Potential of S-containing and P-containing complexones in improving phytoextraction of mercury by Trifolium repens L

Abstract

Mercury is a global pollutant in the modern world. There is a large number of areas in the world where mercury is present in soils in significant quantities. Remediation methods which have traditionally been proposed may pose a risk of secondary mercury contamination and/or adverse health effects for cleaners. Phytoextraction of heavy metals from the soil environment is currently considered one of the promising non-invasive methods of remediation. But this approach has limited effectiveness. Chemically induced phytoextraction can increase the efficiency of this process both by converting less bioavailable mercury compounds to bioavailable fractions in the soil and by increasing the rate of transfer of metals in plants. This paper presents the results of a screening study of various chemical amendments to enhance the phytoextraction of mercury by Trifolium repens L. The results showed good potential for the induction of phytoextraction of phosphorus(P) and sulfur (S)-containing chelates. With this study, for the first time for the phytoextraction of mercury, the monoethanolamine salt of 2,2'-(ethylenedithio) diacetic acid was used as the S-containing chelate, and the disubstituted potassium salt of 1-hydroxy ethylidene-1,1-diphosphonic acid was used as the P-containing chelate. Further attention is given to study the effect that exogenous application of phytohormones and plant growth regulators has on the efficiency of mercury absorption and physiological status of plants, which performed well in combination with a P-containing chelate.

Keywords: Complexones; EDDS, ethylenediamine disuccinic acid; EDTA, ethylenediaminetetraacetic acid; GA3, gibberellic acid; Heavy metals; IAA, indole-3-acetic acid; K2HEDP, potassium salt of diphosphonic acid; MEDBA, monoethanolamine salt of dithiobioacetic acid; NTA, nitrilotriacetic acid; Na2EDTA, disodium salt of ethylenediaminetetraacetic acid; PGRs, plant growth regulators; Phytoextraction of mercury.

Fig. 1

The study of obtaining the 2,2′-(ethylenedithio)diacetic acid.

Fig. 2

The Trifolium repens L. seedlings in vegetation pots on the 33rd day of the experiment (after planting the seeds) with for soil with 5.77 mg Hg (left row on photo) and 11.55 mg Hg (right row on photo) per vegetation pot with a) K₂HEDP; b) MEDBA.

Fig. 3

Dependencies of the Trifolium repens L. seedlings growth on the degree of initial soil mercury contamination and the introduction of various amendments with a) 5.77 mg Hg per vegetation pot; b) 11.55 mg Hg per vegetation pot.

Fig. 4

Dependencies of BAF for the Trifolium repens L. seedlings on the degree of soil contamination with mercury and the introduction of various amendments: a) BAFshoots, b) BAFroots, c) BAFtotal.

Fig. 5

Dependence of TF for the Trifolium repens L. seedlings on the degree of soil contamination with mercury and amendments.

Fig. 6

Dependence of the Trifolium repens L. seedlings growth on the degree of initial soil mercury contamination and the introduction of PGRs and Na (FeEDDHA) and: a) 5.77 mg Hg per vegetation pot; b) 11.55 mg Hg per vegetation pot.

Fig. 7

Dependence of BAF for the Trifolium repens L. seedlings on the degree of soil contamination with mercury and the introduction of PGRs and Na (FeEDDHA): a) BAFshoots, b) BAFroots, c) BAFtotal.

Fig. 8

TF for the Trifolium repens L. seedlings when using MEDBA and K₂HEDP (with and without PGRs and Na (FeEDDHA)).