(3) Koch, H. J., Biebing, H., Thormann, K., East German Patent 68896, International Patent Classification Colg, 1969. (4) Scholten, H. G., Prielipp, G. E., US.Patent 3085859 (1963). (5) Law, S. L., Science, 174,285 (1971). (1972). (6) Moore. F. L.. Enuiron. Sci. Technol.. 6.525 ’ (7) Chem.Eng. k e w s , 48 (52), 48 (1970): (8) Friedman, M.. Waiss. A. C.. Jr., Enuiron. Sci. Technol.. 6, 457 (1972). (9) Roberts, E. J., Rowland, S. P., ibid., 7,522 (1973). (10) Chact, J., Chem. Reu., 48,7 (1951). (11) Kreevoy, M. M., Gilje, J. W., Ditsch, L. T., Batorewiez, W., Turner, M. A., J. Org. Chem., 27,726 (1962).
(12) Lindoy, L. F., Coord. Chem. Reu., 4,41 (1969). (13) Jadamus, H., Fernando, Q., Freiser, H., J . A m . Chem. SOC.,86, 3056 (1964). (14) Snell and Snell, “Colorimetric Method of Analysis”, Vol IIA, p 39, Van Nostrand, New York, N.Y., 1959. (15) S i l l h , K. G., Martell, A. E., “Stability Constants of Metal-Ion Complexes”, The Chemical Society, London, England, 1964.
Received for reuiew July 21, 1975. Accepted April 2, 1976. Work partially supported by the Istituto di Ricerca sulle Acque C N R ( R o ~ Qand ) by the Istituto per lo Suiluppo delle Attiuitd e delle Ricerche Scientifiche in Calabria.
CORRESPONDENCE
SIR: The article, “Evaluating Environmental Impacts of Stack Gas Desulfurization Processes” [ES&T,10,54 (1976)], attempts to assess the impact of considering secondary sources of pollution on the relative merits of five stack gas desulfurization processes. Unfortunately, the author’s choice of basic data (particularly Table 11)leads to seriously erroneous conclusions regarding these secondary sources. The analysis, based on Table I, is intended to apply to a new coal-fired generating station of 500 MW capacity so the use of pollutant generating factors from existing stations in 1972 is completely inappropriate; their use does not recognize that the major part of the utilities requirement would be provided by the plant itself, which would be subject to new source performance standards. In addition, many of the costs associated with control to these levels of emission are already included in the given operating costs since control is frequently achieved through internal recycle of process waste streams. The costs then appear as incremental increases in equipment size and operating costs; thus, total costs associated with these secondary sources should include the costs of control, to the extent they are not already included in operating costs, for a major fraction of the pollutant plus an environmental cost for the actual emission. Viewed in this manner, the conclusions concerning the impact of secondary sources would be considerably different from those arrived at by the author. Relative to the large uncertainties associated with the total costs of these processes, particularly capital costs, byproduct cost/value and those related to reliability, assessments (revised) for secondary sources will be much less significant than is estimated by the author. Incidentally, although “M” generally means lo3 in the article, it appears to mean lo6 in at least two places (Fuel, in Table 11, and annual cost, in Table V). Also, in Table 11, the particulate emissions are not realistic for existing utility sources, as shown by Table 4 of the author’s reference 8, or for gaseous and liquid fuels. Thomas F. Evans Niagara Mohawk Power Corp. Niagara Mohawk 300 Erie Boulevard West Syracuse, N.Y. 13202
SIR: The use of the 1972 pollutant-generating factors for utilities (Table 11) in calculating the secondary effect is considered inappropriate by Dr. Evans on the ground that the major utilities requirements of a plant designed to meet the new source performance standards would be provided by the plant itself. When all utilities requirements are supplied within the plant, the plant would be engaged in the production 934
Environmental Science & Technology
of both final utilities (which are delivered to the users) and intermediate utilities (which are used as inputs within the plant). The final output wastes, defined as the pollutants/ wastes that cannot be reduced through recycling within the plant, would then include the pollutantdwastes from both the primary and secondary sources. Hence, there is no need to estimate the pollutants/wastes from the secondary sources separately. In this case, control processes can be evaluated by comparing their final output wastes from the production of a same given amount of final utilities. However, if the secondary pollutants/wastes are to be estimated separately from the primary pollutants/wastes, in spite of the fact that the intermediate utilities are produced within the plant, the use of new pollutant factors would leave out the very indirect effect this paper attempts to capture. The extra utilities required for a control process cannot be produced with less pollutants without adding an extra burden to the control process. Additional inputs (and hence more pollutants) are required for the control process to produce these intermediate utilities in the less polluted way. It is recognized that the use of the 1972 data is not totally satisfactory. They tend to result in the overestimation of the secondary effect of utilities when the new performance standards achieved through the control processes would reduce the overall pollution level-i.e., the total environmental pollution is less with control than without control. As to the units for fuel in Table I1 and annual cost in Table V, they are indicated by the notation M (with bar), which means 106. Chiou-shuang Yan College of Business and Administration Drexel University Philadelphia, Pa. 19104
SIR: We wish to take exception with the line of reasoning and conclusions presented by Chameides and Stedman in their article, “Ozone Formation from NO, in ‘Clean Air’ ” [ES&T, 10,150 (Feb. 1976)l. Chameides and Stedman presented a photochemical model to explain occurrence of elevated levels of 0 3 (>80 ppb) in rural areas in terms of photochemical reactions of natural methane and urban NO,. The authors’ findings suggest, implicitly, at least, that the only controllable factor causing oxidant formation in rural areas is anthropogenic NO,. Such an implication is extremely important from a control standpoint and prompted us to submit the following critique on the Chameides-Stedman work and conclusions. Key components in the Chameides-Stedman work and reasoning are: Using a 52-reaction step photochemical model for the atmospheric methane/NO, reaction systems, the authors
