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Properties of and heavy metal complexation by aqueous humic extracts
Author(s) -
Fischer W. R.
Publication year - 1986
Publication title -
zeitschrift für pflanzenernährung und bodenkunde
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.644
H-Index - 87
eISSN - 1522-2624
pISSN - 0044-3263
DOI - 10.1002/jpln.19861490405
Subject(s) - polarography , chemistry , metal , humic acid , extraction (chemistry) , aqueous solution , stability constants of complexes , electrical resistivity and conductivity , soil water , heavy metals , inorganic chemistry , conductivity , environmental chemistry , nuclear chemistry , analytical chemistry (journal) , chromatography , organic chemistry , fertilizer , environmental science , soil science , electrical engineering , engineering
Abstract Aqueous extracts of terrestrial and underwater soils were prepared by Soxhlet extractions at temperatures between 100 and 37°C (under reduced pressure). From the law of mass action, stability constants were derived for the complexation of Cd, Cu, and Pb by these extracts. The activity of the heavy metals was determined polarographically, whereas the concentration of acid functional groups was used for ligand activity. Visible spectra, electrical conductivity, organic matter contents, and complexation constants depended on extraction temperature as well as on soil properties. In most cases, complex stability increased with increasing pH of the polarographic medium, but sometimes maximum stability was found around pH 7.