MODIFICATION OF THE COREXIT® 9500 FOR USE IN FRESHWATER

Anita George-Ares ExxonMobil Biomédical Sciences, Inc. 1545 Route 22 East Annandale, New Jersey 08801

Richard R. Lessard Kenneth W. Becker ExxonMobil Research and Engineering Company Consultant 3225 Gallows Road 12302 Burgoyne Drive Fairfax, Virginia 22037 Houston, Texas 77077 Downloaded from http://meridian.allenpress.com/iosc/article-pdf/2001/2/1209/1740885/2169-3358-2001-2-1209.pdf by guest on 25 September 2021

Gerard P. Canevari Robert J. Fiocco G. P. Canevari and Associates R. J. Fiocco Associates 104 Central Avenue 77 Pine Grove Avenue Cranford, New Jersey 07016 Summit, New Jersey 07901

ABSTRACT: Recent inland spills in Latin America have gener- interest in dispersant use for freshwater oil spills. The authors ated interest in dispersant use for freshwater oil spills. However, were asked whether dispersant use could have been a viable primarily are formulated for use in marine response option in the Rio de la Plata spill. The objective of this waters. Dispersants that are designed for saltwater use show study was to investigate the potential applicability of COREXIT® reduced effectiveness when applied in freshwater. The effective- 9500 in freshwater and whether COREXIT® 9500 could be ness of COREXIT® 9500 in low salinity waters varies with the modified so that it would be more effective in freshwater. type of oil, the dispersant-to-oil ratio (DOR), and other factors. Oil spill dispersants primarily are formulated for use in marine The effectiveness of COREXITR 9500 can decrease markedly at waters. Dispersants that are designed for saltwater use show salinities of 15 ppt or less. The authors observed an increase in reduced effectiveness when applied in freshwater. Dispersants are effectiveness of COREXIT® 9500 in freshwater when the dispers- a mixture of dissolved or suspended in . ant was blended with an inorganic, divalent salt, such as calcium Freshwater extracts the surfactants so that interaction of the chloride, prior to use (patent pending). COREXlT~ 9500* refers and oil is reduced or does not occur. When an here to the blend of the salt and dispersant. inorganic divalent salt is added, the surfactant mixture in the The Exxon Dispersant Effectiveness Test (EXDET) was used to dispersant becomes less soluble in freshwater and the dispersant evaluate dispersant performance in deionized water and in river becomes more effective. The authors observed that the water samples from Rio de la Plata, Argentina. COREXTL' 9500 effectiveness of COREXIT® 9500 increased in freshwater when showed 22% effectiveness on Alaska North Slope (ANS) crude oil the dispersant was blended with a solution of calcium chloride in deionized water, a value indicative of poor effectiveness. prior to use (Lessard et al, 1999). This paper reports the authors' Depending on the amount of calcium chloride added, COREXIT® preliminary results. 9500* showed up to 63% effectiveness on ANS crude oil in deionized water, which indicates good effectiveness. The effec- tiveness of COREXIT® 9500* and COREXIT® 9500 was com- Materials and methods pared for three additional crude oils both in deionized water and in river water. In all cases, the effectiveness of COREXIT® 9500 Prior to use, COREXIT® 9500 was modified by blending the was lower compared with COREXIT® 9500*. dispersant with a calcium chloride solution. COREXIT® 9500* refers to the modified COREXIT® 9500. The effectiveness of COREXIT® 9500* and COREXIT® 9500 were evaluated in river Introduction water samples from Rio de la Plata and in deionized water. For comparison, the authors measured the effectiveness of the On January 15, 1999, the container ship Sea Parana collided commercial dispersants Dasic Freshwater, Enersperse 1037, and with the tanker Estrella Pampeana in Rio de la Plata. Argentina. Inipol IPF, which are formulated for freshwater use. Dispersant The collision resulted in a release of 3,741 tons of Hydra crude effectiveness was evaluated using Hydra crude oil, which was the oil (OSIR, 1999a, b). Stranded oil adversely affected marsh crude oil spilled in Rio de la Plata; the Argentine crude oils vegetation, bird habitats, and a resort area (OSIR, 1999c). Escalante and Cañadon Seco; and Alaska North Slope (ANS) In Argentina, as in many countries, dispersant use is not crude oil. permitted in freshwater. France is the only country with an The Exxon Dispersant Effectiveness Test (EXDET) was used approval process for freshwater dispersants (CEDRE, 1998). to evaluate dispersant performance. Becker et al (1991. 1993) Recent inland spills in Latin America, however, have generated

1209 1210 2001 INTERNATIONAL OIL SPILL CONFERENCE contains a detailed description of the EXDET method. The The effectiveness of COREXIT® 9500* and COREXIT 9500 EXDET method used is briefly described here. Glass separatory was compared for three additional crude oils in deionized water. funnels each containing 250 ml of deionized or river water were Table 1 compares the percent dispersion of oil with the type of attached to a Burrell Wrist Action Shaker (Model 75, Fisher 14- crude oil, dispersant, and freshwater source. The average 260). One ml of oil was added to each funnel at the water surface. effectiveness of COREXIT® 9500* in deionized water was 58%, Dispersant was then added to the surface of the oil at a 1:20 15%, and 41% for Hydra, Escalante, and Cañadon Seco crude dispersant-to-oil ratio (DOR). Two to four replicates were used oils, respectively. In each case, the effectiveness of COREXIT® for each treatment. The funnels were shaken for 15 minutes. After 9500 was lower (Hydra, 32%; Escalante, <5%; Cañadon Seco, 15 minutes of shaking, polypropylene sorbent pads (3M) were 10%). added to the water surfaces while the funnels were still shaking. The average effectiveness of COREXIT® 9500 in river water Shaking was continued for an additional 5 minutes. The shaker also was lower compared with COREXIT® 9500*. COREXIT® was stopped, and the water containing the dispersed oil was 9500 showed 49%, 2%, and 21% effectiveness for Hydra, Esca- Downloaded from http://meridian.allenpress.com/iosc/article-pdf/2001/2/1209/1740885/2169-3358-2001-2-1209.pdf by guest on 25 September 2021 removed and extracted with méthylène chloride. This extract is lante, and Cañadon Seco crude oils, respectively. COREXIT® referred to as the dispersed extract. Undispersed oil remaining in 9500* average effectiveness was 63%, 17%, and 25% for Hydra. the funnel and on the sorbent pad also was extracted with Escalante, and Cañadon Seco, respectively. méthylène chloride. The latter extract is referred to as the undispersed extract. The extracts were diluted 9:1 with méthylène chloride. The percent oil dispersed was determined by measuring Discussion the absorbance of the diluted extracts at 460 nanometers using a Bausch and Lomb Spectronic 21. To calculate the percent oil The effectiveness of COREXIT® 9500 in waters of low and dispersed, the following formula was used: varying salinity is of interest to spill responders, regulators, and % Dispersed = 100(1/(1 +A x F). researchers. For example, laboratory studies were conducted to A is the absorbance of undispersed extract divided by the address dispersant effectiveness in conditions of varying salinity absorbance of the dispersed extract. F is the dilution factor for the such as occur in San Francisco Bay (Blondina et al, 1997, 1999). undispersed extract divided by the dilution factor for the The effectiveness of COREXIT® 9500 can decrease markedly at dispersed extract. salinities of 15 ppt or less (Blondina et al., 1997, 1999). COREXIT® 9500 has 83% effectiveness on Hydra crude oil in seawater, but only 32% effectiveness on Hydra in freshwater. Results COREXIT® 9500* consistently had greater effectiveness than COREXIT® 9500 in river water and deionized water. COREXIT® 9500 showed 22% effectiveness on ANS crude oil Dispersant effectiveness varies with crude oil type. All the test in deionized water. Preliminary experiments using ANS crude showed the greatest effectiveness on Hydra, a showed that depending on the amount of calcium chloride relatively light crude oil (API gravity 37.5). Dispersants were less solution added, the effectiveness of COREXIT® 9500* increased effective on the relatively heavier crude oils Cañadon Seco (API from 29% to 63% in deionized water. Other preliminary experi- gravity 26.3) and Escalante (API gravity 24.1). Escalante crude ments showed that there is an optimum blend of COREXIT® oil is difficult to disperse. Even dispersants manufactured for 9500 and calcium chloride solution for oil dispersion to occur in freshwater use were not very effective on Escalante crude oil. The freshwater. For example, adding too much calcium chloride effectiveness of COREXIT® 9500* fell in the range of solution prevented the dispersion of Hydra crude oil in deionized effectiveness observed for the freshwater dispersants on Hydra, water. Escalante, and Cañadon Seco crude oils in deionized water.

Table 1. Percent dispersion of oil in freshwater1. Dispersant Crude oil COREXIT® 9500 COREXIT® 9500*2 Dasic Freshwater Enerspe rse 1037 Inipc Hydra Rio de la Plata 49 56 71 68 58 70 Deionized water 32 58 70 70 65 32 64 Escalante Rio de la Plata 2 17 27 19 ND Deionized water <5 22 27 16 7 13 11 15 Cañadon Seco Rio de la Plata 21 25 34 36 ND Deionized water 10 42 56 37 17 40 Note: ND, no data. 1 Each value is an average percent effectiveness measured in an EXDET. 2 COREXIT® 9500 with calcium chloride solution added. DISPERSANTS 1211

Deionized water was chosen as a test medium since it has few References if any impurities. The source of freshwater (Rio de la Plata or deionized water) did not appear to have an effect on dispersant 1. Becker, K.W., L.G. Coker, and MA. Walsh. 1991. A performance. There were no apparent trends in dispersant Method For Evaluating Oil Spill Dispersants, Exxon effectiveness when river water was compared to deionized water. Dispersant Effectiveness Test (EXDET). Oceans '91 The results of this study are preliminary. Further research is Proceedings. Oceanic Engineering Society of IEEE, New needed on COREXIT® 9500* effectiveness on various crude York, NY. pp. 1486-1490. oils and in freshwater and low salinity environments. In addition, 2. Becker, K.W., M.A Walsh, RJ. Fiocco, and M.T. Curran. the aquatic of COREXIT® 9500* in freshwater has not 1993. A New Laboratory Method for Evaluating Oil Spill yet been evaluated. Dispersants. Proceedings, 1993 International Oil Spill Conference. American Institute, Washington, DC. pp. 507-510. Downloaded from http://meridian.allenpress.com/iosc/article-pdf/2001/2/1209/1740885/2169-3358-2001-2-1209.pdf by guest on 25 September 2021 Conclusions 3. Blondina, G.J., M.M. Singer, I. Lee, M.T. Ouano, R.S. Tjeerdema, and M.L. Sowby. 1999. Influence of Salinity Blending COREXIT® 9500 with a calcium chloride solution on Petroleum Accommodation by Dispersants. Spill markedly increases the dispersant's effectiveness in freshwater, Science and Technology Bulletin. 5:127-134. especially on lighter crude oils. The authors' results show that 4. Blondina, G.J., M.L. Sowby, M.T. Ouano, M.M. Singer, COREXIT® 9500* and to a lesser degree COREXIT® 9500 and R.S. Tjeerdema. 1997. Comparative Efficacy of Two would have dispersed Hydra crude oil in the Rio de la Plata. COREXIT Dispersants as Measured Using California's Modified Swirling Flask Test. Proceedings, 20th Arctic and Marine Oilspill Program (AMOP) Technical Seminar. Acknowledgements Environment Canada, Ottawa, Ontario, pp. 561-573. 5. CEDRE. 1998. Use of Dispersants in Fresh Water [draft The authors thank Oscar Podzun and Rene Estevez (Esso list]. Brest Cedex, France, June 1998. SAPA) for providing Rio de la Plata water samples and Hydra 6. Lessard, R.R., K.W. Becker, G.P. Canevari, A. George- crude oil. The authors also thank Jim Lynn (Elf Atochem North Ares, and RJ. Fiocco. 1999. Chemical dispersant for oil America, Inc.) for providing Inipol IPF and Stephen Thomas spills [patent pending], November 8, 1999. (Dasic International Ltd.) for providing Dasic Freshwater 7. OSIR (Oil Spill Intelligence Report). 1999a. Cutter dispersant. Information Corp., Arlington, MA, January 21, 1999. p.l. 8. OSIR (Oil Spill Intelligence Report). 1999b. Cutter Information Corp., Arlington, MA, February 25, 1999. pp. Biography 5-6. 9. OSIR (Oil Spill Intelligence Report). 1999c. Cutter Anita George-Ares is a senior environmental toxico logist at Information Corp., Arlington, MA, January 28, 1999. p.2. ExxonMobil Biomédical Sciences, Inc. She is senior author of several peer-reviewed papers on dispersant aquatic toxicity and the ExxonMobil Dispersant Guidelines. In addition to dispersant research, she conducts environmental hazard assessments for a variety of chemical products. Downloaded from http://meridian.allenpress.com/iosc/article-pdf/2001/2/1209/1740885/2169-3358-2001-2-1209.pdf by guest on 25 September 2021