Unusually high indoor radon concentrations

Measurements of indoor radon concentrations in the village Umhausen (2600 inhabitants, Ötztal valley, Tyrol, Austria) revealed unusually high indoor radon concentrations up to 274,000 Bq m⁻³. The medians measured on the basements were 3750 Bq m⁻³ in winter and 361 Bq m⁻³ in summer, those on the ground floors were 1180 Bq m⁻³ and 210 Bq m⁻³, respectively. Seventy-one per cent of the houses showed basement radon concentrations above the Austrian action level of 400 Bq m⁻³ in winter, 33% in summer. There are indications that the high radon concentrations are due to a giant rock slide about 8700 years ago. The unusually high radon concentrations in Umhausen coincide with a statistically significant increase in lung cancer mortality. For the period 1970–1991 the age and sex standardized mortality rate is 3.85 (95% confidence interval: 2.9 to 5.1). The control population is the total population of Tyrol (630,000 inhabitants).     

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.     

降雨径流事件对三峡水库香溪河库湾甲烷释放的影响

甲烷是一种重要的温室气体,水库的甲烷源汇效应备受关注,然而观测时间的代表性不足以及缺乏对非良好天气状况的考虑制约了 CH4 排放的准确估计.本研究以三峡水库香溪河库湾为研究对象,针对2019年夏季一场完整降雨径流事件在库湾中游断面开展跟踪连续监测,初步探讨了降雨以及来流过程对库湾甲烷浓度与释放的影响.结果表明,降雨事件...     

Intensive studies of Sierra Nevada cloudwater chemistry and its relationship to precursor aerosol and gas concentrations

Measurements of inorganic aerosol and gas phase species are presented for three sites in central California during a 4 day period in April 1988. The measurement sites were located along an east-west transect at Visalia, Ash Mountain, and Lower Kaweah, with elevations of 90, 550 and 1900 m, respectively. Aerosol compositions were nearly neutral at all locations, however large concentrations of NH₃ at Visalia contributed significant excess alkalinity to the air mass sampled there. Concentrations of all major species were observed to decrease with elevation during most of the sampling periods. Concentrations at the upper two sites exhibited diurnal fluctuations, with peaks in the late afternoon, consistent with the transport of pollutants from San Joaquin Valley sources by daytime upslope winds. Concentrations of most of these species reached a maximum at the elevated sites on 28 April, as a weak cold front approached, reducing the atmospheric stability over the valley floor. Concentrations at Visalia on this day were somewhat lower than those observed earlier in the week.Clouds intercepting the mountain slopes on 28 April were sampled at two locations. The coudwater pH at both sites was observed to fall throughout the event, dropping as low as 4.34. Precursor concentrations of aerosol NO₃⁻, SO₄^2- and NH₄⁺, and gas phase HNO₃ and NH₃, were sufficient to account for the observed cloudwater loadings of NO₃⁻, SO₄^2- and NH₄⁺. In-cloud measurements made near the cloud base indicated a considerable S(IV) oxidation potential in the form of H₂O₂, but only low S(IV) concentrations. Cloudwater concentrations of formic acid were approximately three times acetic acid concentrations. Carbonyl concentrations were dominated by formaldehyde and glyoxal.     

室内氡浓度与建筑材料表面氡析出率的关系研究

采用RAD7测氡仪对某8层教学楼第5层的房间进行24 h连续测定,测得室内氡浓度范围为5.65~48.7 Bq/m3,不超标。测定结果表明,清晨氡浓度较高,在5:00左右氡浓度达最高值;中午氡浓度较低,11:00左右氡浓度达最低值。经测定房间内墙面抛光瓷砖的表面氡析出率大于地板砖的表面氡析出率。房间室内的氡主要来源于建筑材料表面氡的析出和室外空气,利用氡析出率和室外氡计算的室内氡浓度与测定结果相符。     

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.     

Use of natural basement ventilation to control radon in single family dwellings

Natural basement ventilation has always been recommended as a means of reducing radon levels in houses. However, its efficacy has never been documented. In these experiments, natural ventilation has for the first time been studied systematically in two research houses during both the summer cooling season and the winter heating season. Ventilation rates, environmental and house operating parameters, as well as radon levels, have been monitored.It can be definitively concluded from radon entry rate calculations that natural ventilation can reduce radon levels two ways. The first is by simple dilution. The second is by reducing basement depressurization and thus the amount of radon-contaminated soil gas drawn into the structure.Therefore, basement ventilation can be an effective mitigation strategy under some circumstances. It might be especially useful in houses with low radon concentrations (of the order of 370 Bq m ⁻¹) or those with low levels and which cannot be mitigated cost-effectively with conventional technology.     

贵阳地区氡浓度的连续观测

叙述用静电累积氡测量仪对贵阳地区环境氡浓度进行连续四年的观测，氡浓度季节性的变化受气温、降雨量等因素的影响较大，降雨不仅可使环境氡浓度降低，而且在降雨量相近的情况下降雨次数较多氡浓度也会相对偏低。     

The investigation of air quality and acid rain over the Gulf of Mexico

A research cruise was conducted in the summer of 1986 by a group of scientist from the U.S.A. and Mexico to investigate air chemistry over the Gulf of Mexico. Chemical, physical, meteorological and oceanographic measurements were carried out to survey temporal and spatial variations of diverse parameters throughout the Gulf. Emphases were placed on air-sea-land exchange of gases and aerosols, natural air quality, transport of anthropogenic air pollution, and acid rain deposition to the Gulf. Although the prevailing winds were easterly from the sea during the cruise, the air was highly polluted with continental aerosols, probably caused by local shifting winds and the oscillation between sea breeze and land breeze. Aerosol number concentrations were measured from 10⁵ cm⁻³ at ports to 10³ cm⁻³ in the open Gulf. The average aerosol mass concentration was ∼25μg M⁻³, consisting of 60% insoluble crustal particles that contained Si, Al, Fe; 30% seasalt particles that contained Na⁺ and Cl⁻; and 10% anthropogenic sulfate and nitrate particles. Samples of rain water collected near the coast were acidic (pH ∼4). The concentrations of dimethyl sulfide correlated with bio-particle concentrations in surface seawater and could be a significant precursor of atmospheric SO₄²⁻ particles. The life cycles of the aerosols in the Gulf, including sources, transport, transformation, and wet and dry deposition are discussed.     

我国不同类型地下工程中的氡水平

为了解我国地下工程内氡的浓度水平及其可能对人体产生的危害,采用核固体径迹法,在不同季节对全国23个城市的234个地下工程测点的氡浓度进行了测量。根据工程的建筑类型及用途的不同,将所有被测工程分为坑道、干道(包括掘进式地道工程)、地下室(高层建筑地下室和掘开式工程)和停车场四类,各类工程的氡浓度平均值分别为327、619、96.9、59.1 Bq.m-3。对于不同山体岩性的坑道,氡浓度值由高到低的顺序是花岗岩>凝灰岩>石英砂岩>石灰岩>安山玢岩。比较各类工程不同季节的氡浓度,得出,停车场氡浓度季节变化不大,其它三类工程都有氡浓度夏季明显高于冬季的特点,而且通风差的未使用的坑道和干道比使用中的同类工程具有相对高的氡浓度夏/冬比值。     

Surface cloud condensation nuclei and condensation nuclei measurements at Reno,Nevada

Surface aerosol measurements from a moderately populated high mountain valley are interpreted in terms of local wind velocity and meteorology. Diurnal trends are apparent with light winds and especially during wintertime temperature inversions when the concentrations are dominated by local anthropogenic sources. Under conditions of higher wind speeds when the surface concentrations appear to be representative of widespread areas, a seasonal trend is revealed. Cloud condensation nuclei (CCN) concentrations are much higher during the late spring (> 1000 cm⁻³) than during the winter (< 400 cm⁻³) but the condensation nuclei (CN) concentrations are not seasonal. The seasonality of the CCN is probably caused by differences in the long range transport of particles from distant California population centers.     

地下工程中空气离子环境和氡害

近年来国内外大量研究资料表明:环境中空气离子和氡是两个与人舒适感及人体健康密切相关的环境因素。地下工程中空气离子和氡问题比地面室内环境更为突出。随着地下空间广为开发利用,如何改善地下工程中空气离子环境及防氡害问题正在引起人们的极大关注。我们对我国五个地区的37个     

Dependency of radon entry on pressure difference

Radon levels, ventilation rate and pressure differences were monitored continuously in four apartment houses with different ventilation systems. Two of them were ventilated by mechanical exhaust, one by mechanical supply and exhaust, and one by natural ventilation. The two-storey houses were constructed from concrete elements on a slab and located on a gravel esker. It was surprising to find that increasing the ventilation rate increased levels of radon in the apartments. Increased ventilation caused increased outdoor-indoor pressure difference, which in turn increased the entry rate of radon and counteracted the diluting effect of ventilation. The increase was significant when the outdoor-indoor pressure difference exceeded 5 Pa. Especially in the houses with mechanical exhaust ventilation the pressure difference was the most important factor of radon entry rate, and contributed up to several hundred Bq m⁻³ h⁻¹.     

北京地区室内氡浓度研究

本文报道了北京地区14种代表性建筑物室内的氡浓度,并对北京地区室内氡源的相对影响进行了分析。结果表明,房屋下面的地基土壤和建筑材料是室内氡的主要来源,占室内氡全部来源的70—80％;地面和建筑物表面的裂隙、孔道是氡气进入室内的主要途径;生活用水、民用燃煤和燃气对室内氡的影响不到2％。北京地区地面建筑室内平均氡浓度为30Bq/m~3,所致居民年有效剂量当量为0.93mSv。地下建筑中室内平均氡浓厦为35Bq/m~3,所致居民年有效剂量当量为1.3mSv。     

珠海市大气环境中氡浓度的测定

采用固体径迹探测器累积氡测定方法对珠海市不同地质背景、不同的建筑风格的房室内室、外地面水平氡浓度进行了测定。结果表明,珠海市室内、外空气中氡浓度的平均值分别为：１６４。２Ｂｑ／ｍ＾３和７５．２Ｂｑ／ｍ＾３,居全国各大城市之首,仅次于我国的个旧地区,但大多数住房室内氡浓度都低２００Ｂｑ／ｍ＾３。研究发现秋冬季的室外氡浓度高于春夏季的室外氡浓度。而室内氡浓度的浓度的变化情况则相反,春夏季高于秋冬季,室     

闽北570铀矿区周围大气环境氡浓度水平研究

对闽北570铀矿区的大气氡环境地球化学进行了研究。矿区废渣和坑道口释放出来的氡气对周围大气形成了一定的氡污染,特别是在矿区周围0.5～1km范围内的污染较严重。但是空气中的氡污染随着离矿区的距离增大而迅速减弱,矿区周围居民室内氡的浓度较高,是福建省室内氡浓度平均值的1～8倍左右。在进行调查的28个居室中,有6个(占21%)居室内氡浓度超过我国住房内氡浓度控制标准GB/T16146-1995中已建住房的室内氡浓度上限值(200Bq/m3)和国际辐射防护委员会制定的200Bq/m3的上限值。居室中氡浓度的升高,除了受矿区释放出来的氡污染外,还因为本地区属高本底辐射区,房基下的土壤、岩石和建筑材料中的铀、镭等放射性元素的含量高,其放射性衰变产生的氡释放出来进入室内。     

贵阳地铁1号线氡浓度特征及其潜在健康效应评估

地铁轨道交通逐渐成为人们日常出行的首选,但作为较封闭的地下空间环境易导致氡积聚,对于工作人员和乘客存在潜在的电离辐射暴露风险,有必要进行监测评估.贵阳地铁1号线于2018年12月开通运营,所穿越地层主要为碳酸盐岩,该地层风化过程中常常产生氡异常,尤需引起关注.本研究利用RAD-7电子测氡仪,分别于2020年7月29日和...     

北京大气中CFC-11的浓度观测与变化趋势

近几年大气中CFC的浓度在人类活动的影响下发生了迅速变化,考虑到CFC浓度变化对平流层臭氧和全球变暖的影响,采用两步深冷冻浓缩自动进样系统,配以气相色谱/质谱联机对北京大气中的CFC-11进行了连续观测.结果表明,1999～2003年CFC-11的浓度季节变化均呈单峰形态,峰值出现在7～8月,月平均浓度最高值为1149.5±531.9×10^-12(体积分数);谷值出现在春季的3～5月份,月平均浓度最低值为487.5±131.5×10^-12(体积分数);北京大气中CF-11年平均浓度在观测时间段内呈先上升后下降的趋势,其中1995～1998年增长较快,平均增长率为17.9%,1999年后呈缓慢下降趋势,平均下降率为10.7%,平均浓度是Mauna Loa全球基准观测站观测到大气本底CFC-11浓度的3～5倍.     

The vertical distribution of aerosols and acid related compounds in air and cloudwater

Vertical profiles (surface to 5 km) of aerosol particle number concentration, NO_y′ mixing ratio, and cloudwater SO₄²⁻ and NO₃⁻ equivalent concentration were obtained in three field studies: North Bay, Ontario, during the summer of 1982 and the winter of 1983–1984, and Syracuse, New York, during the fall of 1984. The measurements from these locations and different seasons are compared. Generally, airborne concentrations are highest with air-mass back trajectories from the south and lowest with back trajectories from the north. For the southerly trajectories, median particle number concentrations (0.2–2 μm) near ground level (950 mb) vary from 1700 cm⁻³ during the summer project to 800 cm⁻³ during the winter project. At 700 mb, the south trajectory particle number concentration ranged between 60 and 170 cm⁻³. Median NO_y′ mixing ratios for southerly back trajectories were approximately 6 and 9 ppb at 950 mb and 0.4 and 0.8 ppb at 700 mb for the fall and winter projects, respectively. Comparison of particle number concentration profiles outside of cloud with cloud droplet plus interstitial aerosol particle number concentrations inside cloud indicate that cumulus clouds can transport aerosols vertically from below cloud base. In contrast, stratiform clouds have similar concentrations inside the clouds as outside at the same altitude. The vertical variations of cloudwater sulphate and nitrate concentrations and the NO₃⁻/SO₄²⁻ equivalent concentration ratio are discussed for each of the three field studies.     

青藏高原内陆典型冰川区"冰川-径流"汞传输过程

为研究青藏高原内陆典型冰川区"冰川-径流"汞输送过程,于2011年8月15日~9月9日对青藏高原内陆念青唐古拉山脉扎当冰川-曲嘎切流域内雪坑、冰川融水以及径流进行了采样,检测了不同环境介质中汞浓度,并分析了不同介质中汞的控制因素及输送过程.结果表明,扎当冰川-曲嘎切流域内雪坑、冰川融水以及曲嘎切径流中总汞浓度分别为(3.79±5.12)、(1.06±0.77)和(1.02±0.24)ng·L-1,处于全球背景水平.不同环境介质中均以颗粒态汞为主,受到总悬浮颗粒物和径流量的控制.随着气温升高,冰川消融,受其补给的河流径流量增加.不同环境介质间,从冰川末端融水到曲嘎切下游河水,总汞浓度峰值时间分别是14:00、16:00和20:00以后,体现了汞在"冰川-径流"环境系统中随冰川消融、径流量变化的释放和传输过程.冰川补给河流汞的传输受多种因素制约,气候变化背景下,冰川消融和径流增加带来的侵蚀将在汞释放及其向下游传输发挥日益重要的作用.