Article pubs.acs.org/JAFC
In Situ Evaluation of Crop Productivity and Bioaccumulation of Heavy Metals in Paddy Soils after Remediation of MetalContaminated Soils Shin Woong Kim,∥,† Yooeun Chae,∥,† Jongmin Moon,† Dokyung Kim,† Rongxue Cui,† Gyeonghyeon An,§ Seung-Woo Jeong,§ and Youn-Joo An*,† †
Department of Environmental Health Science, Konkuk University, Seoul 05029, Korea Department of Environmental Engineering, Kunsan National University, Kunsan 54150, Korea
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S Supporting Information *
ABSTRACT: Soils contaminated with heavy metals have been reused for agricultural, building, and industrial uses following remediation. This study assesses plant growth and bioaccumulation of heavy metals following remediation of industrially contaminated soil. The soil was collected from a field site near a nonferrous smelter and was subjected to laboratory- and fieldscale studies. Soil from the contaminated site was remediated by washing with acid or mixed with soil taken from a distant uncontaminated site. The activities of various soil exoenzymes, the rate of plant growth, and the bioaccumulations of six heavy metals were measured to assess the efficacy of these bioremediation techniques. Growth of rice (Oryza sativa) was unaffected in acid-washed soil or the amended soil compared to untreated soil from the contaminated site. The levels of heavy metals in the rice kernels remained within safe limits in treated and untreated soils. Rice, sorghum (Sorghum bicolor), and wheat (Triticum aestivum) cultivated in the same soils in the laboratory showed similar growth rates. Soil exoenzyme activities and crop productivity were not affected by soil treatment in field experiments. In conclusion, treatment of industrially contaminated soil by acid washing or amendment did not adversely affect plant productivity or lead to increased bioaccumulation of heavy metals in rice. KEYWORDS: soil remediation, contamination, heavy metal, amendment, rice, field study
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INTRODUCTION Although mining industries yield many vital products for human use, they also result in significant environmental problems.1,2 Mining and smelting activities cause long-term contamination of surrounding soils, streams, and groundwater with heavy metals,3,4 necessitating remediation before such sites can be used for other purposes.5,6 Abandoned mines and smelters are also sources of pollution of terrestrial and aquatic ecosystems,7−9 and the soils and soil ecosystems surrounding them are typically contaminated with heavy metals.10 These contaminated soils can be remediated by a range of physicochemical techniques such as soil washing, electrokinetic remediation, solidification, or stabilization before being repurposed as agricultural or industrial land. 11−13 However, many of these remediation techniques, especially acid washing, can reduce the health and productivity of the soil14−16 and result in secondary contamination through desorption of heavy metals from soil particles.17,18 Additionally, acid washing is fatal to organisms in the soil ecosystem because it induces highly acidic conditions that disrupt the balance of the soil ecosystem. Moreover, acid washing changes the chemical and physical structure of the soil due to mineral dissolution.14 These changes can render the soil unsuitable for plant and animal life. Previous studies have reported that acid-washed soils are unsatisfactory in terms of productivity or crop safety.19−21 In the present study, we assessed the productivity of rice (Oryza sativa), a staple food throughout the world, and the safety of food © 2017 American Chemical Society
products from these plants after growth in contaminated soils following remediation or amendment. We investigated the effects of the soil remediation treatments in laboratory and field experiments.
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MATERIALS AND METHODS
Target Site Description and Soil Characterization. In situ experiments were carried out in village A (36°00′48″ N, 126°39′56″ E) located in western Korea (Figure 1A). Target sites were located near a closed nonferrous metal smelter and contained soils that were contaminated with residual heavy metals. Contaminated soil was collected from the target site and treated with acid (0.5 M H2SO4 and 0.5 M H3PO4). After acid cleaning, soil particles of different sizes were separated, and those of
