Gas Dilution Apparatus for Preparing Reproducible Dynamic Gas Mixtures in any Desired Concentration and Complexity

A portable gas dilution apparatus has been constructed by which reproducible known mixtures of the common air pollutants added to carbon filtered air can be prepared in any desired quantity, complexity, and concentration. Sulfur dioxide mixtures with and without the addition of nitrogen dioxide and/or ozone have been analyzed by the conductimetric, titrimetric, turbidimetric, and colorimetric methods. Excellent analytical agreement with the concentrations obtained from the volumes of sulfur dioxide, nitrogen dioxide, hydrogen sulflde, and air that are mixed has been shown by all these methods when an efficient absorber is used though the titrimetric method tended to give slightly low results. Some common absorbers show reduced efficiency in absorbing some of the gases. Nitrogen dioxide determinations by the Saltzman method are not significantly affected by the addition of sulfur dioxide to the nitrogen dioxide-air mixtures. A modification of the Saltzman reagent, due to Lyshkow, was tested. It accelerates the rate of color development and should be useful in the automatic nitrogen dioxide analyzer. The determination of hydrogen sulfide is not affected by the presence of nitrogen dioxide in the gas mixture but sulfur dioxide increases the sulfide reading by about 5-15% while ozone decreases the reading.     

Nashville Sulfur Dioxide Emission Inventory and the Relationship of Emission to Measured Sulfur Dioxide

A detailed inventory of sulfur dioxide emissions was prepared as part of the Nashville Community Air Pollution Study conducted by the Public Health Service during 1958–59. The primary purpose of the inventory was to provide data for a study of the relationship between the emission of sulfur dioxide and measured ambient levels. The development of the inventory, data collection methods, and calculations are described. Ambient levels of sulfur dioxide were related to average emissions of sulfur dioxide in such a way (correlation coefficient = 0.81) that mean seasonal concentrations of atmospheric sulfur dioxide in square-mile areas could be predicted with fairly good confidence from a knowledge of sulfur dioxide emissions. For these long-period {average) predictions meteorological variables can be disregarded. On a square-mile basis, on the average, one ton of sulfur dioxide emitted per day produced a mean atmospheric sulfur dioxide concentration of 0.022 ppm, and 10 tons of sulfur dioxide per day produced a concentration of 0.067 ppm.     

Problems of Relating Atmospheric Analyses to Effects of Air Pollution on Agriculture

Relating of air pollution concentrations to effects on agriculture is hampered by deficiencies in present methods of atmospheric analysis and by inadequate knowledge about how various factors modify the effects. Analytical methods frequently lack sufficient sensitivity or specificity to determine accurately the substances involved. Typical examples include the difficulty of distinguishing among fluoride compounds with loidely differing phytotoxic activity, the serious interference from concomitant air pollutants with the usual methods of determining ozone, and the common failure or inability to detect short interval concentration extremes which may cause acute injury. The interrelationship of pollutant concentration and length of exposure in determining plant injury is poorly understood, as are the modifying effects of environmental conditions and age of tissue. The identity of some of the phytotoxic components of the urban photochemical pollution complex is still uncertain, making it difficult to select appropriate analytical methods. Caution should be exercised in using atmospheric analysis data to predict effects of air pollution on agriculture until these deficiencies in analytical methods and understanding of the problem are overcome.     

Comparison of EGR ratios determined by four different methods for electronic re-circulation gate control

In this study, low pressure systems have been applied for exhaust gas recycling (EGR), which is applied in certain operating conditions. Induction air, exhaust gas flow, amount of exhaust gas added to the induction air, amount of carbon dioxide (CO₂) in the exhaust gas, and amount of carbon dioxide in the induction air mixed with the exhaust gas, have been measured and the EGR ratio has been determined using four different calculation methods. The obtained results have been compared, and it has been noted that all the four methods have given similar results, and the deviation among them has been noted to be 1% at most. Deviations among the results have been explained. In the concluding section, a relation has been formed between the variables chosen as basic parameters, electronic re-circulation gate control, and variables utilised in EGR ratio determination methods.     

Detection and Measurement of Air Pollutants by Absorptions of Infrared Radiation

A technique of detecting gaseous air pollutants by means of absorption of laser radiation is under development at the NASA Electronics Research Center. The iodine infrared laser and the carbon dioxide infrared laser are forced to emit spectral lines which fall on the infrared absorption bands of atmospheric pollutants. The attenuation of a laser line when passed through an air sample is the measure of the pollutant concentration. The narrow spectral width of the laser emission permits sensitive detection, minimizes interference between pollutants, and allows penetration of atmospheric water bands. The collimation and high power outputs available from lasers permit transmission of the radiation over long straight paths through the atmosphere and over long folded paths in multiple-pass absorption cells. A sample of absorbing gas placed within the laser cavity forces the emission of the selected wavelengths. With a one-half kilometer path to a retro-reflector and back, it is predicted that the following concentrations of air pollutants will be detected by means of the indicated laser lines: carbon monoxide at 2 parts per million in air (ppm), using the 4.86 micron iodine line; nitric oxide at 1 ppm, using the 5.5 micron iodine line; ethylene at 0.1 ppm, using the 10.53 micron carbon dioxide line; sulfur dioxide at 1.5 ppm, using the 9.08 micron carbon dioxide line; and ozone at 0.15 ppm, using the 9.52 micron carbon dioxide line. It seems feasible to extend the technique to other gaseous pollutants such as nitrogen dioxide, methane, butane, and peroxy acetyl nitrate. Continuing effort is being devoted to development and construction of the laser transmitting and receiving equipment. Field testing is planned for the near future.     

纳米TiO2光催化剂负载技术研究

纳米TiO2光催化剂在废水处理、空气净化等环保领域具有诱人的应用前景,将其负载于一定的载体上,并设计出高效的光反应器是其实用化的关键之一.本文对纳米TiO2光催化剂负载所用载体、固定方法及其效果、相关光催化化学反应器作了综合评述.     

Air Pollutant Emissions from Coal-Fired Power Plants,Report No. 2

The Public Health Service and the Bureau of Mines are conducting a joint study to evaluate a number of flue-gas-stream components from coal-burning power plants. Emissions of fly ash, sulfur oxides, nitrogen oxides, polynuclear hydrocarbons, total gaseous hydrocarbons, formaldehyde, certain metals, and carbon dioxide are determined. A previous paper covered air pollutant emissions from vertical-fired and front-wall-fired power plant boilers. This paper includes a comparative evaluation of emissions from a tangential-fired and a turbo-fired power plant boiler.     

Transient and Frequency Response of Air Quality Monitors

Results of dynamic or transient tests and steady state calibration of carbon monoxide and sulfur dioxide continuous air quality monitors are reported. Standard gases and permeation tubes were used to establish low level concentrations bpth for the steady-state calibration and the dynamic testing. The steady-state calibration was in excellent agreement with results obtained from grab samples of the calibration gas stream taken with standard gas bubblers and analyzed by the West and Gaeke procedure. Such tests have been carried out by other investigators with similar results. The important contribution of this paper lies in the application of dynamic testing techniques developed by the senior author and co-workers to determine the transient and frequency response characteristics of these air quality monitors.     

Evaluation of the Sodium Arsenite Method for Measurement of NO2 in Ambient Air

The sodium arsenite method for measurement of nitrogen dioxide in ambient air was evaluated. The method has a constant-high collection efficiency (82%) for nitrogen dioxide, and is insensitive to normal variations in operating parameters. Nitric oxide and carbon dioxide are positive and negative interferents, respectively. The combined average effect of these interferents, over ambient levels, is a positive bias of 9.9 µg/m³. This bias, although statistically significant, is minor ( 10 % ) in relation to the ambient air standard of 100 µg NO₂/m³ and does not warrant modification of the method to remove the interference.     

Correlations between mutagenic activity of organic extracts of airborne particulate matter, NOx and sulphur dioxide in southern Germany: results of a two-year study

Goals, Scope and Background Among other substances, sulphur dioxide (SO2), nitric oxide (NO) and nitrogen dioxide (NO2) are parameters which are routinely measured to describe basic air quality. Organic extracts of airborne particulate matter contain mutagenic chemical compounds of different origins. The aim of the study was to find correlations between routine monitoring data and mutagenic activity of organic extracts of simultaneously drawn samples.Methods Specimens were collected over a period of two years at 8 sampling sites in south-west Germany. Simultaneously, concentrations of NO, NO2, and SO2 were measured on-line within the framework of the official air monitoring network of Baden-Württemberg, Germany. Dust samples were collected for biotesting using high volume air samplers equipped with glass fibre filters. After sampling was completed, filters were extracted and samples were prepared for biological testing. Mutagenic activity was tested by means of the plate incorporation assay (Ames test) using S. typhimurium TA98 and TA100 tester strains. During the first year of the study, all tests have been performed with and without metabolic activation. Additionally, a series of tests has been performed in parallel with TA98 and TA98NR.Results and Discussion Comparison of Ames test data obtained with and without metabolic activation indicates no statistically significant difference between both methods. Therefore, during the second year of the study, all tests have been performed without metabolic activation. Average yearly activities at the sampling sites were between 1 und 27 Revertants per m³ (Rev/m³). High activities were preferably found at congested sites (Karlsruhe, up to 95 Rev/m³). However, peak values of over 100 Rev/m³ were found in other places where pollution by traffic is significantly lower. The reason for these high level values is not evident. Tests performed using TA98NR tester strain indicate a significant share (average 31%) of compounds requiring activation by nitroreductase for mutagenic activity. Average mutagenic activity can be correlated to routine monitoring parameters. Comparison of averaged data for particular sampling sites indicates significant correlation between nitric oxide and mutagenic activity in TA98 (r²=0.90), while correlation between nitrogen dioxide (0.84) or sulphur dioxide (0.52) and mutagenic activity is weaker. For TA100, correlations are generally weaker than for TA98. Comparison of data for mutagenic activity and routine monitoring data of distant sites being sampled simultaneously shows parallel behaviour.Conclusions Results from this study show that mutagenic activity can be compared to seasonal and local variations of gaseous indicator air pollutants. Tester strain TA98 generally shows the best correlations. Although pollution by particle-bound mutagenic substances is significantly higher during the cold season than during summer on average, mutagenic activity of airborne dust is not a continuous effect. During winter, peak levels as well as low pollution periods can occur. Even during winter time mutagenic activity can reach very low levels typical for summertime. Comparison of results for distant sampling sites where samples have been collected simultaneously indicate that “classical” indicators of air pollution and bacterial mutagenicity of organic extracts from airborne particulate matter are influenced by connected effects. Seasonal trend of mutagenic activity, in particular, is similar to the concentrations of nitrogen oxide. NO is a strong indicator for vehicle exhaust gases. It is concluded that the average mutagenic activity at particular sites can be estimated using NO concentrations as an indicator.     

Evaluating sources of indoor air pollution

Evaluation of indoor air pollution problems requires an understanding of the relationship between sources, air movement, and outdoor air exchange. Research is underway to investigate these relationships. A three-phase program is being implemented: 1) Environmental chambers are used to provide source emission factors for specific indoor pollutants; 2) An IAQ (Indoor Air Quality) model has been developed to calculate indoor pollutant concentrations based on chamber emissions data and the air exchange and air movement within the indoor environment; and 3) An IAQ test house is used to conduct experiments to evaluate the model results. Examples are provided to show how this coordinated approach can be used to evaluate specific sources of indoor air pollution. Two sources are examined: 1) para-dichlorobenzene emissions from solid moth repellant; and 2) particle emissions from unvented kerosene heaters. The evaluation process for both sources followed the three-phase approach discussed above. Para-dichlorobenzene emission factors were determined by small chamber testing at EPA's Air and Energy Engineering Research Laboratory. Particle emission factors for the kerosene heaters were developed in large chambers at the J. B. Pierce Foundation Laboratory. Both sources were subsequently evaluated in EPA's IAQ test house. The IAQ model predictions showed good agreement with the test house measurements when appropriate values were provided for source emissions, outside air exchange, in-house air movement, and deposition on "sink" surfaces.     

Exposure analysis of the inhabitants living in the neighbourhood of a mercury-contaminated industrial site

The inhabitants living in the neighbourhood of a deserted mercury-contaminated industrial site are subjected to an age-group differentiated mercury exposure assessment based on a scenario-linked calculation. Analytical input data for the calculation procedure are provided for from soil, air and plants in a large number. The most sensitive group are small children being mainly exposed by soil ingestion which makes up nearly 80% of the ADI, followed by inhalation of mercury contaminated indoor air. On the other hand, inhalation of indoor air has a predominant impact on youth and adults.     

Evaluating Sources of Indoor Air Pollution

Evaluation of Indoor air pollution problems requires an understanding of the relationship between sources, air movement, and outdoor air exchange. Research is underway to investigate these relationships. A three-phase program is being implemented: 1) Environmental chambers are used to provide source emission factors for specific indoor pollutants; 2) An IAQ (Indoor Air Quality) model has been developed to calculate indoor pollutant concentrations based on chamber emissions data and the air exchange and air movement within the indoor environment; and 3) An IAQ test house is used to conduct experiments to evaluate the model results. Examples are provided to show how this coordinated approach can be used to evaluate specific sources of indoor air pollution. Two sources are examined: 1) para-dichlorobenzene emissions from solid moth repellant; and 2) particle emissions from unvented kerosene heaters.

The evaluation process for both sources followed the three-phase approach discussed above. Para-dichlorobenzene emission factors were determined by small chamber testing at EPA’s Air and Energy Engineering Research Laboratory. Particle emission factors for the kerosene heaters were developed In large chambers at the J. B. Pierce Foundation Laboratory. Both sources were subsequently evaluated in EPA’s IAQ test house. The IAQ model predictions showed good agreement with the test house measurements when appropriate values were provided for source emissions, outside air exchange, in-house air movement, and deposition on “sink” surfaces.     

Small-scale variability of metals in soil and composite sampling

Soil pollution data is also strongly scattering at small scale. Sampling of composite samples, therefore, is recommended for pollution assessment. Different statistical methods are available to provide information about the accuracy of the sampling process. Autocorrelation and variogram analysis can be applied to investigate spatial relationships. Analysis of variance is a useful method for homogeneity testing. The main source of the total measurement uncertainty is the uncertainty arising from sampling. The sample mass required for analysis can also be estimated using an analysis of variance. The number of increments to be taken for a composite sample can be estimated by means of simple statistical formulae. Analytical results of composite samples obtained from different fusion procedures of increments can be compared by means of multiple mean comparison. The applicability of statistical methods and their advantages are demonstrated for a case study investigating metals in soil at a very small spatial scale. The paper describes important statistical tools for the quantitative assessment of the sampling process. Detailed results clearly depend on the purpose of sampling, the spatial scale of the object under investigation and the specific case study, and have to be determined for each particular case.     

Asthma and Air Pollution in Two Inner City Areas in New York City

The preliminary analysis of four months of emergency room visits for asthma in two inner city areas containing populations of similar socioeconomic, racial, and ethnic compositions, with similar day to day weather conditions but differing in their day to day levels of air pollution was made, and the relationship of visits to emergency rooms to daily temperature and air pollution levels measured in the areas, are described.

In Harlem no relationship between daily visits to emergency rooms and daily levels of either smokeshade or sulfur dioxide have been observed whereas in Brooklyn a relatively strong correlation between daily visits for asthma and daily levels of sulfur dioxide but not with smokeshade have been observed over and above the effect of temperature. In both areas there was a strong relationship between daily visits for asthma and the first cold spells of the fall season. The average male/female ratio for asthma visits to hospital emergency rooms of both areas in the age group under thirteen years of age was 1.7 and for the over thirteen years of age group was 0.6.

It appears from the data that Brooklyn presents a different picture for the environmental influence on asthma attacks. Even though it has been shown by previous investigators that asthmatics are sensitive to sulfur dioxide, we feel that in our case sulfur dioxide is not necessarily the causative agent, but might rather implicate some other confounding variable (most likely an environmental agent) that is disseminated in the general Bedford-Stuyvesant area in a similar day to day pattern to sulfur dioxide. We infer this from the fact that levels of sulfur dioxide were somewhat higher on the average in the Harlem area than they were in the Brooklyn area.     

Analysis of Motorcycle Exhaust Regular Testing Data—A Case Study of Taipei City

Abstract

In Taiwan, a continuous increase in the number of motorcycles has made exhaust pollution one of the major emission sources of air pollutants. The regular testing program carried out by the Republic of China Environmental Protection Agency was designed to reduce air pollutant emissions by enhancing maintenance and repair. During the execution period, abundant testing results were accumulated to discuss pollutant emissions from motorcycles. Exhaust testing data of motorcycles in Taipei City from 1996 to 2005 were chosen as the basic data to survey changes in motorcycle exhaust. Effects of motorcycle age and mileage on exhaust pollution were studied. The introduction of advanced emission standards enhances the elimination of high-emitting motorcycles. The testing data indicate that the testing rate rose from approximately 50 to 70% and the failure rate changed from approximately 15 to 10%. The operation cycles of two-stroke motorcycles make them high-emitting vehicles. Concentrations of carbon monoxide and hydrocarbons are higher in two-stroke motorcycle exhaust than that in four-stroke motorcycles. In contrast, the concentration of carbon dioxide produced from complete oxidation processes is lower in exhaust from two-stroke motorcycles. Therefore, failure rates of two-stroke motorcycles are higher than those of four-stroke motorcycles and were also observed to deactivate more easily. On the basis of analytical results of testing data, we found that failure rates show a gradually increasing trend for motorcycles older than 3 yr or used for mileages greater than 10,000 km, and failure rates are highly correlated to the age/mileage of motorcycles. We reason that the accumulation of age or mileage means accumulating usage time of engines and emission control systems. Concentrations of pollutant emissions would increase because of engine wear and emission control system deactivation. After discussing changes of failure rates and pollutant emissions, some suggestions are proposed to improve the testing rate and effectiveness of regular testing.     

A Comparison of Conductivity And West-Gaeke Analyses For Sulfur Dioxide

A comparison of the two most common methods used by air pollution control agencies for the analyses of sulfur dioxide is discussed in this paper. Samples were collected simultaneously (502 pairs) for an eight month period at eight sites in the City of Chicago, using the West-Gaeke and conductivity methods. These methods are analyzed statistically to ascertain the existence of a factor describing adequately any differences between methods.     

Quantification and analysis of airborne bacterial characteristics in a nursing care institution

Indoor air quality has become a critical issue because people spend most of their time in the indoor environment. The factors that influence indoor air quality are very important to environmental sanitation and air quality improvement. This study focuses on monitoring air quality, colony counts, and bacteria species of the indoor air of a nursing care institution. The regular colony counts in two different wards range from 55 to 600 cfu m(-3) Regression analysis results indicate that the bacterial colony counts have close correlation with relative humidity or carbon dioxide (CO2) but not with carbon monoxide (CO) or ozone (O3). Real-time PCR was used to quantify the bacterial pathogens of nosocomial infection, including Acinetobacter baumannii, Citrobacter freundii, Escherichia coli, Klebsiella pneumoniae, and methicillin-sensitive Staphylococcus aureus. The most abundant bacteria species in the air of the nursing care institution is E. coli.     

Methyl tertiary hexyl ether and methyl tertiary octyl ether as gasoline oxygenates: assessing risks from atmospheric dispersion and deposition

Methyl tertiary hexyl ether (MtHxE) and methyl tertiary octyl ether (MtOcE) are currently being developed as replacement oxygenates for methyl tertiary butyl ether (MtBE) in gasoline. As was the case with MtBE, the introduction of these ethers into fuel supplies guarantees their introduction into the environment as well. In this study, a screening-level risk assessment was performed by comparing predicted environmental concentrations (PEC) of these ethers to concentrations that might cause adverse effects to humans or ecosystems. A simple box model that has successfully estimated urban air concentrations of MtBE was adapted to predict atmospheric concentrations of MtHxE and MtOcE. Expected atmospheric concentrations of these ethers were also estimated using the European Union System for the Evaluation of Substances (EUSES) multimedia fate model, which simultaneously calculates PECs in the various environmental compartments of air, water, soil, and sediment. Because little or no data are available on the physicochemical, environmental, and toxicological properties of MtHxE and MtOcE, estimation methods were used in conjunction with EUSES to predict both the PECs and the concentrations at which these ethers might pose a threat. The results suggest that these ethers would contaminate the air of a moderately sized U.S. city (Boston, MA) at levels similar to those found previously for MtBE. The risk assessment module in EUSES predicted risk characterization ratios of 10(-3) and 10(-2) for MtHxE and MtOcE, respectively, in Boston, and 10(-2) and 10(-1) in very large urban centers, suggesting that these ethers pose only a minimal threat to ecosystems at the anticipated environmental concentrations. The assessment also indicates that these compounds are possible human carcinogens and that they may be present in urban air at concentrations that pose an unacceptable cancer risk. Therefore, testing of the toxicological properties of these compounds is recommended before they replace MtBE in gasoline.