Ecotoxicity monitoring and bioindicator screening of oil-contaminated soil during bioremediation.

A series of toxicity bioassays was conducted to monitor the ecotoxicity of soils in the different phases of bioremediation. Artificially oil-contaminated soil was inoculated with a petroleum hydrocarbon-degrading bacterial consortium containing Burkholderia cepacia GS3C, Sphingomonas GY2B and Pandoraea pnomenusa GP3B strains adapted to crude oil. Soil ecotoxicity in different phases of bioremediation was examined by monitoring total petroleum hydrocarbons, soil enzyme activities, phytotoxicity (inhibition of seed germination and plant growth), malonaldehyde content, superoxide dismutase activity and bacterial luminescence. Although the total petroleum hydrocarbon (TPH) concentration in soil was reduced by 64.4%, forty days after bioremediation, the phytotoxicity and Photobacterium phosphoreum ecotoxicity test results indicated an initial increase in ecotoxicity, suggesting the formation of intermediate metabolites characterized by high toxicity and low bioavailability during bioremediation. The ecotoxicity values are a more valid indicator for evaluating the effectiveness of bioremediation techniques compared with only using the total petroleum hydrocarbon concentrations. Among all of the potential indicators that could be used to evaluate the effectiveness of bioremediation techniques, soil enzyme activities, phytotoxicity (inhibition of plant height, shoot weight and root fresh weight), malonaldehyde content, superoxide dismutase activity and luminescence of P. phosphoreum were the most sensitive.

[Analysis and Characterization of Multi-modified Anodes via Nitric Acid and PPy/AQDS in Microbial Fuel Cells].

The properties of anode material are crucial for high performances in microbial fuel cells (MFCs). Hereby, a biocompatible, conductive, and high electron transfer ability anode was fabricated by electrodepositing polypyrrole/anthraquinone-2, 6-disulphonic disodium salt (PPy/AQDS) onto nitric acid-soaked carbon felt. The results showed that the multi-modified anode outperformed the pristine one in biomass, electrical conductivity, and exchange current density with between 2.4 and 3.3 times better performance. The multi-modified anode (applied with 0.12 C·cm-2 total charge density) showed the highest peak current density (2.86 mA), the largest amount of biomass loading (0.44 mg·cm-2), the most favoured electrical conductivity (0.33 S·cm-1), and exchange current density (3.65×10-3 A·m-2), as a result, the maximum power density of the MFC equipped with the anode delivered a 2.2-fold increase over that of the control (1060.7 mW·m-2vs. 477.6 mW·m-2), and thus has great potential to be used as an anode for high-power MFCs. Further investigation revealed that the increased energy output might be attributed to the bridging of the carbon fibers by electrically conductive PPy/AQDS composite films, which provided a uniform connection throughout the nitric treated carbon felt as well as the synergetic effects between the newly formed functional groups like pyrrolic N and PPy/AQDS. It was proposed that integrating biocompatibility (BCB) with electrical conductivity (EC) and electron transfer efficiency (ETE) through multi-modification could form high-performance anode. Future efforts to be made for realizing more extraordinary high-performance MFCs anodes were also outlined. This work may also provide a novel universal approach for the development of other types of anode for high-performance MFCs through integrating the BCB with EC and ETE simultaneously.