Mutation Research, 298 (1992) 125-129 © 1992 Elsevier Science Publishers B.V. All rights reserved 0165-1218/92/$05.00
125
MUTGEN 01835
M u t a g e n i c activity o f the l e a c h a t e of m u n i c i p a l solid waste landfill Minoru Omura a, Takeo Inamasu b and Noburu Ishinishi c a Department of Hygiene, Faculty of Medicine, Kyushu University, Maidashi 3-1-1, Higashi-ku, Fukuoka 812, Japan, Department of Public Health, Faculty of Medicine, Fukuoka University, Nanakuma 7-45-1, Jonan-ku, Fukuoka 814-01, Japan and c Nakamura Gakuen College, Befu 5-7-1, Jonan-ku, Fukuoka 814-01, Japan (Received 4 March 1992) Revision received 7 July 1992) (Accepted 8 July 1992)
Keywords: Leachate; Landfill, solid waste, municipal; Salmonella/microsome assay, Ames; XAD resin
Summary
Organic concentrates were recovered using XAD-2/8 resin adsorption from the leachates of municipal solid waste landfills and their mutagenic activities were tested for 8 months using the Ames Salmonella/microsome assay. Highly polluted leachates (COD and BOD >/40 mg/l) generally had equal or higher mutagenic activities than lightly polluted leachates (COD and BOD < 40 mg/l). But there was no clear difference in mutagenicity per amount of concentrate between the two leachates. These results suggest that the mutagenic activity of landfill leachate is decided to some degree by the organic concentration in the leachate. The mutagenic activities detected even in lightly polluted leachates were not so low as those of various kind of surface waters ever reported. It is suggested that it is important to investigate the mutagenic activity of the leachate for evaluation of the impact of landfill leachate on the environment.
Various kinds of chemical substances are included in the wastes which are dumped in landfills. It is indispensable for the management of the final disposal site to evaluate the impact of those chemicals on the environment. It is especially important to investigate the behavior of micropollutants included in the landfill leachate and it gives fundamental information for the assessment of the environmental impact. Among the various kinds of micropollutants, we have been paying attention to the mutagenic sub-
Correspondence: Dr. Minoru Omura, Department of Hygiene, Faculty of Medicine, Kyushu University, Maidashi 3-1-1, Higashi-ku, Fukuoka 812, Japan.
stances. In previous studies, we reported that XAD-2/8 resin adsorption effectively recovered mutagens from the leachate of the municipal solid waste (MSW) landfill (Omura et al., 1991, 1992). In the present study, organic concentrates were recovered using this method from the leachates of the final disposal site of MSW landfills and their mutagenic activities were investigated for 8 months. Materials and methods
Chemicals XAD-2 and XAD-8 resins were purchased from Japan Organo Co. Ltd., Tokyo, Japan. They were purified by sequential solvent extraction with
126 TABLE 1 CHARACTERISTICS LEACHATE B
OF
LEACHATE
A
leachate B. Both leachate mixtures were collected from the mixing tanks before treatment of the leachate. Sample collection was carried out 8 times from July 1989 to February 1990 (samples a-h).
AND
BOD (rag/l)
COD (mg/l)
TOC b (rag/l)
Leachate A
5.3-80.0
40.0-290.0
39.0-260.0
Concentration of mutagens
Leachate B
2.8-10.0
32.0- 49.0
20.0- 53.0
20 l of leachate mixture was filtered with plugged glass wool to remove suspended materials and was divided equally into two samples. X A D - 2 / 8 resin adsorption was used to concentrate mutagens in the sample (Omura et al., 1991, 1992). The procedure was carried out at p H 2.0 (addition of H 2 S O 4) in one sample (acid concentration) and without p H adjustment in the other sample (neutral concentration). Materials adsorbed on the resin were eluted with acetone and the eluate was evaporated to complete dryness under reduced pressure in a rotary evaporator at 45°C.
~ These data were derived from the record of monthly water quality investigation of the leachates from July 1989 to February 1990. h Total organic carbon.
methanol, acetonitrile and diethyl ether according to Junk et al. (1974). Other chemicals were of analytical grade or higher.
Landfill leachate Leachate samples were collected from the same final disposal site in the previous study (Omura et al., 1991). This final disposal site was operational from 1965 to 1988 and has chiefly received MSW. The site is composed of 8 landfills that differed in the operating period, the composition of waste and the type of landfill. Leachates are sent to mixing tanks from those landfills and are aerated. Leachates with B O D and C O D concentrations >/40 mg/1 are biodegraded in the treatment process, leachates with concentrations < 40 m g / l do not. In this report, we call a mixture of the former leachates A and a mixture of the latter B. Characteristics of both leachate mixtures are described in Table 1. Leachate A was more polluted and contained more organic substances than
Mutagenicity test The concentrate obtained from 2 l of the sample was dissolved in 1.0 ml of dimethyl sulfoxide. Mutagenicity was assayed with the plate-incorporation test as described by Maron and Ames (1983). The Salmonella typhimurium tester strains TA98 and TA100 (supplied by Dr. B.N. Ames) were used. Hepatic $9 mix was prepared from male Wistar-King rats (250-300 g) pretreated with polychlorinated biphenyls, KC-500 (Kanegafuchi Kagaku, Osaka, Japan). The assay was carried out at 4 or 5 dose levels ranging from 10 to 200 ml equivalent of the sample per plate in duplicate. The mutagenic activity was described as the
TABLE 2 A M O U N T S OF C O N C E N T R A T E S OF L E A C H A T E A AND L E A C H A T E B Amount of concentrates ( m g / l ) a ~'
b
c
d
e
f
g
h
Leachate A
Acid conc. Neutral conc.
38.3 N.W.
N.W. b N.W.
42.3 21.9
82.3 27.0
37.3 12.4
25.6 9.4
35.6 10.9
78.2 24.9
Leachate B
Acid conc. Neutral conc.
11.9 4.7
N.W. N.W.
28.6 11.9
34.3 12.8
36.8 14.2
26.8 9.9
45.2 12.9
22.7 8.4
Sample collection was carried out on July 13, 1989 (a), July 27, 1989 (b), Sep. 5, 1989 (c), Oct. 12, 1989 (d), Nov. 10, 1989 (e), Dec. 19, 1989 (f), Jan. 22, 1990 (g) and Feb. 28, 1990 (h). b Not weighed.
127
net n u m b e r of revertants per 1-1 equivalent of the sample (rev./1), which was calculated by leastsquares regression analysis of a linear portion of the d o s e - r e s p o n s e curve. Benzo[a]pyrene (BaP) and 4-nitroquinoline N-oxide (4NQO) were used as positive controls. Spontaneous reversion and the number of revertants induced by the positive controls were as follows: spontaneous reversion per plate, 16-44 ( - $ 9 mix) and 25-56 ( + $9 mix) for TA98 and 96-148 ( - $ 9 mix) and 91-155 ( + $ 9 mix) for TA100; revertants per plate induced by the positive controls: 4 N Q O (0.5 /.tg/plate, - $ 9 mix), 271-486 for TA98 and 2424-4616 for TA100; BaP (5 g g / p l a t e , + $ 9 mix), 523-1244 for TA98 and 1010-2372 for TA100. Coefficients of variance of the net number of revertants induced by both positive controis were below 25% in both tester strains. Result and discussion
Table 2 summarizes the amounts of concentrates of leachate A and leachate B from July 1989 to February 1990. Samples e - g of both leachates contained almost equal amounts of concentrates. As for other samples, leachate A contained higher amounts of concentrates than leachate B. Comparing acid and neutral concentrates, acid concentrates were 2 - 4 times greater than neutral concentrates. Fig. 1 summarizes the mutagenic activities of leachate A and leachate B. The assay was carried out using TA98 and TA100 with or without $9 mix. A m o n g 8 samples of leachate B, only 1 sample had a mutagenic activity higher than 500 rev./1 for TA98. In the case of leachate A, 5 samples had mutagenic activities higher than 500 rev./I for TA98 and among them, 4 had mutagenic activities higher than 1000 rev./1. Sample d of leachate A had the highest mutagenic activity for TA98 (16 000 rev./l). Except for samples e - g , leachate A had higher mutagenic activity than leachate B for TA98. There was no clear difference in mutagenic activity between leachate A and leachate B except sample h for TA100 and TA98. Acid concentrates did not exhibit higher mutagenic activities than neutral concentrates though acid concentrates always contained higher amounts than neutral concentrates. The addition
16000 (rev /L) 2500
rev./L)
:~"
2000 1500
e.D (~}
1000 500 0 a b c d e f g h
a b c d e f g h
rev ,/L}
(rev /I
401 201
a b c d e f g h
Leachate
a b c d e f g h
A
Leachate
B
Fig. 1. Mutagenic activity of leachate A and leachate B. Mutagenic activity was described as the net number of reverrants per 1-1 equivalent of the sample. Acid concentrates, + $9 (closed circles); neutral concentrates, + $9 (closed triangles); acid concentrates, -$9 (open circles); neutral concentrates. - $9 (open triangles).
of $9 mix generally increased the mutagenic activities of both leachates especially for TA98. Samples of leachate A, which were more mutagenic than leachate B, also contained higher amounts of concentrates than those of leachate B. Next, the mutagenicity per amount of concentrate was compared between the two leachates. Fig. 2 summarizes the number of revertants per mg of concentrate of leachate A and leachate B. There was no clear difference in the mutagenicities described in this manner between the two leachates except in sample d for TA98. This means that the difference in mutagenic activity between leachate A and leachate B was mainly due to the difference in the amounts of organic substances in the leachates. Sample d of leachate A induced more revertants even per amount of concentrate than leachate B. In this case, it is supposed that the difference in quality of the organic substances contributed to the difference in mutagenic activity between the leachates. Many authors have reported the presence of mutagenic substances in river water, drinking water, and water of treatment plants ( R a p p a p o r t et
128
(rev./mg) 200 160 I 120 ~
00. 00
(rev./mg)
so
4O 0 a I~l~[,~l~lil~,ll cdefgh (rev./mg) 3 2 0 ~ 240 160 80
0
0
abedefgh (rev./mg) 320 240 160 8o
abcdefgh
0
abcdefg
Leachate A Leachate B Fig. 2. Number of revertants per mg of concentrates of leachate A and leachate B. Symbolsare the same as in Fig. 1. al., 1979; Denkhaus et al., 1981; Van H o o f and Verheyden, 1981; Maruoka and Yamanaka, 1983; Meier et al., 1987; Vartiainen et al., 1988). But there are few reports about the mutagenicity of landfill leachate (Koikawa et al., 1989; O m u r a et al., 1991, 1992). In the present study, we investigated the mutagenic activities of MSW landfill leachates 8 times. Mutagcnicity assays were carried out separately for highly polluted leachates ( C O D and B O D > 4 0 mg/1, leachate A) and lightly polluted leachates ( C O D and B O D < 40 rag/l, leachate B). Only 1 sample of leachate B had a mutagenic activity higher than 500 rev./1 for TA98. In the case of leachate A, half of the samples had mutagenic activities higher than 1000 rev./1 and the highest mutagenic activity was 16 000 rev./l for TA98. Leachate A generally had equal or higher mutagenic activity than leachate B, but there was no clear difference in mutagenicity per amount of concentrate between the two leachates. These results suggest that the mutagenic activity of the landfill leachate is decided to some degree by the organic concentration in the leachate. Relationships between mutagenic activity and organic concentration of drinking water and treatment plant water have been reported by some authors (Grabow et al., 1981; Meier et al., 1987; Vartiainen et al., 1988). The mutagenic
activity of a leachate is supposed to decrease following the decrease of organic concentration with age of the landfill. According to the relative mutagenic potency scale suggested by H o u k (1992), even the mutagenic potency of highly polluted leachates in this study (49.0 _+ 20.5 r e v . / m g for TA100, n = 6) was low, although not as low as those of various kinds of surface water ever reported. The result of this study indicates that for evaluation of the impact of landfill leachate on the environment, it is important to investigate the mutagenic activity of the leachate with standard water quality indices like COD, B O D and TOC. In the previous studies, we reported that acid concentrates of landfill leachate exhibited higher mutagenic activity than neutral concentrates (Omura et al., 1991, 1992), though this could not be found in this study and sometimes high mutagenic activities were overlooked (sample b of leachate A, for example). So it appears to be necessary to carry out both acid concentration and neutral concentration when XAD-2,/8 resin adsorption is used for concentrating mutagens from landfill leachate. The addition of $9 mix generally increased the mutagenic activities of the leachates. As for the landfill leachates of the final disposal site in this study, the main mutagens in the leachates are supposed to be promutagens. Acknowledgements
The authors wish to thank M. Hanashima, Y. Matsufuji and S. Koikawa of the D e p a r t m e n t of Engineering, Fukuoka University and T. Someya of the School of Medical Technology, University of Occupational and Environmental Health, for their advice and help with this study. References
Denkhaus, R, W.O.K. Grabow and O.W. Prozesky (1981) Removal of mutagenic compounds in a wastewater reclamation system evaluated by means of the Ames Sa|monella/microsome assay, Water Sci. Technol., 13, 571-589. Grabow, W.O.K., P.G. Van Rossum, N.A. Grabow and R. Denkhaus (1981) Relationship of the raw water quality to mutagens detectable by the Ames Salmonella/microsome assay in a drinking-water supply, Water Res., 15, 10371043.
129 Houk, V.S. (1992) The genotoxicity of industrial wastes and effluents, A review, Mutation Res., 277, 91-138. Junk, G.A., J.J. Richard, M.D. Grieser, D. Witiak, J.L. Witiak, M.D. Arguello, R. Vick, H.J. Svec, J.S. Fritz and G.V. Calder (1974) Use of macroreticular resins in the analysis of water for trace organic contaminants, J. Chromatog., 99, 745-762. Koikawa, S, T. Some~ya, Y. Matsufuji and M. Hanashima (1989) Presented at 5th International Symposium on Microbial Ecology, Kyoto, Japan. Maron, D.M., and B.N. Ames (1983) Revised methods for the Salmonella mutagenicity test, Mutation Res., 113, 173-215. Maruoka, S., and S. Yamanaka (1983) Comparative studies using the Ames Salmonella/microsome test on mutagenicity of the XAD extract recovered from river waters in Kyoto city, Environ. Sci. Technol., 17, 177-180. Meier, J.R., R.B. Knohl, W.E. Coleman, H.P. Ringhand, J.W. Munch, W.H. Kaylor, R.P. Streicher and F.C. Kopfler (1987) Studies on the potent bacterial mutagens, 3-chloro4-(dichloromethyl)-5-hydroxy-2(5 H)-furanone: aqueous stability, XAD recovery and analytical determination in
drinking water and in chlorinated humic acid solutions, Mutation Res., 189, 363-373. Omura, M., T. Inamasu and N. Ishinishi (1991) Mutagenicity assays of leachate from domestic waste landfills in Japan: The establishment of a protocol for measuring mutagenicity levels of leachate, Bull. Environ. Contam. Toxicol., 46, 561-568. Omura, M., S. Koikawa, T. Someya, T. Inamasu, M. Hanashima and N. Ishinishi (1992) Evaluation of 4 methods for concentrating mutagens in Ames Salmonella/ microsome assays on leachate collected from a municipal solid waste landfill (Japanese, summary in English), J. Jpn. Soc. Water Environ., 15, 52-61. Rappaport, S.M., M.G. Richard, M.C. Hollstein and R.E. Talcott (1979) Mutagenic activity in organic wastewater concentrates, Environ. Sci. Technol., 13, 957-961. Van Hoof, F., and J. Verheyden (1981) Mutagenic activity in the river Meuse in Belgium, Sci. Total Environ., 20, 15-22. Vartiainen, T., A. Liimatainen, P. Kauranen and L. Hiisvirta (1988) Relations between drinking water mutagenicity and water quality parameters, Chemosphere, 17, 189-202.
125
MUTGEN 01835
M u t a g e n i c activity o f the l e a c h a t e of m u n i c i p a l solid waste landfill Minoru Omura a, Takeo Inamasu b and Noburu Ishinishi c a Department of Hygiene, Faculty of Medicine, Kyushu University, Maidashi 3-1-1, Higashi-ku, Fukuoka 812, Japan, Department of Public Health, Faculty of Medicine, Fukuoka University, Nanakuma 7-45-1, Jonan-ku, Fukuoka 814-01, Japan and c Nakamura Gakuen College, Befu 5-7-1, Jonan-ku, Fukuoka 814-01, Japan (Received 4 March 1992) Revision received 7 July 1992) (Accepted 8 July 1992)
Keywords: Leachate; Landfill, solid waste, municipal; Salmonella/microsome assay, Ames; XAD resin
Summary
Organic concentrates were recovered using XAD-2/8 resin adsorption from the leachates of municipal solid waste landfills and their mutagenic activities were tested for 8 months using the Ames Salmonella/microsome assay. Highly polluted leachates (COD and BOD >/40 mg/l) generally had equal or higher mutagenic activities than lightly polluted leachates (COD and BOD < 40 mg/l). But there was no clear difference in mutagenicity per amount of concentrate between the two leachates. These results suggest that the mutagenic activity of landfill leachate is decided to some degree by the organic concentration in the leachate. The mutagenic activities detected even in lightly polluted leachates were not so low as those of various kind of surface waters ever reported. It is suggested that it is important to investigate the mutagenic activity of the leachate for evaluation of the impact of landfill leachate on the environment.
Various kinds of chemical substances are included in the wastes which are dumped in landfills. It is indispensable for the management of the final disposal site to evaluate the impact of those chemicals on the environment. It is especially important to investigate the behavior of micropollutants included in the landfill leachate and it gives fundamental information for the assessment of the environmental impact. Among the various kinds of micropollutants, we have been paying attention to the mutagenic sub-
Correspondence: Dr. Minoru Omura, Department of Hygiene, Faculty of Medicine, Kyushu University, Maidashi 3-1-1, Higashi-ku, Fukuoka 812, Japan.
stances. In previous studies, we reported that XAD-2/8 resin adsorption effectively recovered mutagens from the leachate of the municipal solid waste (MSW) landfill (Omura et al., 1991, 1992). In the present study, organic concentrates were recovered using this method from the leachates of the final disposal site of MSW landfills and their mutagenic activities were investigated for 8 months. Materials and methods
Chemicals XAD-2 and XAD-8 resins were purchased from Japan Organo Co. Ltd., Tokyo, Japan. They were purified by sequential solvent extraction with
126 TABLE 1 CHARACTERISTICS LEACHATE B
OF
LEACHATE
A
leachate B. Both leachate mixtures were collected from the mixing tanks before treatment of the leachate. Sample collection was carried out 8 times from July 1989 to February 1990 (samples a-h).
AND
BOD (rag/l)
COD (mg/l)
TOC b (rag/l)
Leachate A
5.3-80.0
40.0-290.0
39.0-260.0
Concentration of mutagens
Leachate B
2.8-10.0
32.0- 49.0
20.0- 53.0
20 l of leachate mixture was filtered with plugged glass wool to remove suspended materials and was divided equally into two samples. X A D - 2 / 8 resin adsorption was used to concentrate mutagens in the sample (Omura et al., 1991, 1992). The procedure was carried out at p H 2.0 (addition of H 2 S O 4) in one sample (acid concentration) and without p H adjustment in the other sample (neutral concentration). Materials adsorbed on the resin were eluted with acetone and the eluate was evaporated to complete dryness under reduced pressure in a rotary evaporator at 45°C.
~ These data were derived from the record of monthly water quality investigation of the leachates from July 1989 to February 1990. h Total organic carbon.
methanol, acetonitrile and diethyl ether according to Junk et al. (1974). Other chemicals were of analytical grade or higher.
Landfill leachate Leachate samples were collected from the same final disposal site in the previous study (Omura et al., 1991). This final disposal site was operational from 1965 to 1988 and has chiefly received MSW. The site is composed of 8 landfills that differed in the operating period, the composition of waste and the type of landfill. Leachates are sent to mixing tanks from those landfills and are aerated. Leachates with B O D and C O D concentrations >/40 mg/1 are biodegraded in the treatment process, leachates with concentrations < 40 m g / l do not. In this report, we call a mixture of the former leachates A and a mixture of the latter B. Characteristics of both leachate mixtures are described in Table 1. Leachate A was more polluted and contained more organic substances than
Mutagenicity test The concentrate obtained from 2 l of the sample was dissolved in 1.0 ml of dimethyl sulfoxide. Mutagenicity was assayed with the plate-incorporation test as described by Maron and Ames (1983). The Salmonella typhimurium tester strains TA98 and TA100 (supplied by Dr. B.N. Ames) were used. Hepatic $9 mix was prepared from male Wistar-King rats (250-300 g) pretreated with polychlorinated biphenyls, KC-500 (Kanegafuchi Kagaku, Osaka, Japan). The assay was carried out at 4 or 5 dose levels ranging from 10 to 200 ml equivalent of the sample per plate in duplicate. The mutagenic activity was described as the
TABLE 2 A M O U N T S OF C O N C E N T R A T E S OF L E A C H A T E A AND L E A C H A T E B Amount of concentrates ( m g / l ) a ~'
b
c
d
e
f
g
h
Leachate A
Acid conc. Neutral conc.
38.3 N.W.
N.W. b N.W.
42.3 21.9
82.3 27.0
37.3 12.4
25.6 9.4
35.6 10.9
78.2 24.9
Leachate B
Acid conc. Neutral conc.
11.9 4.7
N.W. N.W.
28.6 11.9
34.3 12.8
36.8 14.2
26.8 9.9
45.2 12.9
22.7 8.4
Sample collection was carried out on July 13, 1989 (a), July 27, 1989 (b), Sep. 5, 1989 (c), Oct. 12, 1989 (d), Nov. 10, 1989 (e), Dec. 19, 1989 (f), Jan. 22, 1990 (g) and Feb. 28, 1990 (h). b Not weighed.
127
net n u m b e r of revertants per 1-1 equivalent of the sample (rev./1), which was calculated by leastsquares regression analysis of a linear portion of the d o s e - r e s p o n s e curve. Benzo[a]pyrene (BaP) and 4-nitroquinoline N-oxide (4NQO) were used as positive controls. Spontaneous reversion and the number of revertants induced by the positive controls were as follows: spontaneous reversion per plate, 16-44 ( - $ 9 mix) and 25-56 ( + $9 mix) for TA98 and 96-148 ( - $ 9 mix) and 91-155 ( + $ 9 mix) for TA100; revertants per plate induced by the positive controls: 4 N Q O (0.5 /.tg/plate, - $ 9 mix), 271-486 for TA98 and 2424-4616 for TA100; BaP (5 g g / p l a t e , + $ 9 mix), 523-1244 for TA98 and 1010-2372 for TA100. Coefficients of variance of the net number of revertants induced by both positive controis were below 25% in both tester strains. Result and discussion
Table 2 summarizes the amounts of concentrates of leachate A and leachate B from July 1989 to February 1990. Samples e - g of both leachates contained almost equal amounts of concentrates. As for other samples, leachate A contained higher amounts of concentrates than leachate B. Comparing acid and neutral concentrates, acid concentrates were 2 - 4 times greater than neutral concentrates. Fig. 1 summarizes the mutagenic activities of leachate A and leachate B. The assay was carried out using TA98 and TA100 with or without $9 mix. A m o n g 8 samples of leachate B, only 1 sample had a mutagenic activity higher than 500 rev./1 for TA98. In the case of leachate A, 5 samples had mutagenic activities higher than 500 rev./I for TA98 and among them, 4 had mutagenic activities higher than 1000 rev./1. Sample d of leachate A had the highest mutagenic activity for TA98 (16 000 rev./l). Except for samples e - g , leachate A had higher mutagenic activity than leachate B for TA98. There was no clear difference in mutagenic activity between leachate A and leachate B except sample h for TA100 and TA98. Acid concentrates did not exhibit higher mutagenic activities than neutral concentrates though acid concentrates always contained higher amounts than neutral concentrates. The addition
16000 (rev /L) 2500
rev./L)
:~"
2000 1500
e.D (~}
1000 500 0 a b c d e f g h
a b c d e f g h
rev ,/L}
(rev /I
401 201
a b c d e f g h
Leachate
a b c d e f g h
A
Leachate
B
Fig. 1. Mutagenic activity of leachate A and leachate B. Mutagenic activity was described as the net number of reverrants per 1-1 equivalent of the sample. Acid concentrates, + $9 (closed circles); neutral concentrates, + $9 (closed triangles); acid concentrates, -$9 (open circles); neutral concentrates. - $9 (open triangles).
of $9 mix generally increased the mutagenic activities of both leachates especially for TA98. Samples of leachate A, which were more mutagenic than leachate B, also contained higher amounts of concentrates than those of leachate B. Next, the mutagenicity per amount of concentrate was compared between the two leachates. Fig. 2 summarizes the number of revertants per mg of concentrate of leachate A and leachate B. There was no clear difference in the mutagenicities described in this manner between the two leachates except in sample d for TA98. This means that the difference in mutagenic activity between leachate A and leachate B was mainly due to the difference in the amounts of organic substances in the leachates. Sample d of leachate A induced more revertants even per amount of concentrate than leachate B. In this case, it is supposed that the difference in quality of the organic substances contributed to the difference in mutagenic activity between the leachates. Many authors have reported the presence of mutagenic substances in river water, drinking water, and water of treatment plants ( R a p p a p o r t et
128
(rev./mg) 200 160 I 120 ~
00. 00
(rev./mg)
so
4O 0 a I~l~[,~l~lil~,ll cdefgh (rev./mg) 3 2 0 ~ 240 160 80
0
0
abedefgh (rev./mg) 320 240 160 8o
abcdefgh
0
abcdefg
Leachate A Leachate B Fig. 2. Number of revertants per mg of concentrates of leachate A and leachate B. Symbolsare the same as in Fig. 1. al., 1979; Denkhaus et al., 1981; Van H o o f and Verheyden, 1981; Maruoka and Yamanaka, 1983; Meier et al., 1987; Vartiainen et al., 1988). But there are few reports about the mutagenicity of landfill leachate (Koikawa et al., 1989; O m u r a et al., 1991, 1992). In the present study, we investigated the mutagenic activities of MSW landfill leachates 8 times. Mutagcnicity assays were carried out separately for highly polluted leachates ( C O D and B O D > 4 0 mg/1, leachate A) and lightly polluted leachates ( C O D and B O D < 40 rag/l, leachate B). Only 1 sample of leachate B had a mutagenic activity higher than 500 rev./1 for TA98. In the case of leachate A, half of the samples had mutagenic activities higher than 1000 rev./1 and the highest mutagenic activity was 16 000 rev./l for TA98. Leachate A generally had equal or higher mutagenic activity than leachate B, but there was no clear difference in mutagenicity per amount of concentrate between the two leachates. These results suggest that the mutagenic activity of the landfill leachate is decided to some degree by the organic concentration in the leachate. Relationships between mutagenic activity and organic concentration of drinking water and treatment plant water have been reported by some authors (Grabow et al., 1981; Meier et al., 1987; Vartiainen et al., 1988). The mutagenic
activity of a leachate is supposed to decrease following the decrease of organic concentration with age of the landfill. According to the relative mutagenic potency scale suggested by H o u k (1992), even the mutagenic potency of highly polluted leachates in this study (49.0 _+ 20.5 r e v . / m g for TA100, n = 6) was low, although not as low as those of various kinds of surface water ever reported. The result of this study indicates that for evaluation of the impact of landfill leachate on the environment, it is important to investigate the mutagenic activity of the leachate with standard water quality indices like COD, B O D and TOC. In the previous studies, we reported that acid concentrates of landfill leachate exhibited higher mutagenic activity than neutral concentrates (Omura et al., 1991, 1992), though this could not be found in this study and sometimes high mutagenic activities were overlooked (sample b of leachate A, for example). So it appears to be necessary to carry out both acid concentration and neutral concentration when XAD-2,/8 resin adsorption is used for concentrating mutagens from landfill leachate. The addition of $9 mix generally increased the mutagenic activities of the leachates. As for the landfill leachates of the final disposal site in this study, the main mutagens in the leachates are supposed to be promutagens. Acknowledgements
The authors wish to thank M. Hanashima, Y. Matsufuji and S. Koikawa of the D e p a r t m e n t of Engineering, Fukuoka University and T. Someya of the School of Medical Technology, University of Occupational and Environmental Health, for their advice and help with this study. References
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