Light‐induced destruction of the absorbance property of dissolved organic matter in seawater

The absorption spectra of marine humic substances decrease when they are exposed to a known intensity of monochromatic light at various wavelengths or to a polychromatic source such as sunlight. The results of studies of photochemical bleaching of absorption of marine humic substances are presented and compared to the characteristics of total dissolved organic matter to assess the contribution made by the humic fractions. From the absorbance and apparent quantum efficiency data at specific wavelength and the solar fluxes, a model calculation was used to determine the rates of the change of the photoprocess in the ocean. These parameters were determined for the photochemical degradation of Biscayne Bay (Florida, USA) seawater and humic substances collected in the Gulf of Mexico.

Key words:

• Light
• absorption
• organic matter
• seawater
• rates