Measurement of resuspended aerosol in the Chernobyl area

Results of measurements of the resuspended radioactive aerosols in the Chernobyl area are presented which were obtained soon after the Chernobyl reactor accident and in a European project in 1992–1993. The measurements were carried out with the intention of obtaining a data base for dose assessment of resuspended radioactive particles. Potential significant dose contributions may result from inhalation and secondary contamination due to resuspended radionuclides. In this first article of a series of three papers, the instrumentation and the measurement uncertainties are discussed. An effort was made to sample quantitatively giant aerosol particles (particles larger than 10 μm aerodynamic diameter) as well. The comparison of the samplers shows, in general, an agreement of concentration measurements of ¹³⁷Cs and ⁷Be within a factor of two. One sampler was identified with larger discrepancies and needs additional investigation of its sampling characteristics; for another device, the recalibration of the analysing system is recommended. Ordinary integrating samplers have a loss of about 30% in ¹³⁷Cs activity compared to an isokinetic sampler collecting giant particles as well. The mean ratio of ¹³⁷Cs activity concentration between an instrument sampling only particles larger than 10 μm and an ordinary integrating sampler is 0.39 ± 0.15 during anthropogenic-enhanced resuspension. These findings demonstrate the significant contribution of giant particles to resuspended airborne radioactivity. The results of this study concerning integral measurements during wind-driven resuspension proved to be in good agreement with previously published data on resuspension. Received: 15 May 1997 / Accepted: 4 August 1997     

Measurement of resuspended aerosol in the Chernobyl area

Size distribution measurements of particulate radionuclides were performed at two sites in the Chernobyl 30-km exclusion zone using several cascade impactors. The results obtained in the period September 1986 till June 1993 were discussed with regard to the general assumption of a log-normal activity size distribution in inhalation dose assessment. At Zapolie (a site 14 km from the Chernobyl reactor) a bimodal distribution was observed in 91% of all measured distributions. In most cases the medians were about 4 µm and in the range 20–30 µm. According to soil granulometric data this finding was explained by superimposing two processes: local resuspension and advective transport of radioactive aerosol from highly contaminated territories. The mean air concentration showed an increasing proportion of inhalable particles over the years since the accident. In 1993 the inhalable fraction was about 48% of the total concentration. At Pripyat, a site situated within a highly contaminated area, unimodal types of size distributions were predominant with the median diameters in the range 5–10 µm for ¹³⁷Cs. For the three nuclides ¹³⁷Cs, ¹⁴⁴Ce and ¹⁰⁶Ru, very similar types of distribution were observed. Apparently, the radioactive aerosol was of fuel origin. During a forest fire at a distance of 17 km, the majority of the radioactivity was associated with submicrometer particles with median diameters in the range 0.28–0.50 µm.     

Measurement of resuspended aerosol in the Chernobyl area

During anthropogenic activities, such as agricultural soil management and traffic on unpaved roads, size distribution measurements were performed of atmospheric particulate radionuclides at a site in the Chernobyl 30-km exclusion zone. Analysis of cascade impactor measurements showed an increase of the total atmospheric radioactivity. In the cases of harrowing by a tractor and traffic on unpaved roads, a common shape of the size distribution was found with two maxima, the first in the 2–4 μm range, the second in the 12–20 μm range. The size distributions were compared to measurements during wind-driven resuspension. Particle number concentration measurements with an Aerodynamic Particle Sizer showed a dynamic dependence of the particle concentration in different size ranges on anthropogenic action. The increase of the mean concentration was for the large particles more than one order of magnitude higher than for fine particles during anthropogenic enhanced resuspension. From the measurement of the mass concentration, the radioactive loading could be estimated. An enrichment of radionuclides on resuspended particles (compared to soil particles) was found, with the highest enrichment for large particles. Micrometeorological considerations showed that large particles may frequently be subject to medium range transport. The dry deposition velocity was measured; the mean value of 0.026 m s^–1±0.016 m s^–1 is typical for 6–9 μm diameter particles. Received: 17 February 1998 / Accepted in revised form: 17 June 1998     

Measurement of the ice nucleation activity ofPseudomonas syringae CCM 4073

Summary The ice nucleation activity of the bacteriumP. syringae CCM 4073 was determined by a drop freezing technique and expressed through the relative freezing nucleus spectrum — fraction of nucleation active cells vs temperature. The spectrum was found to be independent of cell concentration, quite stable within periods of the order of 1 h, and step-wise, the steps being most conspicuous at –5°C and –9°C.     

Hazardous components and health effects of atmospheric aerosol particles: reactive oxygen species,soot, polycyclic aromatic compounds and allergenic proteins

Abstract

This review outlines recent advances in the investigation of the chemical properties, molecular interactions and health effects of hazardous compounds in atmospheric aerosols, in particular reactive oxygen species (ROS), soot, polycyclic aromatic compounds (PACs) and allergenic proteins. Epidemiological studies show correlations between air particulate matter and adverse health effects of air pollution including allergy, asthma, cardiovascular and respiratory diseases, but the causative relations and mechanisms of interaction on the molecular level are still unclear. ROS generated by photochemical and heterogeneous reactions in the atmosphere seem to play a key role in aerosol health effects and provide a direct link between atmospheric and physiological multiphase processes. Soot and PACs can trigger formation of ROS in vivo, leading to inflammation and cellular damage. PACs as well as allergenic proteins are efficiently oxygenated and nitrated upon exposure to ozone and nitrogen dioxide, which leads to an enhancement of their toxicity and allergenicity.     

Hazardous components and health effects of atmospheric aerosol particles: reactive oxygen species, soot, polycyclic aromatic compounds and allergenic proteins

This review outlines recent advances in the investigation of the chemical properties, molecular interactions and health effects of hazardous compounds in atmospheric aerosols, in particular reactive oxygen species (ROS), soot, polycyclic aromatic compounds (PACs) and allergenic proteins. Epidemiological studies show correlations between air particulate matter and adverse health effects of air pollution including allergy, asthma, cardiovascular and respiratory diseases, but the causative relations and mechanisms of interaction on the molecular level are still unclear. ROS generated by photochemical and heterogeneous reactions in the atmosphere seem to play a key role in aerosol health effects and provide a direct link between atmospheric and physiological multiphase processes. Soot and PACs can trigger formation of ROS in vivo, leading to inflammation and cellular damage. PACs as well as allergenic proteins are efficiently oxygenated and nitrated upon exposure to ozone and nitrogen dioxide, which leads to an enhancement of their toxicity and allergenicity.     

Influence of steroid aerosol treatments on the clearance of inhaled gold particles

Female Long Evans rats were used to test the hypothesis that inhaled triamcinolone acetonide accelerates the rate of clearance of particles from the lung. Three groups of animals inhaled a radioactive gold aerosol, which functioned as a tracer of respiratory tract clearance, and then were subjected to various inhalation treatments. The group treated with triamcinolone acetonide aerosol showed a significant acceleration in the rate of early clearance, but the total amount of tracer particles cleared in the first day was not significantly increased. Inhaled triamcinolone acetonide appears to accelerate the translocation of foriegn particles from small airways to larger ones, but stimulation of clearance does not appear to be a large effect.     

The size distribution of primary biological aerosol particles in the multiphase atmosphere

Primary biological aerosol particles are a ubiquitouscomponent of the atmospheric aerosol and have greatimportance within the whole atmosphere. Besides theireffect on air hygiene (i.e. causing allergic diseases), theycontribute to cloud and rain development. They amountto almost 25% of the total number of aerosolparticles both in dry air and in cloudwater. They showno seasonal variation in concentration but incomposition.     

Measurement of the electrochemical proton gradient in submitochondrial particles

The pH gradient and membrane potential of submitochondrial particles from bovine heart were estimated by the uptake of [14C]ethylamine and [36Cl]perchlorate, using filtration through a glass fiber prefilter and Millipore filter without washing to separate the vesicles from the medium. An external volume probe of [3H] sucrose was also used. Internal volume of the vesicles was measured by the extent of uptake of glucose, which equilibrates slowly across the membrane. The electrochemical potential gradient of H+ (delta micro H+) calculated from uptake of ethylamine and perchlorate, assuming the ions taken up were free in solution inside the vesicles, was 23 to 24 kJ/mol of H+ (240-250 mV) during respiration in the absence of ATP. The ratio of the free energy of ATP synthesis (delta GATP) to delta micro H+ was 2.2 to 2.3 during oxidative phosphorylation and only slightly higher during ATP hydrolysis indicating that the H+-translocating ATPase is close to equilibrium under both conditions. The nonintegral ratio suggests there is a systematic error in the measurement of delta micro H+. The value of delta micro H+ calculated from ion uptake could be too high if some of the ions taken up are bound to the membrane or concentrated into the electric double layer at the inner membrane-water interface. The effects of vesicle volume (varied osmotically) and permeant ions (which affect internal ionic strength and pH) on the ratio of delta GATP to delta micro H+ suggested that ion association with the membrane in fact caused significant overestimation of delta micro H+. Association of ethylammonium and perchlorate ions with unenergized submitochondrial particles was measured by centrifugation, in the presence of a high concentration of impermeant salt to minimize association with the external surface. The results were used to estimate the extent of binding during the ion uptake assays, and delta micro H+ was recalculated taking this binding into account. The resulting values were between 19 and 20 kJ/mol of H+ (197-207 mV) during respiration in the absence of ADP, and the ratio of delta GATP to delta micro H+ was about 3 during oxidative phosphorylation.     

Determination of concentrations of elements in the atmospheric aerosol of the urban and rural areas of beijing in winter

The proton-induced X-ray emission technique is one of the most suitable methods in the study of the multielement content of atmospheric aerosols. Atmospheric aerosol samples were collected in winter using an eight-stage cascade impactor at a site of the urban center and a rural site of Beijing. The aerosol samples collected were analyzed to determine maximum, minimum, and average concentrations of up to 20 elements and the ratios of the average element concentrations for the coarse to fine particles (C/F) by the PIXE technique. It has been found that the average elemental concentrations in the urban center are higher than those in the rural area, except S and Br. The concentrations for S and Pb in the atmospheric aerosols are found to be less than the results of previous measurement, but their concentrations in the fine particles increased in winter in the samples from the urban center. The deposition probability of the International Commission on Radiological Protection (ICRP) mode and the mass particle-size distributions of the elements determined in the urban center have been utilized to evaluate inhalable particulate matter fractions retained in the three regions of one’s respiratory tract and their harm to human health is discussed.     

Detection of genotoxicity of atmospheric particles using a high-throughput microplate umu-test system

A previously developed and highly sensitive umu-microplate test system based on the nitroreductase- and O-acetyltransferase-overproducing strain Salmonella typhimurium NM3009 and the O-acetyltransferase-overproducing strain S. typhimurium NM2009 was applied to the detection of genotoxic activity in atmospheric particles in urban areas using a relatively small sample load. The results showed that the test system was able to detect slight increases in induced genotoxicity in atmospheric particles and that genotoxicity was detected mainly in the fine fraction but also partially in the coarse fraction. The present sensitive microplate test system has potential for application to the screening of various other environmental samples.     

On the direct effect of clouds and atmospheric particles on the productivity and structure of vegetation

The volume of shade within vegetation canopies is reduced by more than an order of magnitude on cloudy and/or very hazy days compared to clear sunny days because of an increase in the diffuse fraction of the solar radiance. Here we show that vegetation is directly sensitive to changes in the diffuse fraction and we conclude that the productivity and structure of vegetation is strongly influenced by clouds and other atmospheric particles. We also propose that the unexpected decline in atmospheric [CO₂] which was observed following the Mt. Pinatubo eruption was in part caused by increased vegetation uptake following an anomalous enhancement of the diffuse fraction by volcanic aerosols that would have reduced the volume of shade within vegetation canopies. These results have important implications for both understanding and modelling the productivity and structure of terrestrial vegetation as well as the global carbon cycle and the climate system.     

两种常见绿化树种对大气颗粒物的滞留与再悬浮

植物叶片对大气颗粒物的作用机制可分为吸附、再悬浮、雨水淋洗、吸收等过程,但却少有研究探讨大气颗粒物沉降于叶片表面后的再悬浮过程,并对叶片表面吸附的颗粒物含量与叶片内部元素含量之间的相关性进行探讨.本研究选择二球悬铃木和广玉兰两种常见绿化树种,分析其叶表大气颗粒物和叶内元素成分与含量及再悬浮比例.结果表明: 二球悬铃木叶片的单位面积滞尘量(4.98 g·m^-2)明显高于广玉兰(2.65 g·m^-2),这可能与二球悬铃木叶片上下表面均粗糙、有绒毛有关.电感耦合等离子体发射光谱(ICP)分析表明,15种不同的元素均可在二球悬铃木和广玉兰叶表和叶内监测出来,在整体上两树种叶表与叶内元素含量间存在明显的相关性.但仅有Cr、Fe、V等 3种元素在二球悬铃木叶表与叶内间存在显著的相关性,而广玉兰中仅有K、Mn、Si、Ti和Zn 等5种元素没有显著的相关性,说明两树种叶片对不同元素的吸收具有较强的选择性.再悬浮分析表明,无论是随着风速的增加还是随着风力作用时间的延长,大气颗粒物的再悬浮比例均随之显著增加.在研究植物对大气颗粒物滞留效果时,必须考虑到颗粒物的再悬浮,才能准确评估植被与大气颗粒物的沉降关系.     

北京市湿地削减大气细颗粒物PM_(2.5)功能

基于野外观测与遥感反演相结合的方法,在点位和区域尺度上研究北京城区湿地在削减大气细颗粒物PM2.5中的作用。结果表明,北京城区湿地能够显著削减周边大气环境中的细颗粒物浓度,其中翠湖湿地附近的PM2.5浓度显著低于周边裸地(P0.05),可削减空气中17%的PM2.5,降低幅度最高可达50%。而且,湖库湿地在削减PM2.5浓度方面作用更加显著,优于河流湿地(P0.05)。北京市PM2.5浓度的空间分布格局表现出西北东南、郊区城区的空间分布规律。因此,在未来的湿地建设中应合理选择湿地类型,更多地考虑紧凑型湿地如湖库湿地的建设,科学配置湿地和植物资源,使湿地更加有效地发挥其增湿、促使局地流场发生变化的作用,最终改善局地微气象条件,削减大气细颗粒物,缓解城市雾霾天气。研究结果为北京市湿地保护管理、规划和布局以及及时制定控制PM2.5的政策和措施提供了科学依据。