Evidence of dispersed oil droplets using the LISST-X100 particle counter

Surface water (collected by bucket) and 1m depth samples from all six stations sampled shows the presence of dispersed oil droplets typically characterized by particles <60 um in diameter.

The highest concentration of dispersed oil particles was observed in the surface water sample at station L001, which was a bucket grab sample between station B12 and B13 on our transect line.

There was little evidence of similar size distribution particles (<60 um) in samples collected at the 2 lower depths (275 and 550 m). These preliminary results show that we could not detect a subsurface plume of chemically dispersed oil.

Our results illustrate the capability of the LISST to resolve particles in the size range expected for both physically and chemically dispersed oil. A LISST particle counter has been deployed today for continuous monitoring at a depth of approximately 3.5m while conducting a SMART protocol survey based on oil fluorescence.

Two hundred samples have been collected and preserved for analysis onshore by ultraviolet fluorescence spectroscopy (UVFS). Our Shimadzu scanning fluorometer is currently set up at the BP office in Port Fourchon and awaits delivery of the samples. In addition, our ability to provide rapid feedback on the degree of oil dispersion on board the RV Brooks McCall requires delivery of the two fixed wavelength fluorometers that were requested in the original science plan. Without this on board feedback, the identification of dispersed oil at depth will be seriously hampered.