Extractability of manganese and iron oxides in typical Japanese soils

Soil Science and Plant Nutrition

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Extractability of manganese and iron oxides in −1 typical Japanese soils by 0.5 mol L hydroxylamine hydrochloride (pH 1.5) Aomi Suda , Tomoyuki Makino & Teruo Higashi To cite this article: Aomi Suda , Tomoyuki Makino & Teruo Higashi (2012) Extractability −1

of manganese and iron oxides in typical Japanese soils by 0.5 mol L hydroxylamine hydrochloride (pH 1.5), Soil Science and Plant Nutrition, 58:6, 684-695, DOI: 10.1080/00380768.2012.742002 To link to this article: http://dx.doi.org/10.1080/00380768.2012.742002

Published online: 13 Dec 2012.

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Date: 21 May 2016, At: 04:53

Soil Science and Plant Nutrition (2012), 58, 684—695

http://dx.doi.org/10.1080/00380768.2012.742002

ORIGINAL ARTICLE

Extractability of manganese and iron oxides in typical Japanese soils by 0.5 mol L1 hydroxylamine hydrochloride (pH 1.5) Aomi SUDA1, Tomoyuki MAKINO2 and Teruo HIGASHI3

Downloaded by [Indira Gandhi Krishi Vishwavidyalaya ] at 04:53 21 May 2016

1

JSPS Research Fellow (DC2), Graduate School of Life and Environmental Sciences, University of Tsukuba, Tennoudai 1-1-1, Tsukuba, Ibaraki 305-8572, Japan, 2National Institute of Agro-Environmental Sciences, Kannondai 3-1-3, Tsukuba, Ibaraki 3058604, Japan and 3Graduate School of Life and Environmental Sciences, University of Tsukuba, Tennoudai 1-1-1, Tsukuba, Ibaraki 305-8572, Japan

Abstract We investigated the extractability of manganese (Mn) and iron (Fe) oxides from typical Japanese soils (Entisols, Inceptisols, and Andisols) by 0.5 mol L1 hydroxylamine hydrochloride (NH2OH-HCl) extraction (pH 1.5; 16 h shaking at 25 C; soil:solution ratio 1:40), referred as to HHmBCR, which is Step 2 (used for the reducible fraction) of the modified BCR (Community Bureau of Reference) sequential extraction procedure. The HHmBCR procedure extracted almost all Mn oxides from the non-Andisol samples, but failed to extract a part of the Mn oxides from some Andisol samples. The procedure extracted most short-range ordered Fe oxides from non-Andisol samples, but it extracted only 7.5% and 13% of the short-range ordered Fe oxides from allophanic and non-allophanic Andisol samples, respectively. This remarkably low extractability of Fe oxides suggests that the HHmBCR method is not suitable for extracting oxide-occluded heavy metals from Andisols. Since the extraction rate of short-range ordered Fe oxides from various soils with the extractant was negatively correlated with the amounts of oxalate- and pyrophosphate-extractable Al even when the variability of the extraction pH was reduced by increasing the soil:solution ratio from 1:40 to 1:500, the extractability of Fe oxides would be negatively affected by the presence of active Al, including allophane/ imogolite, amorphous Al, and Al-humus complexes. Because these Al constituents are abundant in Andisols, they would be at least partially responsible for the lower extractability of Fe oxides by HHmBCR from Andisols. Key words: aluminum, Andisols, extraction method, iron oxides, manganese oxide.

INTRODUCTION Manganese (Mn) and iron (Fe) are important plant nutrients and are involved in redox phenomena and heavy metal dynamics in soils. In soil environments, Mn and Fe exist predominantly as oxides (including oxyhydroxides and hydrated oxides). Mn oxide minerals such as birnessite, vernadite, and lithiophorite scavenge heavy metals in soils by adsorbing them on the mineral surface or incorporating them into the crystal lattice by Correspondence: Aomi SUDA, University of Tsukuba, Tennoudai 1-1-1, Tsukuba, Ibaraki 305-8572, Japan. Tel: þ81-29-853-4621. Fax: þ81-29-853-4605. Email: [email protected] Received 23 November 2011. Accepted for publication 16 October 2012. ß 2012 Japanese Society of Soil Science and Plant Nutrition

isomorphic substitution (Miyata et al. 2007). Hematite, goethite, and ferrihydrite are well-known Fe oxide minerals in soils that have a strong ability to retain heavy metals (Shuman 1985). Barium (Ba), cobalt (Co), and lead (Pb) are predominantly associated with Mn minerals, whereas phosphorus (P), arsenic (As), and chromium (Cr) are more likely to be fixed in Fe oxides (Neaman et al. 2004a, 2008). These oxide-occluded heavy metals in Mn and Fe oxides, which constitute a large fraction of the total contents of heavy metals (Tessier et al. 1979), are released into soil solution by dissolution of the oxides. Therefore, they are potentially available to plants. Various methods for extraction of oxide-occluded metals have been developed to examine metal speciation in soils and sediments and to determine the plant


Extraction of Fe and Mn oxides from soils

availability of the metals. Most of the methods use hydroxylamine hydrochloride (NH2OH-HCl) or oxalate solutions to dissolve Mn and Fe oxides and extract the oxide-occluded heavy metals. For example, Tessier et al. (1979) used 0.04 mol L1 NH2OH-HCl with 25% acetic acid to extract both amorphous and crystalline Mn and Fe oxides, and Chao (1972) used 0.1 mol L1 NH2OHHCl (pH 2.0) to selectively extract Mn oxides from soils. Mixtures of 0.1 mol L1 oxalic acid and 0.175 mol L1 ammonium oxalate solutions (pH 3.25; Miller et al. 1986) and mixtures of 0.2 mol L1 ammonium oxalate (pH 3.25) and 0.1 mol L1 ascorbic acid solutions (Wilcke et al. 1998) have been used to extract amorphous Fe oxides and total Fe oxides, respectively. Dithionite-citrate has also been used to extract both crystalline and amorphous Fe oxides from soils (McKeague and Day 1966). However, this method suffers from the fact that zinc impurities are present in dithionite; in addition, the target elements can precipitate as sulfides or sulfates (Gleyzes et al. 2002). These methods for the extraction of oxide-occluded metals from Mn and Fe oxides in soils have been used in sequential procedures for extraction of trace elements from soils and sediments. Since 1987, the Community Bureau of Reference (BCR) has developed a sequential extraction procedure (BCR method) to harmonize and standardize sequential extraction schemes. The original BCR method was further optimized by Sahuquillo et al. (1999), and the three-step modified BCR (mBCR) method is now one of the most commonly used sequential extraction procedures (Bacon and Davidson 2008). This indicates that the 0.5 mol L1 NH2OH-HCl (pH 1.5) method which was adopted to extract heavy metals in the reducible fraction of mBCR method is currently the most important extraction method for heavy metals from Mn and Fe oxides in soils. This extraction procedure targets metals occluded in Fe and Mn oxyhydroxides, and the amount of Fe extracted is less than the amount of oxalate-extractable Fe (Davidson et al. 2004); however, the results vary greatly among samples. Adoption of the standardized mBCR method for fractionation of heavy metals might be desirable to increase the comparability of data among studies. However, the procedure’s ability to extract Mn and Fe oxides and oxide-occluded heavy metals from Japanese soils has not been fully assessed. This is a potential problem for the Andisols that cover about half of the total land area of upland agricultural fields in Japan. Because of their nature, these soils may require special consideration when the mBCR method is used to extract oxide-occluded metals. Suda et al. (2011) reported that Mn and Fe oxides in Andisol samples were less extractable with 0.1 mol L1 NH2OH-HCl (pH 2.0) than oxides in other Japanese soils, but the mechanisms responsible

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for this reduced extractability have not been investigated thoroughly. Lee et al. (1989) showed that the amounts of Fe extractable with 0.25 mol L1 NH2OH-HCl in 0.25 mol L1 HCl were comparable to those extractable with oxalate even from Andisol samples. However, the ability of NH2OH-HCl to extract Fe and Mn oxides seems to depend on the extraction conditions and the soil properties. Therefore, the objective of the present study was to evaluate the applicability of the extraction method to typical Japanese soils by investigating the extractability of Mn and Fe oxides in Andisols and other major Japanese soil types with acidified 0.5 mol L1 NH2OHHCl (pH 1.5).

MATERIALS AND METHODS Soil samples Twenty-eight soil samples were collected from agricultural and forest areas in Japan (Table 1). Almost half of the soil samples were either allophanic Andisols (AA) or non-allophanic Andisols (NA), and the others were Entisols (E) or Inceptisols (I). The soil samples were air dried and passed through 2-mm mesh sieves before analysis. For Experiment 1, we selected five non-Andisol samples that were less affected by volcanic ash [i.e., low contents of oxalate-extractable aluminum (Al) (Alo) and pyrophosphate-extractable Al (Alp)] and four allophanic and four non-allophanic (Alp/Alo > 0.5) Andisol samples (samples E-1, E-2, E-8, I-1, I-2, AA-1, AA-2, AA-3, AA-7, NA-2, NA-3, NA-4, and NA-6). For Experiment 2, we used all of the samples listed in Table 1.

Methods of analysis of soil properties Soil pH was measured in H2O and in 1 mol L1 potassium chloride (KCl) with a glass electrode pH meter, after adjusting the ratio of soil sample to liquid to 1:2.5 weight/volume (w/v). Total carbon (C) content of the soil samples was measured by a dry combustion method (Sumigraph NC-22 F, SCAS, Osaka, Japan). Dithionite-citrate-extractable Fe (Fed) and ammoniumoxalate-extractable Al, Fe, Mn, and silicon (Si) (Alo, Feo, Mno, and Sio) were extracted as described by Blakemore et al. (1987). Pyrophosphate-extractable Al and Fe (Alp and Fep) were extracted and centrifuged as described by Blakemore et al. (1987), and then the supernatants were filtered through a 0.025-mm filter to minimize the contamination of Fe from dispersed microcrystalline minerals (Schuppli et al. 1983). The elements in all of these extracts were determined by inductively coupled plasma-optical emission spectrometry (ICP-OES; VistaPro, Varian, Palo Alto, California, USA). The clay

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Table 1 Selected information on the soil samples Sample numbery

Soil orderz

Horizon

E-1 E-2 E-3 E-4 E-5 E-6 E-7 E-8 I-1 I-2 I-3 I-4 I-5 I-6 AA-1 AA-2 AA-3 AA-4 AA-5 AA-6 AA-7 NA-1 NA-2 NA-3 NA-4 NA-5 NA-6

Entisols Entisols Entisols Entisols Entisols Entisols Entisols Entisols Inceptisols Inceptisols Inceptisols Inceptisols Inceptisols Inceptisols Andisols Andisols Andisols Andisols Andisols Andisols Andisols Andisols Andisols Andisols Andisols Andisols Andisols

Ap Ap Ap Ap Ap Ap Ap C Ap Ap Ap Bw Bw Bw Ap Ap A Bw Bw Bw Bw A O A A O 2A

Site City, Prefecture

Land use

Suzaka, Nagano Zentsuji, Kagawa Tochigi, Tochigi Kitamoto, Saitama Kamikawa, Hokkaido Fukuyama, Hiroshima Zentsuji, Kagawa Shibata, Niigata Natori, Miyagi Zentsuji, Kagawa Kanuma, Tochigi Natori, Miyagi Katsuyama, Fukui Chichibu, Saitama Tsukuba, Ibaraki Shimono, Tochigi Kitamoto, Saitama Katsuyama, Fukui Tateyama, Toyama Tsukuba, Ibaraki Chichibu, Saitama Oshaki, Miyagi Katsuyama, Fukui Tateyama, Toyama Tateyama, Toyama Chichibu, Saitama Hodatsushimizu, Ishikawa

Paddy field Paddy field Upland field Fallow field Upland field Paddy field Upland field Paddy field Upland field Upland field Upland field Upland field Forest Forest Upland field Upland field Forest Forest Forest Upland field Forest Forest Forest Forest Forest Forest Forest

yE, I, AA and NA represent Entisols, Inseptisols, Allophanic Andisols and Non-allophanic Andisols, respectively. zAccording to USDA Soil Taxonomy (Soil Survey Staff 1998).

contents (