Beyond acid rain Dear Sir: With pleasure we read the article by Gafiey et al. about the role of hydrogen peroxide and organic oxidants as possible causes of adverse ecochemical effects (I). Among other noxious agents, photochemically produced nitrophenols have been mentioned in this article, and the necessity for further research concerning the ecological effects of these and other substances has been stressed. At least for some of these compounds, namely 2,4dinitrophenols and some of their a l b l derivatives, the data base is not as desolate as stated. The dinitrophenols have been well known as insecticides, bactericides, and herbicides since the beginning of the-century (2, 3). The mechanism of biological action (at least during acute poisoning) is well explored (4). Their formation in photochemical reactions has been shown in smog chambers (5, 6) and in rain samples collected during a thunderstorm (7). Assuming that about one percent of the lower aromatic (BTX) hydrocarbons-benzene, toluene, and xylenesemitted are converted to nitrophenols,
we estimate that several thousand metric tons may be formed and deposited, mostly by rain, in West Germany (8). The reaction scheme for this conversion has recently been published by Leone et al. (6).This deposition would be more than the annual amount of these substances applied to soil for agricultural reasons. The analytical data are not yet reliable enough to test the above estimate (7). However, smaller amounts of herbicidal substances may also have adverse long-term effects. Therefore we agree with GaEney et al. in urging more research on the formation, transport, and ecotoxicity of polar, airborne substances. The connection of the formation of the nitrophenols with the composition of gasoline (BTX contents) and NO, production can hardly be overlooked. With regard to the controversy about the c o m t definition and unit of Henry’s coefficient, H, (9, IO) we would su g a t the use of SI units, i.e., Pa (N/ m ) for pressure and mol/m3 for concentration, yielding Pa m31mol for H (11).It would be even better, for environmental purposes, to use a dimen-
F
sionless ratio of concentrations: H = [substance in air]/[substance in water].
W.Kliipffer
G. Rippen Battelle Institute e.V. D-6000Frankfurt am Main West Germany
(sj’Grosjean, D. Environ. sci. Teehnol. 1985,19, 968-74. (6) Leone, I. A. et al. 3. Chcm. Kinetics 1985,17, 177-216. (7) Rippen, G . et al. Environ. Technol. Let-
ters, in press. (8) Rippen, 0. el al. ltanscript of the sympu slum ”New Research Hypotheses” Berlin, December 1985. (9) Blevilt, R. Environ. Sei. Technol. 1987, 21, 828. (IO) Oafiey, 1. S. et al. Environ. Sci. Technol. 1987,21, 828. (11) Mackay, D.; Shiu, W. Y. . I . Phys. Chem. Data 1981, 10, 1175-99.
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Environ. SCi.TeChnol.. Vol. 21. No. 12, 1987 1141
