Dynamics of cadmium concentration in contaminated rice paddy soils with submerging time
Journal
Paddy and Water Environment
Journal Volume
11
Journal Volume
11
Journal Issue
1-4
Journal Issue
1-4
Pages
483-491
Start Page
483
End Page
491
ISSN
16112490
Date Issued
2013-01
Author(s)
Abstract
This study examined the change in the speciation of cadmium (Cd) in contaminated rice paddy soils with prolonged submergence. Three Changhua soils (CH1, CH2, and CH3) from central Taiwan and three Taoyuan red soils (TY1, TY2, and TY3) from northern Taiwan with different levels of heavy metal contamination were selected for the study. The Cd, Fe, Mn, soil pH, and Eh in soil solutions were determined as a function of submerging time. During submergence, the Fe and Mn concentration increased, while the SO42- concentration decreased. The concentrations of Cd immediately increased in the soil solutions after a short submerging time and then decreased with further submergence. The sequential extraction showed that the exchangeable fraction decreased and the oxide-bound fraction increased after submergence. According to preliminary calculations of the MinteqA2 program, sulfate cannot be reduced to sulfite or sulfide under the soil Eh and pH values observed for the soils after prolonged submergence. Thus, the observed decreases of sulfate concentration may result from sulfate reduction in the micro-environments, which cannot be accounted for by the thermodynamic calculation. The reduction of sulfate to sulfide may subsequently result in the formation of CdS precipitate, which attributes to the decreases of Cd concentrations in the soil solutions after prolonged submergence.
Subjects
Cadmium
Flooding incubation
Paddy soils
Soil redox potential
Speciation
SDGs
Publisher
Springer Verlag
Type
journal article