Abstract:

A pilot-scale tower tank was set-up for generation of micro-bubbles under a volume of seawater contaminated with crude oil and crude oil-dispersant mixtures. The impact of generated bubbles on aerosolization of particles from the water surface was studied using particle sizing instruments. Real-time air quality monitoring was conducted before, during and after bubbles were injected into the water column. The influence of bubble bursting on number and mass concentration of the generated aerosols were evaluated and emission factors were estimated. Three cases with surface slicks of either crude oil only, crude oil-dispersant mixture (dispersant to oil ratio of 1:25) or dispersant only were tested over the seawater column.

Suggested Citation:

Nima Afshar-Mohajer and Kaushik Sampath. 2018. An Investigation on Bubble Bursting as a Mechanism for Aerosolization of Seawater Contaminated with Crude Oil and Crude Oil and Dispersant Mixtures. Distributed by: Gulf of Mexico Research Initiative Information and Data Cooperative (GRIIDC), Harte Research Institute, Texas A&M University–Corpus Christi. doi:10.7266/N77H1GZG

Publications:

Sampath, K., Afshar‐Mohajer, N., Chandrala, L. D., Heo, W., Gilbert, J., Austin, D., … Katz, J. (2019). Aerosolization of Crude Oil‐Dispersant Slicks Due to Bubble Bursting. Journal of Geophysical Research: Atmospheres. doi:10.1029/2018jd029338

Afshar-Mohajer, N., Lam, A., Dora, L., Katz, J., Rule, A. M., & Koehler, K. (2020). Impact of dispersant on crude oil content of airborne fine particulate matter emitted from seawater after an oil spill. Chemosphere, 256, 127063. doi:10.1016/j.chemosphere.2020.127063

Purpose:

To estimate the emission factor and emission rate of the nano- and micron-sized particles due to the bubble bursting. To obtain insight into the impact of mixing the crude oil with dispersant on aerosolization of the airborne particulate matter.

Data Parameters and Units:

Concentration units for the particles are in particles per cubic centimeter or microgram per cubic meter. Gas concentrations are expressed in parts per million (ppm). All flow rates are in liter per minute. Aerodynamic Particle Sizer (APS), Scanning Mobility Particle Sizer (SMPS), Total Suspended Particulate (TSP) GCMS_Results.xls: Date received (MM/DD/YYYY); Date prepped (MM/DD/YYYY); Sample number; Air volume (L); Compound (mg/m^3); Compound (ppm); CAS #; Total volatile organic compounds (TVOC) = a summation of all peak areas present in the sample (quantified as toluene) FTIR_Distributions.mat: Wave number (1/cm); Absorbance (arbitrary relative absorbance units) Aerosol_Distributions.mat: Sampled particle diameters by the APS in the micron range (D_APS, microns); Micron size particle number concentration (mean_APS, #/cc); Sampled particle diameters by the SMPS in the nano range (D_SMPS, nm); Nano size particle number concentration (mean_SMPS, #/cc); Standard error (stderror_APS/SMPS, #/cc); TSP mass mass collected divided by the total number of bubbles injected in 20 minutes (TSP_Filters_mean, pg/bubble); Standard error of TSP mass per bubble over repeated measurements (TSP_Filters_stderror, pg/bubble) Bubble_Distributions.mat: Diameters (um); L=large; M=medium; S=small

Methods:

Bubbles were generated by injecting a bubble cloud with controlled size distribution into a vertical seawater column (0.6 m diameter, 1.8 m high). The bubble plume rises to a surface contaminated with an oil-slick with controlled thickness and properties, and the bubbles subsequently burst. The resulting concentration of aerosolized droplets between 0.5 to 20 µm in size was monitored by an aerodynamic particle sizer, whereas a scanning mobility particle sizer measured droplet concentrations in the 10 to 370 nm range. The interface and bubble plume characteristics were monitored with high-speed imaging. Measurements were performed at the same air injection rate for varying bubble diameters (150 to 600 µm), interfacial tensions (crude oil, and crude oil premixed with the dispersant Corexit 9500A (Nalco) at dispersant-to-oil ratio (DOR) of 1:100 and 1:25) and oil-layer thicknesses (0.1 and 0.5 mm).

Instruments:

Scanning mobility particle sizer for detection of nano-sized aerosols Aerodynamic particle sizer for detection of micron-sized aerosols 4-Lpm pump and filter-holder cassettes for capturing airborne particulate matter FTIR system for detection of carbon compounds using IR

Individual Files: