A natural surfactant was studied to simulate the dispersion process of crude oil in water. The interfacial phenomena of this natural dispersant was compared with a commercially available chemical dispersant, COREXIT EC9500A. This functional surfactant was extracted from the mucilage of the Opuntia ficus-indica cactus species. The evaluation to determine the efficacy to disperse crude oil of the cactus-based mucilage extract (nongelling extract, NE) was based on characterizing surface and interfacial tension, dispersion efficiency, mixing effects, salinity effects, stability, and droplets size distributions. We found that surface tension values follow a linear relationship with respect to the natural logarithm of the concentrations of NE. The application of NE in the water phase led to decreasing oil/water interfacial tensions. Surface tension tests were also used to quantify the effect of oil-in-water (O/W) emulsion ratios once either natural or commercialized dispersants were added. A key finding of our work is that the surface tension between typical 6% and 3% v/v O/W emulsions was significantly reduced with the addition of discrete amounts of NE. This result indicated that the dynamic balance between O/W and water-in-oil (W/O) emulsions was thermodynamically more stable toward O/W emulsion states with NE. We also found that O/W emulsions with higher dispersion effectiveness were formed for both 10 and 35 practical salinity units, as the dispersant to oil ratios increased, with a significant correlation to the mixing energy. We observed that the O/W emulsions with natural dispersants had a significantly smaller weighted average diameter compared to those with COREXIT EC9500A. Such a phenomenon can be explained by understanding intermolecular interactions due to the structure and type of dispersant. In conclusion, cactus-based mucilage extracts could be used as environmentally benign dispersants and, therefore, reduce negative social perceptions of the application of dispersants to clean up spilled oil.

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The hormones listed in the screening survey list 2 of the Unregulated Contaminant Monitoring Rule 3 (estrone, 17-β-estradiol, 17-α-ethynylestradiol, 16-α-hydroxyestradiol (estriol), equilin, testosterone and 4-androstene-3,17-dione) were analyzed by liquid chromatography electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS). Two analytical methods were compared: EPA method 539 and the isotope dilution method. EPA method 539 was successfully utilized in river and drinking water matrices with fortified recoveries of 98.9 to 108.5%. Samples from the Hillsborough River reflected levels below the method detection limit (MDL) for the majority of the analytes, except estrone (E1), which was detected at very low concentrations (<0.5 to 1 ng L(-1)) in the majority of samples. No hormones were detected in drinking water samples. The isotope dilution method was used to analyze reclaimed and aquifer storage and recovery (ASR) water samples as a result of strong matrix/solid phase extraction (SPE) losses observed in these more complex matrices. Most of the compounds were not detected or found at relatively low concentrations in the ASR samples. Attenuation of 50 to 99.1% was observed as a result of the ASR recharge/recovery cycles for most of the hormones, except for estriol (E3). Relatively stable concentrations of E3 were found, with only 10% attenuation at one of the sites and no measureable attenuation at another location. These results have substantiated that while EPA method 539 works well for most environmental samples, the isotope dilution method is more robust when dealing with complex matrices such as reclaimed and ASR samples.