Sulfur, atmospheric particulates

For any pollutant, air quality criteria may refer to different types of effects. For example. Tables 22-1 through 22-6 list effects on humans, animals, vegetation, materials, and the atmosphere caused by various exposures to sulfur dioxide, particulate matter, nitrogen dioxide, carbon monoxide, ozone, and lead. These data are from fhe Air Quality Criteria for these pollutants published by the U.S. Environmental Protection Agency. 

Atmospheric particulates (sea salt, carbonaceous soot, and sulfuric acid aerosols) are known to provide a condensed phase for conq>lex heterogeneous chemistry to occur. Although the presence of atmospheric particulates are known to alter trace gas concentrations, details of the specific chemical mechanisms for condensed phase chemistry have not been identified. 

Particulate matter is the term used to describe solid particles and liquid droplets found in the atmosphere. Particulates are produced by a host of natural and anthropogenic sources. Mist and fog are both forms of natural particulates, as are windblown soil, dust, smoke from forest fires, and biological objects, such as bacteria, fungal spores, and pollen. The incomplete combustion of fossil fuels is one of the most important anthropogenic (human-made) sources of particulates. Such processes release unhurned carbon particles, oxides of sulfur and nitrogen, and a host of organic compounds into the air. 

Photoelectron spectroscopy (ESCA) and thermal evolved gas analysis (EGA) have been applied to characterize sulfur- and nitrogen-containing species in atmospheric particulate matter. Particulate amines and amides previously identified only by ESCA have been detected by EGA, a bulk method, for the first time. EGA and ESCA results suggest the existence of a sulfate similar to ammonium sulfate but with some of the ammonium ions replaced by a charged organic nitrogen complex. 

Atmospheric particulates, collected on Whatman 41 cellulose filters, are decomposed with sulfuric acid and hydrogen peroxide for subsequent determination of antimony and bismuth and with sulfuric acid and nitric acid for tin. Each element is analyzed independently by hydride generation/atomic absorption spectrometry. The optimization of instrumental as well as chemical parameters is described. The precision of the entire procedure is generally better than 10%. The detection limits are 0.25 ng m" for antimony and tin and 0.13 ng m for bismuth if 400 m of air are filtered and a 2 ml aliquot of the initial 50 ml sample solution is analyzed. 

The atmosphere is not only a mixture of gases. It also contains a variety of tiny liquid or solid particles, commonly referred to as aerosols. Atmospheric particulate matter may consist of a large variety of species in the lower stratosphere, however, the most abundant aerosol particles are composed of highly concentrated aqueous sulfuric acid droplets. In polar regions during winter, very sparse clouds, called polar stratospheric clouds (PSCs) are also observed. 

Jaenicke, R. (1978b). Physical properties of atmospheric particulate sulfur compounds. Atmos. Environ. 12, 161-169. 

Hitchcock DR, Spiller LL, Wilson WE (1980) Sulfuric acid aerosols and HCl release in coastal atmospheres evidence of rapid formation of sulfuric acid particulates. Atmos Environ 14 165-182... 

The major areas where ion chromatography is used are for the analysis of atmospheric particulates, aerosols, acid rain, sulfur dioxide flue gas, and automobile exhaust Ion chromatographic applications in the area of air hygiene include the determination of ... 

During volcanic eruptions, sulfur-containing particulate matter may be spewed miles into the atmosphere and may take months or even years to eventually settle back down again. During that time, material from the volcano may travel hundreds or even thousands of miles and could encircle the globe. The particulate matter from Krakatoa s eruption formed a thin layer in the atmosphere that reflected sunlight and cooled Earth s surface for about two years following the eruption. 

The chemical composition of atmospheric particulate matter is quite diverse. Among the constituents of inorganic particulate matter found in polluted atmospheres are salts, oxides, nitrogen compounds, sulfur compounds, various metals, and radionuclides. In coastal areas, sodium and chlorine get into atmospheric par-... 

Although most of the atmospheric particulate mass is confined to the troposphere (region below an altitude of 11 km), the stratospheric aerosol can have significant effects on climate. This subject has been reviewed by Pueschel (1996). The primary source of particulate in the stratosphere (altitude fix>m 11 to SO km) is the formation of sulfuric acid droplets by gas-to-particle conversion of SO2 injected into the stratosphere by major volcanic eruptions. These droplets are formed by homogeneous nucleation involving photochemical reactions of SOj and water vapor. They spread widely over the hemisphere (north or south) in which they originated. 

Particulate emissions are controHed mainly through venting, baghouses and water scmbbers. Atmospheric zinc loss is estimated at 100 g/1 or zinc mines, mostly from handling dry ore and concentrate and wind erosion of tailing pHes. Sulfur dioxide emissions have been reduced by installing double absorption acid plants and improved containment of dilute gases. 

When a liquid or solid substance is emitted to the air as particulate matter, its properties and effects may be changed. As a substance is broken up into smaller and smaller particles, more of its surface area is exposed to the air. Under these circumstances, the substance, whatever its chemical composition, tends to combine physically or chemically with other particles or gases in the atmosphere. The resulting combinations are frequently unpredictable. Very small aerosol particles (from 0.001 to 0.1 Im) can act as condensation nuclei to facilitate the condensation of water vapor, thus promoting the formation of fog and ground mist. Particles less than 2 or 3 [Lm in size (about half by weight of the particles suspended in urban air) can penetrate the mucous membrane and attract and convey harmful chemicals such as sulfur dioxide. In order to address the special concerns related to the effects of very fine, iuhalable particulates, EPA replaced its ambient air standards for total suspended particulates (TSP) with standards for particlute matter less than 10 [Lm in size (PM, ). 

The chemical composition of particulate pollutants is determined in two forms specific elements, or specific compounds or ions. Knowledge of their chemical composition is useful in determining the sources of airborne particles and in understanding the fate of particles in the atmosphere. Elemental analysis yields results in terms of the individual elements present in a sample such as a given quantity of sulfur, S. From elemental analysis techniques we do not obtain direct information about the chemical form of S in a sample such as sulfate (SO/ ) or sulfide. Two nondestructive techniques used for direct elemental analysis of particulate samples are X-ray fluorescence spectroscopy (XRF) and neutron activation analysis (NAA). 

Health effects attributed to sulfur oxides are likely due to exposure to sulfur dioxide, sulfate aerosols, and sulfur dioxide adsorbed onto particulate matter. Alone, sulfur dioxide will dissolve in the watery fluids of the upper respiratory system and be absorbed into the bloodstream. Sulfur dioxide reacts with other substances in the atmosphere to form sulfate aerosols. Since most sulfate aerosols are part of PMj 5, they may have an important role in the health impacts associated with fine particulates. However, sulfate aerosols can be transported long distances through the atmosphere before deposition actually occurs. Average sulfate aerosol concentrations are about 40% of average fine particulate levels in regions where fuels with high sulfur content are commonly used. Sulfur dioxide adsorbed on particles can be carried deep into the pulmonary system. Therefore, reducing concentrations of particulate matter may also reduce the health impacts of sulfur dioxide. Acid aerosols affect respiratory and sensory functions. 

Emissions to the atmosphere from ammonia plants include sulfur dioxide (SOj), nitrogen oxides (NOJ, carbon monoxide (CO), carbon dioxide (COj), hydrogen sulfide (HjS), volatile organic compounds (VOCs), particulate matter, methane, hydrogen cyanide, and ammonia. The two primary sources of pollutants, with typical reported values, in kilograms per ton (kg/t) for the important pollutants, are as follows ... 

High levels of sulfur not only form dangerous oxides, but they also tend to poison the catalyst in the catalytic converter. As it flows over the catalyst in the exliaust system, the sulfur decreases conversion efficiency and limits the catalyst s oxygen storage capacity. With the converter working at less than maximum efficiency, the exhaust entering the atmosphere contains increased concentrations, not only of the sulfur oxides but also, of hydrocarbons, nitrogen oxides, carbon monoxides, toxic metals, and particulate matter. 

The process will adversely affect air quality by releasing nitrogen oxides, sulfur oxides, carbon monoxides and other particulates into the atmosphere. Better control of the conversion conditions and better control of emissions can make the process cleaner, yet technology cannot do anything to curb carbon emissions. Since much of the carbon in coal is converted to carbon dioxide in the synthesis process, and is not part of the synthetic fuel itself, the amount of carbon dioxide that will be released to the environment during combustion is 50 to 100 percent more than coal, and around three times more than natural gas. 

Alternatively, in the presence of particulate matter and aerosols, sulfur dioxide may react with atmospheric oxygen to form sulfur trioxide, which forms sulfuric acid, a strong acid, in water ... 

Particles are emitted Into the atmosphere from numerous natural and manmade sources and are also formed upon condensation of gases and vapors. Direct emissions of Suspended Particulate Natter (SPN) arise from a variety of human activities Including combustion. Industrial and agricultural practices the remainder Is formed from gas-particle conversions (chiefly from SOj oxidation to sulfuric acid as sulfate salts). Particles larger than about lOpm In diameter deposit In the vicinity of the sources, but smaller... 

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