Speciation and Release Kinetics of Cadmium in an Alkaline Paddy Soil under Various Flooding Periods and Draining Conditions

This study determined Cd speciation and release kinetics in a Cd–Zn cocontaminated alkaline paddy soil, under various flooding periods and draining conditions, by employing synchrotron-based techniques, and a stirred-flow kinetic method. Results revealed that varying flooding periods and draining co...

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Bibliographic Details
Published in:Environmental science & technology 2011-05, Vol.45 (10), p.4249-4255
Main Authors: Khaokaew, Saengdao, Chaney, Rufus L, Landrot, Gautier, Ginder-Vogel, Matthew, Sparks, Donald L
Format: Article
Language:English
Subjects:
ABSORPTION
Applied sciences
Biological and physicochemical properties of pollutants. Interaction in the soil
CADMIUM
Cadmium - analysis
Cadmium - chemistry
CADMIUM CARBONATES
CADMIUM SULFIDES
Characterization of Natural and Affected Environments
DESORPTION
Drainage
Earth sciences
Earth, ocean, space
Engineering and environment geology. Geothermics
ENVIRONMENTAL SCIENCES
Exact sciences and technology
FINE STRUCTURE
Floods
Floods - statistics & numerical data
FLUORESCENCE
HUMIC ACIDS
Hydrogen-Ion Concentration
KINETICS
Models, Chemical
Pollution
Pollution, environment geology
Rice
Soil - chemistry
Soil and sediments pollution
Soil Pollutants - analysis
Soil Pollutants - chemistry
SOILS
SPECTRA
SPECTROSCOPY
Spectrum analysis
Studies
Water Movements
X-Ray Absorption Spectroscopy
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Summary:This study determined Cd speciation and release kinetics in a Cd–Zn cocontaminated alkaline paddy soil, under various flooding periods and draining conditions, by employing synchrotron-based techniques, and a stirred-flow kinetic method. Results revealed that varying flooding periods and draining conditions affected Cd speciation and its release kinetics. Linear least-squares fitting (LLSF) of bulk X-ray absorption fine structure (XAFS) spectra of the air-dried, and the 1 day-flooded soil samples, showed that at least 50% of Cd was bound to humic acid. Cadmium carbonates were found as the major species at most flooding periods, while a small amount of cadmium sulfide was found after the soils were flooded for longer periods. Under all flooding and draining conditions, at least 14 mg/kg Cd was desorbed from the soil after a 2-hour desorption experiment. The results obtained by micro X-ray fluorescence (μ-XRF) spectroscopy showed that Cd was less associated with Zn than Ca, in most soil samples. Therefore, it is more likely that Cd and Ca will be present in the same mineral phases rather than Cd and Zn, although the source of these two latter elements may originate from the same surrounding Zn mines in the Mae Sot district.
ISSN:0013-936X
1520-5851
DOI:10.1021/es103971y