Ecological assessment of the effect of citric acid and nitrilotriacetic acid on phytoextraction of lead from contaminated soils using Brassica juncea L.

The paper presents the results of studies on the effect of chelating agents on phytoextraction of lead from contaminated sod-podzolic soils by Brassica plants. In a greenhouse experiment with contamination of arable soil horizon at the level of 3 ODC (390 mg/kg soil Pb (CH3COO)2-3H2O) and application of citric acid (at a concentration of 60 mmol/kg soil) and nitrilotriacetic acid (at a concentration of 5 mmol/kg soil), lead accumulation in different parts of Brassica plants was examined and the role of these chelates on growth and biomass accumulation of Brassica plants (Brassica juncea L.) was evaluated. The research results showed that at this level of lead contamination of sod-podzolic soils there is a decrease in root length by 0.35 cm, shoots by 9.5 cm, and a decrease in root dry weight by 33% and shoots by 15% - compared to the control. In case of citric acid treatment of contaminated soil, there was an increase in root length by 14% and root dry weight by 20% with a decrease in shoot length by 14%. In case of treatment with nitrilotriacetic acid - increase in shoot length by 20% and roots by 2%, shoot dry weight by 9%, and roots by 30%. In case of joint treatment with two acids, root length increased most markedly - by 35%. The concentration of lead increased significantly with the application of citric acid: 2.4 times - in roots, 2.1 times - in stems and 4.1 times - in leaves. The content of lead in mustard plants at application of nitrilotriacetic acid increased much less: by 5% - in roots, by 40% - in leaves, and even decreased by 30% in stems. Joint application of citric acid and nitrilotriacetic acid increased lead content in mustard plants to the greatest extent: almost 4.0 times - in roots, 0.4 times - in stems, and 4.1 times - in leaves (in relation to the control - soil contaminated with lead without adding acid). Keywords: ECOLOGICAL ASSESSMENT, CITRIC ACID, NITRILOTRIACETIC ACID, LEAD, PHYTOREMEDIATION, SOIL, HEAVY METALS, SOIL CONTAMINATION, SOIL ECOLOGY, CHELATES, BRASSICA JUNCEA L.