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.     

Relationships Between Sulfur Dioxide Concentration Determined By the West-Gaeke and Electroconductivity Methods

Sulfur dioxide concentrations in the atmosphere are commonly determined by the West-Gaeke and electro-conductivity methods. As a part of the United States-Japan Cooperative Air Pollution Measurement Studies, parallel sampling with a 24-hr bubbler, a 1-hr bubbler, and an electroconductivity instrument was conducted in Kawasaki, Japan, between Jan. 12 and Mar. 25 and between Aug. 19 and Sept. 30, 1966. These time periods were chosen because of the seasonal variation in the air pollution levels. Fair agreement was obtained between the 24-hr sample values and the daily mean values of the 24 hourly samples analyzed by the West-Gaeke method. Sulfur dioxide concentrations determined by the electroconductivity method were greater than those determined by the West-Gaeke method, particularly in the winter season. Relationships between the sulfur dioxide concentrations determined by these two methods are discussed.     

The Lead Dioxide Estimation Of Sulfur Dioxide Pollution

A new system of measuring sulfation is presented. Because of its simplicity, operation of large sulfation networks can be accomplished at extremely nominal costs. Because of increased sensitivity, present 1 -month sampling time intervals may be shortened to approximately 1 day. Use of this system will permit more definitive investigations of the relationship of sulfation to sulfur dioxide concentration.     

Modification of Sulfur Dioxide Injury to Tobacco and Tomato by Varying Nitrogen and Sulfur Nutrition

The body of information presented in this paper is directed to plant scientists who are concerned with factors which modify the susceptibility of plants to air pollutants.

Tobacco and tomato plants grown in sand-solution culture with varying levels of nitrogen or sulfur were exposed to injurious levels of sulfur dioxide. Plants of both species which were deficient in either nutrient exhibited decreased susceptibility to the gas compared with plants grown at optimal levels of each nutrient. Foliage of these plants was also found to have increased stomatal resistance as measured by a porometer and decreased total sulfur accumulations. Plants grown at optimum levels of each nutrient showed increased susceptibility over that of the deficient plants. Stomatal resistance was lower and sulfur accumulation was greater than in the deficient plants. At the supra-optimal nitrogen and sulfur levels, there were differences in susceptibility. Over-abundant nitrogen appeared to decrease susceptibility whereas over-supplies of sulfur increased it.

The response of plants with deficient or optimal supplies of either nutrient might be explained by the effects of nutrition on stomatal activity and hence on ability to absorb SO₂S from the atmosphere, mineral deficiency being known to increase stomatal resistance, and mineral sufficiency, to decrease stomatal resistance by virtue of increased efficiency of water use. The difference in response between plants overfertilized with respect to nitrogen or sulfur is explained by the fact that sulfur is both nutrient and phytotoxicant at the same time. Having already been oyersupplied with sulfur by absorption from the nutrient substrate, the high-sulfur plants were unable to withstand additional sulfur accumulation from the atmosphere and hence were more severely injured.

Increased carbohydrate accumulation in the nitrogen- and sulfur-deficient plants might play an additional role in protection from SO2-injury.     

Modeling Evidence of Incloud Transformation Of Sulfur Dioxide to Sulfate

Methylene chloride (CH₂Cl₂) is presently under study by the U.S. EPA and other agencies to determine if the compound presents an unreasonable risk to human health and to determine if regulatory action is needed to reduce the risk. This paper describes one portion of the study which required the development and validation of a method of sampling and analysis for source emission measurements.

Prior to source sampling, laboratory experiments were conducted to determine the best sample container in which to collect an integrated sample. It was found that CH₂Cl₂ remained stable in Tedlar bags for at least four weeks. The analytical method selected was gas chromatography with flame ionization detection (GC/FID). During the field portion of the study, both manufacturer and user emission sources of CH₂Cl₂ were tested. Multiple sets of simultaneous quadruplicate bag samples were collected to determine the precision of both sampling and analysis in the field. All samples were analyzed at the test site after collection and then returned to Research Triangle Park. Samples were subsequently reanalyzed in the laboratories of Radian and the U.S. EPA using three GC/FID instruments and two types of GC columns. The range of concentrations from the sources was 100 ppm to 27,000 ppm CH₂Cl₂. A statistical analysis of samples collected simultaneously showed no difference in the samples, proving good precision In both sampling and analysis. Some of the sample bags returned from the test sites developed leaks indicating that immediate on-site analysis is best. A comparison of results obtained in the field and the two laboratories showed that interand intra-laboratory precision was within 10 percent.     

The Use of Nahcolite Ore and Bag Filters For Sulfur Dioxide Emission Control

This paper describes some technical and economic aspects of the nahcolite ore injection process for the simultaneous removal of fly ash and sulfur oxides from stack gases. The process is capable of removing greater than 99% of the particulate matter and greater than 70% of the sulfur oxides present in such gases. In the process, nahcolite ore, a naturally occurring material containing 70 to 90% sodium bicarbonate, is ground to 90% passing through —200 mesh screens. Approximately 20% of the ground ore is used to precoat the filter bags in a baghouse filter while the remainder of the material is fed into the flue gas Just ahead of the baghouse. The flue gas is drawn through the baghouse by induced draft fans and sent up the stack. Most of the SO₂ and practically all of the fly ash in the flue gas can be removed as the gas passes through the filter bags. The spent nahcolite ore and fly ash are collected and conveyed to waste disposal as landfill, or alternatively processed for insolubilization by coprecipitation prior to landfilling. The technical feasibility of the process has been demonstrated in both bench scale and pilot scale engineering studies. Economic analyses performed for the cases of plants located in the midwest and southwest indicate lower capital costs for the nahcolite injection process when compared to wet scrubbing. On an annual cost basis, the nahcolite ore Injection process is comparable in cost to wet scrubbing for the case of the southwestern power plant, and somewhat more expensive for the case of the midwestern plant.     

Sulfur Dioxide and Material Damage

Whereas most estimates of material damage are based on industrial surveys, the estimates produced in this study were derived from material damage experiments and ambient air quality data. Air quality data on SO₂ were obtained from 200 or more monitoring sites primarily located in heavily populated or polluted areas. Material threshold damage function data were then compared with SO₂ levels, and an estimate of losses, as reflected in increased maintenance and replacement costs, was determined. Estimates of the total stock of various materials in use were derived from census and industry data and allocated geographically according to population. A substantial decrease in the ambient SO₂ levels, particularly in larger urban areas, has occurred during the past five years. From 1968 to 1972, the estimated amount of material damage from SO₂ in the U. S. decreased from $900 million/yr to less than $100 million. During this period, the estimated percentage of man made materials exposed to SO₂ levels exceeding the proposed secondary annual average standard (60 μg/m³) and primary annual average standard (80 μg/m³) in the U. S. fell respectively, from 20% to less than 5% and from more than 10% to less than 1%. Most of the present loss is attributed to corrosion damage of metallic surfaces that are normally exposed to the ambient environment.     

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.     

Determination of Atmospheric Sulfur Dioxide Without Tetrachloromercurate(II): Further Refinements of a Pararosaniline Method and Field Application.

Results are presented for the field application of a pararosaniline method which determines sulfur dioxide by utilizing a nontoxic thermally stable dilute formaldehyde absorber buffered at pH 4. Parallel results by the Federal Reference Method are reported. Further refinements of the pararosaniline procedure including dye reagent purification and inclusion of a trichloroacetic acid buffer system are described. Merits and limitations of direct and reverse reagent addition are discussed.     

Simultaneous Sulfur Dioxide and Nitrogen Dioxide Removal by Calcium Hydroxide and Calcium Silicate Solids

ABSTRACT

At conditions typical of a bag filter exposed to a coal-fired flue gas that has been adiabatically cooled with water, calcium hydroxide and calcium silicate solids were exposed to a dilute, humidified gas stream of nitrogen dioxide (NO₂) and sulfur dioxide (SO₂) in a packed-bed reactor. A prior study found that NO₂ reacted readily with surface water of alkaline and non-alkaline solids to produce nitrate, nitrite, and nitric oxide (NO). With SO₂ present in the gas stream, NO₂ also reacted with S(IV), a product of SO₂ removal, on the exterior of an alkaline solid. The oxidation of S(IV) to S(VI) by oxygen reduced the availability of S(IV) and lowered removal of NO₂. Subsequent acidification of the sorbent by the removal of NO₂ and SO₂ facilitated the production of NO. However, the conversion of nitrous acid to sulfur-nitrogen compounds reduced NO production and enhanced SO₂ removal. A reactor model based on empirical and semi-empirical rate expressions predicted rates of SO₂ removal, NO₂ removal, and NO production by calcium silicate solids. Rate expressions from the reactor model were inserted into a second program, which predicted the removal of SO₂ and NO_x by a continuous process, such as the collection of alkaline solids in a baghouse. The continuous process model, depending upon inlet conditions, predicted 30-40% removal for NO and 50-90% removal for SO₂. These x 2 results are relevant to dry scrubbing technology for combined SO₂ and NO_x removal that first oxidizes NO to NO₂ by the addition of methanol into the flue duct.     

A Rapid Titrimetric Method for Sulfate in Lead Dioxide Exposed to Atmospheric Sulfur Pollution

A titrimetric method is described for the analysis of sulfate in lead dioxide candles which have been exposed to atmospheric sulfur pollution. The time taken to analyse one sample is 3 hr. Sixty milliliters of 8% ammonium carbonate solution is used to convert the lead sulfate present on the candle to ammonium sulfate. The solution is filtered lc remove lead dioxide, and an aliquot of the filtrate is heated to remove ammonium carbonate. The solution of ammonium sulfate remaining is titrated directly for sulfate with 0.02 M barium perchlorate, using Thoron as indicator. The accuracy of the method is ±10 and ±6 % of theoretical, for 10 mg, and 40 mg or greater amounts of sulfate, respectively. For 2 mg of sulfate, results are about 20% high. Good agreement has been obtained between results for duplicate field candles, analyzed by the standard sodium carbonate gravimetric method, and the method presented, over a five-month period.     

Evaluation of the Effectiveness of The Lead Peroxide Method for Atmospheric Monitoring of Sulfur Dioxide

This paper presents a simplified analysis to determine the variables that affect the empirical correlation factor used in the lead peroxide method. The rate of sulfation has been determined from two different models. In the first model, the mass transfer rate is calculated from the gas phase resistance alone whereas in the second model, the diffusion resistance in the gel phase is assumed to be the rate limiting step. Although the gas phase and the gel phase resistances may be both important in the actual case, it has been found that the correlation factor based on the first model is adequate to describe general experimental observations. Reasonable agreement has been obtained between the measured and the calculated va|ue of the correlation factor.     

Studies on a New Method of Simultaneously Removing Sulfur Dioxide and Oxides of Nitrogen from Combustion Gases

Simultaneous reduction of SO₂ and NO by catalyzed reaction with carbon monoxide at space rates approaching 10⁴ vol/vol/hr has been shown. The reaction of sulfur dioxide with carbon monoxide results in the formation of carbon dioxide and elemental sulfur. Nitric oxide reacts with carbon monoxide to form carbon dioxide and molecular nitrogen. Metals supported on alumina appear to be the preferred catalysts. Among the effective metals are copper, silver, and palladium. A side reaction of carbon monoxide with elemental sulfur to form carbonyl sulfide requires that the initial amount of carbon monoxide be stoichio-metric for the amount of sulfur dioxide plus nitric oxide present. A furnace employing this method would have to be operated at low excess air, near stoichiometric fuel/air, or possibly slightly on the rich side.     

Particulate and Sulfur Dioxide Concentration Measurements in Patras,Greece

Abstract

The purpose of this study was to obtain a better assessment of the Patras, Greece, air quality, in terms of the primary pollutants total suspended particulates (TSPs) and sulfur dioxide (SO₂), because limited and short-duration measurements have been conducted in the past. Installation and operation of a mobile air monitoring station at two different locations in the Patras downtown area and one location in the outskirts of the city was undertaken and covered the periods July 1, 1994-January 30, 1995; March 18-August 23, 1995; and April 19-July 27, 1996, respectively. For both pollutants measured at each location, the monthly average concentrations and typical weekly variation of daily averages, as well as the diurnal variations and frequency concentration distributions in each month of the monitoring periods, were calculated and are presented in bar diagrams. The annual and winter period medians and the annual 98th percentile were also calculated and are compared with the limit and guide values provided by the European Economic Community Council Directive 80/779/EEC. In addition, comparison of SO₂ values is made with the limit values adopted by the more recent Directive 1999/30/EC. It was found that the TSP and SO₂ levels at all locations were very low and were lower than the levels found in Thessaloniki and Athens, Greece. An attempt to explain what had been measured is also undertaken. The data presented are considered essential for future reference and comparison purposes.     

Sulfur Dioxide Removal and Recovery from Pulp Mill Power Plants

The use of soda ash liquor to scrub SO₂ rich power plant flue gases was studied using an Airetron pilot scrubber with a maximum capacity of 3000 cfm. The relative effects of the major operating variables— temperature, soda ash concentration, and the gas/liquid flow ratio—on the absorption phenomenon were determined. Orthogonal factorial experiments were used to derive a response function relating mass transfer values to operating variables. The economics of a full scale NSSC installation are discussed.     

The Continuous Analysis of Sulfur Dioxide in Gaseous Samples

Sulfur dioxide is quantitatively scrubbed from atmospheric and stack gas samples through the use of a unique rotary scrubber which provides collection efficiencies in excess of 97% in the PPB through PPM range. The scrubber in addition permits the use of water as a scrubbing vehicle which, when combined with a bleached pararosanaline reagent, provides high specificity and sensitivity for the analysis. By the elimination of the tetrachloromercurate solution, cell staining is eliminated and the stability required for continuous analysis by the reagent is achieved.     

Sulfur Dioxide Fumigation of Soybeans: Effect on Yield

In order to determine the influence of SO₂ fumigation of soybean plants on yield, a three-year experiment was conducted on 485 plois of soybeans. Single fumigations of S0₂ were applied at 10 different stages of growth in 1968-69 and 7 stages of growth in 1970. A linear relationship was found to exist beiween the percent of leaf area destroyed and ihe percent crop loss with a significant regression coefficient of b = —0.659, or iwo-thirds of one percent crop loss for each percent of area destroyed. No definite significant stage-of-growth effect was found and no treatment effects were significant for the early stages of growth from the 3-leaf to the 15-leaf stage, nor was there any loss in yield without visible leaf injury.