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Many studies have examined the application of soil amendments, including pH change-induced immobilizers, adsorbents, and organic materials, for soil remediation. This study evaluated the effects of various amendments on trace element stabilization and phytotoxicity, depending on the initial soil pH in acid, neutral, and alkali conditions. As in all types of soils, Fe and Ca were well stabilized on adsorption sites. There was an effect from pH control or adsorption mechanisms on the stabilization of cationic trace elements from inorganic amendments in acidic and neutral soil. Furthermore, acid mine drainage sludge has shown great potential for stabilizing most trace elements. In a phytotoxicity test, the ratio of the bioavailable fraction to the pseudo-total fraction significantly affected the uptake of trace elements by bok choy. While inorganic amendments efficiently decreased the bioavailability of trace elements, significant effects from organic amendments were not noticeable due to the short-term cultivation period. Therefore, the application of organic amendments for stabilizing trace elements in agricultural soil requires further study.

Indiscriminate overuse of liquid fertilizer and arsenic (As) contaminated soil by abandoned mines is one of the important environmental issues in Korea. This study was carried out to solve these two problems. Amendments (limestone, red mud and acid mine drainage sludge), liquid fertilizer and plant vegetation (Hairy vetch; Vicia villosa Roth) were simultaneously treated. Some soil chemical properties (pH, dissolved organic carbon, inorganic nitrogen content, and bioavailable As), soil respiration and enzyme activity (urease activity and dehydrogenase activity) were determined for chemical and biological assessment. Amendments decreased bioavailable As in soil, and acid mine drainage sludge had the best reduction efficiency in alkali soil. Liquid fertilizer affects not only soil chemical properties but also biological properties. Through multiple regression analysis, the rhizosphere effect through plant cultivation using specific root length index was reflected in the result of soil microbial and enzyme activity. In the reclamation of As-contaminated soil, the synergistic effect of multiple treatments could be confirmed. In particular, biological assessment indicators could be useful when evaluating the complex treatment of various restoration techniques, including the phytoremediation method. Based on these results, a long-term follow-up study on the field scale will be possible.

When applying an aided phytostabilization in trace-element-contaminated agricultural soil, the cultivation of forage crops instead of edible crops can reduce the trace elements transfer to humans while minimizing the income loss of farmers. The objectives of this study were to compare the effect of the type of forage crops at the "family" level (Poaceae and Leguminosae) on aided phytostabilization using physical (water stable aggregation), chemical (Mehlich-3 extraction), and biological assessments (dehydrogenase activity). Pig manure and acid mine drainage sludge were used as soil amendments, and four plant species (Loliummultiflorum Lam. var. italicum and Secalecereale L. [Poaceae representatives], Viciavillosa Roth, and Trifoliumpratense L. [Leguminosae representatives]) were cultivated after amendment treatments. Chemical assessment showed that the reduction in bioavailability of trace elements was partly observed in legume crops. The positive effects of plant cultivation were determined through physical assessment. The effectiveness of pig manure as an organic amendment was determined by biological assessment. In some treatments, the synergistic effect of the incorporation of chemical stabilization with both plant families was observed but it was difficult to identify a clear distinction between the two families. The translocation of trace elements from root to shoot was low in all plants, indicating that the cultivation of the plants used in this study is safe with regards to the spread of trace elements into the environment. The results suggest that forage crop cultivation in contaminated agricultural soil could ameliorate soil quality after chemical stabilization.

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