Abstract:

To explore the role of soil enzymes and pH in the degradation of tetracycline in Microbial Electrochemical Systems (MES), four types of soils including black soil, moisture soil, yellow brown soil and red soil were collected for study. The results showed that after adding tetracycline (TN treatment, 10 mg/kg) to black soil, moisture soil and red soil, the values of pH increased by 0.08, 0.15 and 1.09 units respectively compared with the control treatment (CK, without tetracycline addition). However, in MES treatment (TC, tetracycline concentration 10 mg/kg), the values of pH in the four types of soil all showed downward trend. Although the soil dehydrogenase, urease and polyphenol oxidase activities exhibited different variation trends in tetracycline contaminated soil, their activities in MES increased by 62.4%-72.1%, 11.3%-80.9% (except red soil) and 12.6%-42.6% compared with TN treatment, respectively. Meanwhile, the degradation rate of tetracycline in TC treatment was respectively increased by 14% (black soil), 26% (moisture soil), 26% (yellow brown soil) and 17% (red soil) compared with TN treatment. Correlation analysis indicated that dehydrogenase activity showed significant positive correlation with tetracycline degradation rate, while pH showed significant negative correlation with degradation rate, indicating that dehydrogenase might participate in the process of tetracycline degradation, and acidic conditions may be more conducive to degradation. This experiment revealed the degradation mechanism of tetracycline by MES based on soil biochemical characteristics, which could provide important support for soil pollution remediation.

Key words: microbial electrochemical system, different types of soil, tetracycline, pH, enzyme activity