Evaluating Chemical Dispersant Efficacy in an Experimental Wave Tank: 2—Significant Factors Determining In Situ Oil Droplet Size Distribution

Abstract

Chemical dispersion is one of the most cost-effective options to remediate oil spill at open sea. Identifying significant factors that determine in situ droplet size distributions facilitates mechanistic understanding of dispersant effectiveness. In this work, in situ dispersed oil droplet size distributions were characterized during testing of chemical dispersant effectiveness of two dispersants (Corexit 9500 and SPC 1000) on two oils [Medium South American (MESA) and Alaska North Slope (ANS)] under three wave conditions (regular nonbreaking, spilling breaking, and plunging breaking waves) in an experimental wave tank. Results showed that physical dispersion generated monomodal lognormal oil droplet size distributions of larger median diameters, whereas chemical dispersion produced bi-or trimodal lognormal oil droplet size distributions of smaller median diameters over a wider range. Factorial analysis of variance (ANOVA) followed by Tukey's paired comparison statistical data analysis indicated that the volume mean diameters of dispersed oil droplets were reduced by 36 mm (from 122 to 86 mm) by plunging breaking conditions. Volume mean diameters were decreased by 92 mm (from 153 to 61 mm) and 37 mm (from 153 to 116 mm), respectively, by Corexit 9500 and SPC 1000. These results are useful in optimizing operational guidelines for dispersant use, and providing input for modeling transport, fate, and biological effects of dispersed oil.

Growth and immune system performance to assess the effect of dispersed oil on juvenile sea bass (Dicentrarchus labrax)

“…Indeed, surfactants increase solubilization of hydrocarbons by forming micelles which will limit the adhesion of oil compounds and stabilize oil droplets. On the contrary, droplets of oil in the MD condition could form more aggregates because of their strong hydrophobic properties and their greater size compared to the CD condition (Li et al, 2009). The results obtained on the size of oil droplets in this study tend to confirm this hypothesis.…”

Fate of Surface Spills of Cold Lake Blend Diluted Bitumen Treated with Dispersant and Mineral Fines in a Wave Tank

“…1). Additional details on the wave tank can be found in Li et al (2009aLi et al ( , 2009bLi et al ( , 2009c and King et al (2013King et al ( , 2014.…”

“…Various oil spill countermeasures were considered and applied to CLB, which are as follows: no treatment, usage of dispersant (Corexit 9500), usage of the mineral fines (MF, Kaolinite clay), and a combination of dispersant + MF. The selected oil spill countermeasures have been successfully used in the past to disperse conventional crude oils in the water column to generate droplet sizes less than 70 lm (Li et al, , 2009a(Li et al, , 2009b(Li et al, , 2009c(Li et al, , 2010. The results sought in this work will improve our knowledge on the fate and transport of diluted bitumen products spilled at sea and how their fate is influenced by oil spill countermeasures.…”

“…The current speed is only around 0.5 cm/s (around 350 m/ day), but it allows the dilution and flushing of applied chemicals, which cannot be achieved in standard wave tanks (see King et al, 2013 for a further discussion on the tank in the context of dispersion effectiveness, DE). The wave tank system has been used to test DE in seawater along with the oil concentration in the dissolved form and in the dispersed form (i.e., droplets) (Li et al, 2009a(Li et al, , 2009b(Li et al, , 2009c(Li et al, , 2010.…”

Physical and Chemical Characterization of Crude Oil-Water Mixtures: Understanding the Effects of Interfacial Process to Chemical Bioavailability

“…Very few studies have shown a comprehensive physical characterization of the particulate oil in the test media and the methods used for this purpose often lack of standardization (microscopy) , do not have enough selectivity towards oil droplets (Coulter Counter particle analyzer) (Hansen et al, 2009;Nordtug et al, 2011a), are limited by the technology used (Laser In-Situ Scattering and Transmissometry, LISST) (Conmy et al, 2014;Li et al, 2011;Li et al, 2009;Trudel et al, 2010) or conducted after the fact by complex solubility calculations once the full chemical characterization is completed (Redman et al, 2012a). All these limitations prevent timely feedback on the evolution of the mixtures before, during and after the test which could be used to manage the longer periods of time required for chronic toxicity testing (> 7 days).…”