Product Guide/1970

Abstract

In Mexico City, the use and composition of fuels determine that carbon monoxide (CO) comes mostly from mobile sources, and sulfur dioxide (SO₂) from fixed and mobile sources. By simultaneously measuring hydrocarbons (HC), CO, and SO₂ in the atmosphere of Mexico City, the relative amounts coming from different sources can be estimated. Assuming that some HC are emitted proportionally to CO emissions, we can establish that [HC]₁= m1? [CO], where the proportionality constant ml corresponds to the ratio of emissions factor for HC and CO in mobile sources. Similarly for fuels containing sulfur, it can be assumed that [HC]₂ = m2 ? [SO₂]. In this way, the total HC are [HC]_total=[HC]₀+ ml ? [CO]+ m2 ? [SO₂], where [HC]₀ corresponds mainly to other sources like solvent evaporation, gas consumption, and natural emissions. In this way, it can be estimated that in Mexico City 75% of average HC comes from mobile sources, 5% from sulfur-related sources, and 19% from natural sources and solvent evaporation. Compared with the HC/CO ratio measured in the exhaust pipe of vehicles, we estimated that 70% of HC emitted from mobile sources are evaporative losses, and only 30% come through the exhaust system.     

Desulfurization of Caribbean Fuel

An American Petroleum Institute study of desulfurization of Caribbean fuel oil was completed in February 1967. The report is unique in that proprietary information was made available to the contractor, the Bechtel Corp., by task force members and licensors of desulfurization processes. Thus confidential information never before available to a single organization was used to develop feasibility and incremental costs of various processes for desulfurization. The report provides needed guideposts for decision-making by governmental units as well as by industry. Incremental costs are presented for intermediate levels of desulfurization from the normal level for Caribbean heavy fuel oil of 2.6% down to 0.5%, as well as the sensitivity of costs to sulfur credits and to rate of recovery of invested capital. Degree of justifiable confidence in the various data is discussed. Effects of desulfurization on other characterisics of the fuel oil are also discussed.     

A Model for Gaseous Pollutant Sorption by Leaves

A model simulating pollutant exchange with isolated leaves that integrates factors which have been found to be important in regulating pollutant uptake by leaves is presented. The model is patterned after an electrical analogue simulator and was designed to emphasize the effects of pollutant and leaf properties on the process. The article discusses the relative significance of factors affecting gas transfer, sorption of pollutants by leaf surfaces, and pollutant solubility and fate on the uptake process. Data is presented showing uptake of ozone by exposed mesophyll and several epidermal surfaces chosen for their different surface characteristics. The model was used to derive a mathematical expression for the exchange process which was rearranged to define internal (average) pollutant solute concentration in terms of external concentration, leaf and boundary layer diffusion resistance, surface sorption and pollutant solubility. The importance of estimating internal solute concentration is discussed.     

On the Relation Between the Indoor and Outdoor Concentrations of Nitrogen Oxides

Simultaneous measurements were made of the concentrations of NO, NO₂, and CO inside and outside of a building. The building is located in the Los Angeles area, which is heavily polluted by photochemical smog, and the experiments were conducted at a time of the year when the pollutants in question tend to be high. The results shows that there is a direct relationship between the inside and outside concentrations, and that the phase lag between the concentrations depends principally on the ratio of the building volume to the ventilation rate. Although the outside concentrations of the pollutants in question did not follow the same pattern every day, peak concentrations seemed to be related to “rush-hour” traffic. By reducing ventilation rates during these periods, it may be possible to reduce the concentration peaks inside of the building. The building involved in the current study was not located in the immediate vicinity of heavy traffic, and the indoor concentrations of NO, NO₂, and CO did not appear to be very severe when compared to those defined by present air quality standards. Finally, the results support the belief that NO and O₃ do not co-exist indoors except in very small quantities.     

An Air Quality Approach to Natural Gas Curtailment

A natural gas curtailment procedure designed to improve air quality is proposed and discussed. Computer simulations of this approach, in comparison with an approach which ignores environmental factors, shows that the air-quality approach will produce significant improvements in air quality over the non-environmental approach.     

Absorption of Gaseous Air Pollutants By a Standardized Plant Canopy

Concentration profiles for hydrogen fluoride(HF), sulfur dioxide(SO₂), ozone (O₃), nitrogen dioxide(NO₂), and nitric oxide(NO) generated in a standardized alfalfa canopy are presented. Wind, light, temperature, and carbon dioxide(CO₂) profiles, canopy pollutant uptake rates, and canopy structural data are also given. Canopy pollutant concentration profile characteristics were studied to evaluate the relative potentials for major air pollutants to penetrate into canopies. The study was conducted in an environmental growth chamber equipped to control automatically environmental conditions and monitor continuously gas exchange rates. HF, SO₂, and NO₂ profiles suggested that these gases were removed efficiently by the upper portion of the canopy as well as by the immediate subsurface vegetation. The steady state HF profile showed the greatest displacement within the canopy. The NO profile was displaced the least. The uptake rate of NO by plants was apparently too slow in comparison with gas transport and mixing within the canopy to affect the internal profile substantially. O₃ appeared to be readily deposited on the surface tissues, but the deeper tissues in the canopy had less effect on the concentration profile. Data are also presented to show the relationship between NO₂ concentration within the canopy and changes in the air concentration above the vegetation. The results indicated that gas transport between the atmosphere and canopy interior was rapid. The data presented should be of current interest to agriculturists, researchers, administrators, and environmental planners concerned with effects of air pollutants on plants and on the fate of pollutants in the microenvironment.     

Air Pollution Control Association Critical Reviews Program

This is the fourth in the series of Critical Reviews commissioned by the APCA Board of Directors. The first Critical Review "Regulations for the Control of Particulate and Sulfur Oxides Emissions" was published in 1974 and the topic is still timely. The second Critical Review "Regulations for the Control of Hydrocarbon Emissions (from Stationary Sources) and Odorous Pollutants" was published in 1975. In light of recent developments concerning hydrocarbon emissions from stationary sources, this Critical Review is again very timely. The third Critical Review "The Effect of Air Pollution Control Regulations on Land Use Planning" will soon be published in final form. Now we have the fourth in the series, "A Critical Review of Air Pollution Index Systems in the United States and Canada" and "Status Report on Federal Regulations for New Source Performance Standards".     

Nitrogen Compounds other than NO in Automobile Exhaust Gas

Recent studies of organic pyrolyses in the presence of nitric oxide have shown that various nitogen compounds, such as hydrogen cyanide (HCN) and aceto-nitrile (CH₃CN) are formed. This suggests the possibility that such compounds will be found in internal combustion processes, and may be present in automobile exhaust gases. The present paper describes some gas-chromatographic and wet analyses of exhaust gases. It is concluded that the amounts of hydrogen cyanide are less than 1 ppm, but that various organic nitrogen compounds may reach a level of about 100 ppm. The significance of these results is discussed.