Transformation of unsymmetrical dimethylhydrazine in soils

Abstract

The transformation of unsymmetrical dimethylhydrazine (UDMH, a propellant component) applied at a rate of 240 g/kg to different soils was studied. The kinetic regularities of a decrease in the UDMH concentration and the accumulation of its transformation products leached out from dry and wet soils were investigated 3, 10, 30, and 90 days after its application. As the UDMH enters the soil, it vaporizes, and the elevated moisture of the soils promotes an increase in the pollutant’s concentration at the initial moment; then, the concentration differences become leveled to the end of observation. It was also shown that the higher the organic matter content in the soil, the higher the UDMH concentration. However, at the end of the observations, on the 90th day, the total UDMH concentration did not exceed 0.5% of its initial content. In order to explain the UDMH behavior in the soils, one should take into account the existence of different forms of this substance and the changes in their ratios with time. The main portion of UDMH retained by the soil in the free form is transformed during the first few days. The products of the UDMH transformation, such as 1-methyl-1,2,4-triazole, formic acid dimethylhydrazide, dimethylguanidine, and dimethylamine are formed in considerable amounts, and their concentrations should be controlled in places of UDMH spills on soils.