Formation of molecular chlorine in dark condition: Heterogeneous reaction of ozone with sea salt in the presence of ferric ion

Uptake coefficients Of O-3 on NaCl and synthetic sea salt (SSS) were found to be enhanced from < 10(-5) to similar to3.5 x 10(-2) in the presence of w ater-soluble Fe3+ in the Fe/Na weight ratio larger than 0.1 %. Cl-2 release was observed without radiation in the reaction Of O-3 and a FeCl3/NaCl mix ture with surface adsorbed water at the yields of 0.48 and 0.28 for Fe/Na r atio of 1.0 and 0.5 weight %, respectively. Only Br-2 release was observed for a FeCl3/SSS sample. These results imply that when bromide is deficient in sea salt, Cl-2 would be released from the sea salt with the coexistence of Fe3+. The estimate was made to show that the Cl-2 releasing rate can be high enough to explain sporadically observed Cl-2 at nighttime in a coastal area.