Chemical Safety Science, 2018, Volume 2, Issue 1, p. 73 — 80
Simulation of chemically hazardous processes
UDC 504.53 
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DOI: 10.25514/CHS.2018.1.12883
DISSIPATION KINETICS OF CONTAMINANTS IN SOIL
I. V. Kumpanenko*, A. V. Roshchin, N. A. Ivanova, V. V. Usin, and I. D. Epinatiev
Semenov Institute of Chemical Physics, Russian Academy of Sciences, Moscow, Russia
Received March 15, 2018
Published June 25, 2018
Abstract — A series of compartmental mathematical models describing dissipation kinetics of contaminants in soil is discussed. These models take into account a spatial variability and heterogeneity of soil. A two-compartment first-order double-exponential decay model is found to be the most suitable for description of dissipation kinetics in soil for O-isobutyl methyl phosphonate and O,O’-diisobutyl methyl phosphonate both of which are known to be the main and much less toxic degradation products of chemical warfare agent Vx, (when compared to the toxicity of Vx itself). In accordance with this model, the dependence of contaminant concentration C on time t can be described by the following equation C(t) = Cp + C1·exp(-k1t) + C2·exp(-k2t), where Cp, C1, C2, k1, k2 are fitting parameters. Comparison of coefficients of determination R2 has revealed that approximation of experimental data using first-order double-exponential formula is more exact than approximation using simple exponential equation C(t) = Cp + C1·exp(-k1t). The calculated fitting constants make it possible to estimate periods of time required for dissipation of 50% and 90% of the contaminants. O-isobutyl methyl phosphonate is found be more stable in soil with moderate moisture levels (50 mass %) whereas O,O’-diisobuthyl methyl phosphonate demonstrates higher stability in soil with an increased moisture levels (70 mass %).
Keywords: contaminants in soil, dissipation kinetics, O-isobutyl methyl phosphonate, O,O’-diisobutyl methyl phosphonate, two-compartment first-order double-exponential decay model.