A Portable Electrical Analyzer for Size Distribution Measurement of Submicron Aerosols

An electrical aerosol analyzer capable of performing rapid, in situ size distribution measurement on aerosols from 0.003 to 1 μm diameter has been described. The instrument is based on the “diffusion charging-mobility analysis” principle first described by Whitby and Clark. The prototype instrument has a total volume of 3.75 ft³ and a total weight of 60 lb, and is sufficiently portable to be used on small airplanes and ground based vehicles for mobile air pollution studies. The paper describes the design, operation, and performance of the instrument. Sample data are presented showing the size distributions of aerosols measured by the instrument on board a small research aircraft over the Los Angeles basin at several different altitudes. In addition, data are presented showing the size distribution of smog chamber aerosols and aerosols produced by a conventional Collison atomizer.     

Flame lonization Hydrocarbon Analyzer

Outbreaks of bronchial asthma, defined by sharp peaks above the average number of emergency room visits at Charity Hospital in New Orleans, have been noted in this city since the early 1950’s. These outbreaks have occurred during the summer and fall, with the months of October and November containing the most frequent and severest episodes. Early work on this problem associated emissions from spontaneous underground burning in abandoned city dumps with the high incidence and extracts for skin testing prepared from the emissions produced a significant number of positive skin tests in persons involved in the asthma outbreaks. Recent investigation showed that other sources of allergenic air pollution in the city were related to the epidemics of asthma. Attention has been focused on a large public grain elevator at the Mississippi River in the southwestern portion of the city. Grain extracts have produced high percentages of positive responses in susceptible patients with low response rate found in control subjects. Persons known to have participated in these outbreaks have been characterized as being allergic; a low incidence of patients with chronic bronchitis and emphysema has been found in this group. New meteorological data regarding the outbreak periods has been collected.     

A Review of Personal/Portable Monitors and Samplers for Airborne Particles

A review of personal and portable particulate monitors and samplers for measuring and sampling airborne particulate matter is presented. These monitors and samplers are proving to be valuable tools for assessing individual exposure to environmental and occupationally generated particulates. The devices are characterized in terms of their sampling characteristics, their monitoring or measurement technique, their particle size separation (50% cut point) capabilities, their sampling flow rate, and their sampling duration per one battery charging cycle. All of the monitors and some of the samplers are commercially available. Commercial sources and originators (in the case of research devices) are made available.     

Field Reliability of the Orsat Analyzer

Results from four field based collaborative tests and from one laboratory based collaborative test of the Orsat analytical procedure are discussed. The results from the five collaborative tests demonstrate that routinely using Orsat data to convert particulate emissions from combustion sources to the reference conditions of 50 % excess air and 12% carbon dioxide may introduce sizeable errors in the corrected particulate loading. Ways to improve the Orsat apparatus and increase the reliability of the data are suggested.

Also reported are the results from field and laboratory studies on the reliability of using individual carbon dioxide and oxygen analyzers of the Fyrite* type to determine stack gas molecular weight. The laboratory study, which was done using three cylinders containing mixtures of carbon dioxide, oxygen, carbon monoxide, and nitrogen of known concentration, determined that these analyzers give carbon dioxide and oxygen analyses of sufficient reliability to yield accurate molecular weights. The results of the field studies, which were done on actual flue gas samples, also support this conclusion.     

Dynamic Calibration of an Acid Aerosol Analyzer

A method is described for dynamic calibration of an acid aerosol analyzer based on a commercial modification of the Thomas Autometer and manufactured by the Instrument Development Company. This automated instrument removes acid aerosol from an air stream by sonic impaction, and the sulfuric acid collected is determined conductometrically. An all-glass aerosol generator based on the reaction of water vapor with sulfur trioxide vapor released from fuming sulfuric acid was built for the calibration. Air samples were withdrawn for instrument calibration before and after the concentration of the acid aerosol was determined by titration. The apparent particle size as determined by an Andersen sampler ranged from 2.0 microns to less than 0.68 micron and exhibited a sharp peak with mass median diameter at 1.3 microns in the distribution curve. The size of the aerosol, within certain limits, could be controlled by humidity. Data indicated a linear response with an aerosol collection efficiency of 80 percent in the important respirable size range.     

Evaluation of Method 25 Nonmethane Organic Analyzer Design

Under contract to the U.S. Environmental Protection Agency, Research Triangle Institute has been conducting research to improve the precision, accuracy and limit of detection attainable with the EPA Method 25 nonmethane organic (NMO) analyzer. In Method 25, volatile organic carbon (VOC) samples are collected by drawing gas from an emitting source through a dry ice cooled sample trap and into an evacuated collection tank. The hydrocarbon concentration emitted from the source is determined on a per-carbon basis by catalytically converting the trap and tank sample fractions to CO₂ and quantitating the amount of CO₂ produced using the NMO analyzer. A reduction catalyst evaluation led to the selection of an NMO analyzer reduction catalyst which operates at a moderate temperature and displays no appreciable effect on peak shape. A gas chromatographlc column system which provides better permanent gas separation and hydrocarbon quantitation was also selected for use in the NMO analyzer.     

Development of a High-Temperature Subtractive Analyzer for Hydrocarbons

This paper discusses the development of a high-temperature subtractive analyzer for separating the hydrocarbons present in gaseous mixtures into two categories— reactive hydrocarbons and unreactive hydrocarbons. The analyzer utilizes the ability of selected substances to absorb certain groups of hydrocarbons and their derivatives from a gas mixture and is designed for operation with a flame ion-ization detector. The body of information presented in this paper is directed to individuals concerned with the analysis of the exhaust gases of gas turbine engines or other combustion sources as stationary power plants. The analyzer grew out of an investigation of a previously reported subtractive analyzer system which operates at ambient temperature. Current state-of-the-art requirements for the accurate determination of total hydrocarbons at the concentrations present in turbine exhaust gases necessitate that sampling and measurements be conducted at elevated temperatures (325-375°F), rather than ambient temperature, to reduce or eliminate condensation and wall adsorption sampling errors. To fulfill this requirement, the sampling lines and flame ionization detector must be heated. After tests determined that the previously reported scrubber system would not remove the same hydrocarbons at elevated temperature levels as it did at ambient temperatures, an investigation of the effectiveness of various absorbents at elevated temperatures was conducted. This led to the development and test of the high-temperature subtractive analyzer concept discussed in this report. In its final form, one path of this unit contains no absorbent, the second contains a column of concentrated H₂SO₄ on Ultraport and a column containing PdSO₄ and H₂SO₄ on Ultraport. The two columns are connected in series. The absorbents remove olefins, aromatics, acetylene, and oxygenated hydrocarbons but pass paraffins. As the final step in this program, a comparison of the two subtractive analyzers was made using the exhaust from a gas turbine combustion system.     

Characterization of the Sunset Semi-Continuous Carbon Aerosol Analyzer

Abstract

The field-deployable Sunset Semi-Continuous Organic Carbon/Elemental Carbon (Sunset OCEC) aerosol analyzer utilizes the modified National Institute for Occupational Safety and Health thermal-optical method to determine total carbon (TC), organic carbon (OC), and elemental carbon (EC) at near real-time. Two sets of OC and EC are available: thermal OC and EC, and optical OC and EC. The former is obtained by the thermal-optical approach, and the latter is obtained by directly determining EC optically and deriving optical OC from TC. However, the performance of the Sunset OCEC is not yet fully characterized. Two collocated Sunset OCEC analyzers, Unit A and Unit B, were used to determine the pooled relative standard deviation (RSD) and limit of detection (LOD) between September 18 and November 6, 2007 in Richland, WA. The LOD of Unit A was approximately 0.2 μgC/m³ (0.1 μgC/cm²) for TC, optical OC, and thermal OC, and 0.01 μgC/m³ (0.01 μgC/cm²) for optical EC. Similarly, Unit B had an LOD of approximately 0.3 μgC/m³ (0.2 μgC/cm²) for TC, optical OC, and thermal OC, and 0.02 μgC/m³ (0.01 μgC/cm²) for optical EC. The LOD for thermal EC is estimated to be 0.2 μgC/m³ (0.1 μgC/cm²) for both units. The pooled RSDs were 4.9% for TC (carbon mass loadings 0.6–6.0 μgC/cm²), 5.6% for optical OC (carbon mass loadings 0.6–5.4 μgC/cm²), 5.3% for thermal OC (carbon mass loadings 0.6–5.3 μgC/cm²), and 9.6% for optical EC (carbon mass loadings 0–1.4 μgC/cm²), which indicates good precision between the instruments. The RSD for thermal EC is higher at 24.3% (carbon mass loadings 0–1.2 μgC/cm²). Low EC mass loadings in Richland contributed to the poor RSD of EC. The authors found that excessive noise from the nondispersive infrared (NDIR) laser in the Sunset OCEC analyzer could result in a worsened determination of OC and EC. It is recommended that a “quieter” NDIR laser and detector be used in the Sunset OCEC analyzer to improve quantification. Future work should re-evaluate the precision of the EC parameters in an environment favorable for EC collection. Investigation among quantification differences using various thermal-optical protocols to determine OC and EC is also in need.     

A Portable Fiber-Optic Chemical Device for the Quantitative Determination of Carbon Monoxide from Automobile Exhaust Emissions

ABSTRACT

A colorimetxic method for the quantitative determination of CO by diffuse reflectance is described. This method is based on the reduction by CO of Mo (VI) from the indicator reagent molybdosilicic acid (H₈Si[Mo₂O₇]₆). The reduction yielded a change of color from clear yellow to dark green on white disk filter chart paper wetted with reagent indicator solution. The gaseous mixture containing CO was forced to pass through this chart paper, initiating the reaction. The intensity of the color produced, measured by diffuse reflectance, was proportional to the CO concentration present in exhaust gases in the range from 0.02 to 12% volume/volume (v/v). A 650-nm light-emitting diode was used as a light source. A two-fiber-optic system carried the light from the source to the detection system, which was composed of a photodiode, an amplification circuit, and a digital display. The method was applied with success in field measurements for automobiles in the Otto cycle. In a previous paper, this method was used for the quantitative determination of exhaust emissions from diesel-fueled vehicles.¹     

Portable Emission Measurements of Yellowstone Park Snowcoaches and Snowmobiles

Abstract

As part of the National Park Service’s Temporary Winter Use Plans Environmental Assessment, the University of Denver has been collecting in-use tailpipe emissions data from snowcoaches and snowmobiles in Yellowstone National Park. During the winter of 2006, using a portable emissions monitoring system, tailpipe data were collected from 10 snowcoaches and 2 four-stroke snowmobiles. These vehicles were operated over a standard route within the park, and the snowcoaches all carried identical passenger loads. These snowcoaches were newer in age with more advanced fuel management technology than those studied earlier, and average emissions were lower as a result (120, 1.7, and 11 g/mi for carbon monoxide [CO], hydrocarbons [HC], and oxides of nitrogen [NO_x]). Large emissions variability was still observed despite using a standardized route and equal passenger loading. A comparison between five nearly identically equipped snow-coaches that had CO emissions ranging between 12 and 310 g/mi suggests that snow and road conditions are the most important factors behind the large emissions variability observed between modern snowcoaches. The first comprehensive emission measurements, using a portable emissions measurement system, on two snowmobiles showed that computer-controlled fuel management systems have increased fuel economy (>25 mpg) and are a major reason that emissions from these winter vehicles have dropped so dramatically. Using all of the tailpipe emissions data collected to date shows that the two primary winter vehicles in Yellowstone National Park are now very similar in their per-passenger emissions.     

中文智能pH在线监控仪及其算法开发

介绍了中文智能ｐＨ在线监控仪的性能、工作原理，功能及软件硬件设置，分析讨论了几咱不同的控制算法。     

间隔流动分析仪测定水和废水中的总氰化物

利用间隔流动分析仪测定水中的氰化物，对测定方法的检出限、重现性进行了实测，用氰化物的有证标样验证其准确性，其相对标准偏差为1．5％，相对误差为6．2％，测定方法的精密度及准确度均较好，并与国标方法进行了比较。     

On-Road Measurement of Vehicle Tailpipe Emissions Using a Portable Instrument

Abstract

A study design procedure was developed and demonstrated for the deployment of portable onboard tailpipe emissions measurement systems for selected highway vehicles fueled by gasoline and E85 (a blend of 85% ethanol and 15% gasoline). Data collection, screening, processing, and analysis protocols were developed to assure data quality and to provide insights regarding quantification of real-world intravehicle variability in hot-stabilized emissions. Onboard systems provide representative real-world emissions measurements; however, onboard field studies are challenged by the observable but uncontrollable nature of traffic flow and ambient conditions. By characterizing intravehicle variability based on repeated data collection runs with the same driver/vehicle/route combinations, this study establishes the ability to develop stable modal emissions rates for idle, acceleration, cruise, and deceleration even in the face of uncontrollable external factors. For example, a consistent finding is that average emissions during acceleration are typically 5 times greater than during idle for hydrocarbons and carbon dioxide and 10 times greater for nitric oxide and carbon monoxide. A statistical method for comparing on-road emissions of different drivers is presented. Onboard data demonstrate the importance of accounting for the episodic nature of real-world emissions to help develop appropriate traffic and air quality management strategies.     

Analytical Performance of Four Portable Gas Chromatographs Under Field Conditions

A field evaluation of the performance of four portable gas chromatographs was conducted at two field sites, one in the Pacific Northwest (chlorinated solvent contamination) and one in the Desert Southwest (primarily jet fuel contamination). The purpose of the study was to compare the performance of four portable GCs under the same conditions. The gas chromatographs had either electron-capture detectors or photoionization detectors. The study evaluated instrument linearity, instrument detection limits, retention time stabilities, response factor stability, and chromatographic performance. Standards and samples contained 1, 1, 2, 2-tetrachloroethane, trichloroethene, tetrachloroethane, 1, 1, 1-trichloroethane, benzene, toluene, and ethylbenzene. In order to ensure data comparability, the same model wide-bore column and computing integrator were used with each instrument, where possible. Significant differences in the performance of the four models were detected under the specific conditions used for this study. The results indicate the need to fully characterize the performance of portable instruments before field use so that appropriate quality control measures can be planned and implemented based on the performance of a specific analytical system.     

高锰酸盐指数在线自动监测仪的现状与问题

高锰酸盐指数在线自动监测仪,已在全国水质自动监测系统中得到广泛的应用,厂家对该产品生产日趋成熟,相关标准逐步出台,仪器性能基本达标。但在实际应用过程中,该仪器仍有许多问题需要进一步认识与改进。文中从标准溶液、终点判定、国家标准、干扰、比对、自动标定等几个方面,分析了该仪器存在的问题,并提出了相关建议。     

An Automatic Atmospheric Fluoride Analyzer With Potential Application to Other Pollutants

The “dichromate” paper developed by Ripley, Clingenpeel, and Hum was used successfully in our laboratory for conversion of nitric oxide to nitrogen dioxide at concentrations up to the 1 ppm level. When this p aper was used for synthetic mixtures with nitric oxide concentrations in the range of 1—3 ppm, the analyses were erratic and values were lower than calculated. After a number of modifications of the procedures for preparing and using the impregnated paper, a modification of the “dichromate” paper was achieved that reduced scatter in the NO analysis and improved conversion efficiency. The efficiency and reproducibility of the modified paper are good enough that efficiency factors may be established to correct data obtained over a period of at least ó hours of continuous use at relative humidities (RH) near 50%.     

Development and Testing of a Portable Wind Sensitive Directional Air Sampler

Abstract

This paper reports on the performance of the Kimoto 180 sampler and the Wedding ambient PM10 beta gauge sampler. Monodisperse ammonium fluorescein test particles were generated in the laboratory and used to determine the penetration curve of the Kimoto 180 cyclonic inlet. It was found that the actual DpaSOof the Kimoto 180 inlet, 3.5 (xm, is much lower than the designated standard value, 10 um. In the field test, the two beta gauge samplers were collocated with an Andersen SA1200 high-volume sampler to compare their measured daily average PM10 concentrations.

The low Dpa50 of the Kimoto 180 inlet serves to explain why its daily average PM10 concentrations were much lower than the actual PM10 concentrations found in the field study. In addition, the PM10 concentrations of the Kimoto 180 beta gauge sampler were found to be seriously affected by the water vapor content of the ambient air. In contrast, the daily average PM10 concentrations of the Wedding beta gauge sampler were found to be more accurate, and influences by ambient conditions were insignificant     

Continuous Determination of Carbon Monoxide and Hydrocarbons in Air by a Modified Infrared Analyzer

The original goals of this project¹ were to establish the shape of a smoke curve for fine suspended particulates in New York City comparable to the International Smoke Curve used in British and other European practice, and to relate two commonly used reporting units of surface concentration, μg/m³ (European practice) and Coh/1000 lineal feet (United States practice), to each other. While not directly a goal of the project, it was essential in the course of work to study the relationship between particulate density readings taken for one hour and two hour sampling periods. Progress toward achievement of these goals is presented in the following pages.