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Trace Metal Speciation in Three Unbuffered Salt Solutions Used to Assess their Bioavailability in Soil
Author(s) -
Lebourg A.,
Sterckeman T.,
Ciesielski H.,
Proix N.
Publication year - 1998
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq1998.00472425002700030016x
Subject(s) - chemistry , bioavailability , genetic algorithm , salt (chemistry) , metal , trace metal , environmental chemistry , zinc , inorganic chemistry , organic chemistry , bioinformatics , evolutionary biology , biology
Three unbuffered salt solutions used to estimate soil trace metal bioavailability were compared. The objective was to evaluate chemical speciation of Cd, Cu, Pb, and Zn in 0.01 M CaCl 2 , 0.1 M NaNO 3 , and 1 M NH 4 NO 3 extracts. The metal in each extract were speciated with a model that was optimized experimentally using an exchange resin. In NH 4 NO 3 , Cd, Cu, and Zn were completely complexed by NH 3 . In extracts of pH lower than 6.5, Pb was essentially present as free Pb 2+ and metal‐organic complexes. In extracts of higher pH, PbCO 3 and free Pb 2+ were dominant. In CaCl 2 , Cu and Zn were mainly present as organic complexes and free Zn 2+ , respectively. In all extracts, 50% of Cd was free Cd 2+ and 50% CdCl + . As pH increased, the proportions of free Pb 2+ and organic complexes decreased while those of inorganic complexes increased. In NaNO 3 , Cd, Cu, and Zn were, respectively, mainly present as free Cd 2+ , organic complexes and free Zn 2+ . Speciation of Pb changed with pH as in NH 4 NO 3 . Similarities were expected between the qualitative composition of the extracts and the soil solution, justifying the use of unbuffered salt solutions, particularly NaNO 3 and CaCl 2 , in the evaluation of soil trace metal availability.