Environ. Sci. Technol. 1987, 21, 248-252
formation of hydrophobic bonds. Acknowledgments We thank M. DitZler, p. IWlefield, and the Worcester Consortium NMR facility NSF Equipment Grant CHE77-09059 for obtaining the solid-state NMR spectra and the UNH Instrumentation Center for performing the elemental analysis. We also thank J. Weber and E. Thurman for s6pplying the SF-2 and SF-3 fulvic acids. Registry No. Pyrene, 129-00-0. Literature Cited (1) McCarthy, J. F.;Jimenez, B. D. Enuiron. Sci. Technol. 1985, 19. 1072-1076.
(2) Caron, G.; Suffet, I. H.; Belton, T. Chemosphere 1985,14, 993-1000. (3) Chiou, C. T.; Porter, P. E.; Schmedding, D. W. Enuiron. Sci. Technol. 1983, 17, 227-231. (4) Wijayaratne, R. D.; Means, J. C. Enuiron. Sci. Technol. 1984,18, 121-123. (5) Gjessing, E. T.; Berglind, L. Arch. Hydrobiol. 1981, 92, 24-30. (6) Wijayaratne, R. D.; Means, J. C. Mar. Enuiron. Res. 1984, 11, 77-89. (7) Hassett, J. P.; Anderson, M. A. Enuiron. Sci. Technol. 1979, 13, 1526-1529. (8) Landrum, P. F.; Nihart, S. R.; Eadie, B. J.; Gardner, W. S. Enuiron. Sci. Technol. 1984, 18, 187-192. (9) Morehead, N. R.; Eadie, B. J.; Lake, B.; Landrum, P. F.; Berner, D. Chemosphere 1986,15, 403-412. (10) Whitehouse, B. Estuarine, Coastal Shelf Sci. 1985, 20, 393-402. (11) Carter, C. W.; Suffet, I. H. Environ. Sci. Technol. 1982,16, 735-740. (12) Voice, T. C.; Weber, W. T., Jr. Enuiron. Sci. Technol. 1985, 19,789-796. (13) Gschwend, P. M.; Wu, S. Enuiron. Sci. Technol. 1985,19, 90-96.
(14) Stevenson, F. T.; Goh, K. M. Geochim. Cosmochim. Acta 1971,18,471-483. (15) Hatcher, P. G.; Rowan, R.; Mattingly, M. A. Org. Geochem. 1980,2, 77-85. (16) Hatcher, P. G.; Schnitzer, M.; Dennis, L. W.; Maciel, G. E. Soil Sci. SOC.Am. J . 1981, 45, 1089-1094. (17) Jackson, T. A. Soil Sci. 1975, 119, 56-64. (18) Diachenko, G. W. Ph.D. Thesis, University of Maryland, 1981. (19) Gauthier, T. D.; Shane, E. C.; Guerin, W. F.; Seitz, W. R.; Grant, C. L. Enuiron. Sci. Technol. 1986,20,1162-1166. (20) Baur, G. A. M.S.Thesis, University of New Hamushire. 1981. (21) Weber, J. H.; Wilson, S. A. Water Res. 1975,9,1079-1084. (22) Wilson, S. W.; Weber, J. H. Chem. Geol. 1977,19,285-293. (23) Thurman,E. H.; Malcolm, R. L. In Aquatic and Terrestrial Humic Materials; Christman, R. F.; Gjessing, E. T., Eds.; Ann Arbor Science: Ann Arbor, MI, 1983; pp 1-35. (24) Rashid, M. A.; King, L. H. Geochim. Cosmochim. Acta 1970, 34, 193-201. (25) Mikinis, F. P.; Bartuska, V. J.; Maciel, G. E. Am. Lab. (Fairfield, Conn.) 1979, 11, 19-29. (26) Wilson, M. A. J . Soil Sci. 1981, 32, 167-186. (27) Newman, R. H.; Tate, K. R. J . Soil Sci. 1984, 35, 47-54. (28) Stuermer, D. H.; Peters, K. E.; Kaplan, I. R. Geochim. Cosmochim. Acta 1978,42, 989-997. (29) Tanaka, N.; Tokuda, Y.; Iwaguchi, K.; Araki, M. J. Chromatogr. 1982,239, 761-772. (30) Levine, I. N. Physical Chemistry; McGraw-Hik New York, 1978; p 730. (31) Voice, T. C.; Weber, W. J., Jr. Water Res. 1983, 17, 1433-1441. (32) Brigg, G. C . J. Agric. Food Chem. 1981,29, 1050-1059.
Received for reuiew June 9,1986. Accepted October 6,1986. This project was funded in part by the Officeof Sea Grant, National Oceanic and Atmospheric Administration, US.Department of Commerce, through Grant RIPMR-84 to the University of New Hampshire.
Volatilization of Ethylene Dibromide from Water Ronald E. Rathbun" US. Geological Survey, Arvada, Colorado 80002
Doreen Y. Tal US. Geological Survey, Gulf Coast Hydroscience Center, National Space Technology Laboratories, Mississippi 39529
Overall mass-transfer coefficients for the volatilization of ethylene dibromide from water were measured simultaneously with the oxygen absorption coefficient in a laboratory stirred tank. Coefficients were measured as a function of mixing conditions in the water for two windspeeds. The ethylene dibromide mass-transfer coefficient depended on windspeed; the ethylene dibromide liquidfilm coefficient did not, in agreement with theory. A constant relation existed between the liquid-film coefficients for ethylene dibromide and oxygen. Introduction EDB (ethylene dibromide) has been used as an additive to leaded gasoline, as a soil fumigant, and as an insecticide for stored grains. It has been detected in groundwater and surface water in a number of locations (1). It also has been rationalized (1) that volatilization is likely to be significant in determining the aquatic fate of EDB, and that both the gas-film and liquid-film resistances 248
Envlron. Sci. Technol., Vol. 21, No. 3, 1987
are likely to be important. Information on the gas-film coefficient was presented previously (I). This paper presents information on the liquid-fim coefficient. The reference substance concept is used in which the liquid-film coefficient for the volatilization of EDB from water is related to the oxygen absorption coefficient for the same water. Background Theory Two-Film Model. Volatilization of organic compounds from water is commonly described by the two-film model of mass transfer (2-4). The basic equation of this model is (1) 1/KoL = l / k L + R T / ( H ~ G ) where KoLis the overall mass-transfer coefficient based on the liquid phase (m/d), kL is the liquid-film coefficient (m/d), R is the gas constant [kPa.m3.(g.mol)-l/l(l, Tis the absolute temperature (K), H is Henry's constant [kPa. m3/(g.mol)], and kG is the gas-film coefficient (m/d). In
Not subject to US. Copyright. Published 1987 by the American Chemical Soclety
laboratory studies, K O L is directly measurable from the rate of change of the concentration of the compound in the water as a function of time. However, the film coefficients kL and kG are directly measurable only under certain limiting conditions. For organic compounds with large values of Henry's constant, the second term on the right-hand side of eq 1 is negligible with respect to the first term. Therefore, the liquid-film coefficient is virtually equal to the overall mass-transfer coefficient and is directly measurable. EDB, however, has a Henry's constant such that both film resistances offer significant resistance to the volatilization from water ( I ) , and therefore, the liquid-film coefficient for EDB cannot be measured directly. This coefficient must be obtained from eq 1 and measured values of the overall mass-transfer coefficient and the gas-film coefficient. The limiting condition for the gas-film coefficient is that' of volatilization of the pure organic compound because only the gas-film resistance is present in the volatilization of a pure liquid. Thus, the overall mass-transfer coefficient equals the gas-film coefficient for pure liquid volatilization. Details of the determination of the gas-film coefficient of EDB by this procedure were presented previously (1). Environmental Considerations. Mixing within an environmental water body is the result of turbulence generated through shear stresses acting on the water body. These shear stresses are generated by wind above the water and by friction forces at the bottom and banks of the water body. The relative importance of these shear stresses depends on the type of water body. In streams and rivers, turbulence is largely generated by friction forces at the bottom and banks. In lakes and ponds, turbulence is largely generated by wind. However, there is no sharp division between types of water bodies. In a deep sluggish river or a wide shallow river, the wind may generate more turbulence in the water than the friction forces at the bottom and banks. Conversely, in some lakes where flow through is significant, bottom and bank friction forces may generate significant turbulence. Mixing within the air above an environmental water body is the result of atmospheric turbulence. This turbulence is commonly characterized by the windspeed. The two-film model (2) assumes that the film coefficients are equal to the molecular diffusion coefficients for the organic compound in the film material divided by the film thicknesses. The film thicknesses are determined by the turbulence within the respective phases. Therefore, it follows that the liquid-film coefficient should be determined primarily by the degree of turbulence in the water and the gas-film coefficient primarily by the degree of turbulence in the air as indicated by the windspeed. Reference Substance Concept. There have been a number of laboratory experimental studies of the volatilization of organic compounds from water (5-15) but only a few field studies of the volatilization of organic compounds from streams and rivers (16). To permit transfer of the laboratory data to the field, the reference substance concept (7-11,13,17,18) has been used. The basis of this concept is the hypothesis that the ratio of the film coefficient for the organic compound to the film coefficient for the reference substance is independent of mixing conditions within the particular phase, whether it is the water or air. Oxygen is commonly used as the reference substance for the liquid-film coefficient because it is generally accepted (17) that virtually all resistance to the absorption of oxygen
is in the liquid film. Therefore, for practical purposes, the oxygen absorption coefficient is identical with the liquidfilm coefficient for the absorption of oxygen. Also, numerous equations exist (19) for predicting the oxygen absorption coefficient as a function of the hydraulic and geometric properties of streams and rivers. The reference substance equation for the liquid film, therefore, has the form kLoRG
=
@kLOXY
(2)
where kLoRGis the liquid-film coefficient for the volatilization of an organic compound from water (m/d), kLoXY is the liquid-film coefficient for the absorption of oxygen (m/d), and CP is a constant assumed to be independent of mixing conditions within the water phase. The constancy of CP with respect to mixing conditions in water has been verified for a number of organic compounds (8, 11, 13). Water is commonly used as the reference substance for the gas-film coefficient because the evaporation of a pure liquid is controlled completely by the gas-film resistance. Also, information exists on the evaporation of water from lakes and reservoirs (20) and a canal (21,22). The reference substance equation for the gas film, therefore, has the form kGoRG
= QkG WATER
(3)
where kCoRGis the gas-film coefficient for the volatilization of an organic compound from water (m/d), kGWAmR is the gas-film coefficient for the evaporationof water (m/d), and is a constant assumed to be independent of mixing conditions within the air phase. The constancy of 9 with respect to windspeed has been verified for EDB (1). The reference substance concept is applied by estimating k L and kG of the reference substances for the stream or river of interest. These values are then used with the laboratory-determined CP and \k values and eq 2 and 3 to predict liquid-film and gas-film coefficients for the organic compound for the stream or river.
Experimental Section General Procedure. The overall mass-transfer coefficients for the volatilization of EDB from water were measured simultaneously with the oxygen absorption coefficient in a stirred water bath in the laboratory. Measurements were completed for a range of water mixing conditions and two windspeeds. Water temperature was 298.2 K. The experimental apparatus and procedure were basically the same as described previously (11). The procedure consisted of lowering the dissolved oxygen concentration of distilled water in the constant temperature bath by stripping with nitrogen gas. A quantity of water containing sufficient dissolved EDB to give the desired initial concentration in the bath water was added. The water was stirred at a constant rate with a constant airflow across the surface of the water. One airflow resulted from the fume hood in which the temperature bath was placed. This fume hood with a rated face velocity of 38 m/min resulted in a windspeed of about 0.1 m/s across the water surface. A second windspeed of about 2.0 m/s was obtained with a window fan with a 0.51-m diameter blade located in front of the fume hood. Windspeeds were measured with a digital eight-vane air meter located about 0.2 m above the water surface. The water surface for low-windspeed low water mixing conditions was smooth; the water surface for high-windspeed high water mixing conditions was rippled. Samples of water for determination of EDB and dissolved oxygen concentrations were Envlron. Scl. Technol., Vol. 21, No. 3, 1987
249
1,500
L U
o
3
A
0.1 m/s 2.0 m/s
/
1,400
- -
0
0.1 m/s
A
2.0 m/S LEAST SQUARES
I
? E
Y
c
1,300
2
.
w
0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
OXYGEN ABSORPTION COEFFICIENT (m/d)
Flgure 1. Overall mass-transfer coefficients for volatilization of EDB as a function of oxygen absorptlon coefficient.
obtained as a function of time by sampling from middepth with a glass siphon. EDB volatilization and oxygen absorption coefficients were calculated from the concentration vs. time data with a two-parameter nonlinear leastsquares procedure (23). Analytical Techniques. EDB concentrations in the water samples were determined by a purge-and-trap technique followed by analysis in a gas chromatographwith a flame ionization detector. The analytical column was a 0.5-m length of 3.2-mm 0.d. nickel alloy tubing packed with 0.1% SP-loo0 on Carbopack. (Use of the brand name in this paper is for identification purposes only and does not constitute endorsement by the U.S. Geological Survey.) Oven temperature was maintained at 353.2 K for 2 min followed by programming at 20 K/min to 393.2 K. Retention time of the EDB peak ranged between 2.5 and 2.7 min. The injection port temperature was 423.2 K, and the detector temperature was 473.2 K. Three standard samples of EDB in water were prepared each day and analyzed by the same procedure as for the unknown samples. Concentrations of these standards covered the range of concentrations observed in the unknowns. Triplicate analyses of samples of EDB ranging from 0.103 to 4.10 mg/L resulted in relative standard deviations ranging from 0.60% to 6.3%. Dissolved oxygen concentrations were determined by a modification of the Winkler technique in which titrations were done directly in the sample bottles (24). Gas-Film Coefficients. Gas-film coefficients for the evaporation of water were determined for the apparatus by the procedure described previously (22). The procedure consisted of determining the rate of change of the water level in the constant temperature bath with time. The vapor pressure difference driving force for evaporation was calculated from measurements of the wet-bulb and drybulb air temperatures, the water temperature, and the barometric pressure. Gas-film coefficients were determined for three water mixing conditions and for the two windspeeds used for the EDB measurements. Results and Discussion
Overall Mass-Transfer Coefficients. The overall mass-transfer coefficient, KoL,for EDB is plotted in Figure 1 as a function of the oxygen absorption coefficient for windspeeds of 0.1 and 2.0 m/s. The lines in Figure 1 are least-squares lines, and least-squares slopes are 0.455 and 0.520 for the low and high windspeeds, respectively. Statistical comparison of these slopes showed they are significantly different at the 5% level, demonstrating that the wind significantly increased the volatilization of EDB from water. This is in agreement with the previous analysis (1) on the basis of Henry's constant, which suggested that both film resistances are likely to be important 250
Environ. Sci. Technol., Vol. 21, No. 3, 1987
0 u. u. w
1,200
0 0
3
d u. (1, 4
0
8oo
I
A
A
c
600 L 2.0
I
I
I
4.0
6.0
8.0
STIRRER REYNOLDS NUMBER
10.0
x
10-4
Figure 2. Gas-film Coefficients for evaporation of water as a function of stirrer Reynolds number.
in the volatilization of EDB from water. Gas-Film Coefficients. The gas-film coefficients for the evaporation of water from the experimental apparatus are plotted in Figure 2 as a function of the stirrer Reynolds number. The stirrer Reynolds number defined as NL2/v is used as an indicator of the degree of mixing in the water. In this expression, N is the revolution rate of the stirrer (rev/min), L is the diameter of the stirrer blade (m), and v is the kinematic viscosity of the water (m2/min). The gas-film coefficients for each windspeed show a small consistent increase with stirrer Reynolds number as indicated by the least-squares lines in Figure 2. However, computation of the 95% confidence limits for the slopes of these lines showed for both windspeeds that the slopes were not significantly different from zero. Therefore, it was concluded that the gas-film coefficients were not statistically dependent on the degree of mixing in the water phase. This conclusion is consistent with the concept of the two-film model (2) that the gas-film coefficient should depend primarily on mixing conditions in the air phase. Because there were no statistically significant dependences of the gas-film coefficients on water mixing conditions, average values were computed for each windspeed. These were 698 m/d with a coefficient of variation of f2.41% for the low windspeed and 1300 m/d with a coefficient of variation of *2.89% for the high windspeed. These gas-film coefficients for the evaporation of water can be converted to gas-film coefficients for the volatilization of EDB from water by use of eq 3 and \k values previously reported (1). At 298.2 K, \k is 0.410, giving gas-film coefficients for EDB of 286 and 533 m/d for the low and high windspeeds, respectively. Liquid-FilmCoefficients. It has been previously estimated (17)that more than 99.8% of the resistance to the absorption of oxygen is in the liquid film for typical streamflow conditions. Therefore, the measured overall mass-transfer coefficients for oxygen absorption plotted in Figure 1 are equal to oxygen liquid-film coefficients. Liquid-film coefficients for EDB can be calculated from eq 1 and the overall mass-transfer coefficients for EDB plotted in Figure 1,the gas-film coefficients calculated in
5.0
= : b
I
2.0
I
was discussed previously (1). The first procedure is based on the concept that the film coefficient is inversely proportional to the square root of the molecular weight (3). The estimated value of @*for EDB and oxygen is
I
= (32.0/187.88)0.6 = 0.413
I
I
W
0 0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
OXYGEN LIQUID-FILM COEFFICIENT (m/d)
Figure 3. Liquid-film coefficients for EDB as liquid-film coefficient.
a
function of oxygen
the previous section, and Henry’s constant. Henry’s constant was previously (1)calculated from vapor pressure data and solubility data from the literature, and the result at 298.2 K was 0.0831 kPa.m3/(g.mol). Substituting these values in eq 1and rearranging gives for the low windspeed l / k L = l/KOL - 0.104 (4) and for the high windspeed l / k L = l/KoL - 0.0558
(5)
Values of the liquid-film coefficient for EDB calculated from eq 4 and 5 and the experimental overall mass-transfer coefficients are plotted in Figure 3 as a function of the oxygen liquid-film coefficient. There appears to be little difference between the highwindspeed and low-windspeed points. To verify this, linear regressions of the EDB liquid-film coefficient as a function of the oxygen liquid-film coefficient were computed for the two windspeeds. Regression slopes were 0.610 for the low windspeed and 0.606 for the high windspeed. Statistical comparison showed no significant difference at the 5% level. Therefore, a single regression was computed with all the data, giving kLEDB= 0.608kLoxy
(6)
The constant of eq 6 corresponds to @ of eq 2. The fact that the liquid-film coefficient of EDB is independent of windspeed is again consistent with the concept of the two-film model (2) that the liquid-film coefficient should depend primarily on mixing conditions in the water phase. The observations with respect to the dependencies of the film coefficients on mixing conditions in the water and air phases are consistent with what would be expected for a stream or river. The gas-film coefficient depended only on the windspeed and not the degree of mixing in the water. The liquid-film coefficient depended only on the degree of mixing in the water and not on the windspeed. Thus under these conditions, there is no reason to expect a constant liquid-film/gas-film coefficient ratio for all streams and rivers or a specific stream or river to have a constant ratio for all times. This ratio and its constancy or nonconstancy for natural water bodies was discussed previously (25, 26). Comparison with Literature Values. When experimental values of Q, and 9 are not available, two procedures are commonly used for estimating the values. These procedures have been widely used but not extensively verified. The values of Q, for EDB determined in this study permit an evaluation of these procedures. The application of these procedures to experimental values of 9 for EDB
(7)
which is 32% less than the experimental value of 0.608. The second procedure is based on the concept that the film coefficient is proportional to the molecular diffusion coefficient raised to some power q , where the magnitude of q depends on the model chosen (8). Values of 9 range from 1.0 for the film model (2) to 0.5 for the penetration model (27),with the fib-penetration model (28)suggesting a value varying from 0.5 for high mixing conditions to 1.0 for low mixing conditions. Experimental values vary considerably, and the difficulty of experimentally determining this exponent has been discussed (29). It was concluded (15) that the most likely value is 0.5. The diffusion coefficient of EDB in water at 298.2 K was estimated by the Hayduk-Laudie procedure as described by Reid, Prausnitz, and Sherwood (30). The result was m2/d. Experimental diffusion coefficients of 8.73 X oxygen in water at 298.2 K fall in two groups (31), with one group having a value of about 22 X lob m2/d and the second having a value of about 17 X lom5m2/d. Using the first oxygen value gives an estimate for of
*
@EST =
(8.73/22)0.60 = 0.630
(8)
which is 3.6% larger than the experimental value of 0.608. An exponent of 0.538 would give agreement. Using the second oxygen value gives an estimate for Q, of @EST = (8.73/17)0.60= 0.717 (9) which is 18% larger than the experimental value. An exponent of 0.747 would give agreement. Thus, the values of @ estimated with both the molecular weight and diffusion coefficient procedures are in reasonable agreement with the experimental values, suggesting the estimation procedures are valid for many environmental applications.
Conclusions This study was limited to the environmentally significant compound EDB. Similar procedures may be applied to other compounds for which volatilization may be a fate-determining step. Generalized relations are not possible at the present time. Registry No. EDB, 106-93-4; H20, 7732-18-5; 02,7782-44-7. Literature Cited (1) Rathbun, R.E.;Tai, D. Y. Environ. Sci. Technol. 1986,20, 949-952. (2) Lewis, W. K.; Whitman, W. G. Ind. Eng. Chem. 1924,16, 1215-1220. (3) Liss, P. S.; Slater, P. G. Nature (London) 1974, 247, 181-184. (4) Mackay, D.;Cohen, Y. In Program and Abstracts. Symposium on Nonbiological Transport and Transformation of Pollutants on Land and Water;NTIS &port PB-257347; U.S.Government Printing Office: Washington, DC, 1976, May; pp 122-129. (5) Dilling, W.L.;Tefertiller, N. B.; Kallos, G. J. Environ. Sci. Technol. 1975,9,833-838. (6) Dilling, W.L. Environ. Sci. Technol. 1977,11, 405-409. (7) Southworth, G.R. Bull. Enuiron. Contam. Toxicol. 1979, 21, 507-514. (8) Smith, J. H.; Bomberger, D. C., Jr.; Haynes, D. L. Environ. Sci. Technol. 1980,14,1332-1337. Environ. Sci. Technol., Vol. 21,
No. 3, 1987 251
Environ. Sci. Technol. 1987, 21, 252-260
Smith, J. H.; Bomberger, D. C., Jr.; Haynes, D. L. Chemosphere 1981, 10, 281-289. Atlas, E.; Foster, R.; Giam, C. S. Environ. Sci. Technol. 1982,16,283-286. Rathbun, R. E.; Tai, D. Y. Water Res. 1981,15,243-250. Rathbun, R. E.; Tai, D. Y. Water,Air, Soil Pollut. 1982, 17, 281-293. Rathbun, R. E.; Tai, D. Y. In Gas Transfer at Water Surfaces;Brutsaert, W.; Jirka, G. H., Eds.; Reidel: Dordrecht, The Netherlands, 1984; pp 27-34. Roberts, P. V.; Dandliker, P. G. Environ. Sci. Technol. 1983, 17, 484-489. Mackay, D.; Yeun, A. T. K. Environ. Sci. Technol. 1983, 17, 211-217. Rathbun, R. E.; Tai, D. Y. J. Enuiron. Eng. Diu. (Am.SOC. Ciu. Eng.) 1982, 108, 973-989. Mackay, D., Yuen, T. K. Water Pollut. Res. J. Can. 1980, 15, 83-98. Rathbun, R. E.; Tai, D. Y. Chemosphere 1984, 13, 1009- 1023. Rathbun, R. E. J. Hydraul. Diu., Am. SOC.Civ. Eng. 1977, 103,409-424. Winter, T. C. Bibliography of U.S. Geological Survey Studies of Lakes and Reservoirs-The First 100 Years;U.S. Geological Survey Circular 895; U.S. Geological Survey. U.S. Government Printing Office: Washington DC, 1982; 35 p. Jobson, H. E.; Sturrock, A. M., Jr. Comprehensive Monitoring of Meteorology,Hydraulics, and Thermal Regime
of the Sun Diego Aqueduct, California;U S . Geological Survey Prof. Paper 1137; U.S. Geological Survey. U.S. Government Printing Office: Washington DC, 1979;29 p. (22) Rathbun, R. E.; Tai, D. Y. J . Environ. Eng. Diu. (Am.SOC. Ciu. Eng.) 1983, 109, 1111-1127. (23) Rathbun, R. E.; Tai, D. Y. Chemosphere 1984,13,715-730. (24) Rathbun, R. E.; Stephens,D. W.; Shultz,D. J.; Tai, D. Y. J. Environ. Eng. Diu. (Am. Soc. Civ. Eng.) 1978, 104, 215-229. (25) Rathbun, R. E.; Tai, D. Y. Environ. Sci. Technol. 1984,18, 133. (26) Berglund, R. L.; Conway,R. A.; Waggy, G. T.; Spiegel, M. H. Environ. Sci. Technol. 1984, 18, 133-134. (27) Danckwerts, P. V. Ind. Eng. Chem. 1951,43,1460-1467. (28) Dobbins, W. E. In Proceedings of the International Conference on Water Pollution Research; Pergamon: London, 1964; pp 61-76. (29) Mackay, D.; Shiu, W. Y.; Bobra, A.; Billington, J.; Chau, E.; Yeun, A.; Ng, C.; Szeto, F. U.S. EPA Report 600/382-019; U.S. GovernmentPrinting Office: Washington DC, 1982; NTIS PB 82-230939. (30) Reid, R. C.; Prausnitz, J. M.; Sherwood, T. K. The Properties of Gases and Liquids;McGraw-Hik New York, 1977. (31) Duda, J. L.; Vrentas, J. S. Am. Inst. Chern. Eng. J. 1968, 14, 286-294. Received for review May 20, 1986. Accepted October 9, 1986.
Effects of Chlorine and Chlorine Dioxide on Mutagenic Activity of Lake Kinnereth Water Naoml Guttman-Bass,
* p t
Mlryam BaIrey-Albuquerque,+ Shlmon UlItzur,$ Alan Chartrand,+ and Chalm Rav-Acha * g t
Environmental Health Laboratory, Hadassah Medical School and School of Public Health, Hebrew University, Jerusalem, Israel, and Department of Food Engineering and Biotechnology, Technion, Israel Institute of Technology, Haifa, Israel
w Water from Lake Kinnereth (Israel) was tested for the presence of mutagenic activity, with and without disinfection by chlorine and chlorine dioxide. The samples were assayed for activity with two Ames Salmonella typhimurium tester strains, TA 104 and TA 100, and by a luminescent genotoxic assay with a dark mutant strain of Photobacterium fischeri. The water concentrates were mutagenic in strain TA 104 and in the luminescent assay, reaching positive mutagenic activities in the equivalent of 20 mL of water. Chlorination did not greatly affect the net mutagenic activity, although C102apparently reduced it. Humic acids were isolated from lake sediment and were assayed with and without disinfection in distilled water and in lake water from which the organic components were removed. The humic acids were mutagenic in both test systems, and treatment with C12generally decreased the net activity. CIOz also tended to decrease the mutagenic activity, and cytotoxic effects were observed in some of the samples. Conversely, commercial humic acid was mutagenic only after chlorination on strain TA 100. Introduction Mutagenic activity has been detected in natural waters in many parts of the world (1-7). Possible sources of the mutagenic components are industrial and domestic wastes and agricultural runoff (8))as well as natural processes occurring in the water (9). The presence of mutagenic f
f
Hebrew University. Technion, Israel Institute of Technology.
252
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21, No. 3, 1987
activity in water that is used as a potable source is of particular concern, due to the possible health effects of drinking mutagens. Finished drinking water has been reported to contain mutagens and carcinogens (10-16). A major source of the mutagenic activity in drinking water is the treatment processes, such as disinfection, which are used to ensure the microbiological quality of the water. In addition, mutagenic activity can increase in distribution systems, following final treatment of the water (17). The specific health effects of the presence of mutagens and carcinogens in drinking water have not been defined, although a number of epidemiological studies have indicated that increased levels of specific cancer types were associated with poorer organic quality of drinking water (8). Lake Kinnereth is a large freshwater lake in Israel that supplies drinking water to about 40% of the population. It has a relatively high content of organic material and bromide, and a high pH. Until recently, the major treatment process was chlorination, but there has now been a partial move to chlorine dioxide. The major reason for this change is the relatively high concentrations of trihalomethanes (THMs), mainly bromoform, detected after chlorination of this water (18). Although CIOz does not form THMs (19) and produces very few nonvolatile chlorinated products (18))its advantage from the point of view of health is questionable, since the organic products it produces in water are largely unknown. The only available information about CIOz organic byproduds in actual water treatment plants was obtained by Stevens (20))who identified some low molecular weight aldehydes formed in Ohio River water after disinfection with C102. Addi-
0013-936X/87/0921-0252$0 1.50/0
0 1987 American Chemical Society
