Biomedical subjects

Guanxiong Chen

Publications and source records attributed to Guanxiong Chen.

7 recordsLinked to original sources

PubMed2005

Study of microbial community structures in UASB sludge treating municipal wastewater by denaturing gradient gel electrophoresis of 16S rDNA.

The structures of microbial communities in lab-scale upflow anaerobic sludge blanket (UASB) reactors for treating municipal wastewater with different ratios of COD soluble/COD total were studied using denaturing gradient gel electrophoresis (DGGE) of 16S rRNA genes. The microbial structure of the inoculum sludge obtained from a full-scale UASB reactor of treating potato processing wastewater was compared with the structures of sludges collected from three lab-scale UASB reactors after eight months feeding with raw municipal wastewater, with CEPS (chemically enhanced primary sedimentation) pretreated municipal wastewater, and with a synthetic municipal sewage, respectively. Computer-aided numerical analysis of the DGGE fingerprints showed that the bacterial community underwent major changes. The sludges for treating raw and CEPS pretreated wastewater had very similar bacterial and archaeal communities (82% and 96% similarity) but were different from that for treating the synthetic sewage. Hence, despite similar % COD in the particulate form in the synthetic and the real wastewater, the two wastewaters were selected for different microbial communities. Prominent DGGE bands of Bacteria and Archaea were purified and sequenced. The 16S rRNA gene sequences of the dominant archaeal bands found in the inoculum, and UASB sludge fed with raw sewage, CEPS pretreated wastewater, and synthetic sewage were closely associated with Methanosaeta concilii. In the UASB sludge fed with synthetic sewage, another dominant band associated with an uncultured archaeon 39-2 was found together with M. concilii.

Anaerobiosis↗

PubMed2004

[Effects of illumination, carbon source and reducing power on N2O emission from maize and soybean seedlings].

The closed chamber measurement of N2O emission from soybean and maize seedlings showed that there were two peaks (10:30 and 14:30) of N2O flux at the daytime. There was a correlation between N2O emission and illumination. The variation of illumination had a significant influence on N2O flux from soybean and maize seedlings. There was a positive correlation between N2O emission and illumination when the illumination was below 11,345 Lx (for soybean, R2 = 0.7332) or 2,000 Lx (for maize, R2 = 0.8711), and a negative correlation when the illumination was over 11,345 Lx (for soybean, R2 = 0.7755) or 20,000 Lx (for maize, R2 = 0.8972). Addition of carbon source (glucose) and NADH (reducing power) decreased N2O flux.

Carbon↗

PubMed2003

[The contribution of maize and soybean to N2O emission from the soil-plant system during seedling stage].

To fractionate the contribution of plant to N2O emission from soil-plant system, the N2O emissions from soybean seedling, maize seedling, sand, soil, sand-plant system and soil-plant system were measured by closed chamber method in greenhouse. At the same time the correlation of plant N2O emission with nitrate reductase activity, nitrate content and nitrite content of the plant leaves was also analyzed. The results clearly indicated that N2O could be a by-product of plant metabolism. The emissions of N2O from maize and soybean accounted for 93%-100% of the total N2O emissions in the sand-plant systems, and 79.18%-92% in the soil-plant systems. The flux of plant N2O emission was significantly correlated (R2 > or = 0.97, n = 6) with the nitrate reductase activities, nitrate content and nitrite content of the maize and soybean leaves.

Nitrate Reductase↗

PubMed2003

[Oxygen-limited autotrophic nitrification and denitrification--a novel technology for biological nitrogen removal].

Oxygen-limited autotrophic nitrification and denitrification (OLAND) is a biological nitrogen removal process coupled with partial nitrification and anaerobic ammonium oxidation. In our study, the nitrification was blocked at nitrite stage by controlling the dissolved oxygen concentration at 0.1-0.3 mg.L-1, and then, the denitrification proceeded, with the residual ammonium at the partial nitrification stage as electron donor. As a completely autotrophic nitrification-denitrification process, the OLAND was of many advantages (e.g., low energy consumption, high nitrogen removal rate and small footprint of system), and suitable in particular for treating low COD/NH4(+)-N ratio wastewater. It has become one of the most prosperous and practicable biological nitrogen removal technologies. The recent research of OLAND was reviewed, and its microbial mechanism as well as its applicable prospect was remarked in this paper.

Ammonia↗

PubMed2002

The Asian nitrogen cycle case study.

We analyzed nitrogen budgets at national and regional levels on a timeline from 1961-2030 using a model, IAP-N 1.0. The model was designed based upon the Inter-governmental Panel on Climate Change (IPCC) methods using Asia-specific parameters and a Food and Agriculture Organization of the United Nations (FAO) database. In this paper we discuss new reactive-nitrogen and its various fates, and environmental nitrogen enrichment and its driving forces. The anthropogenic reactive nitrogen of Asia dramatically increased from approximately 14.4 Tg N yr-1 in 1961 to approximately 67.7 Tg N yr-1 in 2000 and is likely to be 105.3 Tg N yr-1 by 2030. Most of the anthropogenic reactive-nitrogen has accumulated in the environment. We found that an increasing demand for food and energy supplies and the lack of effective measures to improve the efficiency of fertilizer nitrogen use, as well as effective measures for the prevention of NOx emissions from fossil-fuel combustion, are the principal drivers behind the environmental nitrogen-enrichment problem. This problem may be finally solved by substituting synthetic nitrogen fertilizers with new high-efficiency nitrogen sources, but solutions are dependent on advances in biological technology.

Asia↗

PubMed2002

[Important factors controlling rates of N2O emission and CH4 oxidation from forest soil].

In this study, laboratory incubation experiments were conducted to determine the effect of pH, soil water content, temperature, NH4+ and NO3- on N2O emission and CH4 oxidation of mixed broad-leaved Korean pine forest soil. Results showed that there were significant correlations between N2O emission rate, CH4 oxidation rate and soil pH and temperature under certain lab conditions. Meanwhile, the significant positive correlation between N2O emission rate and CH4 oxidation rate was also observed. The results suggested temperature and pH could be the most important factors controlling the rates of N2O emission and CH4 oxidation of a forest soil under this experiment conditions.

Methane↗

PubMed2002

[N2O emission from trees under different light irradiances].

This paper firstly measured in situ N2O emission from branches and leaves of sun plants (Fraxinus mandshurica, Pinus koraiensis, Alnus hirsuta) and shade tolerant plants (Tilia amurrensis) under different light irradiances in closed chamber. Light irradiance had contrast effects on N2O emission flux from sun and shade-tolerant tree species. In the test sun plants, more N2O was emitted under weak light than under strong light. The emission rates decreased with increasing irradiances, and even absorption instead of emission of N2O was detected under strong light. In contrast to sun plants, in the shade tolerant plant T. amurrensis, there was more N2O emission under strong light than under weak light, and N2O absorption from environment was detected under weak light.

Fraxinus↗