Ecotoxicity of Dust from Different Functional Zones of Moscow

Ecotoxicity of dust was assessed for different functional zones in three Moscow districts. Ecotoxicity was estimated by the reaction of higher plants using a new approach to the implementation of biotesting method and by changes in the biomass and respiration of microorganisms in residential and transport zones as compared to recreational zones. The proposed method of assessing urban dust toxicity upon modeling dust transfer to soil-like substrates allowed us to solve the main methodological problem, i.e., the choice of control. By the example of perennial ryegrass (Lollium perenne L.), it was found out that annual volume of dust deposition upon a high load within a one-meter zone from the road surface does not manifest toxicity, whereas a three-year volume suppresses plants up to 27% relative to the control. No significant differences were found between the phytotoxicity of dust in different functional zones; and phytotoxicity did not correlate with any of the studied properties of dust (organic carbon content (C_org), pH, electrical conductivity, moisture capacity, particle-size composition). Basal respiration and carbon content in microbial biomass (C_mic) of dust were maximal in the recreational zones of the city (3.1–7.2 μg C–CO₂ g^–1 h^–1 and 314–435 μg g^–1, respectively) decreasing by 27–71% in residential and by 76–81% in the transport zones. Significant correlations of basal respiration and C_mic with C_org were observed (r_S = 0.57 and 0.61, respectively, p < 0.05, n = 49). High values of microbial metabolic quotient qCO₂ of dust and a small share of C_mic in C_org indicate unfavorable conditions for microorganisms.