Current state of the problem of soil sorption properties as illustrated by interactions of elementary soil particles with soil organic matte and heavy metals

Abstract

Elementary soil particles smaller than 0.01 mm in size and humus play a leading role in the sorption of various elements, including heavy metal ions – Pb²⁺ and Cd²⁺, which are carcinogenic. Given the current level of anthropogenic impact on the environment, this soil property is becoming increasingly important. In the future, the soil self-purification process can be applied to other objects. The aim of this study was to identify the sorption characteristics of heavy metal ions – Pb²⁺ and Cd²⁺ – by soil organic matter and the clay fraction of chernozems, as well as to establish the influence of the profile distribution characteristics of elementary soil particles (ESP)<0.01 mm on the migration of humus and heavy metal ions. The objectives included: studying the morphological structure of leached chernozems with varying degrees of humification, with a wide range of percentages of elementary soil particles smaller than 0.01 mm, which is reflected in their rather diverse particle size distribution; Laboratory and analytical studies aimed at determining the sorption properties of elementary soil particles smaller than 0.01 mm in size for humus and the total content of heavy metal ions – Pb²⁺ and Cd²⁺; identifying patterns in the distribution of heavy metal ions and humus in chernozems of different particle sizes. The obtained data indicate that with an increase in elementary soil particles smaller than 0.01 mm, the sorption capacity of chernozems for humus and heavy metal ions – Pb²⁺ and Cd²⁺ – increases. The results of the model experiment confirmed theoretical assumptions about the influence of particle size on the total content of heavy metals – Pb²⁺ and Cd²⁺ – and humus. The minimum sorption capacities are typical of leached sandy loam chernozems, in which the content of the fine fraction smaller than 0.01 mm does not exceed 20%. Maximum sorption capacities were detected in clayey varieties of leached chernozems, with a fine-grained particle size (less than 0.01 mm) content of over 60%. Humic substances are capable of being sorbed and firmly retained by the silt and colloidal fractions of the studied soils, with maximum humus accumulation (over 7%) recorded in clayey chernozems enriched with a fine-grained particle size (less than 0.01 mm). Varying percentages of physical clay influenced not only the identification of chernozem varieties and types (including the thickness of the humus horizon), but also the total content of the studied transition metal ions. The obtained data can serve as a basis for designing measures to protect the environment from heavy metal pollution.