Chelate-Assisted Heavy Metal Removal by Sunflower to Improve Soil with Sludge

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Abstract
Crops are used to improve land through phytoremediation. When heavy metals are the pollutants, chelates are added to increase their solubility for uptake and removal. The U.S. Environmental Protection Agency recommends recycling of sewage sludge back to land, which results in heavy metal accumulations at sludge farms. However, almost no information is available concerning the efficacy of chelates applied to soil with sludge for heavy-metal removal. The objective of this work was to compare heavy metal uptake by sunflower (Helianthus annuus L.) grown in composted sludge or in soil from a sludge farm, when the chelate ethylenediamine-tetraacetic acid (EDTA) was added to facilitate uptake of the heavy metals. Plants were grown in pots in a greenhouse. Fifty-four days after planting, the tetrasodium salt of EDTA was applied at rates of 0, 1, and 2 g EDTA salt per kg medium (composted sludge or soil with sludge). At harvest, 68 days after planting, three non-essential (Cd, Ni, Pb) and four essential h...

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