Analysis of variations in heavy metal levels and soil microorganism counts resulting from shelling incidents in Ukraine

Military activities affect soil conditions through contamination with metal-containing debris, such asprojectile and rocket fragments, as well as bullet remnants, leading to the release of heavy metals and subsequent environmental contamination. The goal of our study was to examine the concentration of heavy metals in areas affected by shelling and to assess their impact on the population of soil microorganisms, including those exhibiting heavy-metal resistance. Metal concentrations were analyzed via an XRF analyzer. The study involved examining both soil samples and missile fragments. Microorganisms were isolated using Koch’s and Hungate’s roll tube methods. The concentration of iron in soil was the highest, reaching 8,1991.3±132.8 ppm. The concentration of other metals (Ni, Cu, Cr) varied between 407.5±8.0 ppm and 4.6±2.1 ppm. Cobalt compounds were not detected at the projectiles impact sites. The number of aerobic chemoorganotrophic bacteria in all soil samples was in the range of (1.8±0.2) × 105 – (3.7±0.2) × 105 CFU/g, while chromium-resistant bacteria were, on average, an order of magnitude fewer. The number of anaerobic microorganisms ranged from (1.4±0.2) × 105 to (2.6±0.2) × 105 CFU/g. A follow-up study conducted after three months indicated a tendency for an increase in both aerobic and anaerobic bacteria, including metal-resistant strains. Overall, the total number of microorganisms in all soil samples showed an upward trend. These results show that soil microbial communities may play a role in the detoxification of heavy metals in contaminated soils.