Our laboratory is interested in the fate of modern biocide molecules in the environment. Here we present recent work which has been done on the fate of two compounds with fungicidal and bactericidal properties: methylenedithiocyanate (MTC: NCS - CH2 - SCN) and thiocyanomethylthiobenzothiazol (TCMTB). We have studied separately the influence of pH, temperature and ultraviolet irradiation in aqueous media. The results show that the higher the pH (the more basic) and the higher the temperature, the easier these biocides decompose, liberating other compounds, essentially cyanide and thiocyanate ions CN¯ and SCN¯ along with organic decomposition products, namely mercaptobenzothiazole in the case of TCMTB and a thioamide and a diamine in the case of MTC. Moreover, for both of the biocides, we have noticed shown both in the aqueous phase and in the gazeous phase bordering the aqueous phase the formation of CS2 and a sulfur containing heterocyclic compound, i.e. 1,2,4 - trithiolane. The photochemical decomposition of TCMTB (between 350 and 700 nm) in water as such and in presence of traces of H2O2 is significant for long exposition times. In both cases we noticed the formation of mercaptobenzothiazole. On the other hand, MTC is not decomposed in this wavelength interval.

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