Transformation rate of methyl isothiocyanate and 1,3-dichloropropene in water-saturated sandy subsoils.

The transformation rates of methyl isothiocyanate and 1,3-dichloropropene were studied in four water-saturated sandy subsoil materials collected between 2 and 4 m below the soil sur­ face. The experiments were conducted in laboratory incubation systems at 10 °C. In three subsoil materials, transformation of methyl isothiocyanate was fast (less than 10 % was left after 30 days), whereas in the case of the fourth material a half-life of approximately 35 days was found. With regard to the transformation of the (Z)- and (£>isomers of 1,3-dichloropropene in the same subsoil materials, half-lives between 16 and 64 days were found. Incubation in systems where the subsoil materials had been exposed unintentionally to tem­ peratures up to 30 °C before adding the compounds, resulted in much lower transformation rates for methyl isothiocyanate (half-lives ranging from 150 to 570 days) and in only slightly lower rates for (Z)- and (£)-1,3-dichloropropene (half-lives ranging from 38 to 76 days).