Mercury in precipitation and ambient air a new scenario

Abstract

Theoretical calculations and experimental work, mainly consisting of bubbling ambient air through different synthetic solutions and natural waters and also bubbling Hg- and O₃-free air through precipitation samples, have given some new information. The oxidation process of Hg^o by means of O₃ in natural waters and in synthetic solutions has been clarified. The primary products are water soluble Hg-compounds which are reduced by SnCl₂. Subsequently volatile or nonvolatile Hg-species may be formed. These are not reduced by SnCl₂. Further it has been shown that in precipitation those Hg-forms, which are not reducible with SnCl₂ consist of non volatile species only. The dominant one seems to be highly dispersed and easily sorbed on to solid surfaces. It is reducible with NaBH₄. Besides this there is another one consisting of larger particles. Their core contains some Hg which can be released as Hg^o by a high temperature thermal process. Species with the same properties have also been observed in ambient air but in very low concentrations.