ACCUMULATION OF HEAVY METALS AND ARSENIC IN FLOWERS OF THE SMALL–LEAVED LIME GROWING IN AGRICULTURAL AND URBAN ECOSYSTEMS OF THE VORONEZH REGION

Abstract

The aim of this study was to investigate the heavy-metal and arsenic contamination of lime tree flowers collected from urban and agricultural ecosystems in the Voronezh Region exposed to various human impacts. The accumulation of heavy metals (lead, mercury, cadmium, nickel, copper, zinc, cobalt, chromium) and arsenic was studied in 51 samples of small-leaved lime tree flowers using atomic absorption spectrometry with MGA-915MD spectrometer and following pharmacopoeial techniques. All the samples met the regulatory requirements for the content of standardized heavy metals (lead, cadmium, mercury) and arsenic. Comparing the data on content of the heavy metals in the region’s topsoil with their content in lime tree flowers, it can be argued that there are significant physiological barriers to the accumulation of the ecotoxicants in the plants’ reproductive organs, which is particularly noticeable for elements such as lead, mercury, arsenic, cadmium, cobalt and chromium. Lime tree flowers proved to be capable of selectively concentrating some heavy metals involved in the active cores of enzymatic systems (e. g. copper and zinc) if their environmental content was below a certain vital level, and barring their inflow to flowers through physiological mechanisms if the content of the elements in the soil was high. One can therefore suppose that when small-leaved lime trees are exposed to human pressure, a peculiar edaphic type is formed as a result of selection under man-made environmental pollution and the development of adaptations to these conditions. The results of the studies showed that the accumulation of toxic elements from soils in flowers of small-leaved lime trees is minor, which is an important consideration when planning the harvesting of medicinal plant material and assessing its quality.