The Environmentalist

, 29:371 | Cite as

Estimation of “environmentally sensitive” dispersal ratios for chemical dispersants used in crude oil spill control

  • Adebayo A. Otitoloju
  • Temitope O. Popoola


The toxicities of two dispersants (Biosolve and OSD 9460), Forcados light crude oil and their mixtures based on ratios 6:1, 9:1, and 12:1 (v/v) were evaluated against the juvenile stage of African catfish, Clarias gariepinus, in laboratory bioassays. On the basis of the derived toxicity indices, Biosolve (96-h LC50 = 0.211 μl/l) was found to be about 27,284 times more toxic than crude oil (96-h LC50 = 5.757 ml/l) and 6,450 times more toxic than OSD 9460 (96-h LC50 = 1.361 ml/l). OSD 9460 was also found to be four times more toxic than crude oil when acting alone against C. gariepinus. Toxicity evaluations of the mixtures of crude oil/dispersants mixtures varied, depending largely upon the proportion of addition of the mixture components. The interactions between mixture of crude oil and Biosolve at the test ratios of 6:1, 9:1, and 12:1 were found to conform with the model of synergism (SR = 7,655, 14,876, and 8,792, respectively), and the mixtures were therefore more toxic than the crude oil acting singly. Similarly, the interactions between mixture of crude oil and OSD 9460 at the test ratios of 6:1 and 9:1 also conformed to the model of synergism (SR = 2.2 and 1.84, respectively). Interactions between the dispersant OSD 9460 and the crude oil at test ratio 12:1, however, conformed to the model of antagonism (SR = 0.84), indicating that the mixture was less toxic than crude oil acting alone. The results of the emulsification potential of OSD 9460 and Biosolve [measured in terms of optical transmittance (%)] prepared at the dispersal ratios 6:1, 9:1, and 12:1 revealed that the dispersal ratio of 6:1 achieved the highest emulsification of the crude oil with optical transmittance value of 4% and 6%, respectively. Estimation of an “environmentally sensitive” dispersal ratio for OSD 9460 and Biosolve revealed the optimum dispersal ratio for OSD 9460 range between ratios 7.5:1 and 9:1, while for Biosolve such an optimum dispersal ratio was indeterminate within the range of test dispersal ratios. The implications of these results in setting manufacturer’s and regulatory dispersal ratios for chemical dispersants used for oil spill control were discussed.


Crude oil Dispersants Dispersal ratios Spill control Joint action 



The authors are grateful to the Department of Petroleum Resources in Nigeria for assistance rendered in obtaining crude oil used for the study. We are equally grateful to the Late Prof. K.N. Don-Pedro and Dr. L.O. Chukwu for providing us with the dispersants.


  1. Akintonwa A, Ebere A (1990) Toxicity of Nigerian crude oil and chemical dispersants to Barbus sp. and Clarias sp. Bull Environ Contam Toxicol 45:729–733. doi: 10.1007/BF01700993 CrossRefGoogle Scholar
  2. Anderson PD, Weber LJ (1975) The toxicity to aquatic population of mixtures containing certain heavy metals. In: Proceedings of the international conference on heavy metal in the environment, Institute of Environmental Studies, University of Toronto, pp 933–953Google Scholar
  3. Blodina GJ, Sowby ML, Ouano MT, Singer MM, Tjeerdema RS (1997) A modified swirling flask efficacy test for oil spill dispersants. Spill Sci Technol Bull 4(3):177–185. doi: 10.1016/S1353-2561(98)00014-0 CrossRefGoogle Scholar
  4. Don-Pedro KN (1989) Mode of action of fixed oils against eggs of Callosobruchus maculatus (L.). Pestic Sci 26:107–115. doi: 10.1002/ps.2780260202 CrossRefGoogle Scholar
  5. Don-Pedro KN (1996) Investigation of single and joint fumigant insecticidal action of citruspeel oil components. Pestic Sci 45:79–84. doi:10.1002/(SICI)1096-9063(199601)46:1<79::AID-PS319>3.0.CO;2-8CrossRefGoogle Scholar
  6. Enserik EL, Maas-Diepeven JL, Van Leeuwen CJ (1991) Combined effects of metals; an ecotoxicological evaluation. Water Res 25(5):579–687Google Scholar
  7. Fabregas J, Herrero C, Veiga M (1984) Effect of oil and dispersant on growth and Chlorophyll a content of marine microalgae Tetraselmis suecica. Appl Environ Microbiol 47(2):445–447Google Scholar
  8. Fingas MF, Kyle DA, Lambert P, Wang Z (1995) Analytical procedures for measuring oil spill dispersant effectiveness in the laboratory. In: Proceedings of the 18th arctic marine oil spill program technical seminar, Environment Canada, Edmonton, Alberta, pp 339–354Google Scholar
  9. Finney DJ (1971) Probit analysis, 3rd edn. Cambridge University Press, LondonGoogle Scholar
  10. Fisher W, Foss S (1993) A simple test for toxicity of number 2 fuel oil and oil dispersants to embryos of grass shrimp, Palaemonetes purgio. Mar Pollut Bull 26(7):385–391. doi: 10.1016/0025-326X(93)90186-N CrossRefGoogle Scholar
  11. Hewlett PS, Plackett RL (1969) A unified theory for quantal responses to mixtures of drugs: non-interactive action. Biometrics 15:591–610. doi: 10.2307/2527657 CrossRefGoogle Scholar
  12. Kingham JD (1981) Oil spill chemicals: environmental implication and use policy. In: Proceedings of the international seminar on the petroleum industry and the Nigerian Environment. FMW&H/NNPC, PTI, Effurun, Delta State, Nigeria, pp 179–185Google Scholar
  13. Laux H, Rahimian I, Butz T (2000) Theoretical and practical approach to the selection of asphaltene dispersing agents. Fuel Process Technol 67:79–89. doi: 10.1016/S0378-3820(00)00087-4 CrossRefGoogle Scholar
  14. Lindstrom JE, Braddock JF (2002) Biodegradation of petroleum hydrocarbons at low temperature in the presence of dispersant Corexit 9500. Mar Pollut Bull 44:739–747. doi: 10.1016/S0025-326X(02)00050-4 CrossRefGoogle Scholar
  15. Mitchell FM, Holdway AD (2000) The acute and chronic toxicity of dispersants Corexit 9527 and 9500, water accommodated fraction (WAF) of crude oil and dispersant enhanced WAF (DEWAF) to Hydra viridissima (Green Hydra). Water Res 34:343–348. doi: 10.1016/S0043-1354(99)00144-X CrossRefGoogle Scholar
  16. Moles A, Holland L, Short J (2002) Effectiveness in the laboratory of Corexit 9527 and 9500 in dispersing fresh, weathered and emulsion of Alaska North Slope crude oil under subarctic conditions. Spill Sci Technol Bull 7:241–247. doi: 10.1016/S1353-2561(02)00041-5 CrossRefGoogle Scholar
  17. National Research Council (1989) Using oil spill dispersants on the sea. National Research Council Marine Board, National Academy Press, Washington, DC 335 ppGoogle Scholar
  18. Nelson-Smith A (1967) Oil emulsifiers and marine life. In: The journal of the Devon Trust for nature conservation, Ltd. Supplement. Conservation and the Torrey canyon, Kingsbridge, England, pp 29–33Google Scholar
  19. Otitoloju AA (2001) Joint action toxicity of heavy metals and their bioaccumulation by benthic animals of the Lagos lagoon. Ph.D. thesis, University of Lagos, 234 ppGoogle Scholar
  20. Otitoloju AA (2002) Evaluation of the joint action toxicity of binary mixtures of heavy meatls against mangrove periwinkle Tympanotonus fuscatus var radula (L.). Ecotoxicol Environ Saf 53(3):404–415. doi: 10.1016/S0147-6513(02)00032-5 CrossRefGoogle Scholar
  21. Otitoloju AA (2003) Relevance of joint action toxicity evaluations in setting realistic environmental safe limits of heavy metals. J Environ Manag 67(2):121–128. doi: 10.1016/S0301-4797(02)00160-3 CrossRefGoogle Scholar
  22. Otitoloju AA (2005) Crude oil plus dispersant: always a boon or bane? Ecotoxicol Environ Saf 60:198–202. doi: 10.1016/j.ecoenv.2003.12.021 CrossRefGoogle Scholar
  23. Otitoloju AA (2006) Joint action toxicity of spent lubrication oil and laundry detergent against Poecilia reticulata (Telostei: Poeciliidae). Afr J Aquat Sci 31(1):125–129Google Scholar
  24. Oyewo EO (1986) The acute toxicity of three dispersants. Environ Pollut 41:23–31. doi: 10.1016/0143-1471(86)90104-2 CrossRefGoogle Scholar
  25. Ross SI (1997) A review of dispersant use on spills of North Slope crude oil in Prince William Sound and the Gulf of Alaska. Prince William Sound Regional Citizens’ Advisory Council, AnchorageGoogle Scholar
  26. Sterling MC Jr, Bonner JS, Ernest ANS, Page CA, Autenrieth RL (2004) Chemical dispersant effectiveness testing: influence of droplet coalescence. Mar Pollut Bull 48:969–977. doi: 10.1016/j.marpolbul.2003.12.003 CrossRefGoogle Scholar
  27. Westermeyer WE (1991) Oil spill response capabilities in the United States. Environ Sci Technol 25(2):196–200. doi: 10.1021/es00014a607 CrossRefGoogle Scholar

Copyright information

© Springer Science+Business Media, LLC 2009

Authors and Affiliations

  1. 1.Department of ZoologyUniversity of Lagos, AkokaLagosNigeria

Personalised recommendations