[Movement and transformation of heavy metals in water-sediment in water-level-fluctuating zone of Three Gorges Reservoir Area].

According to the off-season regulation model for Three Gorges Reservoir, the characteristic of movement and transformation of Cu, Pb, Cd and Cr in sediment of water-level-fluctuating zone of Three Gorge Reservoir Area was investigated. The results indicated that the chemical fraction composition characteristics of heavy metals are different. Cu mainly existed in organic/sulphidic fraction and residual fraction; Pb mainly existed in carbonates, Fe-Mn oxides and residual fraction; Cd mainly existed in carbonates and Fe-Mn oxides fraction; Cr mainly existed in residual fraction. In flood season, the exposure of sediment from river bottom to atmosphere caused the decrease of TOC, AVS and pH and increase of ORP, and lowered the amount of extractable heavy metals. Heavy metals have the tendency to release to water body. The migration rates of Cu, Pb, Cd and Cr were 30.50%, 26.10%, 33.50%, and 11.77% respectively, the migration ability of heavy metals followed: Cd > Cu > Pb > Cr. The contributions of extractable fractions of Cu, Pb, Cd and Cr to the migrated heavy metals were 77.15%, 86.09%, 94.86%, and 32.34% respectively, extractable fraction was the mainly part of the migrated heavy metals. The off-season regulation model for Three Gorges Reservoir lowered the ecological harm of heavy metals, the concentrations of Cu, Pb, Cr, Cd in the study areas were low.

[Preliminary study on bacterial culture through near-natural pure culture technique].

Based on the ecological features of mutual benefits of different microbes in natural environment, near-natural pure culture technique which was an improvement of conventional pure culture method had been put forward. The key point of this new method was to make hole petri dishes covered with millipore membranes. When these covered dishes being used to culture microorganisms, it could provide incubated microbes active materials from native environment, maintain free communicating with outside microbes, and improve their recovery and culturability of some bacteria. To some degree, this technique enhanced their strengths and overcome their weaknesses of mixed culture method and conventional pure culture method so as to increase microbial culturability and even possibly obtain some nonculturable microorganisms.

[Ecological interpretation and related strategies for low culturability of microorganisms].

Pure culture technique has been a fundamental method since its invention in microbiology, but its isolated and monotonous environment contradicts microbial diversity and cooperation relationship in natural environment. And this contradiction directly results in the uncultivability of some microbes in media. From ecological viewpoint, the recovery barriers of natural microbes mainly include the crash of cooperation in natural environment, the great change of nutrient in new environment and the loss of native niche. The main methods and strategies on low curturability of microorganisms are culture-independent methods, enrichment culture, mixed culture, dilution culture, simulating nature culture and synthetic method, which can to some degree compensate for the traditional approach and improve the low culturability of some bacteria.