大流量大气颗粒物采样器质量控制技术

利用ISA1932喷嘴流量计和2031型采样器，测试了PMS-800大流量大气颗粒物采样器的流量和总采样效率，研究建立了大流量大气颗粒物采样器质量控制方法。结果表明，PMS-800采样器流量计与ISA1932喷嘴流量计的相对偏差小于5%，总采样效率与2031型采样器的相对偏差小于10%，满足全面禁止核试验条约（CTBT）相关技术文件要求。该方法可用于大流量大气颗粒物采样器的质量控制。     

PMS-500 可吸入颗粒物采样器的研制和性能测试

研制了用于环境中可吸入颗粒物(PM10)采样的 PMS-500 采样器.采样器运行流量为560 m3/h,采用变频技术控制流量稳定,用聚丙烯纤维滤材作为PM10的收集介质.设计了一种矩形喷嘴撞击器作为PM10切割器,撞击器的收集介质为容尘量较大的聚氨酯泡沫.对采样器的性能测试结果为切割器的切割粒径为9.9 μm,捕集效率曲线的几何标准偏差为1.4;采样期间流量波动在±2%之内;双层滤材对0.2 μm气溶胶的收集效率不小于99%.采样器可方便地拆分为三部分,机动性较好.本采样器与市售大流量PM10采样器的采样效率相当,其性能可以满足环保行业对PM10采样的要求.     

衡阳市大气颗粒物中~(210)Po的活度-粒径分布测量

利用大流量撞击式分级采样器、放化分离提纯技术和α谱仪测量技术,建立了针对大气颗粒物中210Po的活度及活度-粒径分布的测量方法,并应用该方法分别于春季和秋季对衡阳市城区大气颗粒物中210Po的活度及活度-粒径分布进行了测量。实验测量结果表明,衡阳市城区大气颗粒物中210Po的含量处于正常水平;总体积比活度和质量比活度的分布范围分别为:0.012 5 m Bq·m-3~1.165 8m Bq·m-3、0.459 7 Bq·g-1~13.859 8 Bq·g-1,体积比活度含量占TSP中总含量93%的210Po存在于粒径范围小于3.0μm(PM3.0)的颗粒物中;雾霾天气会提高公众所接受的天然内照射剂量;同时发现雨水对大气颗粒物中210Po的净化作用较为明显。     

高流速下气溶胶取样滤材的性能测试

根据大流量(≥500 m3/h)气溶胶采样器的需求,建立了滤材的收集效率和压力降的测量装置,确定了实验条件,对0.5~1.4 m/s高流速下取样滤材的性能进行了测试。选用两种聚丙烯(NF、HB1)和两种玻璃纤维滤材(SW 39、GF/A),对其理化性质进行了表征,测量了不同流速下空白滤材的收集效率和压力降,并计算了滤材的品质因子,对空白滤材的性能进行了初步评价。结果显示,在测定的4种滤材中,0.5 m/s和1.0 m/s流速下NF滤材的品质因子最高,1.4 m/s流速下SW 39滤材具有较高的品质因子。此结果对于取样滤材的选择具有指导意义。     

大气颗粒物滤材样品探测效率的模拟计算

在简要介绍全面禁止核试验条约(CTBT)组织临时技术秘书处(PTS)组织的2003年度大气颗粒物样品国际比对的基础上,对此次比对活动中使用的高纯锗探测器系统、样品几何形状和屏蔽情况进行了详细描述.采用蒙特卡罗程序模拟计算了高纯锗探测器测量滤材样品条件下的峰效率和总效率,模拟计算结果与PTS提供的参考值分别在3.5%和6.5%内符合,为准确定量分析样品中核素的含量奠定了基础.     

分体式大气气溶胶采样器的研制及应用

大气中放射性核素监测是环境辐射监测的主要内容之一,大气颗粒物采样器是放射性核素监测的关键设备。为了满足气溶胶放射性核素机动监测的要求,研制了分体式大气气溶胶采样器,该采样器日常取样流量450 m3/h,满足每天取样体积大于10 000 m3的取样量要求,拆装方便,拆分后单件部件不大于120 kg,实现了机动灵活地开展大气放射性气溶胶监测。该采样器成功应用于福岛核事故气载污染物以及大气放射性本底监测。     

DQ-2型气载放射性碘采样器的研制

本文主要介绍了DQ 2型气载放射性碘采样器的结构特点和技术性能的测试结果。粒子碘单元采用直径 60mm的高效过滤膜 ,气态碘单元采用 2级以粒径 60～ 80目、厚度为 2cm的浸渍椰壳活性炭为吸附剂的活性炭盒采样。测试结果表明 :1 )气密性好 ,气态碘单元未见可检出的泄漏 ,粒子碘单元的泄漏率小于 0 .1 % ;2 )阻力较小 ,在 8.0m3/h的流量下 ,采样器的总阻力为 3 0kPa;3 )效率高 ,对粒子碘的采样效率可达 99.9% ,甲基碘的吸附效率随采样流量和相对湿度的增加而下降 ,当流量为 3 .0m3/h,相对湿度低于 40 % ,炭层厚度为 2cm时 ,对甲基碘的吸附效率达到 99.997% ,可用于碘吸附器的除碘效率试验 ;4)采样器在 80℃下仍可使用 ;在高相对湿度 (95 % )时 ,推荐的采样流量为不超过 3m3/h。     

基于~(210)Bi的β计数测量~(210)Pb的活度

选用M235型大气颗粒物分级采样器,在上海、衡阳等地开展可吸入大气颗粒物(PM10)的粒径分级采样,对比分析了210Pb活度的不同测量方法。利用210Bi与210 Pb在同一衰变链上活度最终平衡的特点,通过低本底β计数测量并计算得到不同粒径尺度上大气颗粒物中210Pb的活度。结果表明:上海市、衡阳市大气颗粒物中不同粒径范围的210Pb活度分布非常不均匀,分别约91.58%、91.37%活度分布在粒径范围小于或等于1.5μm的颗粒物中;与利用低本底反康普顿效应的γ谱测量方法得到的结果比较,发现两种方法得出的不同粒径范围大气颗粒物中210Pb活度分布具有几乎相同的分布规律。     

恒流控制放射性气溶胶采样器设计

针对传统开环控制的放射性气溶胶采样器存在采样误差较大、采样流量控制精度低、采样流量不可控等问题,设计了可恒流采样的放射性气溶胶采样器。该采样器在ARM嵌入式系统的硬件环境下,将模糊控制和PID控制结合起来构成模糊自整定PID控制器,动态优化PID参数,从而对风机的输出功率进行及时、准确调整,达到使采样器采样流量恒定的目的。测试结果表明:该采样器瞬时流量响应时间小于7 s;瞬时流量测量误差小于±1%;累积采样体积误差小于±3%。     

大气颗粒物中~(210)Pb的活度-粒径分布测量

用M235大气颗粒物分级采样器采样获得不同范围粒径的可吸入大气颗粒物样品,然后分别用β分析方法和γ分析方法测量不同粒径尺度样品中的210Pb的活度分布。得到大气颗粒物样品中210Pb的体积比活度在不同粒径上的分布范围为0.004 4–1.832 1 m Bq·m-3,最大值均落在0.49–0.95μm粒径范围。两种分析方法所测得的数据具有近似的活度-粒径分布关系,其离散性变化规律也基本一致,都是在粒径范围为0.49–1.5μm之间的标准差最大,β计数法测量的数据离散性整体比γ计数法测量的数据偏大。     

Study of particulate emissions near a steel plant in Genova by continuous sampling and PIXE hourly analysis

The particulate emissions near a large steel plant located in a densely inhabited suburb of the town of Genova (Italy) have been studied for a period of six months. We have used two-stage continuous streaker samplers and subsequent PIXE analysis with hourly resolution, to follow both seasonal and daily trends. The first streaker sampler remained installed very close to the plant cokery and furnaces, while another sampler was moved to different locations. Samples have been analysed by PIXE, deducing concentrations for elements from Na to Pb. During part of the campaign, the aerosol fractions with aerodynamic diameter (D_ae) < 2.5 μm (fine fraction) and with 2.5 < D_ae < 10 μm (coarse fraction) have been separately collected. We have measured and analysed about 8500 PIXE spectra: the steel plant emissions have been identified to some extent and resolved from other aerosol sources.     

Recent Developments in Air Particulate Monitoring

During the past 50 years, man has become acutely aware of the air pollution pervading our environment. Thus he has focused a considerable amount of scientific study on the chemical and physical properties of gaseous and particulate contaminants. A key element in the classification of particulate pollution is the sampling procedure used to collect particles, with the emphasis on separating the respirable from the non-respirable fraction. Generally, impaction techniques have been utilized for size collection of particulates, but these procedures can be affected by the nature of the impaction collection technique which can cause the particles to bounce from one stage to the next, particularly when larger sample quantities are desired for chemical analysis and gravimetrics. Recently EPA, working with several other investigators, perfected a dichotomous collection device, based on virtual impaction principles, which separates and collects particles into two size ranges, 0 to 3.5 microns and 3.5 to 20 microns. Particle bounce at the collection surface is not a problem with this sampler because particles are captured by filtration. The operation and design of manual and automated virtual impactors are discussed. In addition, the application of x-ray fluorescence to the analysis of particulates collected with the dichotomous sampler is described.     

秦山核电厂气态流出物监测系统的研究及其改进

秦山核电厂气态流出物取样监测系统采用了较长的水平取样管和垂直取样管．使核电站气态流出物排放监测存在设计上的缺陷由于取样管道过长（特别是水平取样管道）．会造成气溶胶和碘取样过程的管道沉积损失改进后,将气溶胶和碘的取样监测系统移至烟囱底部的校正室．取消了长度为85．4m水平取样管线．取样管改为只有70．6m的垂直管．试验测试及评价结果表明：放射碘的取样校正因子可取作1．65对于放射性气溶胶．按最保守的估计．事故工况下．其校正因子最大也不可能大于1．65;在正常运行期间,气溶胶粒子均以小粒径为主,可将校正因子取作 1.1.     

PIXE和XRF用于北京新镇地区PM2.5源解析研究

大气颗粒物(APM)对人体健康和环境的影响越来越受重视,我国增设了PM2.5标准,同时提出了大气污染的专项治理措施。本文采用GENT二级取样器在北京郊区新镇进行连续取样,并用质子激发X射线荧光分析和能量色散X射线荧光分析对北京新镇地区收集到的140个大气颗粒物样品进行了多元素分析,对测量数据进行了可靠性评价和数据重组,结合取样、气象等参数建立了新镇地区大气颗粒物污染成分数据库,利用正矩阵因子模型进行污染源解析研究。初步认定了5个主要污染源,即燃煤源(29.2%)、汽车尾气和垃圾焚烧源(26.2%)、建筑工业源(23.3%)、土壤源(15.4%)以及含氯工业源(5.9%)。并结合气象数据进行了污染源来源研究,根据条件概率函数和潜在源贡献函数的计算结果作出了污染源来源分布图,发现污染来源与周围环境基本符合。     

Detection of non-sea salt sulphate aerosol at a remote coastal site in South Africa: A PIXE study

An aerosol sampling site based on a single-stage streaker sampler with four-hour time resolution was established in 1993 at Brandt-se-Baai, on the north-western coast of South Africa (31.5°S 18°E, 50 m asl). The site was deployed to monitor the generation of dust from the local mining operations and in part to test the hypothesis of large-scale air mass recirculation over Southern Africa. Streaker samples were analysed by PIXE for the usual crustal derived elements and sulphur. Sulphate aerosols over southern Africa are produced in the atmosphere by oxidation of SO₂, from industry, or DMS, from the ocean. Industrial related sulphate plays a key role in tracing long-range transport of anthropogenic pollutants.

We present results from selected monthly samples collected during 1996. Measured particulate sulphur has been apportioned between contributions from sea spray and non-sea salt sulphate (NSS) aerosols. Marine particulate sulphur, present in the regional background, was traced by its correlation with Na and Cl, which were routinely detected. The NSS content of these air masses was enriched with respect to the expected sea salt sulphur by two orders of magnitude. Al, Si, K, Ca, Ti and Fe, the major crustal elements, were measured only episodically with the occurrence of strong south-easterly winds. These winds are associated with wind blown dust from a mine located 4 km from the site.

These results are the first direct aerosol characterisation of the remote region of the western seaboard of southern Africa. Specifically the sulphur measurements at this site provide insights into relative contributions of natural DMS, industrial and sea salt contributions of particulate sulphate.     

Two years of aerosol pollution monitoring in Singapore: a review

An aerosol sampling campaign was initiated more than two years ago in Singapore. The aim was to determine the average elemental concentrations in fine and coarse aerosol fractions as well as to identify major pollution sources and their impact. For that purpose, two air samplers were employed at two different sampling locations; one sampler was a fine particulate aerosol sampler (PM2.5) located at the vicinity of a major industrial area. The other was a stacked filter unit (SFU) sampler designed for collection of fine and coarse fractions (PM2.5 and PM10) and installed in the residential area. Samples were taken typically twice a week and in several occasions daily. During the period of two years more than 700 aerosol samples were collected and analyzed using PIXE and RBS techniques. All samples were analyzed for 18 elements ranging between Na, Mg, Al, etc. up to As and Pb. Large daily and seasonal variations were found for most of the elements. These variations are attributed mainly to meteorological changes, in particular changes in wind speed and direction. On several occasions, short term sampling was performed to identify fingerprints of major pollution sources such as road traffic, refineries, as well as the rain-forest fires in neighboring countries. A summary of our findings is presented and discussed.     

HTO被动式取样器的制备及其在密闭核动力装置中的应用

针对核动力舰船的环境特点,采用吸附介质为乙二醇与无氚水混合液（体积比为1:1）的被动式取样器来监测密闭核动力装置中HTO的浓度。在不同的工作场所连续监测1个月,该取样器的最大相对偏差小于10 %;将该取样器与硅胶作为吸附介质的被动式取样器进行为期1 a的对比实验,测量误差小于6%。结果表明,该取样器能准确地测量到低浓度的HTO,满足密闭核动力装置中HTO的监测需求。      

基于FPGA的时间序列采集器

叙述了一种同时记录两路脉冲信号到达探测器时刻的时间序列采集器,可对脉冲信号进行时间测量.其时间精度从5ns～1ms可调,单路最高计数率可达105s-1.采集器主要使用可编程逻辑门阵列FPGA技术,通过USB接口将记录的时间数据送入计算机并保存.采集器记录时间范围大,分析时间范围广,具有数据处理灵活、可利用信息量大等优点,可组成多道时间分析系统,进行时间间隔测量.     

高放泥浆研究Ⅲ.高放泥浆取样系统的研制及取样

介绍了我国自行研制的高放泥浆取样系统的设计原则、结构组成及工作原理,并将该系统用于现场取样。取样结果表明,该取样系统安全可靠,可定位定量、方便快捷地完成取样工作,已成功应用到高放泥浆取样工作中。