A practical review on photooxidation of crude oil: laboratory lamp setup and factors affecting it

After an oil spill, crude oil in the marine environment is affected by a variety of processes collectively called weathering. Photooxidation induced by ultraviolet (UV) light from the sun is one of the most significant processes of long-term weathering that changes the chemical nature of oil. Experimental studies on photooxidation in the natural environment are generally not practicable due to the variability of factors that are more readily controlled in a laboratory. The emission spectra and irradiance of artificial lamps are critical factors for simulating sunlight, and the process of acceleration should be differentiated from simulation. We present a comprehensive review of the exposure conditions affecting in vitro photooxidation studies, including the types of lamps, their spectra and irradiance levels and maintenance conditions. The importance of xenon arc, metal halide along with mercury–xenon, high-pressure mercury lamps and other lamps with respect to their spectral characteristics is discussed and the selection guide is provided. A brief discussion on other factors affecting photooxidation rates and outcomes, such as photosensitisers, photodegraders, solvents and the synergistic effects of compounds is also given.