ARCTIC The Fate of Oil in the Water Column Following Experimental Oil Spills in the Arctic Marine Nearshore

ABSTRACT. Petroleum hydrocarbon concentrations in the water column were monitored after a release of crude oil onto the water surface and subsurface release of chemically dispersed oil. During the surface r lease, petroleum hydrocarbons did not disperse into the water column deeper than m. The highest concentrations observed under the slick were less than 2 m g P. The chemically dispersed oil release resulted in concentrations over 5 mg.f ' in the Bay 9 study area for 12 hours, and petroleum hydrocarbons were detectable by in siru fluorometry for more than 4 days. The dispersed oil di not undergo further weathering for 24 hours. Estimated exposures of the benthic communities to oil in the three experimental bays were 3 mgd-'.h, 3 mg.f'.h, and 300 mg#'.h respectively. The highest exposures were to il retaining many of its more toxic components. Key words: dispersant, oil, fluorometry, gas chromatography, oil spill &SUM & La concentration d'hydrocarbures pitroliers a t t t mesur6e dans la colonne d'eau apds un dtversement de p6trole brut en surface, et u dtversement de pitrole disperse chimiquement sous la surface. Lors du dtversement en surface, les hydrocarbures pitroliers ne se sont pas disperses dm la colonne d'eau B plus d ' 1 m de profondeur. Les plus hautes concentrations observtes sous la nappe ne dtpassaient pas 2 mg.1". Le dtversement d pitrole disperst chimiquement a provoqut des concentrations dtpassant 50 m g P pendant 12 heures dans la baie expirimentale no 9, et les hydrocarbure pitroliers ont pu & t r e dttectts par fluoromttrie in siru pendant plus de 4 jours. Le pitrole disperse n'a pas subi de degradation suppltmentaire pendant 2 heures. On a estimt l'exposition au pitrole des communauth benthiques des trois baies expirimentales B 3 mg.l".h, 30 mgd".h et 300 m g P. respectivement. Les taux les plus dlevts ttaient ceux de I'exposition au pitrole contenant encore beaucoup de ses composants les plus toxiques