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The photo-oxidation of hydrogen sulphide and dimethyl sulphide in air∗
Atmosphenc Environment Vol.IO,pp.417-420. PergamonPress1976Printed inGreatBritain
DISCUSSIONS THE PHOTO-OXIDATION OF HYDROGEN SULPHIDE AND DIMETHYL SULPHIDE IN AIR* As pointed out in this article, both hydrogen sulfide and dimethyl sulfide are trace constituents of the atmosphere although little is known concerning their life-cycles. The research described demonstrated that hydrogen sulfide and dimethyl sulfide undergo photo-oxidation in air containing nitrogen oxides and hydrogen peroxide vapor. My only reservation with regard to this research is the authors’ extrapolation of the laboratory-measured reaction rates for dimethyl sulfide (DMS) to residence times in the natural or “ambient” atmosphere. The concentrations of nitrogen oxides employed were about three orders of magnitude greater than those usually found in the ambient atmosphere but comparable to those found in photochemical smog. The authors conclude that the reactivity of DMS is similar to or slightly greater than that of propylene. Altshuller et al. (1968) have found that the residence time of propylene in synthetic photochemical smogs is a matter of hours. Since the rate of photo-oxidation decreases rapidly with decreasing concentration of nitrogen oxides, the residence time of propylene (and thus presumably also of DMS) due to photo-oxidation involving the oxides of nitrogen is probably a matter of days at least instead of hours as suggested by Cox and Sandalls. These authors also refer to a statement by Robinson and Robbins (1968) that the average residence time of * Cox R. A. and Sandalls F. J. (1974) Atmospheric En8, 1269-l 28 1.
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moderately reactive hydrocarbons such as propylene is only a few hours. However, Robinson and Robbins do not indicate how they reached that conclusion. The average residence time of DMS in the atmosphere may indeed be only a few hours, but this is not established by the research of Cox and Sandalls. A recent article by Cadle et al. (1974) suggested that the rate constant for the 0(3P)-DMS reaction at 3COK is about 3.3 x 10” cm3 mole-i s-l, which is considerably smaller than that for the 0(3P)-propylene reaction. The reaction was assumed to be second order, which although likely has not been established. National Center for Atmospheric Research P.O. Box 3CO0, Boulder, CO 80303, U.S.A.
REFERENCES
Altshuller A. P., Kopczynski S. L., Lonneman W. A., Becker T. L. and Wilson D. L. (1968) Photooxidation of propylene with nitrogen oxide in the presence of sulfur dioxide. Environ. Sci. Technol. 2, 696698. Cadle R. D., Wickman H. H., Hall C. B. and Eberle K. M. (1974) The reaction of atomic oxygen with formaldehyde, crotonaldehyde, and dimethyl sulfide. Chemosphere 3, 115-118. Robinson E. and Robbins R. C. (1968) Sources, abundance and fate of atmospheric pollutants. SRI project No. PR-6755 Final Report, Am. Pet. Inst., Washington, D.C.
FURTHER DISCUSSION ON: INFLUENCE OF SURFACE ALBEDO ON THE CHANGE IN THE ATMOSPHERIC RADIATION BALANCE DUE TO AEROSOLS*? In the first paragraph of her reply to my comments on her original paper, Dr. Reck again indulges in the type of speculation I warned against in my comments. She suggests that during the duststorm residue conditions of 30 July 1972 at Phoenix, Arizona, areas of low albedo could have been covered with a surface layer of sand that would have resulted in a net increase in albedo during this period that would have justified her original speculations. In a
note in this issue I present experimental data obtained during this period and three other actual duststorms that indicate that such was not the case for the period in question nor for any of the other duststorm conditions investigated. I have pursued the discussion of this topic for two major reasons. First, it cannot. be over-emphasized that actual data are required to resolve the points in question. Speculations are useful guides, but they must be altered or discarded in light of experimental data subsequently obtained. Second, it is important to be able to evaluate the relative merits of the “visible” and “thermal” theories of surface heating due to aerosols. When both theories indicate the same effect, i.e. heating, it behooves us to critically compare them in light of existing data. The data for the 30 July 1972 event at Phoenix appear to rule against the “visible” theory of Dr. Reck. U.S. Water Conservation
* Reck R. A. (1975) Atmospheric Environment 9, 89-99. t Idso S. B. and Reck R. A. (1975) Discussion. Atmospheric Environment
RICHARDD.CADLE
Laboratory, ARS. USDA Phoenix. AZ 85040, U.S.A.
9, 766761.
417
s. B. IDS0
DISCUSSIONS THE PHOTO-OXIDATION OF HYDROGEN SULPHIDE AND DIMETHYL SULPHIDE IN AIR* As pointed out in this article, both hydrogen sulfide and dimethyl sulfide are trace constituents of the atmosphere although little is known concerning their life-cycles. The research described demonstrated that hydrogen sulfide and dimethyl sulfide undergo photo-oxidation in air containing nitrogen oxides and hydrogen peroxide vapor. My only reservation with regard to this research is the authors’ extrapolation of the laboratory-measured reaction rates for dimethyl sulfide (DMS) to residence times in the natural or “ambient” atmosphere. The concentrations of nitrogen oxides employed were about three orders of magnitude greater than those usually found in the ambient atmosphere but comparable to those found in photochemical smog. The authors conclude that the reactivity of DMS is similar to or slightly greater than that of propylene. Altshuller et al. (1968) have found that the residence time of propylene in synthetic photochemical smogs is a matter of hours. Since the rate of photo-oxidation decreases rapidly with decreasing concentration of nitrogen oxides, the residence time of propylene (and thus presumably also of DMS) due to photo-oxidation involving the oxides of nitrogen is probably a matter of days at least instead of hours as suggested by Cox and Sandalls. These authors also refer to a statement by Robinson and Robbins (1968) that the average residence time of * Cox R. A. and Sandalls F. J. (1974) Atmospheric En8, 1269-l 28 1.
rironmmt
moderately reactive hydrocarbons such as propylene is only a few hours. However, Robinson and Robbins do not indicate how they reached that conclusion. The average residence time of DMS in the atmosphere may indeed be only a few hours, but this is not established by the research of Cox and Sandalls. A recent article by Cadle et al. (1974) suggested that the rate constant for the 0(3P)-DMS reaction at 3COK is about 3.3 x 10” cm3 mole-i s-l, which is considerably smaller than that for the 0(3P)-propylene reaction. The reaction was assumed to be second order, which although likely has not been established. National Center for Atmospheric Research P.O. Box 3CO0, Boulder, CO 80303, U.S.A.
REFERENCES
Altshuller A. P., Kopczynski S. L., Lonneman W. A., Becker T. L. and Wilson D. L. (1968) Photooxidation of propylene with nitrogen oxide in the presence of sulfur dioxide. Environ. Sci. Technol. 2, 696698. Cadle R. D., Wickman H. H., Hall C. B. and Eberle K. M. (1974) The reaction of atomic oxygen with formaldehyde, crotonaldehyde, and dimethyl sulfide. Chemosphere 3, 115-118. Robinson E. and Robbins R. C. (1968) Sources, abundance and fate of atmospheric pollutants. SRI project No. PR-6755 Final Report, Am. Pet. Inst., Washington, D.C.
FURTHER DISCUSSION ON: INFLUENCE OF SURFACE ALBEDO ON THE CHANGE IN THE ATMOSPHERIC RADIATION BALANCE DUE TO AEROSOLS*? In the first paragraph of her reply to my comments on her original paper, Dr. Reck again indulges in the type of speculation I warned against in my comments. She suggests that during the duststorm residue conditions of 30 July 1972 at Phoenix, Arizona, areas of low albedo could have been covered with a surface layer of sand that would have resulted in a net increase in albedo during this period that would have justified her original speculations. In a
note in this issue I present experimental data obtained during this period and three other actual duststorms that indicate that such was not the case for the period in question nor for any of the other duststorm conditions investigated. I have pursued the discussion of this topic for two major reasons. First, it cannot. be over-emphasized that actual data are required to resolve the points in question. Speculations are useful guides, but they must be altered or discarded in light of experimental data subsequently obtained. Second, it is important to be able to evaluate the relative merits of the “visible” and “thermal” theories of surface heating due to aerosols. When both theories indicate the same effect, i.e. heating, it behooves us to critically compare them in light of existing data. The data for the 30 July 1972 event at Phoenix appear to rule against the “visible” theory of Dr. Reck. U.S. Water Conservation
* Reck R. A. (1975) Atmospheric Environment 9, 89-99. t Idso S. B. and Reck R. A. (1975) Discussion. Atmospheric Environment
RICHARDD.CADLE
Laboratory, ARS. USDA Phoenix. AZ 85040, U.S.A.
9, 766761.
417
s. B. IDS0