Environ. Sci. Technol. 1985, 19, 199-199
or 5-day concentration ratios, from estimates of uptake and elimination rates. If all the laboratory-derived bioconcentration factors had been 96-h values, it would have helped explain how field ratios, presumably closer to steady state, could be higher than predictions based on those laboratory values. The field data in Connor’s figures and these corrected calculations suggest that equations developed from laboratory measurements may be useful in predicting the accumulation of CAHs by fish relative to sediments under field conditions. Comparable predictions of fishlsediment ratios for PAHs must account for their more rapid biotransformation in fish. Connor’s approach to predicting fish/sediment ratios thus appears to be more successful than he suggested.
Literature Cited (1) Connor, M. S. Enuiron. Sci. Technol. 1984, 18, 31-35. (2) Kenaga, E. E.; Goring, C. A. I. ASTM Spec. Tech. Publ. 1980, STP 707, 78-115. (3) Veith, G. D.; DeFoe, D. L.; Bergstedt, B. V. J . Fish. Res. Board Can. 1979,36, 1040-1048. (4) Oliver, B. G.; Niimi, A. G. Enuiron. Sci. Technol. 1983,17, 287-291. (5) Karickhoff, S. W.; Brown, D. S.; Scott, T. A. Water Res. 1979,13, 241-248. (6) Mackay, D. Environ. Sci. Technol. 1982, 16, 274-278. (7) Veith, G. D.; Macek, K. J.; Petrocelli, S. R.; Cmol, J. ASTM Spec. Tech. Publ. 1980, STP 707, 116-129. (8) Neely, W. B.; Branson, D. R.; Blau, G. E. Enuiron. Sci. Technol. 1974,8, 1113-1115. (9) Chiou, C. T.; Freed, V. H.; Schmedding, D. W.; Kohnert, R. L. Enuiron. Sci. Technol. 1977, 11, 475-478. (10) Branson, D. R.; Blau, G. E.; Alexander, H. C.; Neely, W. B. Trans. Am. Fish. SOC.1975,104,785-792. t Operated by Martin Marietta Energy Systems, Inc., under Contract DE-AC05-840R21400 with the U.S.Department of Energy. Publication No. 2445, Environmental Sciences Division, ORNL.
James E. Breck
Environmental Sciences Division Oak Ridge National Laboratoryt Oak Ridge, Tennessee 37831
SIR: Breck’s correction of my eq 3 (1)has the happy result of bringing the field data into better agreement with the mathematical predictions. As I noted in the paper, the fish/sediment ratio seems to reach a plateau when flushing times are greater than 100 days. These plateau values also agree nicely with the predicted steady-state ratios from the corrected eq 3. I believe this behavior is less associated with the freshwater nature of these environments as Breck suggests than with the coincidence that all the freshwater data available here happened to be from the environments with the longest flushing times. If all environmental pools were at steady state, presumably flushing time would have little importance. However, input loads can be highly variable, and fishlsediment ratios are one way of reducing this environmental variation.
Breck also shows that a variety of equations could be combined to yield quite different slopes of the fishlsediment ratio with respect to the octanol-water partition coefficient (KO,).Mackay has recently argued that the relationship between the bioconcentration factor (BCF) and KO,should be linear (2). Karickhoff et al. have developed a similar relationship for the soil partition coefficient (K0J (3). Combining these two equations yields a fish/sediment ratio independent of KO,: 0.077 -BCF - KBed fraction organic carbon Of all the various combinations of equations, the simplicity of this relationship makes this equation most appealing. In addition, the variation reported by Mackay and Karickhoff et al. was much smaller than the earlier work of Kenaga and Goring ( 4 ) . From McKay’s and Karickhoff s regression data, I ran Monte Carlo simulations to predict the fishlsediment ratio for a mean log KO, of 4.5 with a variance of 1.0. The resulting fish/sediment ratio had a coefficient of variation of about 14%, a small source of error compared to the other sources of error mentioned in my paper. The predicted fishlsediment ratio (approximately 200) using this equation agrees quite well with the data for the high octanol-water partition coefficient chlorinated hydrocarbons in Figure 3 (1). When the caveats cited in my paper and by Breck are recognized, either version of the corrected eq 3 provides a technique for estimating the maximum concentrations in fish given certain sediment loads. Breck has nicely summarized the appropriate procedures to determine laboratory bioconcentration factors. Much of the earlier data used to develop the first regression equations for bioconcentration factors and octanol-water partition coefficients was based on tests as short as 96 h (ref 5, Table 5-3). Even today the U S . Environmental Protection Agency and the U S . Army Corps of Engineers use only 10-day tests in determining the suitability of dredge spoils for dumping (6).
Literature Cited (1) Connor, M. S. Enuiron. Sci. Technol. 1984, 18, 31-35. (2) Mackay, D. Enuiron. Sci. Technol. 1982, 16, 274-278. (3) Karickhoff, S. W.; Brown, D. S.; Scott, T. A. Water Res. 1979, 13, 241-248. (4) Kenaga, E. E.; Goring, C. A. I. ASTM Spec. Tech. Publ. 1980, STP 707, 78-115. (5) Bysshe, S. E. In “Handbook of Chemical Property Estimation Methods: Environmental Behavior of Organic Compounds”; Lyman, W. J., Ed; McGraw-Hill: New York, 1982; p 5-1. (6) U.S. Army Corps of Engineers “Evaluation of Proposed Discharge of Dredged Material into Ocean Waters”; Environmental Effects Lab: Vicksburg, MI, 1977; G-1.
Michael Stewart Connor U S . Environmental Protection Agency, Boston, Massachusetts 02203
Not subject to U.S. Copyright. Published 1985 by the American Chemical Society
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