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The potential for aerobic NO removal by Alcaligenes faecalis strain NR was investigated. 35 mg/L of NO -N was removed by strain NR under aerobic conditions in the presence of NH . N-labeling experiment demonstrated that NO and N were possible products during the aerobic nitrite removal process by strain NR. The key enzyme genes of nirK, norB and nosZ, which regulate the aerobic nitrite denitrification process, were successfully amplified from strain NR. The gene sequence analysis indicates that copper-containing nitrite reductase (NIRK) and periplasmic nitrous oxide reductase (NOSZ) were both hydrophilic protein and the transmembrane structures were absent, while nitric oxide reductase large subunit (NORB) was a hydrophobic and transmembrane protein. According to the three-dimensional structure and binding site analysis, the bulky and hydrophobic methionine residue proximity to the nitrite binding sites of NIRK was speculated to be related to the oxygen tolerance of NIRK from strain NR. [ABSTRACT FROM AUTHOR]

After the initial impoundment of the Three Gorges Reservoir ( TGR), most of its tributaries have been influenced because of the backwater and the input of nutrients. The spatiotemporal variability in euphotic depth and its major influencing factors were investigated in the Xiaojiang River Basin of the TGR to reveal this change. Analyses were based on the photosynthetically active radiation ( PAR) and water quality indices in five sampling sites of the Xiaojiang River from May 2007 to April 2009. Results showed only slight spatial variation in the average euphotic depth while significant temporal variation was taken place. Moreover, correlation analysis indicated that the diffuse attenuation coefficients for PAR ( Kd( PAR)) was significantly correlated to the total suspended solids ( TSS) ( R2 = 0.6794), but not to chlorophyll-a ( Chl-a) ( R2 = 0.045). The unique hydrological conditions of the TGR might be the determinants of the spatiotemporal variability. [ABSTRACT FROM AUTHOR]

The anaerobic ammonium oxidation(ANAMMOX) granular sludge in the EGSB reactor was divided into three groups according to particle size, which were R1 (0.5-1.4 mm), R2 (1.4-2.8 mm), and R3 (>2.8 mm). Extracellular polymeric substances (EPS) of different sizes from ANAMMOX granular sludge were extracted, and the EPS characteristics and their influence on the surface characteristics of ANAMMOX aggregates were analyzed. With the increased particle size of ANAMMOX granular sludge, the PS content was between (10.69±0.11)-(12.28±0.15) mg·g -1 , while the PN content increased from (56.88±0.86) mg·g -1 to (98.59±2.10) mg·g -1 , and PN/PS increased from 5.32 to 9.05. The EPS functional groups and the content of three-dimensional fluorescent components of different size ANAMMOX granular sludge were different. As the granular sludge size increased, the value of α -helix/( β -sheet + random coil) gradually decreased from 0.60 to 0.43, which is beneficial to the hydrophobicity expression of the sludge. Due to the increased particle size of the granular sludge, the hydrophobicity of the sludge surface increased from 54.2% to 63.1%, and the Zeta potential increased from -41.2 mV to -31.5 mV. The increased hydrophobicity and surface charge are beneficial to the formation of sludge aggregates. EPS can enhance ANAMMOX sludge hydrophobicity and increase Zeta potential. The presence of PN in EPS is essential to this process.

The potential for aerobic NO 2 - removal by Alcaligenes faecalis strain NR was investigated. 35 mg/L of NO 2 - -N was removed by strain NR under aerobic conditions in the presence of NH 4 + . 15 N-labeling experiment demonstrated that N 2 O and N 2 were possible products during the aerobic nitrite removal process by strain NR. The key enzyme genes of nirK, norB and nosZ, which regulate the aerobic nitrite denitrification process, were successfully amplified from strain NR. The gene sequence analysis indicates that copper-containing nitrite reductase (NIRK) and periplasmic nitrous oxide reductase (NOSZ) were both hydrophilic protein and the transmembrane structures were absent, while nitric oxide reductase large subunit (NORB) was a hydrophobic and transmembrane protein. According to the three-dimensional structure and binding site analysis, the bulky and hydrophobic methionine residue proximity to the nitrite binding sites of NIRK was speculated to be related to the oxygen tolerance of NIRK from strain NR.

The old town area of Kaixian county was flooded and showed reservoir characteristics after the water level of Three Gorges Reservoir got 172. 8 m in December 2008. The aquatic ecology and nutritional status of Kaixian drawdown area after water storage are still rarely reported. To understand the current water environment and changes in algal community structure of Kaixian drawdown area after 172.8 m water level, the algal composition, abundance, biomass distribution and changes of its sampling spots including Hanfeng Lake were observed twice during winter storage period in January and December 2009. The trends in phytoplankton community structure were analyzed and the water quality assessment of nutritional status was carried out. The results indicated that 6 phylums, 37 genera, 69 species of phytoplankton in total were identified in the two sampling, and the dominant species were Dinophyta and Cryptophyta. The cell density and biomass in December 2009 were lower than those in January 2009. The evaluation results of algal population structure and pollution indicators showed that the nutrition level of Kaixian drawdown area during the winter storage period was mesotrophic to eutrophic type, while diversity analysis result indicated moderate pollution.

It is very important to investigate the change of nutrient in Three Gorges Reservoir for analyzing the influence after normal storage and proposing reasonable management methods. The water quality parameters were determined monthly from March in 2008 to February in 2009. Six horizontal monitoring sites and one vertical site were set in Three Gorges Reservoir. The period was separated into two different periods with taking account of the water level after the Three Gorges Reservoir storaged water, which were October-February and March-September respectively. Then, the spatial-temporal variation characteristics of nutrient and environmental features in different periods were studied with the water quality data. The results showed that there were no significant differences of water quality parameters except DO in different periods. There were also no significant differences of the vertical distribution of hydrology, water quality indexes among the three observed levels. The concentration of DO in high water level (8.29 mg/L)was higher than that in low water level (7.49 mg/L) and the mean of saturation degree of DO was 83.5%. Total nitrogen (TN), NH4+ -N, total phosphorus (TP) values were 1.42-2.23 mg/L, 0.15-0.36 mg/L, 0.08-0.14 mg/L respectively, and plane of nutrition in high water level was higher than that in low water level. The main factor influenced the concentrations of TN, NH4+ -N and TP were rainfall runoff process. Significantly positive correlation was observed by correlation analysis between nutrients fluxes and the flux at the section Cun Tan. The fluxes of TN, NH4+ -N, TP were 368.4, 97.2, 29.5 thousands tons respectively, and the non-point pollution accounts for more than 55.5%.

The seasonal variation of Chlorophyll a (Chla) in Xiaojiang river backwater area from May 2007 to April 2008 with 115 water samples was studied. Three trophic states i.e. Chla < or = 5 microg x L(-1), 5 microg x L(-1) < Chla < or = 19 microg x L(-1) and Chla >19 microg x L(-1), were applied to represent the potential relationship of Chla, algal cell density (CellD) and biomass (BioM) in Xiaojiang river backwater area. The results showed that the algal cell density, biomass and Chla had significantly positive correlations (r > 0.70, Sig. < or = 0.01) and their seasonal variation processes are synchronous. The average values of Chla and biomass of chlorophyta, diatoms, cyanobacteria, dinoflagellate during the study period in Xiaojiang river backwater area were (9.58 +/- 10.77), (1605 +/- 647), (707 +/- 124), (511 +/- 266) and (4019 +/- 1345) microg x L(-1), respectively. When Chla < or = 5 microg x L(-1), chlorophyta, diatoms and Chla were significantly positively correlated; while under 5 microg x L(-1) < Chla < or = 19 microg x L(-1) level, only cyanophytes and Chla showed a significantly positive correlation; At Chla > 19 microg x L(-1) level, Chla was positively correlated to dinoflagellate, and there were no significant correlations among Chla and other algae.

According to one year's continuous observation on algae in the Xiaojiang backwater area in Three Gorges Reservoir, our group analyzed algae community and its succession in the Xiaojiang backwater area at the beginning of the function of the reservoir. The algae cell density and biomass are the highest in spring and the lowest in winter. The maximal value of cell density is 421.64 x 10(3) cells x L(-1), and the minimal value is 2.06 x 10(5) cells x L(-1); and maximal value of biomass is 39,231.84 microg x L(-1), and the minimal value is 226.17 microg x L(-1). From May 2007 to May 2008, there are 7 phylum, 101 category, 262 genus appeared in the Xiaojiang backwater area, in which 51 categories are Chlorophyta accounting for 50.5%, 22 categories are Bacillariophyta accounting for 21.8%, 18 categories are Cyanophyta accounting for 17.8%, and 4 categories are Dinophyta, 2 categories are Cryptophyta, 3 categories are Euglenophyta, 1 category is Xanthophyta and others. Cryptomonas, Chlorella, Cyclotella, Scenedesmus, Oocystis, Chlamydomonas, Schroederia, Aulacoseira, Stephanodiscus and Fragilaria are familiar categories in the Xiaojiang backwater area. Asterionnella, Aulacoseira, Coelastrunm, Chlorella, Scenedesmus, Aclinastnrum, Dictyosphaerium, Anabaena, Aphanizomenon, Merismopedia, Ceratium, Peridinium and Cryptomonas are the preponderant categories in the Xiaojiang backwater area.

Eutrophication and algal blooms occurred in the backwater areas of tributaries in Three Gorges Reservoir were the hot ecological issues in recent years. A one year field survey on cyanobacteria was put forward from May, 2007 to May, 2008 in Xiaojiang backwater area. 15 genera and 40 species of cyanophyta were detected. Mean value of cyanobacterial cell density was (23.50 +/- 10.30) x 10(5) cells x L(-1), i.e., 24.1% in the algal community, while the biomass was (768.70 +/- 287.40) microg x L(-1) which was 8.9% in the total biomass of algal community. Seasonal variation of cyanobacteria was apparent. Generally, cyanobacteria bloom occurred during late spring and early summer. Its abundance decreased after summer and reached the minimum level in winter. Anabaena, Aphanizomenon, Microcystis, Merismopedia and Phormidium were the common cynaobacterial genera. The cumulated cell density of these five genera of cyanobacteria above accounted up to 79.1% in the total cell density of cyanobacteria, while that of biomass accounted up to 77.6%. Spearman correlation analysis among the cell density, biomass as well as the key environmental factors indicated that utilization of inorganic nitrogen and phosphorus for anabolism was evident; however, nitrate would be the major nitrogen source for cyanobacteria. Moreover, increase of temperature and decrease of depth of euphotic zone had a significant effect on the abundance of cyanobacteria. According to co-analysis of hydrology and rainfall data in the whole year circle, it was found that nitrogen and phosphorus were input by the heavy rain and surface runoff with inorganic sediments, offering the enriched nutrients in water column. Meanwhile, turbidity increased by the inorganic suspended sediments decreased the depth of euphotic zone. The physiological advantage of cyanobacteria in low light and high turbidity environment might be the cause of cyanobacteria bloom in Xiaojiang backwater area.

Phosphorus is regarded as the limiting factor for eutrophication in backwater areas of tributaries in Three Gorges Reservoir (TGR). However, distinct seasonal variation patterns and potential ecological impacts of phosphorus are apparent due to the ultimate hydrodynamic condition in the site. Seasonal variation of different forms of phosphorus in Xiaojiang backwater area (XBA) in Three Gorges Reservoir from Mar. 2007 to Mar. 2008 was reported. It was found that average concentration of total phosphorus (TP) was (61.7 +/- 2.7) microg x L(-1). No remarkable difference was found among sampling sites, while significant variation among seasons were detected. Generally, TP was high in summer and winter while low in autumn. Particulate phosphorus (PP) was the major forms of phosphorus in XBA. The co-analysis among phosphorus and key environmental variables, i.e., chlorophyll, inorganic/organic particles, flows and water levels in river estuary, indicate that inorganic forms of PP should dominate in PP, and might transfer into the water body by rainfall and river flows, resulting in the increase of TP in XBA. This phenomenon was more significant when TGR was set at low water level. Soluble reactive phosphorus (SRP) had a significantly negative correlation with chlorophyll a, indicating the evident assimilation process of phosphorus by algae. It was inferred that heavy rainfall and increased river flow shortened the water renewal cycle and brought in amounts of suspended sediments that increased the light attenuation underwater. With the frequent flood impulse, phytoplankton community should suffered the instable living environment that decreased the concentration level of chlorophyll a in XBA. This might be the potential reason for the negative correlation between TP and chlorophyll a.

Nitrogen is one of the key nutrients for phytoplankton. Seasonal variation of different forms of nitrogen in Xiaojiang backwater area (XBA) in Three Gorges Reservoir from Mar. 2007 to Mar. 2008 was reported. It was found that average concentration of total nitrogen (TN) during the research period was (1553 +/- 43) microg x L(-1). Although remarkable seasonal variability of TN, it showed a general trend of increase of TN during the research period. Dissolved inorganic nitrogen (DIN) was the major form of nitrogen with an average concentration of (1031 +/- 32) micro x L(-1), amounted up to 66.38% in TN. The relatively high level of nitrate in DIN indicated that XBA remained a strong oxidation environment with a good self-purification generally. Mean value of the concentration of dissolved organic nitrogen (DON) and particulate organic nitrogen (PON) were (273 +/- 23) microg x L(-1) and (249 +/- 23) microg x L(-1), taking up to 26.48% and 24.15% in TN separately. However, the DON/PON ratio was only 3.63 +/- 0.93, which represented the intensive nitrogen cycling and high turnover rates. The amount of DIN in TN decreased from 80% in Mar. 2007 to 60% in Mar. 2008, which showed a trend that forms of nitrogen had been transferring from inorganic forms to organic forms. Compared to the lower slope of DIN-TN log-log linear model, the relatively high slope of TON-TN log-log linear model indicated the contribution of total organic nitrogen (TON) to TN would become significant with the increase of TN. Meanwhile, the positive correlation between NH4(+) -N/NO3(-) -N and TON/TN indicated the increase of TON in TN might contribute to a reductive environment in XBA. Nevertheless, it also showed a close relationship between ammonia and DON, but whether the ammonification of DON existed or might become the controlling process of nitrogen cycling in XBA still needs further study.

The Water Level of Three Gorges Reservoir moved up to 156m at the end of October 2006, which represents Three Gorges Project had begun its primary operation period. In order to realize the actuality of water environment and the variation of phytoplankton community of the backwater area of Xiaojiang River, the author has been observing the nutrition level of the area regularly since the beginning of 2007. Based on the data of the routing monitoring in spring (April) 2007, the algal diversity of five sites on Backwater Area of Xiaojiang River was assessed by the diversity index H, richness index d and evenness index J. The values of H, d and J in sample sites are 1.097 5-1.865 5, 1.324 2-1.860 4, 0.263 2-0.435 9 on April. The trophic levels of the five sites are all meso-eutrophic. The water quality of Quma site is not quite right, and the best one is Huangshi site. The highest value of the cell densities and that of the biomass both appeared at Quma April 8th (8.442 x 10(5) cells/L, 1.887 mg/L). It shows the trend that the Chlorophta and Cyanophyta evolve into dominant taxa of the phytoplankton community in early summer instead of Bacillariophyta and Chlorophta in winter on backwater area of Xiaojiang River.