TY - JOUR
T1 - An improved selective extraction method for Mn oxides and occluded metals with emphasis on applicability to Andisols
AU - Suda, Aomi
AU - Makino, Tomoyuki
AU - Higashi, Teruo
N1 - Funding Information:
We thank S. Ono, K. Kamewada (Tochigi Prefecture Agricultural Experiment Station), A. Aoki (Tochigi Prefecture Agricultural Experiment Station) and Y. Nagasaki (National Agricultural Research Center for the Western Region) for soil sampling. We also thank J. Takahashi (University of Tsukuba) for providing some of the soil samples used in this study and for providing physicochemical data for some of the samples. We thank Y. Maejima, I. Akahane (both at the National Institute for Agro-Environmental Sciences) and K. Tamura (University of Tsukuba) for helpful comments. This work was partly supported by a Grant-in-Aid for Research Fellows of the Japan Society for the Promotion of Science (No. 23–444).
PY - 2013
Y1 - 2013
N2 - It has been showed that Chao's method [extraction with 0.1 mol L-1 hydroxylamine hydrochloride (NH2OH-HCl) at pH 2.0 for 30 min], which is commonly used to extract manganese (Mn) oxides and occluded heavy metals from soil samples, is not suitable for Andisols because of low solubility, and thus low extractability, of Mn oxides in such soils. Therefore, a new method is evaluated here, for extracting Mn oxides and occluded heavy metals from Andisols, Entisols and Inceptisols. The method has three steps: (1) reduction of Mn oxides with 0.01 mol L-1 NH2OH-HCl (pH 5.0) for 16 h, (2) recovery of re-adsorbed metals by short-time extraction with 0.5 mol L-1 ammonium chloride in 0.02 mol L-1 hydrochloric acid, and (3) washing with ultrapure water. This method achieves a higher rate of extraction of Mn oxides than does Chao's method, especially from Andisol samples. Standard addition experiments showed that both the new method and Chao's method can successfully extract released cadmium (Cd), cobalt (Co), nickel (Ni) and zinc (Zn) from Mn oxides with little re-adsorption. The selectivity of Mn oxide extraction by the new method, indicated by the rate of extraction of iron (Fe) oxides and the aluminum (Al)/Mn and silicon (Si)/Mn extraction ratios, is comparable to that of Chao's method. Thus, the new method should be useful for extracting Mn oxides and occluded Cd, Co, Ni, and Zn from soil samples. Moreover, because the new method achieved nearly complete extraction of NH2OH-HCl reactive Mn oxides even from Andisol samples, the method is more applicable to Andisol samples than Chao's method.
AB - It has been showed that Chao's method [extraction with 0.1 mol L-1 hydroxylamine hydrochloride (NH2OH-HCl) at pH 2.0 for 30 min], which is commonly used to extract manganese (Mn) oxides and occluded heavy metals from soil samples, is not suitable for Andisols because of low solubility, and thus low extractability, of Mn oxides in such soils. Therefore, a new method is evaluated here, for extracting Mn oxides and occluded heavy metals from Andisols, Entisols and Inceptisols. The method has three steps: (1) reduction of Mn oxides with 0.01 mol L-1 NH2OH-HCl (pH 5.0) for 16 h, (2) recovery of re-adsorbed metals by short-time extraction with 0.5 mol L-1 ammonium chloride in 0.02 mol L-1 hydrochloric acid, and (3) washing with ultrapure water. This method achieves a higher rate of extraction of Mn oxides than does Chao's method, especially from Andisol samples. Standard addition experiments showed that both the new method and Chao's method can successfully extract released cadmium (Cd), cobalt (Co), nickel (Ni) and zinc (Zn) from Mn oxides with little re-adsorption. The selectivity of Mn oxide extraction by the new method, indicated by the rate of extraction of iron (Fe) oxides and the aluminum (Al)/Mn and silicon (Si)/Mn extraction ratios, is comparable to that of Chao's method. Thus, the new method should be useful for extracting Mn oxides and occluded Cd, Co, Ni, and Zn from soil samples. Moreover, because the new method achieved nearly complete extraction of NH2OH-HCl reactive Mn oxides even from Andisol samples, the method is more applicable to Andisol samples than Chao's method.
KW - Andisols
KW - heavy metals
KW - iron oxide
KW - manganese oxide
KW - selective dissolution
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U2 - 10.1080/00380768.2013.857580
DO - 10.1080/00380768.2013.857580
M3 - Article
AN - SCOPUS:84890420466
VL - 59
SP - 840
EP - 851
JO - Soil Science and Plant Nutrition
JF - Soil Science and Plant Nutrition
SN - 0038-0768
IS - 6
ER -