Sulfate pollution

Sidle W. C., Roose D. L., and ShankUn D. R. (2000) Isotopic evidence for naturally occurring sulfate pollution of ponds in the Kankakee River Basin, IlUnois-Indiana. J. Environ. Qual. 29(5), 1594-1603. 

Computer simulations have shown that the majority of acid sulfate pollution in the Northeast comes from outside the region, chiefly from sources in the Ohio Valley/Midwest. For example, the "AIRSOX" model, developed at the Brookhaven National Laboratories, estimates that "87% of the sulfate in New York and New Jersey is due to (long-distance) transport and that 92% of the sulfate in New England is due to transport. The model... 

According to the averaged results of seven computer models considered by the U.S. /Canada Work Group on Transboundary Air Pollution, midwestern somces contribute more than 50% of the airborne sulfate pollution in the Adirondack Mountains, with approximately 20% of the sulfate coming from the Sudbury sector of Canada, and less than 10% coming from the Northeast itseir (Table 5). Other sites in the Northeast may be more heavily influenced by local sources of pollution. At Brookhaven, Long Island as much as 30% of sulfur deposition may come from upwind emissions in the New York metropolitan area. 

Preliminary studies at Watertown, Massachusetts showed that high levels of acid sulfate pollution correlated with winds from the Ohio Valley/Midwest sector, and also contained high levels of selenium. Conversely, winds from the east, i.e., from the city of Boston, contained relatively low levels of acid sulfate and selenium. This suggests that episodes of high acid sulfate at the Watertown site are due to air masses from the Ohio Valley (where sources are predominantly coal-fired) rather than to local sources (which are predominantly oil-fired). The technique was also used at sites in New York State and again implicated midwestem sources of pollution. ... 

Even ia 1960 a catalytic route was considered the answer to the pollution problem and the by-product sulfate, but nearly ten years elapsed before a process was developed that could be used commercially. Some of the eadier attempts iacluded hydrolysis of acrylonitrile on a sulfonic acid ion-exchange resia (69). Manganese dioxide showed some catalytic activity (70), and copper ions present ia two different valence states were described as catalyticaHy active (71), but copper metal by itself was not active. A variety of catalysts, such as Umshibara or I Jllmann copper and nickel, were used for the hydrolysis of aromatic nitriles, but aUphatic nitriles did not react usiag these catalysts (72). Beginning ia 1971 a series of patents were issued to The Dow Chemical Company (73) describiag the use of copper metal catalysis. Full-scale production was achieved the same year. A solution of acrylonitrile ia water was passed over a fixed bed of copper catalyst at 85°C, which produced a solution of acrylamide ia water with very high conversions and selectivities to acrylamide. 

Historically, soda ash was produced by extracting the ashes of certain plants, such as Spanish barilla, and evaporating the resultant Hquor. The first large scale, commercial synthetic plant employed the LeBlanc (Nicolas LeBlanc (1742—1806)) process (5). In this process, salt (NaCl) reacts with sulfuric acid to produce sodium sulfate and hydrochloric acid. The sodium sulfate is then roasted with limestone and coal and the resulting sodium carbonate—calcium sulfide mixture (black ash) is leached with water to extract the sodium carbonate. The LeBlanc process was last used in 1916—1917 it was expensive and caused significant pollution. 

Historically, ferrous sulfamate, Fe(NH2S02)2, was added to the HNO scmbbing solution in sufficient excess to ensure the destmction of nitrite ions and the resulting reduction of the Pu to the less extractable Pu . However, the sulfate ion is undesirable because sulfate complexes with the plutonium to compHcate the subsequent plutonium purification step, adds to corrosion problems, and as SO2 is an off-gas pollutant during any subsequent high temperature waste solidification operations. The associated ferric ion contributes significantly to the solidified waste volume. 

When chlorine dioxide is used for pulp bleaching in conjunction with the Kraft (sulfide) process for chemical pulping, by-product sodium sulfate can be used as a source of makeup sulfur and sodium consumed in the chemical cycle. The demand for sodium and sulfur in pulp bleaching is related to the loss of these chemicals through carryover in unbleached pulp. As process improvements have sought to reduce pollution from pulp mills, less sodium sulfate makeup is required. The trends in pulp bleaching to increase substitution of chlorine with chlorine dioxide have caused an oversupply of sodium sulfate, so that this by-product is often regarded as waste (81). 

This is a favorable process because the side reaction products, nitrogen and water, are not pollutants and the sodium sulfate can be recovered and sold. Also, all of the wash water used to remove the sodium sulfate from the chrome oxide can be recycled. 

Air or biological oxidation of pyrite leads to sulfate formation and dilute sulfuric acid in the mine drainage. This pollutes streams and the water supphes into which the mine water is drained. Means of controlling this problem are under study. 

Several developments are being pursued to utilize coal directly, ie, automation of controls, coal and ash handling equipment for smaller stoker and pulverized coal-fired units, design of packaged boiler units, and pollution control equipment. In the cement industry coal firing has been used, because the sulfur oxides react with some of the lime to make calcium sulfate in an acceptable amount. 

Environment Tube side Brackish, estuarine water (polluted), 2-3 ppm tolyltriazole residual, ferrous sulfate 1 ppm as iron for 2 months for 1 hr/day, dispersant 5-8 ppm... 

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). 

An understanding of the transformation of SO2 and NO. into other constituents no longer measurable as SOj and is needed to explain mass balance changes from one plume cross section to another. This loss of the primary pollutant SOj has been described as being exponential, and rates up to 1% per hour have been measured (30). The secondary pollutants generated by transformation are primarily sulfates and nitrates. 

Particulate matter is the principal air pollutant emitted from ammonium sulfate plants. Most of the particulates are found in the gaseous exhaust of the dryers. Uncontrolled discharges of particulates may be of the order of 23 kg/t from rotary dryers and 109 kg/t from fluidized bed dryers. Ammonia storage tanks can release ammonia, and there may be fugitive losses of ammonia from process equipment. 

The most likely substitute for coal is natural gas, which, as noted earlier, releases about 55 percent of the amount of carbon dioxide that coal, on the average, does. In addition, it produces far fewer other pollutants, such as sulfates and polycyclic hydrocarbons, than coal and oil yield on combustion. 

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