[Application of Fe3[KG-*2/5]O4/Mulberry Stem Biochar Effects on Soil Arsenic Species and Rice Arsenic Content].

The passivation effect of Fe3O4/mulberry pole biochar (Fe-MBC) prepared at different carbonization temperatures on soil available arsenic content was studied through soil culture experiments, and Fe-MBC-800 (prepared by carbonization at 800℃) with good passivation effect was selected and characterized. The effects of 1%-7% (mass fraction of biochar to soil) Fe-MBC-800, MBC-800, and Fe3O4 on soil pH value, soil electrical conductivity, soil arsenic form, rice biomass, and total arsenic (As) content in rice were studied using a pot experiment. The results showed that:①Fe-MBC-800 successfully loaded Fe3O4, and its main functional groups were C=O double bond, O-H bond, C-O bond, and Fe-O bond. The specific surface areas of Fe-MBC-800, MBC-800, and Fe3O4 were 209.659 m2·g-1, 517.714 m2·g-1, and 68.025 m2·g-1, respectively. ②The addition of Fe-MBC-800 could increase the soil pH value, decrease the soil EC value, increase the content of residual arsenic in soil, and reduce the content of water-soluble arsenic and available arsenic in the soil. Under the treatment using 7% Fe-MBC-800 (ω) amendments, the content of water-soluble arsenic and available arsenic in the soil decreased by 81.6% and 56.33%, respectively. ③When the addition ratio of Fe-MBC-800 in the soil was 5%-7%, it could promote the growth of rice plants, increase rice biomass, and reduce the bioaccumulation of arsenic by between 62.5% and 68.75%.

[Preparation of Magnetic Iron Oxide/Mulberry Stem Biochar and Its Effects on Dissolved Organic Carbon and Arsenic Speciation in Arsenic-Contaminated Soils].

In this study, original mulberry-biochar (M-BC) and magnetic iron oxide/mulberry stem biochar (Fe-BC) materials were prepared and characterized using mulberry stems as the raw material. The effects of carbonized temperature of Fe-BC and M-BC on dissolved organic carbon (DOC) and arsenic(As) speciation in soil leaching solutions were studied using soil incubation experiments. The results showed that:① Fe-BC was mainly composed of Fe3O4 and was magnetic, and the main functional groups were a C＝O double bond, O-H bond, C-O bond, and Fe-O bond. The point of zero charge values (pHzpc) of Fe-BC-400, Fe-BC-500, and Fe-BC-600 were 8.92, 8.74, and 9.19, respectively, and the specific surface areas of Fe-BC-400, Fe-BC-500, and Fe-BC-600 were 447.412, 482.697, and 525.708 m2·g-1, respectively. ② With the increase in the carbonization temperature of M-BC and Fe-BC, the ρ(DOC) of soil leaching solution decreased 11.6-315.6 mg·L-1 and 78-365.6 mg·L-1, respectively. The DOC concentration of soil leaching solution was negatively correlated with soil EC. On day 35 of the incubation experiments, compared with that in soil after incubation without biochar (control), the As concentration of the soil leaching solution with Fe-BC-600 decreased by 55.96%, and there was no significant correlation between the As concentration of the soil leaching solution and the DOC concentration of the soil. ③ The available As concentration on day 35 in soil after incubation with Fe-BC was lower than that of the control group; the available As concentration on day 35 in soil incubated with Fe-BC-600 was reduced by 39.21%. ④ The residue As concentration on day 35 in soil incubated with M-BC decreased by 17.76%-49.11%. The residue As content on day 35 in soil incubated with Fe-BC-600 increased by 80%. Fe-BC-600 was most beneficial to reduce the DOC concentration and the available As content in soil leaching solution and increased the residue As content, thus reducing the bioavailability of soil arsenic. Therefore, this study can provide a theoretical basis for magnetic iron oxide/biochar remediation in arsenic-contaminated soil.