Advanced Materials Research Vols. 518-523

Abstract: This study has adopted potted experiment to study systematically the effect on soil microbial quantities of the accumulation of five different plastic film: for 0 year ,for 5years ,for 10 years ,for 15 years ,and for 20 years , and has analyzed the change trends of soil microbial activity. Whose relationship with soil quality has also been explored through analysis of the situation on crop growth, so as to provide scientific basis for law of the accumulation of plastic film on soil microbial activity.

Abstract: A new permeable reactive composite electrode (PRCE) attached with a permeable reactive layer (PRL) of Fe0 and zeolite has been developed for soil pH control and the improved removal efficiency of heavy metal ions (Cd, Ni, Pb, Cu) from soil in electrokinetic remediation process. The effects of different composite electrodes on pH control and heavy metal removal efficiency were studied, and changes in the forms of heavy metals moved onto the electrodes were analyzed. The results showed that with acidic/alkaline zeolite added and renewed in time, the composite electrodes could effectively neutralize and capture H+ and OH- produced from electrolysis of the anolyte and catholyte, avoiding or delaying the formation of acidic/alkaline front in tested soil, preventing premature precipitation of heavy metal ions and over-acidification of soil, and thus significantly improved the heavy metal removal efficiency. Fe0 in composite electrodes could deoxidize and stabilize the heavy metal ions. After that capture and immobilization of the pollutants were achieved. The results also showed that, using "Fe0 + zeolite" PRCE in the cathode with timely renewal, after 15-day remediation with a DC voltage of 1.5 V/cm, the total removal rates of Cd, Pb, Cu and Ni were 49.4%, 47.1%, 36.7% and 39.2%, respectively.

Abstract: The purpose of this study was to investigate the adsorption of Cu(II) on phosphogypsum, a waste material from the manufacture of phosphoric acid by wet process. The removal capacity of phosphogypsum for Cu(II) ions was studied as a function of solution pH, contact time, adsorbent dosage and adsorbate concentration. Before batch adsorption study, phosphogypsum was pre-conditioned by calcine without water. The Langmuir and Freundlich theories were used to describe the Cu(II) adsorption process, and the Freundlich isotherm showed the best fit to the process. The adsorptions of Cu(II) followed pseudo-second-order kinetics. Maximum adsorption capacity of lime-preconditioned phosphogypsum was found to be 2.824 mg/g. The results showed that the phoshogypsum is a suitable adsorbent for the removal of Cu(II) ions from aqueous solutions.

Abstract: CO₂ is the main greenhouse gas leading to global warming. Sequestration strategies of CO₂ have become a popular research topic around the world. Among them, CO₂ biofixation by microalgae is thought to be one of the most effective carbon sequestration means. The flue gas from power plant or waste gas from industry normally contains concentrated CO₂ with concentrations varied from 10% to 95%. In the present study, microalgae growth in a closed raceway pond aerated with high concentration of CO₂ (100%) was examined. The experimental results showed that in the closed raceway pond, microalgae can grow with 100% CO₂ and grow well under certain condition. The present study proved the feasibility of using microalgae for sequestration of concentrated CO₂ emitted from industrial plants.

Abstract: Microbial rhodopsins are photoactive proteins that use retinal molecule as the photoactive center. Because of the structural simplicity and functional diversity, microbial rhodopsins have been an excellent model system for structural biology. In the past decades microbial rhodopisns were identified from diverse environments including salt lakes, fresh water, sea water, human and plant tissues as fungal pathogens. In the present work, we tried to identify microbial rhodopsin genes from salt lake in Inner Mongolia, China. Two bacteriorhodopsin-like genes were identified. The retrieved sequences were analyzed by comparing with four most widely studied haloarchaeal rhodopsins.

Abstract: A short-term experiment was conducted to investigate responses of microbial community composition and nutrients dynamics to biochar-amended brown soil. We examined the effect of biochar on microbial abundance by plate counting method and microbial community composition changes by DGGE, as well as effect on total and available nutrients N, P and K content. Soil pH measurement was also incorporated into our study. The overall results showed that bacterial abundance increased more than actinomycetes, but fungal abundance decreased slightly in biochar amended soil in later sampling times. In terms of microbial community composition, DGGE analysis for bacteria exhibited some specific lanes in biochar treatments. Bacterial community was more sensitive to sampling time, but fungal community was influenced greatly by biochar addition. In our study, total C content increased significantly, as biochar rate and sampling time preceded. Total N increased slightly in later sampling time, and thus C and N ratio increase was obtained. Total P and K changes were not obvious. Extractable N and pH increased. Microbial utilization was assumed to contribute to extractable P and K decrease in later sampling times. Results suggested that biochar incorporation to brown soil might bring potential benefit to soil fertility from N retention in soil. Microbial turnover may feedback P and K to soil as well in the long term. There may also be an implication of beneficial effect on disease alleviation lead by microbial community imbalance.

Abstract: Florfenicol is an effective antibacterial that is widely used in aquaculture farms. The current paper aims to investigate the potential influences of florfenicol on the growth and activities of microorganisms in the sediments of the Dalian coastal area using spiked experiments. The florfenicol resistance of heterotrophic bacteria in the sediment samples from different stations is also analyzed. The results show that florfenicol inhibits the growth and nitrification rates of both ammonia- and nitrite-oxidizing bacteria. Moreover, the sediment samples from stations which previously used florfenicol or other antibacterials had higher percentages of florfenicol-resistant bacteria, indicating that the resistance of heterotrophic bacteria in the sediments developed due to the use of antibacterials.

Abstract: The incidence of algae blooms is increasing in China and worldwide, causing serious environmental problem. A protozoan P1 was isolated from the water samples of Lake Dianchi, which had potent grazing effect on some kind of cyanobacteria. It should be belonged to Ciliophore, Oligohymenophorea, Philasterida based on morphological characters observed by the optical microscope. The main influencing factors of the protozoan grazing properties including: algae species, protozoan density, culture temperature, time and pH value were investigated in batch experiments. The results showed that the protozoan P1 had strong ability to graze the cells of Microcystis wesenbergii. The greater the initial protozoan density, the faster the degradation of chlorophyll-a. The removal rate of chlorophyll-a after 4 days was 78% at the optimum temperature 25°C, pH 7 when using a lower inoculation quantity of 2%. The protozoan P1 was easy to cultivate and reproduce rapidly. It could be applied in the ecological environment to control the Microcystis water bloom.

Abstract: In this study, a scientific method which can be used to improve nitrification process at low temperature in the sewage treatment plant was introduced. The activated sludge samples were taken from aeration tank of the sewage treatment plant when the outside temperature was below 0°C (water temperature below 12 °C). Five kinds of nitrobacteria strains with cold-resistance and higher activity of ammonia degradation were isolated from aeration tanks. The physiological properties showed the five strains were identified into Sphingobacteriaceae、Rhodanobacter sp.、Pseudomonas sp.、Pandoraea sp. and Perlucidibaca piscinae. All of the strains could convert ammonia-nitrogen or NO2- into NO3- in the medium at 10°C. The ammonia and nitrate removal efficiency could be reached 80.9% and 80.3% respectively. Comparing to the unvaccinated one, the removal efficiency can be increased by 50%, which proved the isolated nitrobacteria could be applied to biological nitrification process of sewage treatment at low-temperature.

Abstract: Mycobacterium spp. with the ability to degrade polycyclic aromatic hydrocarbons (PAHs) have attracted great attention. This study aims to isolate pyrene-degrading Mycobacterium spp. through direct plating and selective enrichment from sediment and paddy soil from several sites in Shenfu Wastewater Irrigation Area, and the diversity, catabolic genes and substrate utilization patterns of these pyrene-degrading Mycobacterium isolates was investigated. The Mycobacterium community dynamics was monitored during enrichment cultures by Denaturing Gradient Gel Electrophoresis (DGGE) to determine whether the Mycobacterium sp. detected in DGGE gels was successfully recovered. The results showed that a total of 20 unique Mycobacterium isolates were collected including 3 strains from direct plating and 17 from enrichment cultures. In addition to pyrene, most of the isolates could also degrade phenanthrene and fluoranthene and contained nidA and nidA3 genes, and only half of isolated strains were found to possess the pdoA2 gene. DGGE results showed that the Mycobacterium community had a shift in diversity during enrichment process. phylogenetic analysis based on 16SrDNA sequences from bands excised from DGGE gels and from these isolates revealed that isolated Mycobacterium spp. were represented of bands excised from DGGE gels in a small proportion. This collection of isolates will be valuable in bioremediation of PAH-contaminated sites.