LEAD DISTRIBUTION AND FORMS OF LEAD-CONTAINING COMPOUNDS IN THE TECHNOGENIC SOIL, SVIRSK TOWN, SOUTH BAIKAL REGION
The relevance. Currently, the heavy metal contamination of soil in industrial cities is an urgent problem. One of such examples is Svirsk town where, in addition to arsenic, the second most important pollutant contained in the production wastes of the Angarsk Metallurgical Plant, is lead, which average concentration in the dump soils amounted to 1,5…3,0 %. The main aim of the study was to assess the degree of technogenic soil contamination by lead and the peculiarities of lead migratory mobility in the soils of the Angarsk Metallurgical Plant production facilities after the plant liquidation. Object: technogenic soils in the area of the former Angarsk Metallurgical Plant, located in Svirsk town. Methods. Forms of Pb compounds in soils were studied by the method of sequential extraction. The chemical analysis of the extracts and the total lead content in the soil were determined using the atomic absorption method. Results. It was found that the lead content in technogenic soils after the liquidation of Angarsk Metallurgical Plant exceeds the approximate permissible concentration by 60-150 times in the area of former dumps, which is the main source of pollution. At a distance from this zone, the degree of soil pollution decreases, and the migration mobility of lead increases, which can lead to its accumulation in biological objects. With depth, there are processes of lead immobilization in clays. They can prevent lead entry into the groundwater and the Angara River. The main factors influencing lead immobilization in soil were pH, the presence of organic matter, iron hydroxides, carbonates, and clays. A significant part of lead remains associated with the fraction of easily degradable minerals and solid residue that suggests its relatively low mobility. The studied mechanism of lead mobility can be of practical importance for the reclamation of transformed technogenic soils.