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Abstract

The use of a combination of electrokinetic remediation and phytoremediation to decontaminate two metal-polluted soils has been demonstrated in laboratory-scale reactors. One soil was heavily contaminated with copper, the other with cadmium and arsenic (2500 microg g(-1) Cu; 300-400 microg g(-1) Cd and 230 microg g(-1) As, respectively). Test reactors with two separated chambers, each with a capacity of 5.25 kg soil, were constructed, then the respective chambers were filled with either a mixture of the polluted soil and a control topsoil (75:25) or topsoil alone. Reactors were sown with perennial ryegrass (Lolium perenne cv Elka) and a constant voltage of 30 V was applied continually across the soils in each reactor. Soil sampling took place at the start and the end of the test run, whilst plant foliage was sampled after approximately 3 weeks (both reactors) 6 weeks (Cd soil reactor only) and at the conclusion of each test run (98 days Cu soil, 80 days Cd soil). Soil and plant metal concentrations were measured, together with soil pH. Results showed that in both soils there was a significant re-distribution of metals from anode to cathode in the test reactors, coupled with an enhancement of plant Cu uptake in the cathode region for the Cu soil. Patterns of plant Cd uptake were less clear cut and were not as clearly related to the redistribution of Cd measured in the soil. There was significant acidification of soil at the anode in each test reactor, but soil pH in other parts of the reactor changed little during the course of the experiment. Plant growth was affected at the anode, but was not affected in other parts of the reactor. There was no visual evidence of metal toxicity in the ryegrass in either polluted soil. Some effects on soil fungi were apparent, with a stimulation of Fusarium infection of ryegrass in the cathode region of all reactors and the appearance of sporophores of Coprinus in the same location. It is concluded that the combination of the two techniques represents a very promising approach to the decontamination of metal polluted soils that now requires validation in field conditions.

Coupled Electrochemical Processes for Removing Dye from Soil and Water

“…The germination index (GI) was calculated by counting the number of the germinated seeds and the average root length observed in each sample compared to control treatments. [24][25][26] The results were expressed according to the following equations:…”

Alternating current electrical field effects on lettuce (Lactuca sativa) growing in hydroponic culture with and without cadmium contamination

“…The plasma membrane of the plant root cell is often negatively charged [7], so the external electrical field might increase the affinity of the charged ions to the membrane including minerals and nutrients. The increased root growth under the electrical field could enable a higher transport of nutrient from the root to the shoot, which further enhances the shoot mass for a higher trans-evaporation rate of the plant [3]. The shoot mass of the plant growing in non-contaminated nutrient under AC 10 Hz was 40 ± 3.0 g, under AC 50 Hz was 64.3 ± 13.2 g and for the control was 31.2 ± 6.9 g (Fig.…”

“…However, this was mostly the application of a low voltage direct current (DC) field used in electro-bioremediation and electro-phytoremediation [1][2][3][4]. Several studies have demonstrated improved biodegradation of organic pollutants under the influence of a low voltage DC field, due to the induced movement of water, nutrients, contaminants and microorganisms, which led to an overall homogenization of the contaminated soil [2,5].…”

“…Several studies have demonstrated improved biodegradation of organic pollutants under the influence of a low voltage DC field, due to the induced movement of water, nutrients, contaminants and microorganisms, which led to an overall homogenization of the contaminated soil [2,5]. It was noted by O'Conner et al that the application of a DC field stimulated the growth and metal uptake of ryegrass growing near the cathode region, and the plant growth was slightly lower near the anode [3]. Moreover, a reduced growth of potato plants in a multi metal contaminated soil was found by Aboughalma et al [4], due to the acidic soil conditions created by the DC field.…”

Sustainable Phytoremediation of Soils Enhanced with Electric Field

“…Moreover, the appropriate electrode distribution may extend the remediation area out of the rhizosphere due to the transportation of the contaminants towards the roots [2]. Several studies showed that the presence of an electric field around a growing plant might exert some negative effects that compromise survival of the plants [7,8]. Those negative effects are related to critical pH changes in soil due to the electrolysis of water that yields H + ions on the anode and OH − ions on the cathode.…”