Indoor/outdoor relationships of airborne ionic substances: Comparison of electronic equipment room and factory environments

In previous work, the indoor and outdoor airborne concentrations and indoor surface accumulation rates of ionic substances contained in fine (<2.5) and coarse (2.5–15 μm) particles were determined for low-occupancy electronic equipment rooms. This work has now been extended to an electronic equipment manufacturing environment.Comparison of indoor and outdoor concentrations at the manufacturing facility for both fine and coarse particles show substantially different behavior from that seen for the electronic equipment rooms.As was found previously, the dominant species in fine particles are ammonium and sulfate, which closely track each other. Their indoor and outdoor concentrations also track, but the indoor/outdoor ratios are larger by a factor of 4–5 than those found for the electronic equipment rooms. Sodium shows tracking behavior similar to ammonium and sulfate and its indoor/outdoor ratio is also large. Other ions in fine particles show elevated indoor/outdoor ratios for some sampling intervals and tracking is not evident, thought it may be masked by the large fractional error associated with species with low concentrations. There is no dominant species in the coarse fraction. Sodium and chloride track each other strongly indoors and outdoors and the indoor and outdoor concentrations of each track closely. Potassium, as well as chloride, exhibit indoor/outdoor ratios that are sometimes much larger than 1.Modelling of indoor/outdoor relationships using a mass-balance model has shown that indoor concentrations can be accurately predicted from outdoor concentrations for species with no indoor sources. The model also shows that the source generation rates for fine and coarse particles indoors range from 0 to 6.6 and 2.3 to 5.8 mg min⁻¹, respectively, for a room with a volume of 6336m³.     

苏州工业园区室内外颗粒物中多溴联苯醚污染特征及人体暴露水平

利用大流量主动采样技术在苏州市工业园区工厂车间、办公室、住宅区和风景区,采集PM₁₀样品,GC-MS测定PM₁₀中8种PBDEs的含量.室内PM₁₀中PBDEs总浓度范围为9.22~64.15 pg·m^-3（均值为20.93 pg·m^-3）,室外样品中PBDEs总浓度范围为1.06~8.44 pg·m^-3（均值为5.11 pg·m^-3）,室内含量显著高于室外含量.PM₁₀中∑₈PBDEs平均浓度从高到低顺序依次为工业车间、办公室、住宅区和室外大气,与其他地区室内外颗粒物含量相比,苏州室内外大气颗粒物中PBDEs都处于较低水平.室内外大气中BDE-209是最主要化合物（平均占总PBDEs的63%）,其次为BDE-99和BDE-47.车间员工、办公室员工和儿童的PBDEs日呼吸摄入剂量分别为3.75、2.78和2.60 pg·（kg·d）^-1,这表明苏州居民呼吸暴露PBDEs的潜在健康危害并不明显.     

Scavenging ratios and deposition of sulphur,nitrogen and chlorine species in eastern England

Measurements of wet deposited NH₄⁺, SO₄²⁻, NO₃⁻ and Cl⁻, as well as airborne concentrations of these species and gaseous HNO₃, HCl and NH₃, have been made at a site in eastern England. Scavenging ratios based solely upon aerosol-associated species and upon aerosol plus gaseous airborne species are presented and compared with literature values. It appears that HCl and HNO₃ have only a rather minor influence upon wet deposition at our site. Gaseous NH₃ influences ground-level air chemistry appreciably, but scavenging ratios for NH₄⁺ are low, even when based upon aerosol NH₄⁺ concentrations alone, presumably due to altitudinal gradients in this species. The problems inherent in interpretation of scavenging ratios are discussed. Deposition of nitrogen in various chemical forms is estimated from rainwater and air composition. If a transport-limited deposition velocity is assumed for ammonia gas, dry deposition of this species accounts for around 40% of total nitrogen deposition to the ground.     

Atmospheric concentrations and deposition of nitrogen and major ions in conifer forests in the United States and Federal Republic of Germany

Emission densities of air pollutants are higher in Europe than in the U.S. as a whole, suggesting similar differences in atmospheric deposition. We determined air concentrations and deposition during the warm season at conifer forests in Tennessee and northern Germany. Our results confirmed major differences in both chemistry and fluxes. Atmospheric and precipitation concentrations of all ions except H⁺ were higher at the German site, most significantly for the nitrogen species. The much higher levels of NH₄⁺ at this site reflect higher emissions of NH₃, which was the species largely responsible for the lower levels of H⁺. Total airborne nitrate was dominated by HNO₃ in Tennessee. In Germany we found comparable amounts of HNO₃ and aerosol NO₃⁻, the concentration of which varied seasonally, apparently in response to agricultural emissions of NH₃ that reacted to form NH₄NO₃. Total deposition of all major ions was much higher at the German site, particularly for the nitrogen species, which exhibited a marked edge effect in throughfall. Dry deposition was determined from air concentrations by using a canopy resistance model and from a statistical model of throughfall fluxes, each of which yielded comparable fluxes for several ions. Dry deposition contributed 10–70% of the ion input and was most important at the German site. Both forest canopies absorbed 40–50% of total deposited nitrogen, primarily from dry deposition.     

北京某小学室内外VOC浓度及有毒害物种识别

采用美国EPA推荐的TO14/15方法定量分析了北京市某小学室内外夏季观测的空气样品,得到82种挥发性有机物（VOCs）的浓度水平及组成特征,对其中可能危害儿童健康的有毒有害物质进行了识别.结果表明,室内总VOCs浓度高于室外,烷烃是含量最丰富物种,平均占室内外空气中定量VOCs总浓度的32.8%.室内外VOCs组成相似,异戊烷、苯、甲苯、丙醛、丙烯和二氯甲烷为浓度优势物种,受到室外源的影响较大,室内的对二氯苯、环己烷及间二氯苯较为特征,前2种物质室内/室外浓度比例平均值分别为65.8和10.5,间二氯苯室内平均浓度为2.02×10^-9（体积分数）,而室外浓度低于检测限,这3种物质可能来自室内源. 1, 3-丁二烯、氯乙烯、苯和氯甲烷4种物质在学校室内、室外及儿童家中都超过1×10^-6的癌症风险值,平均风险值分别为1.3×10^-5、 6.4×10^-6、 5.1×10^-6和3.3×10^-6,小学室外、室内及儿童家中的累积癌症风险超过1×10^-6的癌症风险值24～39倍.丙烯醛未确认具有致癌性,但具有毒有害性,在室内外及儿童家中超过基准浓度13～72倍.     

Removal of reactive gases at indoor surfaces: Combining mass transport and surface kinetics

The rate of deposition of reactive gaseous pollutants onto indoor surfaces is examined, taking into account mass transport processes and the kinetics of gas-surface interactions. A conceptual model for predicting indoor deposition velocities is proposed, and approximate analysis based on this model is used to obtain algebraic expressions for the deposition velocity of reactive gases under three model airflow conditions: (1) forced laminar convection parallel to a flat plate, (2) laminar natural convection flow along an isothermal vertical plate, and (3) homogeneous turbulence in an enclosure. Numerical simulations are used to refine the approximate analysis results and to predict reactive gas deposition under laminar natural convection flow in an enclosure. The kinetics of gas-surface interactions are modeled in terms of the reaction probability γ, defined as the fraction of pollutant molecular collisions with a surface that result in irreversible removal. Values of γ for the reaction of ozone with surfaces are obtained from published reaction chamber and tube penetration experiments. For common indoor materials, values range from as low as O(10⁻⁷) for glass and aluminium to O(10⁻⁵–10⁻⁴) for materials such as bricks, concrete and latex paint. Our results indicate that ozone deposition occurs at the transport-limited rate when γ > − 3 × 10⁻⁴ for typical indoor air flow conditions, and that ozone deposition can be predicted by surface kinetics alone if γ < ∼ 5 × 10⁻⁷.     

The spatial distribution and particle size of some inorganic nitrogen,sulphur and chlorine species over the North Sea

The use of filter packs and a cascade impactor during a series of research cruises in the southern area of the North Sea has yielded detailed spatial distribution patterns of aerosol concentrations, Cl⁻, NO₃⁻, SO₄²⁻¹ and NH₄⁺ and gaseous concentrations, HCl, HNO₃ and NH₃. The overall distribution of the atmospheric concentrations closely parallels published modelled results for metallic species. The chemical transformations of these aerosols and gases are investigated together with their interactions with the seasalt aerosol. Aerosol chloride loss is greatest in the more polluted areas, whilst concentrations products of NH₃ with HNO₃ and HCl appear insufficient to sustain the existence of NH₄NO₃ and NH₄Cl. Nitrate is associated predominantly with larger particles and appears to be present substantially as a surface coating on marine aerosol. The total dry deposition input for nitrogen species is calculated for the southern sector with extrapolation to the whole of the North Sea, using particle size weighted deposition velocities of 0.63 and 0.21 cm s⁻¹ for NO₃⁻¹ and NH₄⁺, respectively, and literature-derived values for the gaseous constituents. Finally the use of air-mass back trajectories illustrates the role of source regions in influencing the chemical composition of the North Sea atmosphere.     

Sulfur dioxide,hydrogen sulfide,total reduced sulfur,chlorinated hydrocarbons and photochemical oxidants in southern California museums

Indoor and outdoor concentrations of the air pollutants ozone, NO₂, SO₂, H₂S, total reduced sulfur (TRS), peroxyacetyl nitrate (PAN), methyl chloroform and tetrachloroethylene, have been measured at three southern California museums. Indoor maxima were 175 ppb for NO₂, 77 ppb for O₃, 0.7 ppb for PAN, 1.2 ppb for C₂Cl₄, >6.3 ppb for CH₃CCl₃, 2.5 ppb for SO₂, 1.4 ppb for TRS, and 46 ppt for H₂S. Indoor levels and indoor/outdoor (I/O) ratios for the chlorinated hydrocarbons pointed out to indoor sources. Outdoor and indoor levels of SO₂ and TRS were low at all three museums, but I/O ratios for SO₂ were high and averaged 0.89. H₂S concentrations were low, 16–46 ppt at one museum and less than 6 ppt at the other two museums. I/O ratios for the air pollutants with outdoor sources (ozone, PAN and NO₂) showed substantial variations, from low values of 0.02–0.33 at locations without influx of outdoor air to high values of 0.85–0.88 at locations experiencing high influx of outdoor air. Of the 10 institutions we have surveyed in southern California to date, eight exhibit high I/O ratios, e.g. 0.60–1.00 for PAN. Of the four museums surveyed that were equipped with HVAC and chemical filtration, only two yielded the expected low I/O ratios.     

The chemical composition of intercepted cloudwater in the Sierra Nevada

The chemical composition of cloudwater in the Sierra Nevada is dominated by NO₃⁻, SO₄²⁻, and NH₄⁺. Cloudwater pH is determined largely by the balance between the concentrations of these three species, although inputs of formic and acetic acid also are believed to be important, particularly when anthropogenic inputs are small. Cloudwater samples collected in Sequoia National Park (SNP) exhibited pH values ranging from 3.9 to 6.5; Yosemite National Park (YNP) cloudwater samples had pH values ranging from 3.8 to 5.2. Samples collected at YNP were more acidic than those collected at SNP. The difference in pH between the two regions appears to be due to relatively small differences in inputs of NO₃⁻, SO₄²⁻, and NH₄⁺. In the absence of inputs of NH₃, cloudwater pH values in the Sierra may fall below 3.Over 250 h of cloud interception were observed during a 12 month period at a cloud monitoring site at 1856 m elevaton in SNP. Estimates of cloudwater deposition of NO₃⁻, SO₄²⁻, and NH₄⁺ indicate that cloud interception contributes significantly to regional acid deposition for closed forest canopies. Cloud interception may be the dominant deposition mechanism for isolated conifers and ridgetop canopies, where wind speeds are higher and cloudy air parcels can impact directly on foliar surfaces.     

养鸡场空气中抗性基因和条件致病菌污染特征

集约化养殖场被认为是空气环境中抗性基因和致病菌的重要来源.本研究采集了养鸡场粪便和舍内外空气样本,对其抗生素抗性基因和条件致病菌的种类进行分析,包括五类抗生素(β-内酰胺类的23个基因、四环素23个基因、喹诺酮5个基因、磺胺类5个基因和红霉素2个基因)抗性基因、5种条件致病菌(肠球菌属、大肠杆菌属、葡萄球菌属、弯曲杆菌属和产气荚膜梭状芽胞杆菌属各1个基因)以及一类整合子(int I1)特异基因;并利用荧光定量PCR对检出率较高的典型基因浓度进行检测.结果显示,空气中5类抗生素抗性基因分别检出8、7、2、3和2个,同时检测到两种致病菌.目标基因在舍内空气中的检出率小于等于粪便样本.蛋鸡和肉鸡舍内空气中总细菌基因(16S r DNA)浓度为106copies·m-3,其他典型基因浓度约104copies·m-3,且在舍外的浓度要远低于舍内.抗生素抗性基因和条件致病菌基因在空气中所占比例高于粪便,舍内高于舍外.初步研究结果表明,粪便可能是舍内抗生素抗性基因、条件致病基因以及一类整合子的重要来源.本研究结果将为集约化养殖场抗生素抗性基因和致病菌的来源分析,以及养殖场对周边空气环境污染的风险评估提供基础数据.     

Estimates of ion sources in deciduous and coniferous throughfall

Estimates of external and internal sources of ions in net througfall deposition were derived for a deciduous and coniferous canopy by use of multiple regression. The external source component appears to be dominated by dry deposition of Ca²⁺, SO₂ and NO₃⁻ during dormant and growing seasons for the two canopy types. Increases in the leaching rates of K⁺ and Mg²⁺ during the growing season reflect the presence of leaves in the deciduous canopy and increased physiological activity in both canopies. Internal leaching rates for SO₄²⁻ doubled during the growing season presumably caused by increased physiological activity and uptake of SO₂ through stomates. Net deposition of SO₄²⁻ in throughfall during the growing season appears highly dependent on stomatal uptake of SO₂. Estimates of SO₂ deposition velocities were 0.06 cm s⁻¹ and 0.13 cm s⁻¹ for the deciduous and coniferous canopies, respectively, during the dormant seasons, and 0.30 cm s⁻¹ and 0.43 cm s⁻¹ for the deciduous and coniferous canopies, respectively, during the growing season. For the ions of major interest with respect to ecosystem effects, namely H⁺, NO₃⁻ and SO₄²⁻, precipitation inputs generally outweighed estimates of dry deposition input. However, net throughfall deposition of NO₃⁻ and SO₄²⁻ accounted for 20–47 and 34–50 per cent, respectively, of total deposition of those ions. Error estimates of ion sources were at least 50–100 per cent and the method is subject to several assumptions and limitations.     

典型高校公共场所室内空气微生物分布特征

公共场所室内空气中有害微生物引起的健康风险越来越受到人们的关注.本研究针对典型高校公共场所室内空气,考察了不同类型场所空气中总异养菌的浓度水平及其与颗粒物浓度、活动人数、温度、湿度等影响因素的相关性.结果表明,某高校体育场馆空气中总异养菌浓度显著高于教室、宿舍等场所,为13~154 CFU·m-3.针对多个体育场馆的分析结果表明,活动人数对室内空气中微生物浓度影响最大,与总异养菌浓度呈线性正相关,回归分析得到的R2达0.92.室内空气中PM_(2.5)、PM10及温度、湿度均与空气微生物浓度无显著相关关系.针对空气中抗生素抗性菌的研究表明,室内空气中具有氨苄青霉素、四环素和青霉素抗性的总异养菌比例为20%~50%,其中,可吸入异养菌中氨苄青霉素抗性菌比例可达40%.     

Rainwater composition in Athens,Greece

Wet precipitation-only samplers were used to collect wet deposition at two sites in the Athens basin, Greece for the period March 1986–February 1987.Concentrations of major cations (H⁺, NH⁺₄, Na⁺, K⁺, Ca²⁺ and Mg²⁺) and major anions (Cl⁻, NO⁻₃ and SO²⁻₄) were determined for the first time in rainwater samples in Greece. Bicarbonate concentrations were calculated. The relative importance of natural and anthropogenic sources were estimated by a chemical balance. The majority of rain collected has a neutral or alkaline character. Acidity was due to the presence of H₂SO₄ and HNO₃. The statistical analysis of the correlation between the concentration of chemical species confirm the influence of natural and anthropogenic sources. In all samples, SO²⁻₄ concentrations exceed NO⁻₃ concentrations despite the dominance of low S oil burning in the region. The wet flux of S was calculatd to be 0.34 gm⁻²a⁻¹.     

In-cloud scavenging and deposition of sulfates and nitrates: Case studies and parameterization

Scavenging of sulfates and nitrates—two most common ions leading the cloudwater acidity—was investigated during field studies atop a site in Mt. Mitchell (35°44′05″N, 82°17′15″W) State Park where the highest peak (2038 m MSL) of the eastern U.S. is located. Experiments were conducted during the growing seasons (15 May–30 September) of 1986 and 1987 using an instrumented meteorological tower (16.5 m tall) and a passive cloudwater collector. A cloud episode that occurred on 12 October 1987, was also comprehensively investigated. Clouds were frequently observed in which the Fraser fir and red spruce stands stayed immersed 28% and 41% of the time during the 1986 and 1987 seasons, respectively. Rate of cloudwater deposition on the forest canopy was determined using an inferential cloud deposition model. It was found by analysing nine short duration (lasting 8 h or less) and 16 long duration cloud events that the ionic concentration (SO₄²⁻ and NO₃⁻) is inversely proportional to the rate (I_c) of cloudwater deposition (in mm h⁻¹) and can be expressed by the following relationship: [SO₄²⁻] = aI_c^−b or [NO₃⁻] = aI_c^−b. Theoretical arguments leading to these relationships are presented. The b values for predicting NO₃²⁻ concentration are found in the range of 0.14–1.24 (mean = 0.48) for short duration and 0.062–0.63 (mean = 0.27) for long duration cloud events, respectively. The corresponding b values for predicting NO₃⁻ concentrations are 0.19–1.16 (mean = 0.49) and 0.072–0.59 (mean = 0.27), respectively. When the b parameter was between 0.2 and 0.6, the correlation coefficients between measured and predicted ionic concentrations were found to exceed 0.7. The parameter a is shown to represent the maximum ionic flux for a given cloud event. The ratio of the a parameter for SO₄²⁻ to NO₃⁻ varied between 1.75 and 6.95, indicating that the SO₄²⁻ contributes to the total ionic concentration substantially more than the NO₃⁻ leading to the conclusion that the cloudwater acidity is primarily due to the presence of sulfuric acid which has been demonstrated to cause foliar injury and growth retardation in red spruce trees. The above parameterization is similar to the one that is frequently used to relate ionic concentration in precipitation to the rainfall rate. In order to understand physico-chemical processes leading to the proposed parameterization schemes, meteorological and chemical variables are comprehensively analysed for one short duration and two long duration cloud events. The concentrations of principal ions (SO₄²⁻, NO₃⁻, H⁺ and NH₄⁺) during the short duration cloud events were found to be much higher than those during the long duration ones, especially at colder temperatures. Such short cloud events have a potential of causing foliar narcosis in red spruce stands because of unusually acidic cloudwater to which these stands stay exposed intermittently during each growing season.     

Chemical characterization of acid precipitation in Albany,New York

Chemical composition of precipitation in Albany, NY from July 1986 to December 1988 has been studied. Mean volume-weighted concentrations (μeq^ℓ−1) were: acidity, 104.0; alkalinity, −63.7; SO₄²⁻, 52.8; NO₃⁻, 29.8; Cl⁻, 5.6; F⁻, 0.50; NH₄⁺, 19.3; Ca²⁺, 6.5; Mg²⁺, 2.8; Na⁺, 3.5; and K⁺, 1.4. Mean pH was 4.2 . Seasonal patterns were pronounced for most species. Concentrations of H⁺, SO₄²⁻, NO₃⁻, NH₄⁺ and Ca²⁺ peaked in the summer and spring. Deposition was related to rainfall amount by a power law relationship in which the exponent of the equation was ∮.6. Wet SO₄²⁻ deposition was 2.35 keq ha⁻¹ over a 30-month period. The SO₄²⁻ and NO₃⁻ deposition rates observed at Albany indicate that transport from midwestern sources have a major influence at this site. On the average, free H⁺ ion concentrations determined from pH measurements accounted for 51% of the measured total acidity. There were unknown species, most likely organic acids, that could contribute to the acidity. Correlation and regression analyses indicated that major anions, SO₄²⁻ and NO₃⁻, were closely associated with H⁺ and NH₄⁺ ions. Factor analysis revealed four common factors which are related to fossil-fuel combustion, sea spray, cement factory and biomass burning.     

Fogwater chemistry at Riverside,California

Fog, aerosol, and gas samples were collected during the winter of 1986 at Riverside, California. The dominant components of the aerosol were NH₄⁺, NO₃⁻, and SO₄₂₋. Gaseous NH₃ was frequently present at levels equal to or exceeding the aerosol NH₄⁺. Maximum level were 3800, 3100, 690 and 4540 neq m⁻³ for NH₄⁺, NO₃²⁻ and NH_3(g), respectively. The fogwater collected at Riverside had very high concentrations, particularly of the major aerosol components. Maximum concentrations were 26,000 29,000 and 6200 μM for NH₄⁺, NO₃⁻ and SO₄²⁻, respectively. pH values in fogwater ranged from 2.3 to 5.7. Formate and acetate concentrations as high as 1500 and 580 μM, respectively, were measured. The maximum CH₂O concentration was 380 μM. Glyoxal and methylglyoxal were found in all the samples; their maximum concentrations were 280 and 120 μM, respectively. Comparison of fogwater and aerosol concentrations indicates that scavenging of precursor aerosol by fog droplets under the conditions at Riverside is less than 100% efficient.The chemistry at Riverside is controlled by the balance between HNO₃ production from NO_x emitted throughout the Los Angeles basin and NH₃ emitted from dairy cattle feedlots just west of Riverside. The balance is controlled by local mixing. Acid fogs result at Riverside when drainage flows from the surrounding mountains isolate the site from the NH₃ source. Continued formation of HNO_3(g) in this air mass eventually depletes the residual NH_3(g). A simple box model that includes deposition, fog scavenging, and dilution is used to assess the effect of curtailing the dairy cattle feedlot operations. The calculations suggest that the resulting reduction of NH₃ levels would decrease the total NO₃⁻ in the atmosphere, but nearly all remaining NO₃⁻ would exist as HNO₃. Fogwater in the basin would be uniformly acidic.     

贡嘎山地区地表水化学特征及水环境质量评价

在系统采集贡嘎山地表水样的基础上,综合运用描述性统计、Gibbs图和阴阳离子三角图,分析了贡嘎山地区地表水化学主离子(K~+、Na~+、Ca~(2+)、Mg~(2+)、CO_3~(2-)、HCO_3~-、Cl~-、SO_4~(2-)),)特征及其控制因素、重金属元素(Cu、Cd、Pb、Zn)和营养元素(N、P)的空间分布特征,并利用单因子评价法对贡嘎山地区地表水质进行评价.结果表明,贡嘎山地区总溶解固体(total dissolved solid,TDS)质量浓度均值为103.22 mg·L~(-1),为低矿化度水,全流域水化学类型以HCO_3-Ca型为主.全区水化学主离子主要来自碳酸盐岩风化,但大气降水对东部地区河流的化学离子来源具有重要影响.研究区地表水中重金属元素和营养元素的质量浓度总体较低,且东部明显高于西部.贡嘎山地区地表水水质总体优良,并呈现西部优质,东部良好的空间分布特征,该特征主要受自然因素控制,但东南坡的部分水体已受到人类影响.     

Transport and deposition of indoor radon decay products—I. Model development and validation

Commonly used mathematical models of indoor radon decay product behavior are based on macroscopic mass-balances, often referred to as ‘uniformly-mixed models’. The uniformly-mixed model's applicability is limited by its inability to track the movement of pollutants from their sources to other areas within the enclosure, to permit spatial- or time-dependent sources, or to take proper account of interactions with macroscopic surfaces. Although the uniformly-mixed model parameterizes the deposition process as a constant volumetric removal rate, in reality the deposition process is actually a surface phenomenon and is strongly affected by environmental conditions.This paper describes the development of RADTRAN, a two-dimensional radon progeny transport model that begins with the differential conservation equations describing the motion of air and the transport of reactive pollutants, introduces appropriate boundary conditions to represent surface deposition, and then calculates the concentration distribution of radon progeny throughout the entire region of interest. Knowing the concentration gradient near the surface, a local mass-transfer coefficient (the deposition velocity) can be determined as a function of environmental conditions. RADTRAN simulations have been based on several flow conditions: buoyancy-driven recirculating enclosure flows, free and forced-convection boundary layer flows, and one-dimensional diffusion. Free progeny diffusivity, D^f, and attachment rate, X, were varied over representative ranges. For these conditions, RADTRAN calculated free deposition velocities of u^f = 0.014–0.079 cm s⁻¹, for ²¹⁸Po. RADTRAN predictions are compared to a range of experimental measurements. It was found that the predicted range of deposition velocities is in rough agreement with findings from experiments conducted in flow conditions similar to the simplified flows used in RADTRAN.     

Characteristics of airborne particles inside southern California museums

The concentrations and chemical composition of suspended particulate matter were measured in both the fine and total size modes inside and outside five southern California museums over summer and winter periods. The seasonally averaged indoor/outdoor ratios for particulate matter mass concentrations ranged from 0.16 to 0.96 for fine particles and from 0.06 to 0.53 for coarse particles, with the lower values observed for buildings with sophisticated ventilation systems which include filters for particulate matter removal. Museums with deliberate particle filtration systems showed indoor fine particle concentrations generally averaging less than 10 μg m⁻³. One museum with no environmental control system showed indoor fine particle concentrations averaging nearly 60 μg m⁻³ in winter and coarse particle concentrations in the 30–40 μg m⁻³ range. Analyses of indoor vs outdoor concentrations of major chemical species indicated that indoor sources of organic matter may exist at all sites, but that none of the other measured species appear to have major indoor sources at the museums studied. Significant fractions of the dark-colored fine elemental (black) carbon and soil dust particles present in outdoor air are able to penetrate to the indoor atmosphere of the museums studied, and may constitute a soiling hazard to works of art displayed in museums.     

Transport and deposition of indoor radon decay products—II. Influence of environmental conditions

The effects of indoor radon decay product behavior on overall concentrations have generally been characterized using uniformly-mixed models, mathematical formulations based on steady-state macroscopic mass-balances, assuming uniform concentrations within the enclosure. The uniformly-mixed model parameterizes the deposition process as a constant volumetric removal rate, given different values for the free and attached progeny. The model requires prior knowledge of the deposition rates, and assumes them to be constant, independent of environmental conditions, and identical for all decay products. There has generally been little agreement regarding the actual values of the deposition rates, and the uncertainty in these required values presents an important limitation.In response to the limitations of existing mass-balance models, an indoor radon mass-transport model, RADTRAN, was developed using a microscopic mass-balance. Deposition by molecular diffusion is accounted for through boundary conditions, and deposition velocity is calculated based on the concentration distribution near the wall. Parametric sensitivity studies using RADTRAN examined the sensitivity of the deposition of radon decay products to several factors: the size of the free progeny (measured by its diffusivity, D^f), particle concentration (using the attachment rate, X), and air motion. Deposition is described in terms of the deposition velocities of the free and attached progeny, u^f and u^a. The development of RADTRAN is described in a companion paper. This paper presents the results of the parametric sensitivity studies examining the influence of environmental conditions on radon progeny deposition. Results primarily focus on the influence on the free mode of the first radon decay product, ²¹⁸Po. RADTRAN is also used to examine the variations of deposition velocity between the decay products.