Environmental impact of the launch vehicle "Soyuz-FG" emergency falling in Kazakhstan

On October 11, 2018, in the Ulytau region of the Republic of Kazakhstan, the Soyuz-FG launch vehicle carrying a crewed MS-10 spacecraft failed. It resulted in the release into the fragile arid ecosystems of rocket propellants, i.e., jet fuel of toxic hazard class 4 and carcinogenic unsymmetrical dimethyl hydrazine (heptyl, UDMH). In this paper, we described the results of soil surveys conducted in 2018, 2019, 2022, and 2023. In the fragile arid ecosystems in Central Kazakhstan, due to the emergency falling of the launch vehicle, environmental consequences were registered at a total area of about 1350 m², including spillage of jet fuel and UDMH in the territories of 400 m² and 9 m², respectively. The third stage disintegrated and fell down within an area of 4.4 km². Immediately after the emergency crash of the second stage, the content of total petroleum hydrocarbons (TPHs) reached 1645 mg/kg, decreasing 10 times in 3.5 years. At the fuel tank falling site, the concentration of highly toxic carcinogenic UDMH and nitrosodimethylamine (NDMA) reached 22 and 9 mg/kg, which is many times higher than the maximum permissible concentrations. Four years after reclamation, the content of both substances did not exceed 0.05 mg/kg-the lower limit of sensitivity of a highly performed liquid chromatography. The content of TPHs, water-soluble Cl^- and SO₄^2-, and alkalinity from CO₃^2- was significantly (p < 0.05) higher in autumn of 2022, and the content of total N, water-soluble NO₃^- and NO₂^-, and alkalinity from HCO₃^- was higher in spring of 2023. In spring and autumn, the content of exchangeable Ca²⁺ and Mg²⁺, cation exchange capacity was similar (p > 0.05). The presented materials can be used to optimize the restoration of disturbed arid ecosystems and future monitoring work at sites of regular landing of the first stages and emergency crash sites of launch vehicles.