Korean Journal of Soil Science and Fertilizer ISSN:0367-6315(Print) 2288-2162(Online) 한국토양비료학회 학회지

Many soil amendments are used to remediate paddy soils polluted with heavy metals, including arsenic (As) and lead (Pb). This study was conducted to assess the efficacy of three inorganic soil amendments, such as calcium carbonate (CaCO₃), calcium sulfate (CaSO₄), and ferrous sulfate (FeSO₄), on As and Pb co-contaminated paddy soils. The amendments were applied alone and/or in combinations to compare theirs efficacy for the As and Pb stabilization and the rice growth. In addition, two single extraction methods, 1 M ammonium nitrate (NH₄NO₃) and Mehlich-3, were used to assess the effects on As and Pb immobilization using amendments. The alone (CaSO₄ and FeSO₄) and combined (CaCO₃ + CaSO₄, FeSO₄ + CaCO₃, FeSO₄ + CaSO₄) amendment treatments significantly decreased the extractable As concentrations in NH₄NO₃ and Mehlich-3 extraction of the treated soil. Furthermore, FeSO₄ alone treatment indicated the maximum reduction of the extractable As concentration in Mehlich-3 extraction of the treated soil. The extractable Pb concentrations by FeSO₄ alone treatment were significantly increased in both extractions of the treated soil, but no significant differences were observed in CaSO₄ alone and combined amendment treatments, relative to the concentrations in the untreated soils (As and Pb co-contaminated paddy soils). Shoot dry weight (DW) of rice plants slightly decreased with the application of alone and combined amendments compared with that of the untreated soils. However, As concentrations in the leaf sheath of rice plants were reduced 21 - 41% by the alone and combined amendment treatments, but no significant difference was observed in the leaf blade relative to the untreated control. On the other hand, Pb concentration in the rice plants with FeSO₄ + CaSO₄ (1:1) treatment significantly increased in the leaf sheath and leaf blade, but no significant differences were observed in all organs with other amendments compared with the untreated control. Therefore, FeSO₄ can be applied to a feasible approach for alleviating As stress in rice plants and reducing the affect of the As accumulation of As and Pb co-contaminated paddy soils.

As (A and B) and Pb (C and D) concentration in the soils with the extracting solution of Mehlich3 as affected by CaSO₄, FeSO₄, CaCO₃ + CaSO₄ (1:1), FeSO₄ + CaCO₃ (1:1), FeSO₄ + CaCO₃ (2:1), and FeSO₄ + CaSO₄ (1:1), treated before transplanting rice seedlings. The Mehlich3-extractable As and Pb concentration in soil were measured at 6 and 12 weeks after transplant (WAT) of rice seedlings, respectively. Means denoted by the same letter are not significantly different at the p < 0.05 level according to Fisher’s least significant difference (LSD) test.