Hidden Contamination Patterns: A Stochastic Approach to Assessing Unsymmetrical Dimethylhydrazine Transformation Products in Kazakhstan’s Rocket Crash Area
Radelyuk I. Zhakupbekova A. Zhumadildinova A. Kashtanov A. Baimatova N.
November 2025Multidisciplinary Digital Publishing Institute (MDPI)
Toxics
2025#13Issue 11
Unsymmetrical dimethylhydrazine (UDMH), a highly toxic rocket propellant, remains a significant environmental concern in Kazakhstan due to repeated rocket stage falls near the Baikonur Cosmodrome. This study integrates chemical analysis with stochastic contamination transport modeling to evaluate the persistence and migration of UDMH transformation products (TPs) in soils collected 15 years after the rocket crash. Vacuum-assisted headspace solid-phase microextraction coupled with gas chromatography–mass spectrometry (Vac-HS-SPME-GC-MS) was used to determine five major TPs. Among these, pyrazine (PAN) and 1-methyl-1H-pyrazole (MPA) were consistently detected at concentrations ranging from 0.04–2.35 ng g−1 and 0.06–3.48 ng g−1, respectively. Stochastic simulations performed with HYDRUS-1D indicated that the long-term persistence of these compounds is mainly controlled by physical nonequilibrium transport processes, including diffusion-limited exchange, weak sorption, and slow inter-domain mass transfer, rather than by degradation. Sensitivity analysis demonstrated that low dispersivity and diffusion coefficients enhance solute retention within immobile domains, maintaining residual levels over extended periods. The results demonstrate the efficacy of combined long-term monitoring and predictive modeling frameworks for assessing contamination dynamics in rocket impact zones.
contamination transport modeling , Kazakhstan , rocket fuel , soil analysis , transformation products , unsymmetrical dimethylhydrazine , Vac-HS-SPME-GC-MS
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Department of Chemistry and Chemical Technologies, Toraighyrov University, Pavlodar, 140008, Kazakhstan
Faculty of Chemistry and Chemical Technology, Center of Physical Chemical Methods of Research and Analysis, Al-Farabi Kazakh National University, Almaty, 050040, Kazakhstan
Environmental and Analytical Chemistry Laboratory, Al-Farabi Kazakh National University, Almaty, 050040, Kazakhstan
Department of Chemistry and Chemical Technologies
Faculty of Chemistry and Chemical Technology
Environmental and Analytical Chemistry Laboratory
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