| مستخلص: |
AbstractMicrobially induced calcium carbonate precipitation (MICP) has been proposed as an environmentally friendly method for immobilizing heavy metals (HMs). However, the stability of immobilized HMs through MICP may be affected by fertilization, potentially leading to the re-release of HMs. This study aimed to investigate the effect of diammonium hydrogen phosphate (DAP) fertilizer on the stability of immobilized zinc (Zn) following the MICP process. Zn was initially immobilized in contaminated soil using the biologically produced (MICP) and 50 g kg−1 chemical calcium carbonate (CaCO3). Untreated contaminated soil was regarded as control (C). After 7 d, DAP fertilizer was added to half of the replications of previously treated samples to investigate the fertilization effect on the stability of immobilized Zn. The soil soluble-exchangeable and carbonate fractions of Zn and the soil available phosphorus were measured in fertilized and unfertilized treatments at 0, 7, 14, 21, and 28 days of incubation. After 7 d of incubation, the amount of the soil soluble-exchangeable fraction of Zn decreased in the MICP and CaCO3 treatments compared to the C, while a significant increase in the soil carbonate fraction of Zn was observed (p ≤ .05). In the fertilized C treatment, the soil soluble-exchangeable fraction of Zn decreased by 30.12% at the end of the incubation period rather than on the 7th day. However, fertilization in the MICP and CaCO3 treatments increased the soluble-exchangeable fraction of Zn. Additionally, fertilization led to a significant increase in the soil soluble-exchangeable fraction of Zn in the CaCO3 treatment compared to the MICP treatment. At the end of the incubation, the soil carbonate fraction of Zn in the fertilized C, MICP, and CaCO3 treatments decreased by 43.5%, 35.2%, and 39%, respectively. The soil available phosphorus in the MICP and CaCO3 treatments decreased during incubation due to the formation of calcium phosphate and Zn-phosphate precipitates. The results suggested that the MICP process can effectively immobilize HMs in contaminated soils, even in the presence of phosphorus fertilizers. Nevertheless, it is essential to evaluate the stability of HMs immobilized by MICP after fertilization to prevent the potential risk of HMs re-releasing into the environment. [ABSTRACT FROM AUTHOR] |