Abstract:
Biogeobattery is a natural phenomenon in which biotic processes generate electrical currents within a redox interface on the surface of the earth. The biogeobattery is caused by microbes driving electrons flow that is coupled to spatially separated biogeochemical processes. The herbicide penoxsulam is common used in paddy field. The herbicides into the soil will simultaneously occur in a series of physical, chemical and biological reactions, which may ultimately alter their ecological toxicities. This project will focuse on the effect of biogeobattery on the environmental degradation behavior of herbicide penoxsulam in paddy soil. The research starting point is produced from the electrochemically-activity of electricigenic bacteria, the mineralization and electron transfer capacities of dissolved organic matter (DOM), and the dissimilatory iron reduction and sulfate reduction in a soil microbial fuel cell. The study main line is performed on the pathways of biological and chemical transformation of herbicide, and the electron transfer mechanisms for the herbicide degradation by the paddy field microbial fuel cell (PFMFC). The associated bridge is established by the reactions of herbicide electrocatalytic oxidation and bioelectrochemical degradation in soil under the biogeobattery effect. Based on above these research results, the connections between the biogeobattery effect and the transformation of herbicide in soil are constructed, and the mechanisms that biogeobattery mediated biotic and abiotic degradation of the herbicide are proposed by the identification of intermediate and final products of penoxsulam degradation.This study investigates the electrochemical performance and its effect on degradation of pentachlorophenol using a dual chamber microbial fuel cell (MFC) with rGO/Ag composite modified graphite felt (GF) as anode. It was found that, with desulfovibriode sulfuricans as the electroproducing bacterium and the initial concentration of pendimethalin at 10 mg/L, the electroproduction performance of MFC and its degradation of pendimethalin were improved after rGO/Ag composite modification of the MFC’s GF anode, of which, when the GF electrode and the rGO/Ag/GF composite electrode were used as the anode, the bilayer electroproduction performance of MFC and the degradation of pendimethalin were improved, respectively. When the GF electrode and the rGO/Ag/GF composite electrode were used as the anode, the bilayer capacitance of MFC was 1.46×10
-3 and 3.85×10
-3 mF, the electron transfer impedance was 114 and 61 Ω, and the degradation rate of pendimethalin was 53.6% and 67.3%, respectively; the change of the initial concentration of pentaflumuronium and the pH value could affect the MFC power generation and the degradation effect of pendimethalin. The maximum power density of MFC and degradation rate of pendimethalin were 140.4 mW/m
2 and 70.5%, respectively, but with the increase of initial pendimethalin concentration, its power production performance and degradation would be suppressed to a certain extent; when the initial pH value was weakly alkaline and neutral, the power production performance and degradation of MFC were higher, with power density and degradation rate of 136.54 mW/m
2 and 64.9%, respectively. It was shown that the MFC could utilize pentaflumizone as a fuel and generate electricity in the process of degradation at the same time. The research results will provide a scientific basis for the potential environmental risk assessment of herbicide, the ecological function and utilization of biogeobattery, and the in-situ remediation of herbicide contaminated soil.