DETERMINATION OF EDTA IMPACT ON THE CONTENT AND DISTRIBUTION OF LEAD IN THE SYSTEM «SOIL-PLANT» DURING PHYTOREMEDIATION

Abstract

Like any other biogeochemical process, the transition of heavy metal ions from the soil through the root system to the terrestrial part of the plants is characterized by the rate, which depends on a number of factors. These factors include: the physicochemical characteristics of the soil itself (pH, humus content); properties of heavy metal ion (radius, oxidation number, surrounding ligands); ambient temperature, daylight hours; morphological features of plants. In the present paper, at the same values of the factors of first three groups, the ability of some species of agricultural plants (oats, white mustard, maize and sunflower) to extract lead compounds from the soil and accumulate them in the underground and ground parts was investigated. The results of analysis showed that the lead content in the soil in all cases after the 30-day growing cycle was decreased. The most significant decrease in the concentration of heavy metal in the soil was observed for the samples where oats were grown. The smallest change is for the samples where the sunflower was grown. It was found that, under the conditions of the experiment, the efficiency of lead extraction increases with its concentration in the soil. Addition of EDTA to contaminated soil increases the rate of absorption of lead compounds by plants. For maize, a lead reduction of 5% was observed when EDTA was added to the soil. For mustard and oats, the lead content of the soil was almost unchanged when EDTA was added. The most significant reduction in lead concentration with the addition of EDTA was observed for the soil on which the sunflower was grown - by 63%. The calculations showed that during the first 30 days of growth, the terrestrial parts of the studied plants absorb only about 0.1% of the total lead content in the soil-plant system. According to the results of the conducted studies, the cumulation coefficients for the investigated crops were determined: for sunflower the maximum value was 2.47 (in the presence of EDTA), for mustard - 0.94, for corn - 0.79, for oats - 1.58. Therefore, oats and sunflowers have the best cumulative properties among the studied crops. Maximum lead uptake was set for sunflower in the presence of EDTA.