A Laboratory Study on Formation of Oil-SPM Aggregates Using the NIST Standard Reference Material 1941b

• Main Authors: Ali Khelifa, Ben Fieldhouse, Dominic Pjontek, Zhendi Wang, Chun Yang, Merv Fingas, Carl E. Brown, Lloyd Gamble
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Fid; Alaska North Slope; north slope; Alaska
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.636.9285; http://www.crrc.unh.edu/sites/crrc.unh.edu/files/media/docs/Publications/khelifaal2007_amop_paper-2.pdf

Aggregation between suspended particulate matter (SPM) and oil droplets, which leads to the formation of Oil-SPM Aggregates (OSA), is widely acknowledged as a natural process that enhances dispersion of spilled oil in aquatic environments. A new laboratory study was performed to investigate the formation of OSA using the Standard Reference Material 1941b. The experiments were performed using Arabian Medium, Alaska North Slope and South Louisiana crudes. Sediment concentrations varied from 25 to 300 mg/L. A new procedure was developed to separate the OSAs from the bulk water, measure the oil trapped in OSAs by GC-FID analysis, and isolate the sediment trapped in sinking OSAs for gravimetric quantification. Results showed that this method is appropriate for measuring small amounts (less than 2 mg in this study) of oil trapped in OSAs and does not overestimate the mass of oil trapped in large OSAs as observed in a previous method based on image analysis. For the three oils, results showed also that the percentage of oil trapped in sinking OSAs increases rapidly from about 0.5 % to about 30 % of the initial oil mass when sediment concentration increases from 25 to 100 mg/l. Further increase of sediment concentration to 300 mg/l showed slower increase of oil trapping to reach about 40 to50 % depending on the type of oil. Measurements of the mass of sediment trapped in OSAs showed that the highest trapping efficiency is obtained when the sediment to oil ratio is close to 0.5. This value decreases exponentially with oil density. 1