Content of phenolic compounds in leaves of trees growing on devastated lands at iron waste rock dump

Abstract

Knowledge about the content of phenolic compounds in tree leaves growing on devastated lands may be important for foresting of the post-mining landscapes and for improving environmental quality in industrial areas. The object of this study was on standpoint of an ecosystem approach to determine the phenolic compounds concentrations in the leaves of the trees that grow naturally on the devastated lands at iron waste rock dump. Petrovsky waste rock dump areas at Kryvyi Rih Iron Ore Mining & Metallurgical District (central part of Ukraine) were chosen for the present research. During 2017–2021, the 5 research plots in the dump’s area and 1 research plot in the background area (natural ecosystems of the Hurivskyi forest, Kirovohradska oblast) were established. The content of phenolic compounds was investigated in the leaves of three woody plants species: silver birch (Betula pendula Roth.), ashleaf maple (Acer negundo L.) and black locust (Robinia pseudoacacia L.). The extracts of leaves were prepared by extraction of 80% isopropanol. The phenols concentration was determined using Folin-Ciocalteu reagent. The absorbance was measured by spectrophotometer at wavelength of 725 nm. The calibration curve was constructed using standard solutions of gallic acid. The phenols concentration was expressed as gallic acid equivalents in milligrams per gram dry weight of plant material (mg GAE * g-1 dw). The results showed that in background area the values for phenolic compounds content vary within minimal limits: from 26,90 to 27,49 mg GAE * g-1 dw in leaves of silver birch, from 17,53 to 18,11 mg GAE * g-1 dw in leaves of ashleaf maple and from 10,98 to 11,65 mg GAE * g-1 dw in leaves of black locust. In all the samples, the concentrations of phenolic in the leaves of silver birch and black locust were generally within natural limits. The concentrations of phenolic in the leaves of ashleaf maple were below the natural levels. According to the leaves analyses, the phenolic compounds content in all woody plants species from all research plots on the devastated lands were statistical significant differences than the reference samples (P < 0,05). The levels of phenolic in samples of ashleaf maple and black locust were found to be greater (P < 0,05) than the background values about 15–65% and 115–165%, respectively. The concentration of phenolic in leaves of silver birch was lower (about 10–28%, P < 0,05) than those values recorded as control. The woody plants species according to resistance to the devastated lands of the Petrovsky waste rock dump were in the following decreasing order: silver birch (Betula pendula Roth.) > ashleaf maple (Acer negundo L.) > black locust (Robinia pseudoacacia L.).