Assessment of soil pollution with polycyclic aromatic hydrocarbons in Ulan-Ude

Abstract

: For the first time, polycyclic aromatic hydrocarbons (PAH) contamination of the soil cover of Ulan-Ude, the capital of the Republic of Buryatia, was studied. The content of 16 individual polyarenes was analyzed in the upper horizon of background chestnut and urban soils, sampled during soil and geochemical survey in July–August 2022. The average concentration of total PAHs in the soil cover of Ulan-Ude was 735 ng/g, which was 8 times as much as the concentration in the background soils (87 ng/g). The PAH amount in the soil of various functional zones decrease in the following order: railway transport > motor traffic > industrial > one-story residential > multi-story residential > recreational. At the same time, the amount of PAHs in the railway transport zone was 2.6–5.2 times higher than in other functional zones, which indicates that railway transport is the most powerful source of PAHs in the city. Contamination of soils with polyarenes in all functional zones is determined primarily by medium- (46%) and high-molecular-weight (41%) compounds. Among PAHs with low molecular weight, phenanthrene prevailed (9% of the total PAHs), but medium-molecular-weight fluoranthene (18%) and pyrene (13%) showed higher share; high-molecular-weight compounds dominated by benzo(ghi)perylene (12%), benzo(b)fluoranthene (10%), indeno(1,2,3-cd)pyrene (8%) and benzo(a)pyrene (6%). The total amount of 16 PAHs in the soil cover of the city varied within the range of 17–9 540 ng/g. The highest levels of pollution (3 226–9 540 ng/g) were recorded at 9 sampling points (4% of the city), which form the most contrasting local PAH anomalies. In more than half of the territory of Ulan-Ude, the total amount of PAHs did not exceed 500 ng/g. The indicator ratios of individual PAHs made it possible to determine the dominant types of sources, which include railway transport and coal combustion. The contribution to the environmental hazard of soil contamination with PAHs in Ulan-Ude was mainly made by benzo(a)pyrene (64%) and, to a lesser extent, by benzo(b)fluoranthene (9.6%), indeno(1,2,3-cd)pyrene (7.2%), dibenzo(ah)anthracene (6.5%) and benzo(a)anthracene (6.1%).

Keywords

• pahs
• anthropogenic anomalies
• industrial emissions
• transport pollution
• environmental hazard
• indicator ratios