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Fate of oil dispersants in aquatic environment
The Science o f the Total Environment, 32 (1983) 93--98 Elsevier Science Publishers B.V., Amsterdam -- Printed in The Netherlands
93
Short Communication
F A T E OF OIL D I S P E R S A N T S IN A Q U A T I C E N V I R O N M E N T
D. LIU National Water Research Institute, Burlington, Ontario L7R 4A6 (Canada)
(Received April 5th, 1983; accepted May 15th, 1983)
ABSTRACT Chemical oil dispersants have been used throughout most of the world to combat oil spills. However, their fate in aquatic environment remains uncertain. This study was conducted to investigate the persistence of five oil dispersants in the aquatic environment. The results indicate that petroleum utilizing bacteria possess high potential for the biodegradation of oil dispersants. The order of biodegradability for the five oil dispersants was as follows: Magnus 1 0 1 ~ B P l l 0 0 X ~ B P l l 0 0 ~ L i n c o No. 4~Corexit 8666. From the results of this study and a review of the literature data, it can be concluded that treatment of oil spills with chemical dispersants is unlikely to cause any build-up of organic contaminants in the aquatic environment. INTRODUCTION A c c i d e n t i a l spillage o f c r u d e oil o r p e t r o l e u m p r o d u c t s appears t o be an inevitable c o n s e q u e n c e d u r i n g t h e ' p r o c e s s e s o f extracting, m a n u f a c t u r i n g a n d t r a n s p o r t a t i o n o f p e t r o l e u m h y d r o c a r b o n s (Atlas, 1981). U n f o r t u n a t e l y , m o s t o f these spillages o c c u r in aquatic e n v i r o n m e n t s because o f the substantial i n v o l v e m e n t o f w a t e r t r a n s p o r t a t i o n f o r such c o m m o d i t i e s as well as with t h e increased oil drilling activities in t h e c o n t i n e n t a l shelf. Oil spills are, p r o b a b l y o n e o f the m a j o r sources o f organic c o n t a m i n a n t s f o r t h e a q u a t i c e n v i r o n m e n t . T h e ecological c o n s e q u e n c e s o f each oil spill i n c i d e n t varies, d e p e n d i n g o n t h e m a g n i t u d e o f t h e spill, t h e c h e m i c a l c o m p o s i t i o n o f t h e oil a n d t h e n a t u r e o f t h e c o n t a m i n a t e d e c o s y s t e m . Various p h y s i c a l a n d c h e m i c a l t e c h n i q u e s have been d e v e l o p e d for cleaning oil spills. T h e p h y s i c a l a p p r o a c h is i n t e n d e d to c o n f i n e o r r e m o v e the spilt oil f r o m t h e surface water. H o w e v e r , t h e c u r r e n t s t a t e - o f - t h e - a r t f o r c o n t a i n m e n t a n d r e m o v a l o f oil spills f r o m o f f s h o r e waters has d i s t i n c t l i m i t a t i o n s {McCarthy et al., 1978). F o r instance, c o n t a i n m e n t b o o m s o n l y can be applied t o seas with waves n o t e x c e e d i n g t w o feet or c u r r e n t s less
0048-9697/83/$03.00
© 1983 Elsevier Science Publishers B.V.
94 than t w o knots. Other available physical options such as burning, sinking, gelling, or the use of sorbents are even less desirable, being either environmentally unacceptable or technically unfeasible. The chemical control of oil spills mainly involves the use of dispersants to break up oil slicks and thus disperse the oil in the water column, which, otherwise, may threaten to pollute shoreline areas (Mulkins-Phillips and Stewart, 1974). Other advantages of using dispersants are the removal of a potential fire hazard, facilitation of evaporation, and enhancement of biodegradation processes (Slade, 1982). Consequently, chemical oil dispersants have been used t h r o u g h o u t most of the world to c o m b a t oil spills (Albers and Gay, 1982). Much knowledge has been gathered regarding the toxicity of oil dispersants towards birds (Albers and Gay, 1982), fish (Slade, 1982), and algae (Heldal et al., 1978). There has been, in general, a lack of information concerning the persistence of oil dispersant in the aquatic environment. This study was c o n d u c t e d to assess the fate of off dispersants in the aquatic ecosystem using an oil degrading bacterium.
MATERIALS AND METHODS Medium
The basal mineral medium used for growing the crude oil degrading bacterium had the following ingredients (g 1-1 ): K2HPO4, 0.66; KH2PO4, 0.41; MgC12"6H20, 0.10; FeC12"4H20, 0.05; MnC12"4H20, 0.002; and (NH4)2SO4, 0.50. The final pH of the medium was 6.9, and it was sterilized at 121°C for 15min. The crude oil (Norman Wells)was sterilized separately under the same conditions and was added aseptically to the medium at a concentration of 4 ml l- 1. Culture
The crude off-degrading bacterium, CM01, used in this study was originally isolated from a local refinery soil (Liu and Dutka, 1972). The culture was grown in a 2-1 Bellco spinner flask containing 11 of basal mineral medium and 4 ml of crude oil. The flask was incubated on a magnetic stirrer with agitation at room temperature (21°C). Since hydrocarbon-utilizing bacteria can only grow at the oil--water interface (Traxler and Bhattacharya, 1978), the magnetic spindle inside the flask was set at the fast spin setting, (300--400 rpm) to increase the area of such interfaces. With 10% inoculum, an incubation time of 18--20 h was adequate to harvest the cells for use in manometric experiments. Manometric S tu dies
The cells were harvested by centrifugation at 10,000 × g for 2 0 m i n at 4°C, followed by two washes with 0 . 0 2 M phosphate buffer at pH 7.0. The resulting packed cells were resuspended in cold 0.05 M phosphate buffer (pH 7.0) to give a cell concentration of approximately 2 0 m g dry weight
95
m1-1. The overall oxygen consumption as determined in a Gilson differential respirometer was taken as a measure of the biodegradation potential (Qo~ = p l O 2 h - l m g -1 cell dry weight) of culture CM01 against oil dispersants. The composition of the assaying preparation, unless otherwise stated, consisted of 1 ml of cell suspension (approx. 20 mg), 1 ml o f 0.05 M phosphate buffer, 0.8--0.9 ml o f distilled water, 100--200/~1 substrate, and 0.2 ml of 20% KOH (in the center well of the Warburg flask for CO2 absorption). Total volume of the reaction mixture was 3.2ml. The experiments were performed at 20°C with a steady shaking rate of 105 strokes min - 1
Dry weight Thirty ml o f the culture broth were centrifuged at 15,000 x g for 20 min, followed by two washes in distilled water. The cell pellet was taken up in 5 ml of distilled water and dried for 2 0 h at 105°C.
RESULTS AND DISCUSSIONS
The bacterial culture, CM01, was selected for this study from 7 isolates, on the bases of its rapid growth on crude oil. The culture exhibited good potential for the biodegradation of the oil dispersant, B P l l 0 0 X (Fig. 1). In these experiments, various amounts of B P l l 0 0 X were added to 250-ml erlenmeyer flasks, containing 100 ml o f basal mineral medium, and 1 ml of inoculum. Dry weight determinations were followed at various time intervals (10, 20, and 24 h). The CM01 culture was f o u n d to be capable of growing rapidly in different B P l l 0 0 X concentrations (100--10,000ppm) as sole carbon and energy source w i t h o u t acclimatization. At B P l l 0 0 X concentrations below 3 ml 1-1 , there was a linear relation between cell yield (dry
0.8
Dry w , -
0.6
>" 0.4 u 0.2
//"
..// \
5~ ~
m
,
pH
,0 ,e I 2
I
I
4 6 BP1100X Added mill
I
I
8
10
Fig. 1. E f f e c t o f B P l l 0 0 X c o n c e n t r a t i o n s o n cell yield a n d final m e d i u m pH.
96
weight) and substrate utilization with a rate of 0.218 ml B P l l 0 0 X h-1 g-1 cell dry weight. The cell yield, however, leveled off at higher B P l l 0 0 X concentrations (4--10 ml 1-1 ), possibily due to the lowering of the medium pH by the culture activity. For instance, an increase of B P l l 0 0 X concentration in the growth medium from 3 ml 1-1 to 5 ml 1-1, was found to cause a corresponding decrease of the medium pH from 6.0 to 4.8 (Fig. 1). The ability of the culture CM01 to degrade the oil dispersant B P l l 0 0 X is further supported by the manometric experiments. In these studies, various amounts of B P l l 0 0 X (1, 2, 5, 25, 50, 100 and 2 0 0 p l ) were subjected to oxidation by CM01 in the Warburg flasks. The results presented in Fig. 2 indicate a good correlation between BP1100X concentration and total oxygen consumption. Since B P l l 0 0 X was the only substrate in the Warburg reaction mixture, the a m o u n t of oxygen uptake by CM01 would indicate that B P l l 0 0 X was utilized by the culture for respiration. Between the BP1100X concentration ranges of 0 to 2 5 p l flask -1 ( 0 - - 8 3 3 3 p p m ) , the a m o u n t o f oxygen used by the culture CM01 was a direct function of the B P l l 0 0 X concentrations. It should be noted that with all concentrations of BP1100X used in these experiments, there was no lag period for oxygen uptake, suggesting that the culture CM01 was capable of immediately oxidizing the oil dispersant B P l l 0 0 X at all concentrations used. Various oil dispersants have been used for the treatment of oil spills (McCarthy et al., 1978; Albers and Gay, 1982). It would be advisable to determine the order of their persistence in aquatic environment. Thus, high concentrations {33,332 ppm) o f five oil dispersants (Magnus 101, B P l l 0 0 X , B P l l 0 0 , Linco No. 4, Corexit 8666) and on crude oil (Norman Wells) were 700 /
600
500
a
400
o,.
O~ 300 ,..y
200
/
/
f
/
/
~o
/
100
I
I
50
100
I
150
I
200
B P l l 0 0 X Added t41/ Flask
Fig. 2. T o t a l o x y g e n c o n s u m p t i o n (60 m i n ) as a f u n c t i o n o f B P 1 1 0 0 X c o n c e n t r a t i o n s in t h e Warburg flasks.
97
Crude oil + x BP 1100X
1200
0
Crude oil+ 8666
1000 x
800
, ~
1~ Magnus
$
,,oox
a
~ 600 d
,,~
• BP 1100
400 •
8666
200 -
-
~
a
~
.__~__~ o _~_____ o ___----- o ,
10
20
30 40 Time in Min.
,
,
50
60
Endogenous
Fig. 3. Oxidation of various oil dispersants by culture CM01.
subjected to culture CM01 oxidation in the Warburg flasks {Fig. 3). Oil dispersant concentrations used in these experiments were about 2.7 times higher than those employed under field situations (Mulkins-Phillips and Stewart, 1974). The immediate response in oxygen uptake (Fig. 3) by the culture CM01, upon addition of the dispersants, suggests t h a t the hydrocarbon utilizing bacteria possess an inherent potential to degrade oil dispersants, i.e., playing an important role in the removal of dispersant from aquatic environment. The order of biodegradability for the five oil dispersants was determined in terms of Qo2 : Magnus 101 (Qo2 = 34.0), B P l l 0 0 X (Qo2 = 31.1), B P l l 0 0 (Qo~ = 24.6), Linco No. 4 (Qo~ = 16.3) and Corexit 8666 (Qo~ = 13.5). The overall lower Qo~ values (13.5--34.0) for these oil dispersants compared to the crude oil Qo~ {40.0) is probably more desirable in that the dispersants would n o t be preferentially utilized as carbon sources over the oil by aquatic microorganisms. Petroleum utilizing microorganisms are k n o w n to be widely distributed in aquatic environment (Atlas, 1981) and the results in this study demonstrate the susceptibility of oil dispersants to immediate biodegradation by such microorganisms. Thus, it appears t h a t t r e a t m e n t of oil spills with dispersants is not likely to have any significant impact on the build-up of organic contaminants in aquatic environment. REFERENCES Albers, P. H. and M. L. Gay, 1982. Effects of a chemical dispersant and crude oil on breeding ducks. Bull Environ. Contam. Toxicol., 29: 404.
98 Atlas, R. M., 1981. Fate of oil from two major oil spills: Role of microbial degradation in removing oil from the A m o c o Cadiz and Ixtoci spills. Environ. International, 5 : 33. Heldal, M., S. Norland, T. Lien and G. Knutsen, 1978. Acute toxicity of several oil dispersants towards the green algae Chlamydomonas and Dunaliella. Chemosphere, 7: 247. Liu, D. and B. J. Dutka, 1972. Bacterial seeding techniques: Novel approach to oil spill problems. Can. Res., 5(4): 17. McCarthy, L. T., G. P. Lindblom and H. F. Walter, 1978. Chemical Dispersants for the Control of Oil Spills. ASTM special technical publication No. 659. ASTM, Philadelphia., PA, 307 pp. Mulkins-Phillips, G. J. and J. E. Stewart, 1974. Effect of four dispersants on biodegradation and growth of bacteria on crude oil. Appl. Microbiol., 28: 547. Slade, G. J., 1982. Effect of Ixtoc 1 crude oil and Corexit 9527 dispersant on Spot (Leiostomus xanthurus) egg mortality. Bull. Environ. Contam. Toxicol., 29: 525. Traxler, R.W. and L.S. Bhattacharya, 1978. Effect of a chemical dispersant on microbial utilization of petroleum hydrocarbons. In: L. T. McCarthy, G. P. Lindblom and H. F. Walter (Eds.), Chemical Dispersants for the Control of Oil Spills. ASTM special technical publication No. 659. ASTM, Philadelphia, PA, 307 pp.
93
Short Communication
F A T E OF OIL D I S P E R S A N T S IN A Q U A T I C E N V I R O N M E N T
D. LIU National Water Research Institute, Burlington, Ontario L7R 4A6 (Canada)
(Received April 5th, 1983; accepted May 15th, 1983)
ABSTRACT Chemical oil dispersants have been used throughout most of the world to combat oil spills. However, their fate in aquatic environment remains uncertain. This study was conducted to investigate the persistence of five oil dispersants in the aquatic environment. The results indicate that petroleum utilizing bacteria possess high potential for the biodegradation of oil dispersants. The order of biodegradability for the five oil dispersants was as follows: Magnus 1 0 1 ~ B P l l 0 0 X ~ B P l l 0 0 ~ L i n c o No. 4~Corexit 8666. From the results of this study and a review of the literature data, it can be concluded that treatment of oil spills with chemical dispersants is unlikely to cause any build-up of organic contaminants in the aquatic environment. INTRODUCTION A c c i d e n t i a l spillage o f c r u d e oil o r p e t r o l e u m p r o d u c t s appears t o be an inevitable c o n s e q u e n c e d u r i n g t h e ' p r o c e s s e s o f extracting, m a n u f a c t u r i n g a n d t r a n s p o r t a t i o n o f p e t r o l e u m h y d r o c a r b o n s (Atlas, 1981). U n f o r t u n a t e l y , m o s t o f these spillages o c c u r in aquatic e n v i r o n m e n t s because o f the substantial i n v o l v e m e n t o f w a t e r t r a n s p o r t a t i o n f o r such c o m m o d i t i e s as well as with t h e increased oil drilling activities in t h e c o n t i n e n t a l shelf. Oil spills are, p r o b a b l y o n e o f the m a j o r sources o f organic c o n t a m i n a n t s f o r t h e a q u a t i c e n v i r o n m e n t . T h e ecological c o n s e q u e n c e s o f each oil spill i n c i d e n t varies, d e p e n d i n g o n t h e m a g n i t u d e o f t h e spill, t h e c h e m i c a l c o m p o s i t i o n o f t h e oil a n d t h e n a t u r e o f t h e c o n t a m i n a t e d e c o s y s t e m . Various p h y s i c a l a n d c h e m i c a l t e c h n i q u e s have been d e v e l o p e d for cleaning oil spills. T h e p h y s i c a l a p p r o a c h is i n t e n d e d to c o n f i n e o r r e m o v e the spilt oil f r o m t h e surface water. H o w e v e r , t h e c u r r e n t s t a t e - o f - t h e - a r t f o r c o n t a i n m e n t a n d r e m o v a l o f oil spills f r o m o f f s h o r e waters has d i s t i n c t l i m i t a t i o n s {McCarthy et al., 1978). F o r instance, c o n t a i n m e n t b o o m s o n l y can be applied t o seas with waves n o t e x c e e d i n g t w o feet or c u r r e n t s less
0048-9697/83/$03.00
© 1983 Elsevier Science Publishers B.V.
94 than t w o knots. Other available physical options such as burning, sinking, gelling, or the use of sorbents are even less desirable, being either environmentally unacceptable or technically unfeasible. The chemical control of oil spills mainly involves the use of dispersants to break up oil slicks and thus disperse the oil in the water column, which, otherwise, may threaten to pollute shoreline areas (Mulkins-Phillips and Stewart, 1974). Other advantages of using dispersants are the removal of a potential fire hazard, facilitation of evaporation, and enhancement of biodegradation processes (Slade, 1982). Consequently, chemical oil dispersants have been used t h r o u g h o u t most of the world to c o m b a t oil spills (Albers and Gay, 1982). Much knowledge has been gathered regarding the toxicity of oil dispersants towards birds (Albers and Gay, 1982), fish (Slade, 1982), and algae (Heldal et al., 1978). There has been, in general, a lack of information concerning the persistence of oil dispersant in the aquatic environment. This study was c o n d u c t e d to assess the fate of off dispersants in the aquatic ecosystem using an oil degrading bacterium.
MATERIALS AND METHODS Medium
The basal mineral medium used for growing the crude oil degrading bacterium had the following ingredients (g 1-1 ): K2HPO4, 0.66; KH2PO4, 0.41; MgC12"6H20, 0.10; FeC12"4H20, 0.05; MnC12"4H20, 0.002; and (NH4)2SO4, 0.50. The final pH of the medium was 6.9, and it was sterilized at 121°C for 15min. The crude oil (Norman Wells)was sterilized separately under the same conditions and was added aseptically to the medium at a concentration of 4 ml l- 1. Culture
The crude off-degrading bacterium, CM01, used in this study was originally isolated from a local refinery soil (Liu and Dutka, 1972). The culture was grown in a 2-1 Bellco spinner flask containing 11 of basal mineral medium and 4 ml of crude oil. The flask was incubated on a magnetic stirrer with agitation at room temperature (21°C). Since hydrocarbon-utilizing bacteria can only grow at the oil--water interface (Traxler and Bhattacharya, 1978), the magnetic spindle inside the flask was set at the fast spin setting, (300--400 rpm) to increase the area of such interfaces. With 10% inoculum, an incubation time of 18--20 h was adequate to harvest the cells for use in manometric experiments. Manometric S tu dies
The cells were harvested by centrifugation at 10,000 × g for 2 0 m i n at 4°C, followed by two washes with 0 . 0 2 M phosphate buffer at pH 7.0. The resulting packed cells were resuspended in cold 0.05 M phosphate buffer (pH 7.0) to give a cell concentration of approximately 2 0 m g dry weight
95
m1-1. The overall oxygen consumption as determined in a Gilson differential respirometer was taken as a measure of the biodegradation potential (Qo~ = p l O 2 h - l m g -1 cell dry weight) of culture CM01 against oil dispersants. The composition of the assaying preparation, unless otherwise stated, consisted of 1 ml of cell suspension (approx. 20 mg), 1 ml o f 0.05 M phosphate buffer, 0.8--0.9 ml o f distilled water, 100--200/~1 substrate, and 0.2 ml of 20% KOH (in the center well of the Warburg flask for CO2 absorption). Total volume of the reaction mixture was 3.2ml. The experiments were performed at 20°C with a steady shaking rate of 105 strokes min - 1
Dry weight Thirty ml o f the culture broth were centrifuged at 15,000 x g for 20 min, followed by two washes in distilled water. The cell pellet was taken up in 5 ml of distilled water and dried for 2 0 h at 105°C.
RESULTS AND DISCUSSIONS
The bacterial culture, CM01, was selected for this study from 7 isolates, on the bases of its rapid growth on crude oil. The culture exhibited good potential for the biodegradation of the oil dispersant, B P l l 0 0 X (Fig. 1). In these experiments, various amounts of B P l l 0 0 X were added to 250-ml erlenmeyer flasks, containing 100 ml o f basal mineral medium, and 1 ml of inoculum. Dry weight determinations were followed at various time intervals (10, 20, and 24 h). The CM01 culture was f o u n d to be capable of growing rapidly in different B P l l 0 0 X concentrations (100--10,000ppm) as sole carbon and energy source w i t h o u t acclimatization. At B P l l 0 0 X concentrations below 3 ml 1-1 , there was a linear relation between cell yield (dry
0.8
Dry w , -
0.6
>" 0.4 u 0.2
//"
..// \
5~ ~
m
,
pH
,0 ,e I 2
I
I
4 6 BP1100X Added mill
I
I
8
10
Fig. 1. E f f e c t o f B P l l 0 0 X c o n c e n t r a t i o n s o n cell yield a n d final m e d i u m pH.
96
weight) and substrate utilization with a rate of 0.218 ml B P l l 0 0 X h-1 g-1 cell dry weight. The cell yield, however, leveled off at higher B P l l 0 0 X concentrations (4--10 ml 1-1 ), possibily due to the lowering of the medium pH by the culture activity. For instance, an increase of B P l l 0 0 X concentration in the growth medium from 3 ml 1-1 to 5 ml 1-1, was found to cause a corresponding decrease of the medium pH from 6.0 to 4.8 (Fig. 1). The ability of the culture CM01 to degrade the oil dispersant B P l l 0 0 X is further supported by the manometric experiments. In these studies, various amounts of B P l l 0 0 X (1, 2, 5, 25, 50, 100 and 2 0 0 p l ) were subjected to oxidation by CM01 in the Warburg flasks. The results presented in Fig. 2 indicate a good correlation between BP1100X concentration and total oxygen consumption. Since B P l l 0 0 X was the only substrate in the Warburg reaction mixture, the a m o u n t of oxygen uptake by CM01 would indicate that B P l l 0 0 X was utilized by the culture for respiration. Between the BP1100X concentration ranges of 0 to 2 5 p l flask -1 ( 0 - - 8 3 3 3 p p m ) , the a m o u n t o f oxygen used by the culture CM01 was a direct function of the B P l l 0 0 X concentrations. It should be noted that with all concentrations of BP1100X used in these experiments, there was no lag period for oxygen uptake, suggesting that the culture CM01 was capable of immediately oxidizing the oil dispersant B P l l 0 0 X at all concentrations used. Various oil dispersants have been used for the treatment of oil spills (McCarthy et al., 1978; Albers and Gay, 1982). It would be advisable to determine the order of their persistence in aquatic environment. Thus, high concentrations {33,332 ppm) o f five oil dispersants (Magnus 101, B P l l 0 0 X , B P l l 0 0 , Linco No. 4, Corexit 8666) and on crude oil (Norman Wells) were 700 /
600
500
a
400
o,.
O~ 300 ,..y
200
/
/
f
/
/
~o
/
100
I
I
50
100
I
150
I
200
B P l l 0 0 X Added t41/ Flask
Fig. 2. T o t a l o x y g e n c o n s u m p t i o n (60 m i n ) as a f u n c t i o n o f B P 1 1 0 0 X c o n c e n t r a t i o n s in t h e Warburg flasks.
97
Crude oil + x BP 1100X
1200
0
Crude oil+ 8666
1000 x
800
, ~
1~ Magnus
$
,,oox
a
~ 600 d
,,~
• BP 1100
400 •
8666
200 -
-
~
a
~
.__~__~ o _~_____ o ___----- o ,
10
20
30 40 Time in Min.
,
,
50
60
Endogenous
Fig. 3. Oxidation of various oil dispersants by culture CM01.
subjected to culture CM01 oxidation in the Warburg flasks {Fig. 3). Oil dispersant concentrations used in these experiments were about 2.7 times higher than those employed under field situations (Mulkins-Phillips and Stewart, 1974). The immediate response in oxygen uptake (Fig. 3) by the culture CM01, upon addition of the dispersants, suggests t h a t the hydrocarbon utilizing bacteria possess an inherent potential to degrade oil dispersants, i.e., playing an important role in the removal of dispersant from aquatic environment. The order of biodegradability for the five oil dispersants was determined in terms of Qo2 : Magnus 101 (Qo2 = 34.0), B P l l 0 0 X (Qo2 = 31.1), B P l l 0 0 (Qo~ = 24.6), Linco No. 4 (Qo~ = 16.3) and Corexit 8666 (Qo~ = 13.5). The overall lower Qo~ values (13.5--34.0) for these oil dispersants compared to the crude oil Qo~ {40.0) is probably more desirable in that the dispersants would n o t be preferentially utilized as carbon sources over the oil by aquatic microorganisms. Petroleum utilizing microorganisms are k n o w n to be widely distributed in aquatic environment (Atlas, 1981) and the results in this study demonstrate the susceptibility of oil dispersants to immediate biodegradation by such microorganisms. Thus, it appears t h a t t r e a t m e n t of oil spills with dispersants is not likely to have any significant impact on the build-up of organic contaminants in aquatic environment. REFERENCES Albers, P. H. and M. L. Gay, 1982. Effects of a chemical dispersant and crude oil on breeding ducks. Bull Environ. Contam. Toxicol., 29: 404.
98 Atlas, R. M., 1981. Fate of oil from two major oil spills: Role of microbial degradation in removing oil from the A m o c o Cadiz and Ixtoci spills. Environ. International, 5 : 33. Heldal, M., S. Norland, T. Lien and G. Knutsen, 1978. Acute toxicity of several oil dispersants towards the green algae Chlamydomonas and Dunaliella. Chemosphere, 7: 247. Liu, D. and B. J. Dutka, 1972. Bacterial seeding techniques: Novel approach to oil spill problems. Can. Res., 5(4): 17. McCarthy, L. T., G. P. Lindblom and H. F. Walter, 1978. Chemical Dispersants for the Control of Oil Spills. ASTM special technical publication No. 659. ASTM, Philadelphia., PA, 307 pp. Mulkins-Phillips, G. J. and J. E. Stewart, 1974. Effect of four dispersants on biodegradation and growth of bacteria on crude oil. Appl. Microbiol., 28: 547. Slade, G. J., 1982. Effect of Ixtoc 1 crude oil and Corexit 9527 dispersant on Spot (Leiostomus xanthurus) egg mortality. Bull. Environ. Contam. Toxicol., 29: 525. Traxler, R.W. and L.S. Bhattacharya, 1978. Effect of a chemical dispersant on microbial utilization of petroleum hydrocarbons. In: L. T. McCarthy, G. P. Lindblom and H. F. Walter (Eds.), Chemical Dispersants for the Control of Oil Spills. ASTM special technical publication No. 659. ASTM, Philadelphia, PA, 307 pp.