Size and seasonal distributions of airborne bioaerosols in commuting trains

Aerobiological studies in commuting trains in northern Taiwan were carried out from August, 2007 until July, 2008. Two six-stage (>7 μm, 4.7～7 μm, 3.3～4.7 μm, 2.1～3.3 μm, 1.1～2.1 μm, 0.65～1.1 μm) cascade impactors of 400 orifices were used to collect viable bacteria and fungi, respectively. The levels of carbon monoxide (CO), carbon dioxide (CO₂), formaldehyde (HCHO), temperature, and relative humidity in the commuting trains were also recorded during the sampling period. Results show that bacterial concentrations ranged from 25 to 1530 CFU m^?3, and averaged 417 CFU m^?3. The fungal concentrations ranged from 45 to 1906 CFU m^?3, and averaged 413 CFU m^?3. Additionally, the highest fractions occurred in the fifth stage (1.1～2.1 μm) for both bacteria and fungi. The respirable fractions, R_b and R_f, for bacteria and fungi were 62.8% and 81.4%, respectively, which are higher than those in other studies. Furthermore, the bacterial concentration reached its highest level in autumn, and its lowest level in winter. However, the fungal concentration was highest in spring and lowest in winter. Though the total bacterial or fungal concentration did not exceed the recommendation standard in Taiwan, the relatively high respirable fraction in commuting trains probably implies a higher adverse health risk for sensitive commuters. This study further conducted multiple regression analysis to determine the relationship of various stage fractions of airborne bacteria and fungi with indoor air pollutants (CO and HCHO) and environmental parameters (CO₂, temperature, and relative humidity). The correlation coefficients of multiple regression analysis for total bacteria and fungi concentrations with indoor air pollutants and environmental parameters were 0.707 (p < 0.00376) and 0.612 (p < 0.00471), respectively. There are currently no formally regulated laws for indoor air quality (IAQ) in Taiwan, and this preliminary study can provide references to the Taiwan government on IAQ management.     

太仓大气细颗粒物的粒径分布及来源分析

超大城市大气环境日益改善的同时,其周边卫星城市的大气环境将逐步得到关注.利用静电低压撞击器(ELPI)在线测量上海周边卫星城市太仓大气细颗粒物(PM2.5)粒子数浓度和质量浓度的粒径分布;结合太仓大气PM2.5样品中Ca、Ti、V、Cr、Mn、Fe、Co、Ni、Cu、Zn、As、Se、Sr、CA和Pb等15种元素的浓度...     

空气微生物研究方法进展与展望

着重论述了空气微生物气溶胶的研究方法,主要有培养基法和非培养基法。培养基法是传统的微生物研究方法,需要花费大量的时间和劳动力,只能够检测活的能够在培养基上生长的微生物,可以大致反映空气中的微生物气溶胶。非培养基法,主要是PCR法,具有敏感性高、快速、特异性强等特点,能够检测出环境样品中绝大多数的微生物,是一种微生物气溶胶检测的有效途径。最后指出实时持续的监测是将来空气微生物研究的努力方向和发展趋势。     

空气微生物研究方法进展与展望

着重论述了空气微生物气溶胶的研究方法，主要有培养基法和非培养基法。培养基法是传统的微生物研究方法，需要花费大量的时间和劳动力，只能够检测活的能够在培养基上生长的微生物，可以大致反映空气中的微生物气溶胶。非培养基法，主要是PCR法，具有敏感性高、快速、特异性强等特点，能够检测出环境样品中绝大多数的微生物，是一种微生物气溶胶检测的有效途径。最后指出实时持续的监测是将来空气微生物研究的努力方向和发展趋势。     

Size distributions and formation of dicarboxylic acids in atmospheric particles

The PM2.5 concentrations and the size distributions of dicarboxylic acids in Hong Kong were studied. Eleven sets of daily PM2.5 samples were obtained at a downtown sampling site during the period of 5–16 December 2000 using an R&P speciation PM2.5 sampler. About 6–12% of the total oxalic acid was found in the gas phase in some samples. A good correlation between succinate and sulfate (R²=0.88) and a moderate correlation between oxalate and sulfate (R²=0.74) were found. Sampling artifacts of oxalate, malonate and succinate were found to be negligible. A total of 18 sets of 48–96 h size distribution data on dicarboxylic acids, sulfate, nitrate and sodium at an urban site and a rural site from June 2000 to May 2001 were obtained using a Micro-Orifice Uniform Deposit Impactor. Data from both sites show similar size distribution characteristics of the dicarboxylic acids. The condensation mode of oxalate was usually observed at 0.177–0.32 μm. The location of the peak of the droplet mode of oxalate was associated with that of sulfate. When the peak of sulfate in the droplet mode appeared at 0.32–0.54 μm, the peak of oxalate sometimes appeared at 0.32–0.54 μm and sometimes shifted to 0.54–1.0 μm. When the peak of sulfate in the droplet mode appeared at 0.54–1.0 μm, the peak of oxalate sometimes appeared at 0.54–1.0 μm and sometimes shifted to 1.0–1.8 μm. Oxalate, succinate and sulfate found in the droplet mode were attributed to in-cloud formation. The slight shift of the oxalate peak from 0.32–0.54 to 0.54–1.0 μm or from 0.54–1.0 to 1.0–1.8 μm was ascribed to minor oxalate evaporation after in-cloud formation. The maximum peak of malonate sometimes appeared in the droplet mode and sometimes appeared at 3.1–6.2 μm. The formation of malonate is associated to the reactions between sea salt and malonic acid.     

Spatial and temporal distributions of airborne sulfate in parts of the United States

The current knowledge of the spatial and temporal distribution of airborne, water soluble sulfate is surveyed for two “scales” of atmospheric activity. The “urban” scale with episodes extending over a day or two over distances of about 100 km is illustrated for two comparable American cities, Los Angeles and New York. The regional scale with episodes extending up to several days over distances of 1000 km is exemplified by case studies in the greater eastern United States. Examination of available data reveals several features of the spatial and temporal variation in sulfate occurrence, including seasonal changes, and correlations with aerometric parameters. The importance of water vapor and air mass character on sulfate concentrations is assessed in both the urban and regional conditions. The results of initial attempts to simulate the impact of sulfur oxide emissions on ambient sulfate distributions are compared with an episode case extending over several days in July 1974.     

Size distribution and anthropogenic sources apportionment of airborne trace metals in Kanazawa,Japan

Aerosol samples were collected from Kanazawa, Japan to examine the size distribution of 12 elements and to identify the major sources of anthropogenic elements. Key emission sources were identified and, concentrations contributed from individual sources were estimated as well. Concentrations of elements V, Ca, Cd, Fe, Ba, Mg, Mn, Pb, Sr, Zn, Co and Cu in aerosols were determined with ICP-MS. The results showed that Ca, Mg, Sr, Mn, Co and Fe were mainly associated with coarse particles (>2.1 μm), primarily from natural sources. In contrast, the elements Zn, Ba, Cd, V, Pb and Cu dominated in fine aerosol particles (<2.1 μm), implying that the anthropogenic origin is the dominant source. Results of the factor analysis on elements with high EF_Crust values (>10) showed that emissions from waste combustion in incinerators, oil combustion (involving waste oil burning and oil combustion in both incinerators and electricity generation plants), as well as coal combustion in electricity generation plants were major contributors of anthropogenic metals in the ambient atmosphere in Kanazawa. Quantitatively estimated sum of mean concentrations of anthropogenic elements from the key sources were in good agreement with the observed values. Results of this study elucidate the need for making pollution control strategy in this area.     

Size distribution and anthropogenic sources apportionment of airborne trace metals in Kanazawa, Japan

Aerosol samples were collected from Kanazawa, Japan to examine the size distribution of 12 elements and to identify the major sources of anthropogenic elements. Key emission sources were identified and, concentrations contributed from individual sources were estimated as well. Concentrations of elements V, Ca, Cd, Fe, Ba, Mg, Mn, Pb, Sr, Zn, Co and Cu in aerosols were determined with ICP-MS. The results showed that Ca, Mg, Sr, Mn, Co and Fe were mainly associated with coarse particles (>2.1 μm), primarily from natural sources. In contrast, the elements Zn, Ba, Cd, V, Pb and Cu dominated in fine aerosol particles (<2.1 μm), implying that the anthropogenic origin is the dominant source. Results of the factor analysis on elements with high EF_Crust values (>10) showed that emissions from waste combustion in incinerators, oil combustion (involving waste oil burning and oil combustion in both incinerators and electricity generation plants), as well as coal combustion in electricity generation plants were major contributors of anthropogenic metals in the ambient atmosphere in Kanazawa. Quantitatively estimated sum of mean concentrations of anthropogenic elements from the key sources were in good agreement with the observed values. Results of this study elucidate the need for making pollution control strategy in this area.     

Size distribution of airborne particulate matter and associated heavy metals in the roadside environment

The size distributions of airborne particulate matter (PM) and associated heavy metals Pb, Cd, Ni, Cr, V, Mn, Cu and Fe in different inhalable fractions (< 0.8 microm, 0.8-1.3 microm, 1.3-2.7 microm, 2.7-6.7 microm and > 6.7 microm) were determined at a traffic-orientated urban site in the city of Thessaloniki, northern Greece. The airborne PM displayed a bimodal distribution with most of the mass (52%) contained in the submicron size range (< 0.8 microm) and an additional minor mode (20%) in the coarse size fraction (> 6.7 microm). Characteristic size distributions of heavy metals allowed identification of three main behavioral types: (a) metals whose mass was resided mainly within the accumulation mode (Pb,Cd), (b) those which were distributed between fine, intermediate and coarse modes (Ni,Cu,Mn), and (c) those which were mainly found within particles larger than 2.7 microm in diameter (Fe). The mean mass median aerodynamic diameter (MMAD) of PM was found at 0.85+/-0.71 microm, while the mean MMADs of heavy metals followed the order Pb (0.96 +/- 0.71 microm) < Cd (1.14 +/- 0.82 microm) < V (1.38 +/- 0.63 microm) < Ni (1.45 +/- 0.88 microm) < Cu (2.04 +/- 0.77 microm) < Mn (2.61 +/- 1.23 microm) < Cr (2.91 +/- 1.40 microm) < Fe (3.82 +/- 0.88 microm). The measured distributions are believed to result from a combination of processes including local anthropogenic and natural sources, such as traffic, industrial emissions and resuspension of road dust.     

Compartmental human respiratory tract modeling of airborne dust exposure from feeding in swine buildings

A simple size-dependent compartmental model was developed to describe airborne dust exposure dynamics for the human respiratory tract (HRT) in mechanically ventilated swine buildings. Transport mechanisms of airborne dust for HRT include respiration, gravitational settling, turbulent diffusive deposition, inertial impaction, interception deposition loss, and dust clearance. The dominant deposition mechanism in the lung regions was found to be the inertial impaction rate, in which the order of magnitude ranged from 10(-3) to 10(-1) sec(-1). Results demonstrate that the extrathoracic region has a higher airborne dust mass lung/indoor ratios (0.71-0.87) than do the bronchial regions (0.41-0.74), the bronchiolar region (0.12-0.61), and the alveolar-interstitial region (0.01-0.49). The predictions from the HRT model agreed favorably with the experimental deposition profiles in the nasal passage, pharynx, bronchial, bronchiolar, and alveolar-interstitial regions, whereas the rms errors of the total deposition fraction between predicted values and ICRP66 and Non-ICRP66 were 0.15 and 0.07, respectively. Simulation results show that breathing via the nose has both a higher deposition fraction and a higher exposure dose in the size ranges 0.01-10 microm than does breathing orally.     

Size distributions of trace metals in atmospheric aerosols in the United Kingdom

The size distributions of Ba, Cd, Co, Cu, Hg, Mn, Ni, Pb, Sn, Se, Sr, Zn and Fe in atmospheric aerosols were measured using impactors at three background sites in central England and southern Scotland. Coarse aerosols (>10.0 μm) were found to be undercollected by a micro-orifice uniform deposit impactor (MOUDI) when compared to an isokinetic technique, to a degree dependent on the size distribution of individual metals. The size distributions obtained in Scotland, which were typically trimodal, differed from those in central England, where modes were more variable.Characteristic size distributions allowed identification of three main behavioural types: (i) metals whose mass resided mainly within the accumulation mode (Cd, Sn, Pb, Se), (ii) those which were distributed between fine, intermediate and coarse modes (Ni, Zn, Cu, Co, Mn, Hg), and (iii) those which were mainly found within coarse particles (Fe, Sr, Ba). The measured distributions are believed to result from a combination of processes including local anthropogenic and natural sources, long-range transport and resuspension.     

Determination of airborne particle size distributions: Calculation of cross-sensitivity and discreteness effects in cascade impaction

A theory is developed which permits numerical evaluation of errors associated with the determination of aerosol size distributions using cascade impactors. Account is taken of errors due to the overlap of a given particle size between adjacent impaction stages and to the discrete nature of cascade impaction. The theory is applied to both log-normal and polynomial functional approximations to an aerosol size distribution.Numerical determination of errors considered shows that the mass of large and small particles present in the wings of a log-normal aerosol distribution is over-estimated manyfold by most cascade impactors but that the mass of particles having aerodynamic diameters close to the aerosol mass median diameter is generally subject to quite small (<20%) negative errors. Even under extremely unfavorable conditions the mass median diameter of an aerosol can be determined to well within 25% of the true value.     

On the use of residential thermal stations in different types of buildings

Environmental Science and Pollution Research - Increasing the level of energy efficiency and using renewable energy sources in the design and existing buildings is an important aspect in minimizing...     

上海市郊节假日大气颗粒物中碳和离子的粒径分布

由于人类节日活动,节日大气污染与平时相比有独特性,了解其污染特征对指导人类生活有重要意义。用Staplex公司分粒径的大流量采样器采集上海嘉定区2009—2010年节日(春节、劳动节、中秋节、国庆节)及相应临近非节日(以下简称非节日)的大气颗粒物样品,分析了颗粒物中主要化学组分的节日特征。在所研究的4个节日中,春节由于受到大量烟花爆竹燃放的影响,节日效应最为严重,且其影响主要在细粒径段(3.00μm)。春节细粒径段颗粒物质量浓度、有机碳和元素碳质量浓度分别为99.2、30.2、9.5μg/m3,与非节日的比值分别为1.5、2.6、3.4;而影响最严重的离子是K+和Mg2+,其与非节日的比值分别为29.0和23.7。总体而言,春节颗粒物浓度最高和化学组分污染最严重,其次是劳动节、国庆节、中秋节。     

Size distribution and seasonal variation of airborne particulate matter in five areas in Istanbul,Turkey

Goal, scope, and background  

Many studies have focused on measuring fine and course particulate matter (PM) in urban and rural sites around the world. The aim of this research is to gain information on the size distribution of particles. The physical characteristics of PM in the urban air of Istanbul were determined.     

Degradation of metribuzin in two soil types of Lebanon

The degradation of metribuzin [4-amino-6-tert-butyl-3-methylthio-1,2,4-triazin-5(4H)-one] as influenced by soil type, temperature, humidity, organic fertilizers, soil sterilization, and ultra-violet radiation was studied in two soil types of Lebanon under laboratory conditions. The two soil types were sandy loam and clay. Deamination of metribuzin in the sandy loam soil to its deaminometribuzin (DA) derivative was basically a result of biological activity. In the clay soil the first metabolite diketometribuzin (DK) was a result of oxidative desulfuration, while diketo-deaminometribuzin (DADK) was the product of reductive deamination. The two soils represented major differences in the pesticide transformation processes. Photodecomposition on the soil surface and in aqueous media was also an important process in the degradation of metribuzin. Furthermore, the increase in soil organic matter enhanced degradation.     

Size and composition distributions of particulate matter emissions: part 1--light-duty gasoline vehicles

Size-resolved particulate matter (PM) emitted from light-duty gasoline vehicles (LDGVs) was characterized using filter-based samplers, cascade impactors, and scanning mobility particle size measurements in the summer 2002. Thirty LDGVs, with different engine and emissions control technologies (model years 1965-2003; odometer readings 1264-207,104 mi), were tested on a chassis dynamometer using the federal test procedure (FTP), the unified cycle (UC), and the correction cycle (CC). LDGV PM emissions were strongly correlated with vehicle age and emissions control technology. The oldest models had average ultrafine PM0.1 (0.056- to 0.1-microm aerodynamic diameter) and fine PM1.8 (< or =1.8-microm aerodynamic diameter) emission rates of 9.6 mg/km and 213 mg/km, respectively. The newest vehicles had PM0.1 and PM1.8 emissions of 51 microg/km and 371 microg/km, respectively. Light duty trucks and sport utility vehicles had PM0.1 and PM1.8 emissions nearly double the corresponding emission rates from passenger cars. Higher PM emissions were associated with cold starts and hard accelerations. The FTP driving cycle produced the lowest emissions, followed by the UC and the CC. PM mass distributions peaked between 0.1- and 0.18-microm particle diameter for all vehicles except those emitting visible smoke, which peaked between 0.18 and 0.32 microm. The majority of the PM was composed of carbonaceous material, with only trace amounts of water-soluble ions. Elemental carbon (EC) and organic matter (OM) had similar size distributions, but the EC/OM ratio in LDGV exhaust particles was a strong function of the adopted emissions control technology and of vehicle maintenance. Exhaust from LDGV classes with lower PM emissions generally had higher EC/OM ratios. LDGVs adopting newer technologies were characterized by the highest EC/OM ratios, whereas OM dominated PM emissions from older vehicles. Driving cycles with cold starts and hard accelerations produced higher EC/OM ratios in ultrafine particles.