Plant uptake and leaching of copper during EDTA-enhanced phytoremediation of repacked and undisturbed soil

EDTA-enhanced phytoremediation of copper contaminated soil was evaluated. Up to 740 μg g-1 of Na2H2 EDTA in solution was added to repacked soil columns, and intact cores of a sandy loam of volcanic origin, that was growing Agrostis tenuis. The soil contained up to 400 μg g-1 of copper due to a history of fungicide spraying. EDTA application increased the herbage copper concentration of the grass growing in repacked soil from 30 to 300 μg g-1, but the same application to an intact core only brought about an increase from 10 to 60 μg g-1. More copper accumulated in the herbage when the EDTA was applied in numerous small doses than in just one or two larger amounts. Calculation of the concentration of copper in the water taken up by the grass revealed this to be two orders of magnitude lower than that in the soil solution. As a result of the EDTA applications, about 100 times more copper was leached than was taken up by the herbage. This means that a strategy for managing leaching losses needs to be part of any plan for EDTA-enhanced phytoremediation.