Preparation Of ¹⁴C-Labelled Natural Organic Matter And Tetrabromobisphenol A (TBBPA) And Their Degradation And Transformation In Soil

Radioisotope tracer technique is a technology that can be applied to study the movement and change of tracer atoms of one compound to show the transformation of this compound. By using this technique one can accurativly and sensitively monitor transformation and degradation of organic compounds in environmental medium. In this thesis, we synthesized labeled compounds, i.e. Soil Organic Matter (14C-SOM) and Tetrabromobisphenol A (14C-TBBPA), and studied their degradation and transformation in soil.Soil organic matter plays an important role in global carbon cycle; small changes of the soil carbon pool can significantly affect the atmospheric CO2 concentration. Soil macrofauna are key organisms controlling soil carbon stability. Using 14C-labelled SOM of microbial origin, which was prepared from long-term humification of 14C-glucose in soil, we studied mineralization and distribution of the 14C-SOM in two soils in presence and absence of the geophagous earthworm Metaphire Guillelmi and in earthworm-free cast, as well as incorporation of 14C-SOM into earthworm body. In presence of the earthworm, the mineralization of the 14C-SOM was significantly stimulated within 15 days of incubation at 20℃in two soils, about 1.5-and 1.7-fold of the mineralization in the earthworm-free control soils, respectively. However, when the earthworm was removed from the soil, the mineralization of the residual 14C-SOM was lower than in the control soils within further 40 days of incubation. About 4.2-4.8% of the initial 14C-SOM was incorporated into the earthworm tissue. Distribution of the residual 14C-SOM after the totally 55 days of incubation showed that a significant reduction of 14C in dissolved organic matter fraction and an increase in humin fraction. No significant difference between the control soil and the earthworm-free cast was observed in both mineralization and residual distribution of 14C-SOM. These results indicate that the earthworm affected the degradation and distribution of SOM of microbial origin via the gut passage and the effects may include two aspects:stimulating mineralization of SOM at initial incubation stage and stabilizing residual SOM afterwards. Further studies should pay attention to transformation of SOM of different origins by geophagous earthworms and to control mechanisms for SOM stability by earthworms.Using 14C-phenol, acetone and n-bromosuccinimide as initial materials, we synthesized Bisphnol A (14C-BPA) and 14C-TBBPA, and we studied the bioremediation of TBBPA-contaminated soil by BPA-degrading bacterium Sphingomonas sp. TTNP3. Our results showed that TBBPA was able to be degraded and further mineralized in soil slurry, and two metabolites were formed within 20 days of incubation. When TTNP3 was present, the degradation was accelerated. One metabolite less hydrophilic than TBBPA was identified as TBBPA methyl ether. As compared to the control without TTNP3 addition, the mineralization of TBBPA was significantly increased (P