大气采样流量校准问题探讨

大气采样流量校准问题探讨临沂市环境监测站刘忠林，王勇《空气和废气监测分析方法》（以下简称《方法》）中规定，空气中总悬浮微粒物的采样每月校准流量至少一次，２４小时恒温恒流大气采样器中限流孔的流量每周至少校准一次。流量校准是大气采样的一项重要的质量控制措...     

大气采样中流量变化的控制

人工大气采样是环境监测工作中对大气质量进行调查的一个重要手段，我国目前仅有少数的大气地面自动采样系统能局部替代人工采样，绝大部分地区的大气质量调查仍依赖于手工采样，因此在采样中采气流量的稳定是采样质量的保证措施之一。本人在长期的大气环境监测工作中发现和探索了人工大气采样中流量不稳定问题和规律。虽然我们在每次大气采样前对采样仪器进行了一系列的常规校验，如大气采样器、KB—120泵等的流量校准，对U型吸收管的筛板阻力进行了测试筛选。但在整个采样过程中仍会因各种因素产生一些有规律的变化，主要是采样中仪器流…     

碘量法测定固定源废气中高浓度硫化氢的应用

固定源废气中硫化氢含量的测定-碘量法,是分析废气样品中硫化氢含量比较经典的分析方法.该方法准确可靠,测量范围广.但在实际工作中,常常遇到如何把握和控制取样时间和采样流量(尤其是含量较高的硫化氢).为此本文着重从样品的取样时间、流量及滴定分析几方面的细节入手,并进行相应的阐述.     

为柴油车排气烟度检验采样方法的认识

本文对柴油车排气烟度检验的采样方法进行了分析，提出了对采样嘴的改进意见，并指出采样时采样嘴应正对烟气流采样，同时应进行等速采样。     

环境空气监测流量计算中应注意的一个问题

环境空气监测中，为了保证采样流量的准确可靠和监测结果的可比，要进行流量校正和标准状况体积的换算。目前，流量的计算还比较混乱，影响了监测结果的可比性。现就这一问题探讨如下：     

对柴油车排气烟度检验采样方法的认识

本文对柴油车排气烟度检验的采样方法进行了分析，提出了对采样嘴的改进意见，并指出采样时采样嘴应正对烟气流采样，同时应进行等速采样。     

气体污染源中总氟的监测方法研究

通过对玻璃纤维滤筒的预处理,在等速采样情况下达到完全捕捉烟气中的总氟。     

基于大气采样器在室内空气污染物采样中流量误差分析及解决方法探究

室内空气污染物检测是环境检测工作的重要组成部分,通常需要进行采样检测,采样器存在一定的流量误差,可能影响检测结果的准确性,对此就要重视采样环节,注重采样中流量误差的控制。本文分析了流量误差的主要来源,并提出了科学的误差控制方法。     

沥青烟等速采样监测方法的研究

沥青烟由液态烃类颗粒物和气态烃类衍生物组成。本研究设计并制做了沥青烟富集采样装置，将色谱固定要涂在滤筒上，用串联的二级玻璃纤维筒进行了等速采样，该方法为执行辽宁省沥青烟排放标准建立了准确可靠的监测方法。     

烟尘等速采样流量简化公式推导与应用

该文论述了烟尘浓度测试时等速采样的几种方法，供同行商榷。     

利用POCIS技术监测城市地表水中全氟化合物

采用一种针对水体中全氟化合物的改进的极性有机化合物整合采样技术(POCIS)进行了不同水流速度下污染物的吸附动力学,以及水流速度对全氟化合物在该采样器上采样速率的影响研究.结果表明,在不同水流速度下7种全氟化合物在放置时间10d内呈线性关系.POCIS对全氟化合物的采样速率随着水流速度(0.085~0.0018m/s)的降低而减小,但是对个别物质如全氟十一酸的采样速率无明显影响.将所建立的POCIS采样方法应用于南京市地表水中,并与常规的主动监测方法进行比较,发现利用POCIS采样技术推算出的污染物时间权重浓度和两次主动采样测定浓度基本一致.     

Does chorionic villus sampling compromise fetal umbilical blood flow?

A possible association of limb reduction defects with chorionic villus sampling (CVS) may be related to compromised umbilical blood flow from the trauma of the procedure. We hypothesized that because CVS may disrupt or compromise umbilical blood flow to the fetus, either by vasoconstriction, bradycardia, or emboli, we would detect these changes using Doppler velocimetry. A cohort of 21 consecutive consenting patients undergoing first-trimester elective CVS for prenatal diagnosis were entered into a prospective longitudinal study. Colour flow Doppler velocimetry was performed on fetal umbilical arterial blood flow immediately before and after CVS to measure the pulsatility index, fetal heart rate, per cent flow time, and maximum flow velocity. Measurements were obtained from three consecutive cardiac cycles in three different umbilical segments and averaged. Potentially confounding variables also recorded included gestational age, method of CVS, number of passes, number of aspirations, placental location, tissue sample size, and operator. Umbilical velocimetry values before and after CVS were compared using the paired t-test and showed no statistically significant differences. No differences were found when data were analysed by gestational age, sample size, method, number of aspirations, placental location, or operator. We were unable to detect any significant change in fetal umbilical arterial blood flow velocimetry or heart rate after performing CVS. Umbilical blood flow does not appear to be routinely compromised by CVS.     

TSP(IP)采样方法研究及比较

对现行的颗粒物采样的几种方法进行了对比研究。用几种方法同地点进行同步采样，样品微观观测结果表明；几种采样方法所采集的样品中，最大颗粒物的几何尺寸有明显的不同；样品分析及统计结果表明：几种采样方法所得监测结果之间存在着非常好的相关性。通过计算可相互通用，具有可比性；同时给出几种方法相互间的计算公式，可信度区间及可信度。     

基于浮动车数据的机动车排放实时测算模型

根据浮动车检测技术可针对单车采集,所收集数据中的平均速度按照采样间隔连续的特点,利用道路实测数据建立了面向其应用的轻型车尾气排放实时测算模型.模型中引入平均速度增量(ASI)指标对平均速度进行细分,并以其来反映相同平均速度下的排放变化.结果表明,与实测数据相比,模型对CO2的计算误差在10%以内;NOx、HC和CO的计算误差在15%以内.同时提出了模型使用方法,可以实现对路网中交通尾气污染的实时测算和动态评估.     

SO2采样方式改变后的质量分析

环境空气SO2采样由每天采样3次,每次采样30分钟的瞬时采样变成24小时的连续采样,其测定浓度都降低了。其原因主要有,监测点位重新布设后,有些采样点位向郊区转移、进气管接胶管采样、进气管有水、采样流量变小及延迟化验分析等,都影响采样结果。     

离子色谱法测定烟气中的氟和氯

采用试验对比研究的方法测试武汉某玻璃窑烟气中氟和氯的浓度,结果表明:采用EPA Method 26A方法进行采样,一次采样可获得气态氟、气态氯、卤化氢和卤素浓度等多个数据,相对误差小,具备节省时间和人力的优势。分析烟气吸收液优化的色谱条件:设定EG40淋洗液自动发生器KOH浓度为30 mmol/L;淋洗液流速为1.2 mL/min;进样量为25 μL。该方法相对标准偏差小于3.0%,精密度高,样品加标平均回收率为96.7%~104.3%,准确度良好,完全满足烟气样品吸收液氟离子和氯离子浓度的检测要求。     

Fetal ductus venosus flow velocity waveforms and maternal serum afp before and after first-trimester transabdominal chorionic villus sampling

Doppler flow velocity waveform recording in the fetal ductus venosus and umbilical artery as well as maternal blood sampling for serum alpha-fetoprotein (MSAFP) was performed before and after transabdominal chorion villus sampling (TACVS) in 36 women of advanced maternal age (≥ 36 years). Gestational age ranged between 11 and 13 weeks. No chromosomal anomaly was detected. No statistically significant difference was observed in ductus venosus velocity parameters or in the umbilical artery pulsatility index (PI) before and after CVS in 35 women with a normal pregnancy outcome. One case resulted in fetal loss. Post-CVS median MSAFP levels at 12 weeks (25 kIU/1) and 13 weeks (35 kIU/1) were significantly higher than pre-CVS levels. In three cases, post-CVS MSAFP levels were higher than 600 kIU/1, correlating with feto-maternal transfusions of approximately 1.0–1.4 ml, i.e., of around 40 per cent of feto-placental blood volume. One of these cases displayed absence of fetal peripheral blood flow velocities and fetal bradycardia following TACVS, resulting in fetal loss 1 week later. The remaining two cases had a normal pregnancy outcome, but showed a more than 50 per cent reduction in ductus venosus velocity after TACVS, whereas umbilical artery PI remained unchanged. However, similar velocity changes were associated with only small feto-maternal transfusions. Umbilical artery PI values remained unchanged.     

烟道中高负压对二氧化硫测定影响及对策研究

目前中国对二氧化硫的手工监测主要采用定电位电解法,但该方法在实际监测过程中受到高负压干扰选择低、中、高三种浓度的二氧化硫标气,用过减压阀控制采样流量,设定流量为0．4L／min、0．6L／min、0．8L／rain、1．0L／min、1．2L／min和1．4L／min等6种流量,模拟固定污染源的负压流量进行测试。流量在0．4L／min的时候监测结果相对误差最大,监测结果严重偏小,在流量为1．4L／min的时候监测结果相对误差最小,在实验室质控范围内。     

气溶胶在采样管中的沉积特性研究

为了正确评价气溶胶在采样管道中的粒子沉积损失,文章通过实验研究确定了采样管道中粒子沉积与有关参数之间的关系。气溶胶粒子粒径为0.04~8.30μm、采样流量为10~30 L/min、采样管道长度为10~35 m。结果表明,当气溶胶粒径约小于1μm时,穿透率随粒径增大而增加,当气溶胶粒径约大于1μm时;穿透率随粒径增加而减小;气溶胶粒子的穿透率随流速增大而增加;气溶胶粒子的穿透率随采样管长增加而减小。     

Simulation of flow field and steel/slag interface in the mold region of a thin slab steel continuous caster with tetra-furcated nozzle

A three dimensional steady flow field model in the mold region of a thin slab steel continuous caster is presented using real geometrical dimension starting from the inlet port of the nozzle. The results indicate a special flow pattern in the caster while using a tetra-furcated nozzle. The fluid pattern in the mold region is shown to have two large downward and upward recirculation zones with a classic double-roll and two small vortices generated by the upward flow from the upper ports of the submerged entry nozzle. The flow pattern agrees well with the real observation obtained by full scale water model. This study investigates the interface wave behavior and its mechanism that leads to the breakup of the steel/slag interface, and thus the induction of impurities inside the final steel product. It is shown that a maximum wave height occurred because of the fluid contact from the upper ports. A critical casting speed was defined as the casting speed lead to wave instability, mostly associated with emulsification phenomena.