THREE-DIMENSIONAL ANALYSIS OF THE CITY ENVIRONMENT CONTAMINATION WITH HEAVY METALS BASED ON THE FINDINGS OF THE SNOW COVER STUDY

Abstract

Analysis of the air environment and atmospheric emissions is an efficient method for assessing the ecological situation in cities. Assessment of the chemical composition of deposit environments (soil, snow) shows long-term contamination. The snow cover (SC), being a natural accumulating plate, reflects environmental contamination with heavy metals (HM) caused by entry from various sources. The work aims to study the three-dimensional dynamics of large city contamination with HM. Sampling (in 2019 - 100, in 2020-100, in 2021 - 280) was performed in the first decade of March. The samples were analyzed for the HM content by atomic absorption method on apparatus AAS 3. Simultaneously, the content of Cd, Cu, Zn,/, Ni, and Mn in the solid residue (mg/kg of dust), along with the HM fallout density per unit area for dissolved and solid phases (mg/m2) during winter period were calculated. The average daily dust load on the city territory was confirmed by relatively weak temporal variation, the difference in dust release during the winter seasons of the years 2019-2021 did not increase by 20%. In 2019, the SC dust level was characterized mainly as low (85.5 kg/km2/day). High dust level was observed only at the sites adjacent to large industrial enterprises (816 kg/km2 -day). In 2020, the dust level of the city of SC was the lowest (40.8 kg/km2/day). Along with the decrease of the total dust weight, which entered the SC, a decrease of HM entry as part of dust was registered too. The element-by-element analysis showed that Fe (80-87%), Zn (5-6.8%), Mn (3.45-3.6%), and Cu (1.3-2.7%) made the highest proportion in the dust. Ranking in value of the concentration coefficient (C-) was as follows: Cd 327 > -u 51 > Zn 38 > / 18 > / 13 > Ni 11 > n 1.3. The spread of Cd data in selected measurement points in dust fallouts on SC was achieved 900 times. In urbanized systems, the Cd behavior is regulated by the transformation of hydrocarbons, which involves the structure of atmospheric emissions in the city of Kazan. Correlation between the HM content as part of liquid and solid phases of the city SC indicates a statistically significant relationship with their technogenic entry into the atmosphere from one or several sources, and the composition of HM geochemical association in SC depends largely on the set and relationship of elements in other components of the urban environment. The assumption of the integrity of -d, Pb, Cu, and Zn source of entry (Spearman correlation coefficient 0.55-0.92) was confirmed. Data on the SC contamination not only deepen our knowledge, reflecting peculiarities of the atmospheric pollution spread, but also allow preventing the contamination of water bodies and soils.