Development of a new aerosol monitoring system and its application in Fukushima nuclear accident related aerosol radioactivity measurement at the CTBT radionuclide station in Sidney of Canada

A high volume aerosol sampler ("Grey Owl") has been designed and developed at the Radiation Protection Bureau, Health Canada. Its design guidance is based on the need for a low operational cost and reliable sampler to provide daily aerosol monitoring samples that can be used as reference samples for radiological studies. It has been developed to provide a constant air flow rate at low pressure drops (∼3 kPa for a day sampling) with variations of less than ±1% of the full scale flow rate. Its energy consumption is only about 1.5 kW for a filter sampling over 22,000 standard cubic meter of air. It has been demonstrated in this Fukushima nuclear accident related aerosol radioactivity monitoring study at Sidney station, B.C. that the sampler is robust and reliable. The results provided by the new monitoring system have been used to support decision-making in Canada during an emergency response.     

Performance of data acceptance criteria over 50 months from an automatic real-time environmental radiation surveillance network

The automatic real-time environmental radiation surveillance network of Catalonia (Spain) comprises two subnetworks; one with 9 aerosol monitors and the other with 8 Geiger monitors together with 2 water monitors located in the Ebre river. Since September 2006, several improvements were implemented in order to get better quality and quantity of data, allowing a more accurate data analysis. However, several causes (natural causes, equipment failure, artificial external causes and incidents in nuclear power plants) may produce radiological measured values mismatched with the own station background, whether spurious without significance or true radiological values. Thus, data analysis for a 50-month period was made and allowed to establish an easily implementable statistical criterion to find those values that require special attention. This criterion proved a very useful tool for creating a properly debugged database and to give a quick response to equipment failures or possible radiological incidents. This paper presents the results obtained from the criterion application, including the figures for the expected, raw and debugged data, percentages of missing data grouped by causes and radiological measurements from the networks. Finally, based on the discussed information, recommendations for the improvement of the network are identified to obtain better radiological information and analysis capabilities.     

Analysis of surface and aerosol polarized reflectance for aerosol retrievals from polarized remote sensing in PRD urban region

A precise estimate of polarization induced by surface is crucial for polarized remote sensing dedicated to monitoring aerosol properties over urban area. The accurate knowledge of interaction between surface and aerosol polarized reflectance is essential for accurately achieving aerosol properties. In order to study surface and aerosol polarized reflectance for aerosol retrievals over urban area, a new airborne directional polarimetric camera (DPC) with high spatial resolution (4 m at 4000 m a.g.l) was developed. The surface polarized reflectance over distinct surface covers of urban area (forest, shrub, and soil) were studied using DPC measurements during a field campaign in the Pearl River Delta (PRD), China. The large variations were found in surface polarized reflectance of distinct urban covers due to surface type variability. For all surface types, the empirical BPDF model cannot describe accurately surface polarized reflectance at all possible illumination and observation geometries. From the quantitatively study of relationship between surface and aerosol polarized contribution to DPC measurements, we show that the polarized contributions of aerosol, which optical properties were defined by ground-based measurements, are much larger than the polarized contribution of surface, and found that the polarized contribution of surface covers increases with decreasing NDVI. The effect of polarization accuracy of measurements on aerosol retrieval was also investigated using DPC measurements, and found that 0.1% polarization accuracy of measurements can be neglected when AOD is retrieved using polarized measurements. Based on the information of effects of polarized reflectance differences between distinct surface covers and polarization accuracy of polarized measurements on retrieved aerosols over urban area, we found that the accuracy of aerosol retrieval over forest covers is higher than other surface types using polarized remote sensing.     

Regional differences of column-related aerosol parameters in Germany

With the development of satellite experiments supplementary and validating ground-based measurements are gaining growing importance for the inference and evaluation of radiation-related aerosol parameters. Both kinds of measurements have been conducted and interpreted mainly under globally or locally restricted aspects for a limited time period only. Results are presented from four rural regions (coastal zone, lowlands, highlands, high mountain); they are column-related aerosol parameters, deduced from monitoring programs of spectral aerosol optical depth (AOD) as well as almucantar sky irradiance measurements. After 13 years of continuous measurements of trends and variations in aerosol optical depths, these results are based on 5 years of data collection (1994–1998). There are significant differences among the parameters of the four regions when related to the inversion method of the AOD spectra. A clear interdependence was found between all column-related parameters and the real part of the refractive index, which in turn depends on the chosen retrieval method. The differences among the four regions are characterized mainly by their different altitudes, with relative humidity being responsible for their internal variation. An increase in the relative humidity from 35 to 55–60% influences the most interesting parameters such as refractive index (real part), hemispheric backscattered fraction b, and direct radiative forcing ΔF as follows: The real part of the refractive index decreases from 1.6±0.05 to 1.42±0.04, b decreases by 8–10%, and, due to the increase in AOD, ΔF increases by about 20% in the spectral region 0.4–1.0 μm. The quantities of the parameters depend on the retrieval methods too.     

太湖上空大气气溶胶光学厚度及其特征分析

基于高精度的太阳光度计(CE-318)得到太湖上空气溶胶长期观测数据,获得了太湖上空从2005年9月～2010年10月的气溶胶光学厚度(AOT)以及相应的ngstrm参数α.5 a的观测资料表明,太湖上空AOT的高值区出现在夏季的6～7月,低值区出现在秋冬季节的10月～次年1月;α的低值区和高值区分别出现在春季的3～4月和秋季的9～11月,AOT及对应的α的变化主要与该地区的天气形势有关.从频率分布来看,AOT(500 nm)只有一个峰值,最高频率值为0.4～0.6,约占总样本的26%,年均值为0.80.按照平均AOT(500 nm)计算,气溶胶造成的太阳直射辐射的透过率衰减至少为50%,致使太湖地区的大气较为混浊,形成严重的雾霾天气;ngstrm波长指数α有2个峰值,最高频率区间为1.1～1.3和1.3～1.5,分别占总样本的30%,年平均值为1.17.结果还表明AOT(500 nm)和α的日均值变化范围均较大,表明太湖上空有不同类型的气溶胶粒子共存;当α增大时,AOT(500 nm)的均值呈递减趋势.总体结果分析表明,太湖上空的AOT值随时间变化较大,属于城市-工业型气溶胶类型.     

Application of an aerosol electrical mobility spectrum analyzer: Charged-particle polarity ratio measurement in the Antarctic and Arctic regions

An aerosol electrical mobility spectrum analyzer (AEMSA), developed at Hanyang University, was employed to investigate the particle charge characteristics in the Antarctic and Arctic regions. The particle charge characteristics in these areas were compared with the charging state in Ansan, South Korea, located in the midlatitude, where artificial factors, such as human activity, urbanization, and traffic, might result in a higher total concentration. Furthermore, in Ansan, South Korea, the charged-particle polarity ratio was very stable and was close to 1. However, notably different particle charge characteristics were obtained in the Antarctic and Arctic regions. The imbalance between the numbers of positively and negatively charged particles was evident, resulting in more positive charges on the atmospheric particles. On average, the positively charged particle concentrations in the Antarctic and Arctic areas were 1.4 and 2.8 times higher, respectively, compared with the negatively charged particles. The developed AEMSA system and the findings of this study provide useful information on the characteristics of atmospheric aerosols in the Antarctic and Arctic regions and can be further utilized to study particle formation mechanisms.     

Aerosol optical properties and the mixing state of black carbon at a background mountainous site in Eastern China

In-situ measurements of aerosol optical properties were conducted at Mt. Huang from September 23 to October 28, 2012. Low averages of 82.2, 10.9, and 14.1 Mm~(-1) for scattering coefficient(σ_(sp, neph, 550)), hemispheric backscattering coefficient(σ_(hbsp, neph, 550)), and absorption coefficient(σ_(ap, 550)), respectively, were obtained. Atmospheric aging process resulted in the increase of σap, 550 but the decrease of the single scattering albedo(ω_(550)) at constant aerosol concentration. However, the proportion of non-light-absorbing components(non-BCs) was getting higher during the aging process, resulting in the increase of aerosol diameter, which also contributed to relatively higher σ_(sp, neph, 550) and ω_(550). Diurnal cycles of σ_(sp, neph, 550) and σ_(ap, 550) with high values in the morning and low values in the afternoon were observed closely related to the development of the planetary boundary layer and the mountain-valley breeze. BC mixing state, represented by the volume fraction of externally mixed BC to total BC(r), was retrieved by using the modified Mie model.The results showed r reduced from about 70% to 50% when the externally mixed non-BCs were considered. The periodical change and different diurnal patterns of r were due to the atmospheric aging and different air sources under different synoptic systems. Local biomass burning emissions were also one of the influencing factors on r. Aerosol radiative forcing for different mixing state were evaluated by a "two-layer-single-wavelength" model,showing the cooling effect of aerosols weakened with BC mixing state changing from external to core-shell mixture.     

Size-resolved carbonaceous components and water-soluble ions measurements of ambient aerosol in Beijing

A MOUDI-120 sampler was used in Beijing to collect multi-stage samples in the summer and winter of 2013 to 2015. Thirty-three sample sets were collected during the daytime,nighttime, and different pollution levels. The actual relative humidity in the impactors was calculated for the first time. The carbonaceous components(organic and elemental carbon,OC and EC, respectively) and water-soluble inorganic ions(Na~+, NH_4~+, K~+, Mg~(2+), Ca~(2+), Cl~-, NO_3~-,and SO_4~(2-)) were analyzed in each sample. The characteristics of the mass concentration distribution and charge balance were discussed. On the basis of relative humidity in the impactors, aerosols less than 1.0 μm were sampled under relatively dry conditions in most cases. The concentration levels for the chemical species were higher in the winter than in the summer. Three modes(condensation mode, droplet mode, and coarse mode) could be identified from the distributions of NH_4~+, NO_3~-, SO_4~(2-), Cl~-, K~+, OC and EC. The distribution characteristics for the pollution dissipation process were different from the pollution accumulation process. NO_3~-and NO_2~-contributed most of the negative electric charges in the stage below 0.1 μm. In the condensation mode, the cations were dominated by NH_4~+, which was sufficient to balance the anions. In the droplet mode of the heavily polluted samples,the ammonium was not sufficient to balance the anions. In the coarse mode, the positive electric charges were primarily composed of metal cations. The analyzed anions were not sufficient to neutralize the measured cations.     

The characterization of heat transfer fluid P-NF aerosol combustion: Ignitable region and flame development

Heat transfer fluids tend to form aerosols due to the operating conditions at high pressure when accidental leaking occurs in pipelines or storage vessels, which may cause serious fires and explosions. Due to the physical property complexity of aerosols, it is difficult to define a standard term of “flammability limits” as is possible for gases. The study discussed in this paper primarily focuses on the characterization of ignition conditions and flame development of heat transfer fluid aerosols. The flammable region of a widely-used commercial heat transfer fluid, Paratherm NF (P-NF), was analyzed by electro-spray generation with a laser diffraction particle analysis method. The aerosol ignition behavior depends on the droplet size and concentration of the aerosol. From the adjustment of differently applied electro-spray voltages (7–10 kV) and various liquid feeding rates, a flammable condition distribution was obtained by comparison of droplet size and concentration. An appropriate amount (0.3–1.2 ppm) of smaller droplets (80–110 μm) existing in a given space could result in successful flame formation, while larger droplets (up to 190 μm) have a relatively narrowed range of flammable conditions (0.7–0.9 ppm). It is possible to generate a more useful reference for industry and lab scale consideration when handling liquids. This paper provides initial flammability criteria for analyzing P-NF aerosol fire hazards in terms of droplet size and volumetric concentration, discusses the observation of aerosol combustion processes, and summarizes an ignition delay phenomenon. All of the fundamental study results are to be applied to practical cases with fire hazards analysis, pressurized liquid handling, and mitigation system design once there is a better understanding of aerosols formed by high-flash point materials.     

对大气气溶胶降尘与降雨相关性分析的探讨

为了了解大气气溶胶降尘与降水的关系,本文通过对例行监测数据进行统计整理,并进行相关性检验分析,得出大气气溶胶降尘与降水pH值具有一定的相关性,且呈正相关,降水pH值与降雨量、降尘与降雨量之间则无相关性。