sciences (No.XDB05010200)the Natural Science Foundation of China (Nos.41025012,41121063)the Bureau of Science,Technology and Information of Guangzhou (No.201300000130)
文摘In fall–winter, 2007–2013, visibility and light scattering coefficients（b sp） were measured along with PM_（2.5）mass concentrations and chemical compositions at a background site in the Pearl River Delta（PRD） region. The daily average visibility increased significantly（p 〈 0.01） at a rate of 1.1 km/year, yet its median stabilized at ~13 km. No haze days occurred when the 24-hr mean PM_（2.5）mass concentration was below 75 μg/m^3. By multiple linear regression on the chemical budget of particle scattering coefficient（b sp）, we obtained site-specific mass scattering efficiency（MSE） values of 6.5 ± 0.2, 2.6 ± 0.3, 2.4 ± 0.7 and 7.3 ± 1.2 m2/g,respectively, for organic matter（OM）, ammonium sulfate（AS）, ammonium nitrate（AN） and sea salt（SS）. The reconstructed light extinction coefficient（b ext） based on the Interagency Monitoring of Protected Visual Environments（IMPROVE） algorithm with our site-specific MSE revealed that OM, AS, AN, SS and light-absorbing carbon（LAC） on average contributed 45.9% ± 1.6%,25.6% ± 1.2%, 12.0% ± 0.7%, 11.2% ± 0.9% and 5.4% ± 0.3% to light extinction, respectively.Averaged b ext displayed a significant reduction rate of 14.1/Mm·year（p 〈 0.05）; this rate would be 82% higher if it were not counteracted by increasing relative humidity（RH） and hygroscopic growth factor（f（RH）） at rates of 2.5% and 0.16/year-1（p 〈 0.01）, respectively, during the fall–winter, 2007–2013. This growth of RH and f（RH） partly offsets the positive effects of lowered AS in improving visibility, and aggravated the negative effects of increasing AN to impair visibility.
基金the Key Research Program of Frontier Sciences,Chinese Academy of Sciences (No. QYZDB-SSW-DQC045)the National Natural Science Foundation of China (No. 41775116)。
文摘Depending on various government policies,COVID-19(Corona Virus Disease-19) lockdowns have had diverse impacts on global aerosol concentrations.In 2022,Changchun a provincial capital city in Northeast China,suffered a severe COVID-19 outbreak and implemented a very strict lockdown that lasted for nearly two months.Using ground-based polarization Light Detection and Ranging(LiDAR),we detected real-time aerosol profile parameters(EC,extinction coefficient;DR,depolarization ratio;AOD,aerosol optical depth),as well as air-quality and meteorological indexes from 1 March to 30 April in 2021 and 2022 to quantify the effects of lockdown on aerosol concentrations.The period in 2022 was divided into three stages:pre-lockdown(1-10 March),strict lockdown(11 March to 10 April),and partial lockdown(11-30 April).The results showed that,during the strict lockdown period,compared with the pre-lockdown period,there were substantial reductions in aerosol parameters(EC and AOD),and this was consistent with the concentrations of the atmospheric pollutants PM_(2.5)(particulate matter with an aerodynamic diameter ≤2.5 μm) and PM_(2.5)(particulate matter with an aerodynamic diameter ≤10 μm),and the Oconcentration increased by 8.3%.During the strict lockdown,the values of EC within0-1 km and AOD decreased by 16.0% and 11.2%,respectively,as compared to the corresponding period in 2021.Lockdown reduced the conventional and organized emissions of air pollutants,and it clearly delayed the time of seasonal emissions from agricultural burning;however,it did not decrease the number of farmland fire points.Considering meteorological factors and eliminating the influence of wind-blown dust events,the results showed that reductions from conventional organized emission sources during the strict lockdown contributed to a 30% air-quality improvement and a 22% reduction in near-surface extinction(0-2 km).Aerosols produced by urban epidemic prevention and disinfection can also be identified using the EC.Regarding seasonal sources of agricultural straw burning,the concentrated burning induced by the epidemic led to the occurrence of heavy pollution from increased amounts of atmospheric aerosols,with a contribution rate of 62%.These results indicate that there is great potential to further improve air quality in the local area,and suggest that the comprehensive use of straw accompanied by reasonable planned burning is the best way to achieve this.
基金supported by National Natural Science Foundation of China(60907021,60977035,60877029)Tianjin Natural Science Foundation(11JCYBJC00300)
文摘Lanthanum hexaboride nanopartieles, with high emission electrons in cathode materials and peculiar blocking near infrared wavelengths, were applied for many aspects. Based on the quasi-static approximation of Mie theory, the size dependent optical prop- erties of LaB6 nanoparticles were researched, such as refractive index n（ω）, extinction coefficient k（ω）, reflectivity R（ω）, absorption coefficient a（ω）, and electron energy loss L（ω）. Due to the localized surface plasmon resonance （LSPR）, the extinction coefficient k（ω） and absorption coefficient a（ω） depended on the size, and the LSPR peaks red-shifted with sizes increased, which was different from that of bulk materials. In addition, electron energy-loss spectrum L（co） showed electrons oscillation reinforced, since electrons absorbed the photon energy and generated resonance. Further, reftectivity R（ω） and refractive index n（ω） indicated that the light in near infrared region could not be propagated on the surface of LaB6 materials, which exhibited metallic behaviors. So the resonance peak of LaB6 nanoparticle was located in near-infrared region, making use of this property for solar control glazing and heat-shielding application.
