Plastic photochemistry has caught the attention of many researchers, who have irradiated plastic with wide-spanning light sources and observed a multitude of effects. These light sources (e.g., solar simulators, low and medium pressure mercury lamps, UVA blacklight blue lamps, etc.) emit different electromagnetic radiation, spanning high energy UV (e.g., 254 nm) to visible light, yet there is little known about which wavelengths drive plastic photolysis, a so-called wavelength sensitivity. Research from industrial polymer chemists has shown that plastic exhibits strong wavelength sensitivities for plastic yellowing and the formation of chain scission products, with a general trend of high energy (short wavelength) UV light producing greater effects than low energy (longer wavelength) UV and visible light. Yet, at this time, we do not know the wavelength sensitivities for sunlight-driven plastic photo-degradation and -dissolution processes, which are critical to estimating real-world plastic photolysis rates. To understand which solar wavelengths drive plastic photodissolution processes, we determined the excitation wavelength dependent generation of dissolved organic carbon (DOC) from a series of commercial and postconsumer plastics. From DOC photo-generation rates, we calculated quantum yield coefficients that represent the amount of DOC generated from plastic per photon absorbed. Using these quantum yield coefficients, we calculated solar quantum yield activation spectra that describe plastic photodissolution as a function of solar excitation wavelength. Results provide insight into which solar wavelengths generate the highest photodissolution rates and are thus most important for plastic photodissolution in the environment.

Wavelength sensitivities of plastic photodissolution

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