Comparison of characteristics of biochar modified by earthworm and potassium permanganate

Abstract

Biochar has is widely used for environmental remediation, carbon sequestration and crop growth promotion. However, its limited effects are becoming increasingly apparent, therefore, it is necessary to modify biochar to enhance its effects. Earthworms are important biological components of soil, and their daily activities impact the soil environment. However, the effects of earthworm modification of biochar are not clearly understood. Earthworms were placed in straw charcoal (CSBC) and fruit charcoal (FCBC) and cultured for 30 days to prepare earthworm-modified biochar (EW-CSBC and EW-FCBC). Potassium permanganate was also used to modify biochar (MnOx-CSBC and MnOx-FCBC). The effects of biochar modification were analyzed by comparing the properties of unmodified and modified biochars. The results of Fourier transform infrared spectrometer and X-ray diffraction showed that the number of functional groups (-OH, -NH, C-H, C=C, and C=O) and elemental composition (SiO2 and CaCO3) of biochar modified by EW and MnOx significantly increased. Field emission scanning electron microscopy results showed tube wall rupture, collapse, and increased pore size in biochars modified by MnOx and EW. Meanwhile, the specific surface areas of CSBC and FCBC significantly decreased. Functional Annotation of Prokaryotic Taxa function prediction showed an increase in the relative abundance of chemoheterotrophy and aerobic_chemoheterotrophy functions of EW biochar, which can participate in the carbon cycle of biochar. In summary, the excellent effects of earthworm-modified biochar can play a key role in future ecological environments.