Photoreactions of Chlorophyll at the Salt Water-air Interface

Glancing angle laser induced fluorescence was used to monitor the kinetics of the photodegradation of chlorophyll at the surface of various salt solutions. The loss was measured using varying wavelengths of actinic radiation in the presence and absence of gas phase ozone. The loss rate of illuminated chlorophyll was faster on salt water surfaces than fresh water surfaces, both in the presence and absence of ozone. On salt water surfaces, the dependence of the loss rate on [O3(g)] was different under illuminated conditions than in the dark. This was further investigated by measuring the excitation spectra and the dependence of chlorophyll loss on the concentration of salts at the salt water surface. The possible production of reactive halogen atoms is the likely reason for the observed enhancement. The following results provide evidence of photosensitized oxidation of halogen anions, in the UV-visible range of the spectrum, resulting in halogen atom release.MAS