A comparative study of the effects of EDTA and citric acid on soil enzyme activities and growth performances of Talinum triangulare

Abstract

Ethylene diamine tetraacetic acid (EDTA) and citric acid are two different chelants that have been used in several studies to enhance the phytoremediation process. Though numerous reports are available to prove the efficacy of these chelants toward enhancing the metal uptake and translocation, there are very few studies focusing on the minimization of hazards posed by the chelants. EDTA is an effective synthetic chelant that aids phytoremediation, whereas citric acid, an organic chelant, poses minimum level of toxicity to the soil. Application of a single chelant may be effective for pollutant removal but poses toxic symptoms on the soil as well as plants at higher concentrations. Nevertheless, a combination of two different chelants may prove to be effective both in terms of pollutant removal and safety. This may be attributed to the alleviating effect of one chelant over the other, which needs further investigation. The number of reports on the combined treatment of chelants, their overall effects on plant growth and soil enzymes are also limited. The present study was conducted to evaluate the individual as well as the combined effects of EDTA and citric acid on the soil enzyme activities and plant growth parameters on Talinum triangulare. The soil was treated with chelants, and plants were grown over this soil for 50 days. Growth parameters such as leaf count, shoot length, root length and girth were analyzed. The activity of three soil enzymes—amylase, invertase and cellulase—was examined. The study revealed the toxicity of chelants themselves when used in excess. Though it was found that 250 mg kg⁻¹ concentration of EDTA has the best performance in terms of plant growth, it has been noticed that plant growth and soil enzymes were least affected at 500 mg kg⁻¹ concentration of mixed chelants.

Keywords

T. triangulare / Chelants / EDTA / Citric acid / Soil enzymes

References

[1] Chen YX, Lin Q, Luo YM, He YF, Zhen SJ, Yu YL, Tian GM, Wong MH. The role of citric acid on the phytoremediation of heavy metal contaminated soil. Chemosphere, 2003, 50(6): 807-811

[2] Dagari MS, Umar GW. Impacts of EDTA on uptake and accumulation of Cu²⁺ by spinach (Spinacia oleracea L.) seedlings replanted in hydroponic solutions. Chem Search J, 2017, 8(1): 74-80

[3] Evangelou MW, Ebel M, Schaeffer A. Chelate assisted phytoextraction of heavy metals from soil. Effect, mechanism, toxicity, and fate of chelating agents. Chemosphere, 2007, 68(6): 989-1003

[4] Hosseini S, Lakzian A, Halajnia A. Effect of EDTA and Citric acid on soil enzyme activities and phytoextraction of lead by sun flower and Indian mustard from a contaminated soil. J Agric Nat Resour, 2017, 24(1): 47-65

[5] Jean L, Bordas F, Gautier-Moussard C, Vernay P, Hitmi A, Bollinger JC. Effect of citric acid and EDTA on chromium and nickel uptake and translocation by Datura innoxia. Environ Pollut, 2008, 153(3): 555-563

[6] Jean-Soro L, Bordas F, Bollinger JC. Column leaching of chromium and nickel from a contaminated soil using EDTA and citric acid. Environ Pollut, 2012, 164: 175-181

[7] Khan AH, Butt TA, Mirza CR, Yousaf S, Nawaz I, Iqbal M. Combined application of selected heavy metals and EDTA reduced the growth of Petunia hybrida L. Sci Rep, 2019, 9(1): 1-2

[8] Mohanty M, Patra HK. Effect of Cr⁺⁶ and chelating agents on growth, pigment status, proline content and chromium bioavailability in rice seedlings. Int J Biotechnol Appl, 2011, 3(3): 91-96

[9] Qu J, Yuan X, Cong Q, Wang L. The effect of sodium hydrogen phosphate/citric acid mixtures on phytoremediation by alfalfa & metals availability in soil. J Soil Sci Plant Nutr, 2011, 2: 86-96

[10] She W, Cui GX, Jie YC, Bai YC, Cao Y, Xiao CX. Comparative effects of chelants on plant growth, cadmium uptake and accumulation in nine cultivars of Ramie (Boehmeria nivea). Acta Agric Scand B Soil Plant, 2014, 64(1): 71-78

[11] Sinhal VK, Srivastava A, Singh VP. EDTA and citric acid mediated phytoextraction of Zn, Cu, Pb and Cd through marigold (Tagetes erecta). J Environ Biol, 2010, 31(3): 255-259

[12] Sivakumar S, Nityanandi D, Barathi S, Prabha D, Rajeshwari S, Son HK, Subbhuraam CV. Selected enzyme activities of urban heavy metal-polluted soils in the presence and absence of an oligochaete, Lampito mauritii (Kinberg). J Hazard Mater, 2012, 227: 179-184

[13] Sun YB, Zhou QX, An J, Liu WT, Liu R. Chelator-enhanced phytoextraction of heavy metals from contaminated soil irrigated by industrial wastewater with the hyperaccumulator plant (Sedum alfredii Hance). Geoderma, 2009, 150(1–2): 106-112

[14] Turgut C, Pepe MK, Cutright TJ. The effect of EDTA and citric acid on phytoremediation of Cd, Cr, and Ni from soil using Helianthus annuus. Environ Pollut, 2004, 131(1): 147-154

[15] Wang A, Luo C, Yang R, Chen Y, Shen Z, Li X. Metal leaching along soil profiles after the EDDS application—a field study. Environ Pollut, 2012, 1(164): 204-210