Dissolution behavior of As and Cd in submerged paddy soil after treatment with stabilizing agents

doi:10.1016/j.geoderma.2015.11.036

Geoderma

Volume 270, 15 May 2016, Pages 10-20

https://doi.org/10.1016/j.geoderma.2015.11.036 Get rights and content

Highlights

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The dissolution behavior of Cd and As was verified in submerged paddy soil.
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Steelmaking slag and limestone were applied as the stabilization agent.
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Cd and As bound to Fe/Mn oxides were observed during column tests.
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Steelmaking slag was highly effective to stabilize As and Cd at soils.

Abstract

Steelmaking slag (SS) is an industrial byproduct generated through metal refining processes. It has been applied as an agent to stabilize farmland soils contaminated both by arsenic and heavy metals in the Republic of Korea. However, the efficacy of this technique has not been established yet under anoxic conditions such as in the case of submerged rice paddy fields. Under anoxic conditions, As might be dissociated easily from solid surfaces where it is adsorbed reversibly. In this study, laboratory-scale column tests were conducted to artificially manipulate anoxic conditions in submerged paddy fields and we observed the release behavior of As and heavy metals, mainly cadmium (Cd). Limestone (LS) was also applied in the test for the purpose of comparison because it is usually applied as a common additive. The leachate samples were collected and chemical changes were monitored during the test period. Results suggest that anoxic conditions were developed during submersion, and that As or heavy metal fractions bound to ferrous (Fe)/manganese (Mn) oxides were easily dissociated. However, it was also shown that SS and LS significantly decreased the dissolution of Cd and As in the pore water; their removal rates in the SS-treated soil were 87% and 32%, respectively, of those in the control soil. On the other hand it appeared that SS was more effective than LS to stabilize Cd as well as As under submerged conditions. Therefore, SS might be an optimal stabilizing agent for dealing with As and other heavy metal contaminants in rice paddy soils that are periodically exposed to reducing environments.

Introduction

According to the Korean Ministry of Environment (KMoE) (2008), a remedial investigation of the quality of farmland soils and water resources near abandoned metal mines (AMMs) in 2007–2009 found that 284 out of 310 investigated sites exceeded regulatory levels for heavy metals and metalloids.

Especially, such pollution problems of rice paddy fields are of serious concern in Asia as well as in the Republic of Korea, where rice is a staple crop and the principal source of dietary intake of these elements (Meharg et al., 2009, Zhang et al., 1999).

From 2008 to 2012, 48 feasibility studies and remedial actions (termed FS/RAs) were implemented in the Republic of Korea to rehabilitate or remediate farmlands contaminated by AMMs (MIRECO, 2012). In these FS/RAs, a sustainable framework for the remediation of contaminated farmland was required because farmers (or landowners) demanded the continuation of farming immediately after FS/RAs. Because of financial problems, a combination of both stabilization method and capping (covering) was selected to remediate contaminated farmland soils. Stabilization method is widely used to immobilize heavy metals, and often used to immobilize arsenic in soils (Bolan et al., 2003, Janoš et al., 2010, Jeon et al., 2010, Kaasalainen and Yli-Halla, 2003, Kim, 2010, Kumpiene et al., 2008, United States Environmental Protection Agency (U.S. EPA), 1).

Two kinds of stabilization agent have been primarily applied during remediation actions in the Republic of Korea; namely, limestone (LS) and steelmaking slag (SS). Limestone was a calcareous material like lime and usually applied to soils contaminated by heavy metals as an agent. Steelmaking slag is not usually applied to soils contaminated by heavy metals, but is preferentially used when targeting arsenic components (Mine Reclamation Crop, MIRECO, 2012).

On the other hand, arsenic usually co-exists with several heavy metals (i.e., Cd, Zn and Pb). Thus, an effective method to address both heavy metals and arsenic at once is required. SS contains various oxides, including 20–40% iron, 10% aluminum, 5–10% magnesium and manganese, < 2% sulfur and over 30% calcium. The adsorptive potential of iron oxides (as well as remaining metal ions) and iron oxide surfaces has been shown to be involved in the adsorption of arsenic from soils (Jacobs et al., 1970, Mench et al., 1998, Waychunas et al., 1993, Belluck et al., 2003). Yet, for the optimal adsorption of arsenic and heavy metals onto iron oxides simultaneously, Carabante et al. (2012) suggest that iron oxides should be added in combination with certain alkaline materials, such as lime or fly ash. Therefore, SS was expected to be an effective alternative for stabilizing soils containing complex mixtures of heavy metals with arsenic (Basta and McGowen, 2004, Hartley et al., 2004, Kumpiene et al., 2008, Lee et al., 2004).

However, the use of SS has not yet attracted enough attention for lack of research to verify its effectiveness on certain types of soils, such as those in rice paddy fields. The reducing and oxidizing state of the paddy system differs to other soil types because of the irrigation and drainage processes used during the cultivating season (leading to water levels varying by 10 times during cultivation). Therefore, the efficacy of SS as a stabilization agent should maintain their performance in the submerged paddy condition.

In this study, laboratory-scale column tests were conducted to verify the dissolution behavior of As and Cd with the treatment of stabilization agent, and to clarify the stabilization effects of SS on As and Cd when applied to submerged paddy condition.

Section snippets

Soil sampling

Soil samples were obtained from an agricultural field near an actual abandoned gold mine site in Kyeongbuk Province, Korea. The gold mine was established in 1936 and closed in 1992. The farmlands at the site (paddy) were left fallow from 2005 onward because of heavy metal contamination resulting from mining activities (Korea Ministry of Environment, KMoE, 2005). For the laboratory-scale column test, contaminated soil was sampled according to the Standard Method for Soil Pollution (Korea

Physicochemical properties of soil sampled

Table 3 shows physicochemical properties of the soil and the total Cd, Zn, Pb, and As contents. The Cd content of the soil was 4.53 mg kg^− 1, the Zn content was 344 mg kg^− 1, and the As content was 45.6 mg kg^− 1, all of which exceed the permitted soil quality level (Korea Ministry of Environment, KMoE, 2010a). The paddy soil was slightly acidic (pH 6.47) and moderately sandy with the following texture: 55% sand, 27% silt, and 18% clay. Such sandy paddies are relatively widely distributed in South Korea (

Conclusions

The results of this study revealed that the solubility of reducing materials, such as Mn and Fe, increases with the progress of the reducing conditions in the submerged paddy condition, insoluble heavy-metal components adsorbed to and precipitated with Fe–Mn oxides are eluted abruptly and temporally, and As is steadily increased in the forms that have high toxicity and mobility. Furthermore, it was verified that calcareous materials, limestone (LS) in this study, which contribute to the

Acknowledgments

This work (Grant no. C0189305) was supported by Business for Cooperative R&D between Industry, Academy, and Research Institute funded Korea Small and Medium Business Administration in 2014.

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Dissolution behavior of As and Cd in submerged paddy soil after treatment with stabilizing agents

Highlights

Abstract

Introduction

Section snippets

Soil sampling

Physicochemical properties of soil sampled

Conclusions

Acknowledgments

Soil Technol.

Environ. Pollut.

J. Hazard. Mater.

Soil Till Res.

Adv. Agron.

Environ. Pollut.

J. Hazard. Mater.

Geoderma

Environ. Pollut.

Geoderma

Waste Manag.

Chemosphere

Agric. Ecosyst. Environ.

Sci. Total Environ.

J. Geochem Explor.

Environ. Pollut.

Adv. Agron.

Geoderma

Hydrometallurgy

Appl. Geochem.

Geochim. Cosmochim. Acta

Anal. Chim. Acta

Toxicol. Lett.

Changes in chemical properties of paddy field soils as influenced by regional topography in Jeonbuk Province

Korean J. Soil Sci. Fert.

Rainwater chemistry at Mt. Etna (Italy): natural and anthropogenic sources of major ions

J. Atmos. Chem.

Analysis of acid-volatile sulfide (AVS) and simultaneously extracted metals (SEM) for the estimation of potential toxicity in aquatic sediments

Environ. Toxicol. Chem.

Concentration, pH, and surface charge effects on cadmium and lead sorption in three tropical soils

J. Environ. Qual.

Widespread arsenic contamination of soils in residential areas and public spaces: an emerging regulatory or medical crisis?

Int. J. Toxicol.