Wavelength Sensitive Plastic Photodissolution: Elucidating Quantum Yield Trends for Solar Activation Spectra

Plastic photodissolution into dissolved organic carbon (DOC) is a key proposed loss pathway for plastic in aquatic environments. However, the specific solar excitation wavelengths that drive photodissolution remain unknown, limiting our ability to model and predict photodissolution rates in natural aquatic environments. To better understand the impact of solar excitation wavelength on plastic photodissolution rates, we measured the wavelength sensitivity of photodissolution for a variety of transparent and semitransparent commercial and postconsumer plastic films with wide-spanning polymer chemistries. We irradiated plastic films using custom-built light-emitting diode (LED) photoreactors that emit light in the range of 275 to 445 nm and found that plastics exhibit a strong wavelength sensitivity, producing the highest DOC release rates for short wavelength ultraviolet (UV) light. We additionally calculated photodissolution quantum yield trends for transparent plastic films and then calculated photodissolution activation spectra. We found that solar UV light between 300–350 nm is responsible for most of the plastic photodissolution for all plastic compositions and predicted plastic photodissolution rates within water columns. Results advance our ability to model plastic photodissolution in natural aquatic environments.