The Effect of Amendments On Stabilizations of Pb, Zn, and As In Contaminated-Upland Soils.

Although many agricultural areas are contaminated by toxic metals, those are still used to crop production. These produced crops are ones of the main exposure pathways of toxic metals to human. The applications of amendments into contaminated soils are environmental-friendly and cost-effective techniques for in situ chemical stabilization of toxic metals. Restorations by pH change in metals and metalloid co-contaminated areas could be occurring improve As mobility. For evaluating the effect of three amendments (dolomite, DOL; agricultural lime, AL; and steel slag; SS) on stabilizations of Pb, Zn, and As, the experimental plot installed in cultivated upland soils. Those areas were found to be heavily contaminated by Pb, Zn, and As (4265.16, 498.76, 993.48 mg kg^-1, respectively). Nine months after amendments treatment, red pepper and spring onion successively cultivated in the prepared experimental plots. We assessed NH₄NO₃-extractable concentrations and total concentrations of those in soils and shoots of plants, respectively. Most of amended soils significantly increased soil pH (p < 0.05). Soil pH increased from 6.59 to approximately 8.25, 7.66, and 8.21 in DOL-, AL-, and SS-amended soils, respectively. The amount of NH₄NO₃-extractable Pb and Zn was reduced, but As was increased than reduced in all amended-soils. However, concentrations of not only Pb, Zn but also As in plant shoot were decrease except for As in AL-amended soils. The results of 1 M NH₄NO₃ extraction method were showed similar trends with concentration of plant uptake only in cationic metals. However increasing of soil pH cannot lead to increase the As concentration in plant shoot. Increasing exchangeable Ca in amended soil might be forms Ca-Arsenate precipitation, this is one of the reasons why the concentration plant uptake As was decreased. This suggested that Ca-reached, and pH increasing amendment can be applied in multi-elements contaminated farm land for production of safe vegetables.