Polycyclic aromatic hydrocarbons （PAHs） were measured in precipitation from March to August 2005 in Guangzhou, South China. Fourteen PAHs were studied, and their total concentrations varied from 616.6 to 3486.7 ng/L...Polycyclic aromatic hydrocarbons （PAHs） were measured in precipitation from March to August 2005 in Guangzhou, South China. Fourteen PAHs were studied, and their total concentrations varied from 616.6 to 3486.7 ng/L in dissolved phase and from 403.8 to 3125.5 ng/L in particulate phase. The estimated deposition loading of PAHs was 3568 ug/m^2 during the monitoring period. The deposition of PAHs was a potential source for Pearl River comparing with the contents of surface water. In addition, the high concentration in precipitation here implied that PAHs pollution was a potential environmental problem in Guangzhou. Most precipitation concentrations of PAHs in March （the last month in winter in Guangzhou） were higher than in the other months （in rainy season）. PAHs inclined to be adsorbed to particulate phase with the increase of molecular weight in rainwater. Combustion of fossil fuel and biomass might be the major source of PAHs, while the direct leakage or volatilization from petroleum products might be insignificant.展开更多
In microbial fuel cell (MFC), the rate of electron transfer to anode electrode is a key intrinsic limiting factor on the power output of MFCs. Using Klebsiella pneumoniae (K. pneumoniae) strain L17 as biocatalyst, we ...In microbial fuel cell (MFC), the rate of electron transfer to anode electrode is a key intrinsic limiting factor on the power output of MFCs. Using Klebsiella pneumoniae (K. pneumoniae) strain L17 as biocatalyst, we studied the mechanism of electron shuttle via self-producing mediator in a cubic air-chamber MFC. To eliminate the influence of biofilm mechanism, the anode electrode was coated with microfiltration membrane (0.22 μm). Data showed that the microfiltration membrane coated and uncoated MFCs achieved the maximum voltage outputs of 316.2 and 426.2 mV after 270 and 120 h, respectively. When the medium was replaced in MFCs that had the highest power generation, the power output dropped by 62.1% and 8.8%, and required 120 and 48 h to resume the original level in the coated and uncoated MFCs, respectively. The results suggested an electron-shuttle mechanism rather than biofilm mechanism was responsible for electricity generation in the membrane coated MFC. Cyclic voltammetric measurements demonstrated the presence of an electrochemical active compound produced by K. pneumoniae strain L17, which was identified to be 2,6-di-tert-butyl-p-benzoquinon (2,6-DTBBQ) by GC-MS. 2,6-DTBBQ, as a recyclable electron shuttle, could transfer electrons between K. pneumoniae L17 and the anode electrode.展开更多
基金supported by the Guangdong Natural Science of Foundation (No. 8151065003000004)the National Natural Science Foundation of China (No.20807012), and the GIGCAS (No. IS-1048).
文摘Polycyclic aromatic hydrocarbons （PAHs） were measured in precipitation from March to August 2005 in Guangzhou, South China. Fourteen PAHs were studied, and their total concentrations varied from 616.6 to 3486.7 ng/L in dissolved phase and from 403.8 to 3125.5 ng/L in particulate phase. The estimated deposition loading of PAHs was 3568 ug/m^2 during the monitoring period. The deposition of PAHs was a potential source for Pearl River comparing with the contents of surface water. In addition, the high concentration in precipitation here implied that PAHs pollution was a potential environmental problem in Guangzhou. Most precipitation concentrations of PAHs in March （the last month in winter in Guangzhou） were higher than in the other months （in rainy season）. PAHs inclined to be adsorbed to particulate phase with the increase of molecular weight in rainwater. Combustion of fossil fuel and biomass might be the major source of PAHs, while the direct leakage or volatilization from petroleum products might be insignificant.
基金supported by the National Natural Science Foundation of China (No 20777013)Natural Science Foundation of Guangdong Province, China (No 07006759)The Sci & Tech Innovation project of Guangdong Academy of Sciences, China (Gtard No CX200704)
文摘In microbial fuel cell (MFC), the rate of electron transfer to anode electrode is a key intrinsic limiting factor on the power output of MFCs. Using Klebsiella pneumoniae (K. pneumoniae) strain L17 as biocatalyst, we studied the mechanism of electron shuttle via self-producing mediator in a cubic air-chamber MFC. To eliminate the influence of biofilm mechanism, the anode electrode was coated with microfiltration membrane (0.22 μm). Data showed that the microfiltration membrane coated and uncoated MFCs achieved the maximum voltage outputs of 316.2 and 426.2 mV after 270 and 120 h, respectively. When the medium was replaced in MFCs that had the highest power generation, the power output dropped by 62.1% and 8.8%, and required 120 and 48 h to resume the original level in the coated and uncoated MFCs, respectively. The results suggested an electron-shuttle mechanism rather than biofilm mechanism was responsible for electricity generation in the membrane coated MFC. Cyclic voltammetric measurements demonstrated the presence of an electrochemical active compound produced by K. pneumoniae strain L17, which was identified to be 2,6-di-tert-butyl-p-benzoquinon (2,6-DTBBQ) by GC-MS. 2,6-DTBBQ, as a recyclable electron shuttle, could transfer electrons between K. pneumoniae L17 and the anode electrode.
