title: Comparison of natural humic substances and synthetic ethylenediaminetetraacetic acid and nitrilotriacetic acid as washing agents of a heavy metal-polluted soil.
abstract: Ethylenediaminetetraacetic acid (EDTA), nitrilotriacetic acid (NTA), and other synthetic polycarboxylic acids have been shown to possess substantial capacity as washing agents of heavy metal-polluted soils, but they are environmentally problematic. Therefore, a sample of natural soluble humic substances (HS) was tested as a possible substitute. The efficiency of HS to extract cadmium (Cd), copper (Cu), and lead (Pb) from a strongly polluted calcareous urban soil was compared with that of EDTA and NTA. The influence of extractant concentration (25-100 mmol L(-1) C), solution/soil ratio (5-100 L kg(-1)), and single-step vs. multistep extraction on heavy metal removal from the soil was investigated. The extracted pools were assessed by sequential extraction. Ethylenediaminetetraacetic acid and NTA extracted up to 86, 77, and 30% of total soil Cd, Cu, and Pb, respectively, whereas HS extracted 44, 53, and 4%. Extracted amounts of Cd, Cu, and Pb increased with increasing extractant concentration and solution/soil ratio in the range 5 to 100 L kg(-1). Single-step extraction removed about the same amounts of the three metals as multiple-step extraction. The metal-extracted pools of the soil depended on the metal and on the extractant. The overall conclusion is that soluble HS can replace synthetic EDTA and NTA as washing agents for Cd- and Cu-polluted soils, whereas HS is not a promising substitute of EDTA or NTA for cleaning Pb-polluted, calcareous soils.
authors.affiliation: Dep. of Soil Science, Isfahan University of Technology, Isfahan, 84156-83111, Iran. soleimani57@yahoo.com
authors.forename: Mohsen
authors.initials: M
authors.lastname: Soleimani
authors.forename: Mohammad A
authors.initials: MA
authors.lastname: Hajabbasi
authors.forename: Majid
authors.initials: M
authors.lastname: Afyuni
authors.forename: Samira
authors.initials: S
authors.lastname: Akbar
authors.forename: Julie K
authors.initials: JK
authors.lastname: Jensen
authors.forename: Peter E
authors.initials: PE
authors.lastname: Holm
authors.forename: Ole K
authors.initials: OK
authors.lastname: Borggaard
mesh_terms: D003247:Conservation of Natural Resources; D004492:Edetic Acid / Q000737:chemistry*; D006812:Humic Substances / Q000032:analysis*; D019216:Metals, Heavy / Q000737:chemistry*; D009571:Nitrilotriacetic Acid / Q000737:chemistry*; D012987:Soil / Q000032:analysis*; D012989:Soil Pollutants / Q000737:chemistry*
chemical_list: D006812:Humic Substances; D019216:Metals, Heavy; D012987:Soil; D012989:Soil Pollutants; D004492:Edetic Acid; D009571:Nitrilotriacetic Acid