Cross e t al. (19) have suggested that fish may be actively regulating concentrations of essential elements in their tissues. Our results indicate that the two fish species studied regulate both essential and toxic trace elements in their tissues even in polluted environments. However, one should not exclude factors such as the mobility of fish and the timescale of their element turnover that smooth the temporal and spatial variations in seawater concentrations (13). Variations in trace element concentrations found in this study probably reflect differences between species and differences in size, life histories, and dietary habits (17-19) rather than in concentrations in the marine environment. Sargus annularis and Gobius niger from the upper Saronikos Gulf and Mytelene Harbor are not dangerous for human consumption. The maximum Hg value found in this study in Mytelene Harbor (0.46 ppm, wet weight using a 4.13 wetldry factor as determined) is lower than the provisional maximum permissible limit of 0.50 ppm wet weight. On the other hand, As values, as mentioned, for these two species are comparable to natural background levels. More research is needed on the ecology of commercially important fish to design better sampling and on the biochemical mechanisms of trace element uptake (chemical form of element, gill vs. food uptake, etc.) as well as on the relation of trace elements with age or length and dietary habits. Acknowledgment
We thank E. Moraitopoulou-Kassimati and G. Kanias for fish species identification and E. Hadjelli-Handrinou and M. Aravantinou-Draina for their valuable technical assistance. Literature Cited (1) Ackefors, H., Lofroth, G., Rosen, C. G., Mar. Biol. Ann. Reu., 8,
203-24 (1970). (2) Wright, D. A., Mar. Pollut. Bull., 7,36-8 (1976). (3) Hardisty, M. W., Huggins, R. J., Kartar, S., Sainsbury, M., ibid., 5,12-15 (1974). (4) Dean, J. D., Bosqui, F. L., Lanouette, K. H., Enuiron. Sci. Technol., 6,518-22 (1972). (5) Helz, G. R., Geochim. Cosrnochim. Acta, 40,573-80 (1976). (6) Grimanis, A. P., Vassilaki-Grimani, M., Griggs, G . B., J. Radioanal. Chem., 37,761-71 (1977). (7) Papadopoulou, C., Grimanis, A. P., Hadjistelios, I., Thalassia Jugosl., 9, 211-18 (1973). (8) Grimanis, A. P., Papakostidis, G., Papadopoulou, C., VassilakiGrimani, M., Papacharalambus, N., Plassaras, G., Kotoulas, D., Int. Atomic Energy Agency, Tech. Rep. 157, pp 29-51, Vienna, Austria, 1973. (9) Bock-Werthmann, W., Papakostidis, G., Grimanis, A. P., Petrou, J., Georghiou, D., Vassilaki-Grimani, M., “Actanal. A Comprehensive Computer Program for Routine Activation Analysis Using Ge (Li) Detectors”, Nuclear Research Center “Demokritos”, Athens, Greece, Rep. DEMO 74/15,1974. (10) Bohn, A., Mar. Pollut. Bull., 6,87-9 (1975). (11) Guinn, V. P., de Goeij, J.J.M., Int. Atomic Energy Agency, Tech. Rep. 157, pp 163-73, Vienna, Austria, 1973. (12) Guinn, V. P., Di Casa, M., de Goeij, J.J.M., Young, D. R., “Neutron Activation Analysis Studies of Marine Biological Species and Related Marine Sediments”, Proc. 2nd Int. Conf. on Nuclear Methods in Environmental Research, pp 24-31, Columbia, Mo., July 1974. (13) Preston, A., Nature, 242,95-7 (1973). (14) Hallcrow, M. W., Mackay, P. W., Thornton, I., J. Mar. Biol. Assoc. UK, 53,721-39 (1973). (15) Eustace, I. J., Aust. J . Mar. Freshwater Res., 25, 209-20 (1974). (16) Roth, I., Hornung, H., Enuiron. Sci. Technol., 11, 265-9 (1977). (17) Hardisty, M. W., Huggins, R. J., Kartar, S., Sainsbury, M., Mar. Pollut. Bull., 5,12-15 (1974). (18) Hardisty, M. W., Kartar, S., Sainsbury, M., ibid., pp 61-3. (19) Cross, F. A., Hardy, L. H., Jones, N. Y., Barber, R. T., J . Fish. Res. Board Can., 30,1287-91 (1973). Received for review August 1,1977.Accepted January 3,1978. Partial support by the National Research Institute. 726
Environmental Science & Technology
CORRESPONDENCE
SIR: Orel and Seinfeld recently published an account of their calculations of equilibrium nitrate and sulfate levels in aqueous systems in the presence of a number of atmospheric contaminants, including NO, NO2, and SO2 (1).Their work included the appropriate combination of a number of equilibrium expressions, with the application of a range of atmosphere-level concentrations, and yielded values of nitrate concentrations for the range of conditions. The authors also considered the heterogeneous oxidation of sulfite to sulfate by oxygen in the aqueous systems. They concluded that due to the dissolved NO,, the acidity of the solutions would be too high for the rate of SO2 oxidation by oxygen to be significant. They cited McKay’s treatment (2) of the data of Fuller and Crist ( 3 ) ,who found that although the rate of sulfite oxidation by oxygen increases with increased acidity, the degree of oxidative conversion is inversely related to the acidity. Thus, below about p H 6, the oxidation effectively ceases. The model was developed assuming the absence of catalytic metal ions and any photochemical component. The authors have eliminated oxidation by atmospheric oxygen as a significant process in these systems, but they apparently have not considered the potentially rapid oxidation of SO2 by HONO. The reaction is important in the Chamber Process to produce sulfuric acid and has been studied extensively ( 4 ) . I t is second order in N(III), does not require light, and obviously takes place in acidic environments. I t is appropriate to consider if the reaction is adequately rapid under conditions close to those found in the atmosphere. In some preliminary work, we have found that it is. Thus, a t 25 OC in 10%sulfuric acid, we find that HONO oxidizes S02H2O completely a t characteristic reaction times of 15-30 s. Both reactants are in the to M range. The reaction rate is unaffected by the presence of M nitric acid, and M) alone in the same medium does not oxinitric acid ( dize S02aH20, a t least at very high rates. The N(II1)-S(1V) reaction could, therefore, play a significant role in the heterogeneous chemistry of the atmosphere. Finally, although the gas-phase reaction of NO, with SO2 is slow a t ambient temperatures under anhydrous conditions, the presence of water vapor remarkably enhances the rate (5). Similarly, when ammonia is added to these systems, the formation of ammonium sulfate is highly promoted by the presence of water vapor (6). The question of a heterogeneous component might be raised with regard to these studies. However, these data suggest that the water-promoted oxidation of SO2 by NO, in a nonphotochemical process could be significant in the homogeneous chemistry of the atmosphere. Literature Cited (1) Orel, A. E., Seinfeld, J. H., Enuiron. Sci. Technol., 11 (lo), 1000
(1977). (2) McKay, H., Atrnos. Enuiron., 5,7 (1971). (3) Fuller, E., Crist, R., J . Am. Chern. SOC.,63,1644 (1941). (4) “The Manufacture of Sulfuric Acid”, W. Duecker and J. West, Eds.. Amer. Chem. SOC.Monograph -~ Series No. 144, Amer. Chem. SOC.,pp 111-16,1959. (5) Kunin, T., Epifanov, V., I t u . Vyssh. Uchebn. Zaued., Khim. Khim. Tekhnol.. 11.912 (1968):Stomerka. K.. Wolf. F.. Suess. G., Z. Anorg. Allg. Cheh., 359,14 (196’8j. (6) Haber, T., Malvsa, K., Pawlikowska-Czubak, J., Pomianowski, A,, Z. Anorg. Allg. Chem., 418, 179 (1975). David S. Ross
Chemistry Laboratory SRI International 333 Ravenswood Avenue Menlo Park, Calif. 94025
