Influence of humic acids in lowland peat on the remediation properties of wheat plants against heavy metal contamination

Phytoremediation is a promising technology for removing heavy metals from soil and water. Despite the pronounced increase in heavy metal accumulation by cultivated plants under the influence of naturally occurring complexing agents, such as humic acids, their efficiency in phytoremediation has been poorly studied. In this regard, the aim of this work is to elucidate the effect of peat humic acid formulations on the remediation potential of wheat plants (Triticum aestivum L.) against heavy metal contamination. The influence of polymetallic pollution on the remediation properties of wheat was studied in model vegetation experiments using a culture solution. Plants were grown in a Hoagland nutrient solution. A complex exposure to heavy metals was simulated using 10 pmol/L CdSO₄, 25 and 50 pmol/L CuSO₄, 500 and 1000 pmol/L Pb(NO₃)₂ in various combinations with or without the addition of a peat humic acid formulation (0.005%).

The phytoremediation efficiency of the humic acid formulation was determined by the removal of heavy metals during the heading stage of wheat growth. The research results showed that the phytoremediation efficiency of the humic acid formulation is defined by both an increase in the absorption of heavy metals and a decrease in their toxic action on the plants. In the case of mixed contamination of the solution with highly toxic heavy metals, the samples with humic acids showed a 1.2-2.5-fold increase in the accumulation of copper and cadmium by wheat plants. The data demonstrates the possibility of using the formulation of peat humic acids in phytoremediation technologies as an effector of heavy metal phytoextraction.

1. Lyanguzova IV. Dynamic trends of heavy metal contents in plants and soil under different industrial air pollution regimes. Russian Journal of Ecology. 2017;48(4):311-320. https://doi.org/10.1134/S1067413617040117

2. Giniyatullin RH, Baktybaeva ZB. Features of Cd and Ni accumulation by Larix sukaczewii Dyl. under technogenesis. Vestnik Tomskogo Gosudarstvennogo Universiteta. Biologiya = Tomsk State University Journal of Biology. 2020;51:141-161. (In Russian) https://doi.org/10.17223/19988591/51/8

3. Kabata-Pendias A, Pendias Kh. Trace elements in soils and plants. Moscow: Mir; 1989, 439 p. (in Russian)

4. Prasad MNV. Phytoremediation of metal-polluted ecosystems: hype for commercialization. Russian Journal of Plant Physiology. 2003;50(5): 686-701. https://doi.org/10.1023/A:1025604627496

5. Baker AJM. Accumulators and excluders -strategies in the response of plants to heavy metals. Journal of Plant Nutrition. 1981;3(1-4):643-654. https://doi.org/10.1080/01904168109362867

6. Pilon-Smits E. Phytoremediation. Annual Review of Plant Biology. 2005;56:15-39. https://doi.org/10.1146/annurev.arplant.56.032604.144214

7. Prieto MJ, Acevedo SOA, Prieto GF, Nallely TG. Phytoremediation of soils contaminated with heavy metals. Biodiversity International Journal. 2018;2(4):362-376. https://doi.org/10.15406/bij.201 8.02.00088

8. Yan A, Wang Y, Tan SN, Mohd Yusof ML, Ghosh S, Chen Z. Phytoremediation: A promising approach for revegetation of heavy metal-polluted land. Frontiers in Plant Science. 2020;11:359. https://doi.org/10.3389/fpls.2020.00359

9. Evangelou MWH, Robinson BH, Gunthardt-Goerg MS, Schulin R. Metal uptake and allocation in trees grown on contaminated land: implications for biomass production. International Journal of Phytoremediation. 2012;15(1):77-90. https://doi.org/10.1080/15226514.2012.670317

10. Salt DE, Blaylock M, Kumar NP, Dushenkov V, Ensley BD, Chet I, Raskin I. Phytoremediation: a novel strategy for the removal of toxic metals from the environment using plants. Biotechnology. 1995; 13(5):468-475. https://doi.org/10.1038/nbt0595-468

11. Vamerali T, Bandiera M, Mosca G. Field crops for phytoremediation of metal-contaminated land. A review. Environmental Chemistry Letters. 2010;8(1):1-17. https://doi.org/10.1007/s10311-009-0268-0

12. Lee M, Yang M. Rhizofiltration using sunflower (Helianthus annuus L.) and bean (Phaseolus vulgaris L. var. vulgaris) to remediate uranium contaminated groundwater. Journal of Hazardous Materials. 2010;173(1-3):589-596. https://doi.org/10.1016/j.jhazmat.2009.08.127

13. Jensen JK, Holm PE, Nejrup J, Borggaard OK. A laboratory assessment of potentials and limitations of using EDTA, rhamnolipids, and compost-derived humic substances (HS) in enhanced phytoextraction of copper and zinc polluted calcareous soils. Soil and Sediment Contamination: an International Journal. 2011;20(7):777-789. https://doi.org/10.1080/15320383.2011.609198

14. Halim M, Conte P, Piccolo A. Potential availability of heavy metals to phytoextraction from contaminated soils induced by exogenous humic substances. Chemosphere. 2003;52(1):265-275. https://doi.org/10.1016/S0045-6535(03)00185-1

15. Evangelou MWH, Daghan H, Schaeffer A. The influence of humic acids on the phytoextraction of cadmium from soil. Chemosphere. 2004;57(3):207-213. https://doi.org/10.1016/j.chemosphere.2004.06.017

16. Kirdey TA. The influence of humate on the phytoremediation properties of wheat with increasing concentrations of lead nitrate. Izvestiya Vuzov. Prikladnaya Khimiya i Biotekhnologiya = Proceedings of Universities. Applied Chemistry and Biotechnology. 2017;7(4):110-115. (In Russian) https://doi.org/10.21285/2227-2925-2017-7-4-110-115

17. Churakov AA. Peat reserves in Russia. Lesnoi vestnik = Forestry bulletin. 2003;3:22-25. (In Russian)

18. Kalinnikov JA, Vashurina IJ, Kirdej TA. Method for production of liquid peat humates. Patene RF, no. 2310633; 2006. (In Russian)

19. Hoaglond DR, Arnon DE. The water-culture method for growing plants without soil. California Agriculture Experimental Station. 1950. Available from: https://ia800306.us.archive.org/6/items/wa-tercultureme3450hoag/watercultureme3450hoag.pdf [Accessed 25th Novemder 2020].