Velocity oscillations and plume dispersion in a residential neighborhood during wintertime nights

Measurements of velocity and tracer plume concentrations during stable atmospheric conditions were obtained in the Boise River Valley as part of the EPA Integrated Air Cancer Project during December, 1986. Wind speed, temperature, and wind direction were measured at two levels on a 30 m tower. Spectral and autocorrelation analyses of the velocity component data clearly indicate the occurrence of wave-like oscillations in the flow and the almost complete lack of turbulent energy. The predominate wave-like motion had an oscillation period of about 1000 s. Halogenated atmospheric tracers were released from as many as four houses during the night-time drainage conditions. Hourly averaged horizontal dispersion coefficients were very large compared to the Pasquill-Gifford curves and the urban McElroy-Pooler dispersion curves. The time-averaged dispersion coefficients formed an upper bound on very short-term dispersion coefficients obtained from mobile traverses of the tracer plume with a continuous SF₆ analyzer. These results agree with the concept of a narrow instantaneous plume with a broad meander driven by the observed 1000 s oscillation. Vertical dispersion rates were slightly smaller than the Pasquill-Gifford class F curve. Results from a single tracer release from a side canyon near the neighborhood showed that drainage flow from the tributary impacted the main residential sampling site at Elm Grove Park and represented a significant fraction of the upstream air flow at Elm Grove Park. For sources with equal emission rates, a source in the tributary adds about 10% to the mean of the concentration caused by a neighborhood source.     

Building amplification factors for sources near buildings: A wind-tunnel study

The aerodynamics of a building can strongly influence the dispersion of pollutants released from nearby sources. Low releases may be entrained into the building's highly turbulent flow region and result in high pollutant concentrations on the building surface where building air intakes are located. High releases may result in increased concentrations at ground level downwind of the building as a result of the building's influence on the mean flow field. High releases at distances far upwind of the building can produce significant concentrations on the building surfaces if the building extends up into the elevated plume. Concentration measurements from a wind-tunnel study for numerous release locations upwind, above and downwind of each of four rectangular buildings are presented and compared with some previous measurements and calculations. Both building surface and ground-level values are presented. The concentrations are used to compute “building amplification factors”, which are defined as the ratios of the maximum concentration from a given source near the building to the maximum concentration from the same source in the absence of the building. This simple measure of the building's influence showed a significant influence of the building on concentrations from sources far upwind of the building, sources well above the building cavity and sources in the near wake of the building.     

典型荧光示踪剂在包气带中的迁移、吸附特性

为研究荧光示踪剂在包气带土壤中的迁移-吸附特性，指导填埋场渗漏检测过程的示踪剂选择、投加和采样.采用土柱实验、参数反演手段，研究3种典型荧光示踪剂在包气带中的吸附、滞后和穿透规律，确定其迁移表征方法、表征参数和最佳模型.结果表明：在土壤有机碳相对较高和较低时，分别可用非线性平衡和线性平衡模型准确拟合罗丹明B在其中的穿透数据，而非线性平衡模型同时准确拟合了荧光素和荧光素钠在两种有机碳土壤中的穿透数据.基于最优反演模型，在低有机碳土壤中示踪剂迁移参数为：罗丹明B、荧光素和荧光素钠的分配系数分别为84.99，1.80，1.48cm³/g，滞后因子分别为393.27，8.18，7.81，吸附容量分别为6.14×10^-3，0.15×10^-3，0.14×10^-3mg/g，均出现罗丹明B>荧光素>荧光素钠的顺序.荧光素钠在包气带中迁移时固相吸附浓度最小、迁移速率最快、吸附消耗量最小，建议在进行填埋场渗漏示踪中选用.     

Receptor modeling of the Antwerp aerosol

Receptor modeling, using factor analysis, was applied for the source identification and source apportionment of air particulate samples which were collected during two sampling campaigns in Antwerp, Belgium, and analyzed by particle-induced X-ray emission (PIXE) analysis. In a summer campaign (July 1986), 16 12-h samples of total aerosol were taken using conventional low volume filter equipment. In a winter campaign (February–March 1987) 120 24-h samples, consisting of 40 coarse, 40 fine and 40 total aerosol samples, were collected using a stacked filter unit and a total filter sampler. In both campaigns between three and five sources were discerned, most of which could be attributed to existing urban sources of air particulate matter. For each source, source profiles and absolute elemental contributions were calculated.     

Building wake dispersion at an Arctic industrial site: Field tracer observations and plume model evaluations

Ten multi-hour atmospheric dispersion SF₆ tracer experiments were conducted during October and November of 1987 near a large oil gathering facility in the Prudhoe Bay, Alaska, oilfield reservation. The purpose of this study was to investigate dispersion under arctic conditions and in situations where building-generated airflow disturbances dominate downwind distributions of ground level pollutant concentrations. This was accomplished with a network of micrometeorological instruments, portable syringe tracer samplers, continuous tracer analyzers, and infrared visualization of near source plume behavior.Atmospheric stability and wind speed profiles at this arctic site are influenced by the smooth (surface roughness = 0.03 cm), snow covered tundra surface which receives negligible levels of solar isolation in winter. The dispersion of pollutants emitted from sources within the oil gathering facility, however, is dominated by the influence of nearby buildings when high winds generate elevated ground level concentrations. An order of magnitude increase in maximum ground level concentration was observed as wind speeds increased from 5 to 8 m s⁻¹ and another order of magnitude increase was observed as winds increased from 8 to 16 m s⁻¹. Variation in maximum concentrations was also observed with changes in wind direction. Vertical plume diffusion (σ_z) near the buildings was a factor of 2–3 greater than that observed in open terrain and was dependent on both wind speed and the projected building width and location of nearby buildings. Wind tunnel tracer distributions for east winds agree with field observations but also indicate that a significant increase in plume downwash occurs with other wind directions. Concentration distributions were calculated using several versions of the Industrial Source Complex (ISC) model. Model estimates of ground level concentrations were within a factor of three depending on wind direction. The model predictions are extremely sensitive to the ratio of plume height to vertical plume diffusion which is significantly influenced by a complex aerodynamic wake in the field.     

现代环境监测研究中的一种新示踪指示剂(SO_4)

拥有一种理想的示踪剂是研究地球化学过程必不可少的手段,尤其是在现代环境监测研究中,如洞穴滴水对大气降水的响应时间以及地表环境的监测。而在目前的研究中,通常使用的示踪剂(天然的和人造的)有其优点的同时,都不可避免地存在许多不足,因此需要根据具体情况选择最佳示踪剂。本文通过分析荔波5个不同地上植被生物量大小的样地土壤水硫酸根离子(SO4)浓度,以及贵州4个洞穴系统中土壤水和滴水等的SO4,分别从理论和试验检验两方面对其作为一种可能的新示踪指示剂进行论述。结果首次表明,其具有其他示踪剂不具备的一些优点,在一定条件下完全可作为一种示踪剂示踪指示某一区域地表植被生物量的大小以及滴水对大气降水的响应时间。最后通过实测数据(5个样地的地上生物量和土壤水SO4离子浓度,以及滴水的SO4离子浓度和NaCl示踪所得的滴水对大气降水响应时间)的Freundlich拟合,分别得到了研究区的经验公式:[SO4]=3.34ln(b)+5.20和[SO4]=-9.17ln(t)+31.61。     

Wind tunnel measurements of line integrated concentration

Visibility through aerosol plumes is related to the integral of the aerosols concentrations along the line of vision. A novel method for measuring the mean and fluctuating values of such integrals in wind tunnel simulated plumes is presented together with measurements of Vertical Integrated Concentrations (VIC) in a neutrally buoyant plume generated by a ground-level source in a simulated, neutrally stratified atmospheric boundary layer. The data depict the similar structure of the intermittent VIC fluctuations. The relative fluctuations of VIC are shown to be close to the relative fluctuations of the ground-level concentration fluctuations.     

Spatially resolved monitoring for volatile organic compounds using remote sector sampling

Sector sampling for volatile organic compounds (VOCs) is conducted within an integrated sampling scheme and relies on a wind direction sensor. The wind sensor directs whole air, sampled at a constant rate, into either an “IN” sector canister or an “OUT” sector canister; when the wind comes from the suspected emissions area, sample is routed into the IN sector canister; otherwise, sample is collected in the OUT sector canister. This method is analogous to “upwind/downwind” sampling but does not require two distinct sites or manual sampler control. For this set of experiments, the IN and OUT sectors were 90 and 270°, respectively, and the IN sector was centered on the VOC source. Two sampling sites were used. The first was about 2 miles north-northeast of a group of industrial facilities, and the second was located about 1 mile south-southeast of the same sources. Sites were operated concurrently with one sampler each; a third sampler was rotated between the sites to obtain duplicate samples. The air samples were analysed by gas chromatography for VOCs. The resultant data comparisons between IN and OUT duplicate samples show good correlation with expected VOC emissions, which were determined by grab samples within the target area. A t-test method for interpreting the sometimes subtle differences between IN and OUT sample data is presented.     

淹水条件下三峡库区典型消落带土壤释放DOM的光谱特征:荧光光谱

作为水体DOM的重要来源,消落带土壤淹水释放过程十分重要.本文以三峡库区典型消落带土壤为例,通过模拟正常淹水和厌氧淹水的两种条件,利用荧光光谱,着重定性地分析并讨论了土壤向上覆水体释放DOM的动态特征.结果表明,消落带4个区域土壤淹水后产生的DOM荧光特性,呈现出和可见-紫外光谱相似特征,对上覆水体DOM荧光特征有重要贡献.淹水初期的快速释放及后期去除机制,是水体DOM荧光组分的动态"源-汇"平衡的关键;其中类腐殖峰(A和C)受无机矿物相的吸附-释放影响明显,而类蛋白峰(B和T)受微生物影响较为明显.另外,所有土壤淹水释放后水体DOM均呈现出"内源+外源"的复合特征.除忠县石宝寨(SB)外,整个淹水周期,其余区域土壤在厌氧和正常淹水条件下,水体DOM荧光特征的差异性不明显,这可能和土壤自身组成(例如无机矿物组成和有机组分)的复杂程度有关.结合可见-紫外光谱,两种技术相互补充,证明了土壤释放("源")和去除("汇")机制是控制DOM动态变化的重要因素;而淹水初期的较强芳香性和腐殖化程度,以及较强的陆源特征,无疑有利于进一步解释污染物在淹水过程中的环境行为,为进一步了解DOM的环境角色提供数据基础和实验支撑.     

Improvement of the modelling of daytime nitrogen oxide oxidation in plumes by using instantaneous plume dispersion parameters

The effect of concentration fluctuations on the modelling of non-linear chemical reactions in the atmosphere will be considerable when hourly mean dispersion parameters are used. This effect can be reduced by introducing instantaneous dispersion parameters, as will be shown in this paper for the modelling of the oxidation of NO emited into an O₃ containing atmosphere.We used the results of atmospheric tracer gas experiments to derive the dimensions of the instanteneous plume. With these results model calculations were carried out for the NOO₃ reaction. Results were compared with airborne measurements of NO oxidation in the plumes of Dutch power plants.The introduction of the instantaneous plume leads to better agreement between model calculations and measurements. It is also found that the deviation from photochemical equilibrium in the plume is considerably smaller when instantaneous, instead of hourly, mean dispersion parameters are used. The dimension of the instantaneous plume did not show a dependence on atmospheric stability.     

Diffusion in building wakes for ground-level releases

A time-based model for estimating centerline concentrations from ground-level releases in building wakes is developed from theoretical considerations. Variables in the model are distance from the release point, wind speed, atmospheric stability, and projected building area. The model is evaluated using experimental data obtained in experiments made at seven nuclear reactor sites, and is compared with other building-wake diffusion models. The new model is slightly biased with a median ratio between predicted and observed concentrations of 1.07 and accounts for about 55% of the variation in the observed concentrations. Previous models have median ratios between predicted and observed concentrations greater than 2 and account for less than 30% of the observed variation in concentrations.     

A theoretical comparison between intentional elemental and isotopic atmospheric tracers

A theoretical comparison has been made between intentional elemental and intentional isotopic tracers for the study of the fate of emissions into the atmosphere. The use of an elemental tracer requires a very large signal to background ratio because the latter cannot be determined while the tracer experiment is in progress. It is shown that the variation in the ambient background is the major source of uncertainty for the elemental tracer. The use of a stable isotopic tracer is definitive because the isotopic composition of the background is constant and can be measured in real time during the isotopic analysis of the sample. Simple error analysis suggests that the isotopic tracer is intrinsically definitive and more accurate compared to the elemental tracer. This is because elemental tracers are subject to inherent biases of unknown magnitude that do not exist for isotopic tracers. If it is assumed that the background can vary by a factor of two during a tracer experiment, then for a given confidence in the detection of the tracer signal more than 10⁴ times more elemental tracer is required than isotopic tracer. It is concluded that stable isotopic tracers are inherently superior to elemental tracers; however; this conclusion now needs to be demonstrated in an actual field experiment.     

Potential bias from non-continuous monitoring of ambient ozone concentrations for characterizing hourly and daily 7- and 12-hour average concentrations

Researchers using chamber experiments to investigate O₃ effects on vegetation do not always monitor O₃ concentrations continuously. Errors introduced because of non-continuous monitoring during experimental treatments may result in the inadequate characterization of hourly average concentrations, with the consequence that summarized exposure indices may provide inaccurate linkages between experimental results and the standard-setting process. We have investigated the uncertainties associated with limited sampling to characterize (1) hourly average and (2) daily 7- and 12-h average O₃ concentrations. As expected, accuracy increased with increased sampling; over- and underestimation of hourly values was directly related to whether the actual concentrations were increasing, decreasing or stable from one hour to the next. When non-continuous sampling was used at sites experiencing small changes from one hour to the next, more than 85 and 60% of the estimated hourly average values were within ±5 and ±2.5 ppb of the actual values, respectively. For a site where average O₃ concentrations changed rapidly from one hour to the next, a greater error was observed. For the daily 7- and 12-h average values, when hourly average concentrations did not change rapidly from one hour to the next, 85% or more of the estimated values agreed within ±2 ppb, independent of sampling frequency. Greater uncertainty was experienced when hourly average concentrations changed at a faster rate. When considering the uncertainties associated with non-continuous sampling, investigators should specify the level of accuracy needed to characterize hourly average concentrations and then select the number of samples per hour required to meet that objective.     

浙江省中西部典型地区PM2.5中二次有机气溶胶示踪物的分布特征

为了解我国中小城市地区SOA（二次有机气溶胶）的质量浓度及来源,采集了浙江省中西部典型地区——兰溪市城区和近郊2个站点2016年四季的PM_2.5样品,利用GC/MS（气相色谱/质谱）分析了PM_2.5中11种指示不同来源的SOA示踪物的质量浓度水平,利用示踪物产率法估算了不同来源前体物对SOC（二次有机碳）的贡献.结果表明:兰溪市PM_2.5中ρ（异戊二烯SOA示踪物）的年均值为40.79 ng/m3,约占检测示踪物总质量浓度的89%;ρ（α-蒎烯SOA示踪物）、ρ（β-石竹烯SOA示踪物）和ρ（甲苯SOA示踪物）的年均值分别为4.09、0.36和1.01 ng/m3.ρ（异戊二烯SOA示踪物）和ρ（α-蒎烯SOA示踪物）存在夏季 > 秋季 > 春季 > 冬季的季节性变化趋势,ρ（β-石竹烯SOA示踪物）为秋季、冬季 > 春季、夏季,而ρ（甲苯SOA示踪物）的季节性变化不显著,表明不同类型VOCs（挥发性有机物）前体物排放量的季节性变化明显不同.基于示踪物产率法的估算结果表明:夏季异戊二烯等植物源VOCs可能是兰溪市PM_2.5中SOA的主要来源;而春季、秋季、冬季甲苯等人为源VOCs是SOA的主要前体物,贡献了兰溪市PM_2.5中ρ（SOC）的60%左右.研究显示,减少人为源VOCs的排放对相关地区灰霾及大气细颗粒物污染的防控具有重要作用.      

Measurements of wind speed and plume rise with a rapid-scanning Lidar

A series of 30-min means of plume rise and dispersion parameters were measured at Fawley power station on Southampton Water between May and December 1989 using a rapid-scanning Lidar. Where possible, plume parameters were determined at three distances, typically 250, 750 and 1500 m, from the stack. Simultaneous measurements of temperature profiles were made using model aircraft and of wind speed and direction using a cup anemometer and wind vane at a height of 44 m on a transmission tower. By matching time series of plume heights at different distances, absolute measurements of wind speed at plume height could be made. These measurements gave a more reliable estimate of plume rise than did surface wind speeds. It was found that, for travel distances out to 1.5 km, the Briggs formula gave a robust prediction of plume heights with C₁ = 1.38±0.07 (95% confidence limits). At Fawley, the standard error in the predicted plume height at 500 m was then 21.0 m, or 19% of the 30-min mean plume rise. For plume-level winds of less than 20 m s⁻¹, analysis of the dependence of plume height on distance, wind speed and power-station load gave a virtual source height of 195.2±10.3 m (95% confidence limits). This is identical with the physical stack height of 198.1 m.     

福建惠安核电厂址SF6示踪试验研究

2 0 0 2年 7月在福建惠安核电拟选厂址复杂地形进行了 15次SF6示踪试验 .试验发现 ,在不同天气条件下 ,SF6烟羽呈现过宽、过窄扩散及越山、绕流等现象 .将此次试验推荐的扩散参数与P G扩散参数系及其它实验结果进行了比较分析 .     

浙北地区真菌气溶胶示踪物季节分布特征

于2014年12月—2015年11月收集了浙江北部地区4个采样点的PM2.5样品,利用高效液相色谱-串联质谱仪分析获得真菌气溶胶示踪物阿糖醇和甘露醇的浓度,研究了浙北地区真菌气溶胶的季节性变化特征及其来源.观测结果显示,浙北地区阿糖醇和甘露醇的年均浓度分别为(5.6±0.7)和(5.7±1.3)ng·m-3.真菌气溶胶示踪物夏季浓度最高,可能是由于当地夏季频繁的生物质燃烧和温暖湿润的气候条件促进了真菌孢子的释放;另外,在该地区真菌孢子对气溶胶中有机碳(OC)的贡献并不显著(1%).主成分分析显示,真菌气溶胶示踪物(阿糖醇、甘露醇)和生物质燃烧示踪物(左旋葡聚糖、甘露聚糖、半乳聚糖、nss-K+)在整个采样过程中都包含在同一个因子中,表明浙北地区大气中真菌气溶胶持续受到生物质燃烧排放源的影响.     

Measurement of tire tread in urban air by pyrolysis-gas chromatography with flame photometric detection

The concentration of tire tread in suspended particulate matter (SPM) was measured by a new method based on benzothiazole generated by pyrolysis of vulcanization accelerator. The variation of production yields of benzothiazole was examined for 24 kinds of tire treads currently used in Japan Pyrolysis was carried out at 670°C using a Curie-point pyrolyzer.The vertical profile and diurnal pattern of tire tread were investigated with 4-h samples continuously collected for 24 h at a heavy traffic density area in Tokyo. The diurnal percentage of tire tread in SPM at the sampling site of 86 m height showed two peaks following the trend of traffic density throughout the day. The concentration of tire tread collected at the 86 m level was about 30% of that at the 0 m level during the daytime. The seasonal variation of concentration of tire tread in SPM was measured at the sampling site located 20 km SW of Tokyo. The weight percentage of tire tread in SPM varied between 1.3 and 3% in winter with NE-NW wind and varied between 0.5 and 1.5% in spring with SE-SW wind.     

泰山夏季PM2.5中生物源SOA的分子组成及影响因素

为探究泰山夏季PM_2.5中生物源二次有机气溶胶（BSOA）的分子组成、昼夜变化特征、及影响因素,于2016年7~8月在泰山山顶进行PM_2.5样品采集,并对碳质组分、无机离子和BSOA示踪物进行分析.结果表明,元素碳（EC）和左旋葡聚糖质量浓度处于较低水平且昼夜差异较小（t检验,P < 0.05）,表明采样期间泰山山顶气溶胶受人为污染排放的影响较小.BSOA示踪物的总质量浓度呈昼高夜低的变化特征,表明白天较强的温度和太阳辐射使得气溶胶的氧化程度比夜间强.其中,异戊二烯类SOA示踪物的质量浓度最高达（77.64±51.79）ng/m³,其次为单萜烯类和倍半萜烯类SOA示踪物,分别为（33.68±21.29）和（6.97±3.28）ng/m³.基于示踪物-产率法估算得出SOC_异戊二烯对有机碳（OC）的贡献率（15.3%）最高.由BSOA示踪物与RH（R￡-0.45）和pH_is（R￡-0.53）的负相关性可知,高湿条件可以降低气溶胶的酸度进而抑制BSOA通过酸催化氧化反应的形成.由BSOA与温度和人为源指示物（左旋葡聚糖和EC）的相关性分析得出,采样期间泰山地区BSOA主要受当地BVOCs氧化反应的影响,而受长距离传输人为污染源的影响较小.     

淹水条件下三峡库区典型消落带土壤释放DOM的光谱特征:紫外-可见吸收光谱

消落带土壤在淹水发生时释放溶解性有机质(DOM),是上覆水体DOM的重要来源.但同时对淹水释放DOM进行定量定性分析的报道并不多见.本文以三峡库区典型消落带为研究对象,通过模拟实验,利用紫外-可见吸收光谱,研究了厌氧淹水和正常淹水条件下,淹水土壤释放DOM的光谱特征.结果表明,消落带4个区域土壤淹水均呈"快速释放-下降-动态平衡"释放规律;释放速率和通量计算表明,DOM释放呈现出"源-汇动态交换"特征.对比两种淹水处理,尽管溶解性有机碳(DOC)和有色溶解性有机质(CDOM)无显著差异,但厌氧淹水DOM芳香性(SUVA280)高于正常淹水,而光谱斜率比值(SR)对不同淹水条件不敏感.同时,厌氧淹水时,DOC和CDOM的相关性也明显高于正常淹水.另外,各区域土壤淹水释放DOM存在差异,以忠县石宝寨土壤释放强度最高,尽管土壤有机质含量是影响各区域土壤淹水释放DOM差异的重要原因之一,但其他地化因素仍需考虑.因此,仅仅关注DOC浓度变化并不足以完全描述DOM的释放特征.