Characteristics and influence factors of NO2 exchange flux between the atmosphere and P. nigra

Nitrogen dioxide(NO_2)is an important substance in atmospheric photochemical processes and can also be absorbed by plants.N02 fluxes between the atmosphere and P.nigrc seedlings were investigated by a double dynamic chambers method in Beijing from June 15to September 3,2017.The range of N02 exchange fluxes between P.nigra seedlings and the atmosphere was from-14.6 to 0.8 nmol/(m~2.sec)(the positive data represent N02 emissior from trees,while the negative values indicate absorption).Under ambient concentrations the mean NO_2 flux during the fast-growing stage(Jun.15-Aug.4)was-3.0 nmol/(m2·sec)greater than the flux of-1.5 nmol/(m2-sec)during the later growth stage(Aug.8-Sept.3)The daily exchange fluxes of NO_2 obviously fluctuated.The fluxes were largest in the morning and decreased gradually over time.Additionally,the N02 fluxes were larger undei high light intensities than under low light intensities during the whole growth period.The effects of temperature on N02 fluxes were different under two growth periods.The NO_2exchange fluxes were larger in a range of temperatures close to 44℃in the fast-growing stage,whereas there were no evident differences in N02 exchange fluxes under widel differing temperatures in the later growth stage.Under polluted conditions,the uptake ability of N02 was weakened.Additionally,the compensation point of N02 was 5.6 ppb ir the fast-growing stage,whereas it was 1.4 ppb in the later growth stage.The depositior velocities of NO_2 were between 0.3 and 2.4 mm/sec.     

Elevated CO2 facilitates C and N accumulation in a rice paddy ecosystem

Elevated CO₂ can stimulate wetland carbon (C) and nitrogen (N) exports through gaseous and dissolved pathways, however, the consequent influences on the C and N pools are still not fully known. Therefore, we set up a free-air CO₂ enrichment experiment in a paddy field in Eastern China. After five year fumigation, we studied C and N in the plant–water–soil system. The results showed: (1) elevated CO₂ stimulated rice aboveground biomass and N accumulations by 19.1% and 12.5%, respectively. (2) Elevated CO₂ significantly increased paddy soil TOC and TN contents by 12.5% and 15.5%, respectively in the 0–15 cm layer, and 22.7% and 26.0% in the 15–30 cm soil layer. (3) Averaged across the rice growing period, elevated CO₂ greatly increased TOC and TN contents in the surface water by 7.6% and 11.4%, respectively. (4) The TOC/TN ratio and natural δ¹⁵N value in the surface soil showed a decreasing trend under elevated CO₂. The above results indicate that elevated CO₂ can benefit C and N accumulation in paddy fields. Given the similarity between the paddies and natural wetlands, our results also suggest a great potential for long-term C and N accumulation in natural wetlands under future climate patterns.     

Cyanobacterial bloom dynamics in Lake Taihu

<正>Lake Taihu is the third largest freshwater lake in China and serves as an important drinking water source for the local populace;however,decades of excessive nutrient loading fueled by anthropogenic activities have resulted in hypertrophic conditions,promoting the annual formation of nuisance phytoplankton blooms(Chen et al.,2003;Duan et al.,2009)     

The first metagenome of activated sludge from full-scale anaerobic/anoxic/oxic (A2O) nitrogen and phosphorus removal reactor using Illumina sequencing

The anaerobic/anoxic/oxic (A2O) process is globally one of the widely used biological sewage treatment processes. This is the first report of a metagenomic analysis using Illumina sequencing of full-scale A2O sludge from a municipal sewage treatment plant. With more than 530,000 clean reads from different taxa and metabolic categories, the metagenome results allow us to gain insight into the functioning of the biological community of the A2O sludge. There are 51 phyla and nearly 900 genera identified from the A2O activated sludge ecosystem. Proteobacteria, Bacteroidetes, Nitrospirae and Chloroflexi are predominant phyla in the activated sludge, suggesting that these organisms play key roles in the biodegradation processes in the A2O sewage treatment system. Nitrospira, Thauera, Dechloromonas and Ignavibacterium, which have abilities to metabolize nitrogen and aromatic compounds, are most prevalent genera. The percent of nitrogen and phosphorus metabolism in the A2O sludge is 2.72% and 1.48%, respectively. In the current A2O sludge, the proportion of Candidatus Accumulibacter is 1.37%, which is several times more than that reported in a recent study of A2O sludge. Among the four processes of nitrogen metabolism, denitrification related genes had the highest number of sequences (76.74%), followed by ammonification (15.77%), nitrogen fixation (3.88%) and nitrification (3.61%). In phylum Planctomycetes, four genera (Planctomyces, Pirellula, Gemmata and Singulisphaera) are included in the top 30 abundant genera, suggesting the key role of ANAMMOX in nitrogen metabolism in the A2O sludge.     

Effects of nitrogen dioxide and its acid mist on reactive oxygen species production and antioxidant enzyme activity in Arabidopsis plants

Nitrogen dioxide (NO₂) is one of the most common and harmful air pollutants. To analyze the response of plants to NO₂ stress, we investigated the morphological change, reactive oxygen species (ROS) production and antioxidant enzyme activity in Arabidopsis thaliana (Col-0) exposed to 1.7, 4, 8.5, and 18.8 mg/m³ NO₂. The results indicate that NO₂ exposure affected plant growth and chlorophyll (Chl) content, and increased oxygen free radical (O₂⁻) production rate in Arabidopsis shoots. Furthermore, NO₂ elevated the levels of lipid peroxidation and protein oxidation, accompanied by the induction of antioxidant enzyme activities and change of ascorbate (AsA) and glutathione (GSH) contents. Following this, we mimicked nitric acid mist under experimental conditions, and confirmed the antioxidant mechanism of the plant to the stress. Our results imply that NO₂ and its acid mist caused pollution risk to plant systems. During the process, increased ROS acted as a signal to induce a defense response, and antioxidant status played an important role in plant protection against NO₂/nitric acid mist-caused oxidative damage.     

Effect of the C:N:P ratio on the denitrifying dephosphatation in a sequencing batch biofilm reactor (SBBR)

A series of investigations were conducted using sequencing batch biofilm reactor(SBBR) to explore the influence of C:N:P ratio on biological dephosphatation including the denitrifying dephosphatation and the denitrification process.Biomass in the reactor occurred mainly in the form of a biofilm attached to completely submerged disks.Acetic acid was used as the source of organic carbon.C:N:P ratios have had a significant effect on the profiles of phosphate release and phosphate uptake and nitrogen removal.The highest rates of phosphate release and phosphate uptake were recorded at the C:N:P ratio of 140:70:7.The C:N ratio of 2.5:1 ensured complete denitrification.The highest rate of denitrification was achieved at the C:N:P ratio of 140:35:7.The increase of nitrogen load caused an increase in phosphates removal until a ratio C:N:P of 140:140:7.Bacteria of the biofilm exposed to alternate conditions of mixing and aeration exhibited enhanced intracellular accumulation of polyphosphates.Also,the structure of the biofilm encouraged anaerobic–aerobic as well as anoxic–anaerobic and absolutely anaerobic conditions in a SBBR.These heterogeneous conditions in the presence of nitrates may be a significant factor determining the promotion of denitrifying polyphosphate accumulating organism(DNPAO) development.     

Research progress and prospects of complete ammonia oxidizing bacteria in wastewater treatment

• Comammox bacteria have unique physiological characteristics. • Comammox bacteria are widely distributed in natural and artificial systems. • Comammox bacteria have the potential to reduce N₂O emissions. • Coupling comammox bacteria with DEAMOX can be promoted in wastewater treatment. • Comammox bacteria have significant potential for enhancing total nitrogen removal. Complete ammonia oxidizing bacteria, or comammox bacteria (CAOB), can oxidize ammonium to nitrate on its own. Its discovery revolutionized our understanding of biological nitrification, and its distribution in both natural and artificial systems has enabled a reevaluation of the relative contribution of microorganisms to the nitrogen cycle. Its wide distribution, adaptation to oligotrophic medium, and diverse metabolic pathways, means extensive research on CAOB and its application in water treatment can be promoted. Furthermore, the energy-saving characteristics of high oxygen affinity and low sludge production may also become frontier directions for wastewater treatment. This paper provides an overview of the discovery and environmental distribution of CAOB, as well as the physiological characteristics of the microorganisms, such as nutrient medium, environmental factors, enzymes, and metabolism, focusing on future research and the application of CAOB in wastewater treatment. Further research should be carried out on the physiological characteristics of CAOB, to analyze its ecological niche and impact factors, and explore its application potential in wastewater treatment nitrogen cycle improvement.     

Removal of nitrogen and phosphorus by eight strains of microalgae and their growth characteristics in Penaeus vannamei sewage北大核心CSCD

Microalgae are the most important primary productive forces in shrimp aquaculture systems. Microalgae not only provide oxygen and natural food for aquaculture objects, but they also absorb nitrogen (N) and phosphorus (P) to reduce water eutrophication. However, there are great differences in N and P absorption among different strains of microalgae. To maintain the sustainable development of shrimp aquaculture, the growth performances of eight microalgal strains in Penaeus vannamei sewage and N and P removal rates were investigated under laboratory conditions. The results indicated that the eight microalgal strains could reduce the N and P content in P. vannamei sewage to some extent. Microcystis aeruginosa, Chlamydomonas sp., and Chlorella pyrenoidosa grew very well, with average growth rates of 0.309 3, 0.246 9, and 0.215 5, respectively. There were significant differences in the removal efficiency among the different strains. The removal rates of total N by M. aeruginosa, Chlamydomonas sp., and C. pyrenoidosa were 74%, 69%, and 60%, respectively, at the end of the experiment, which were higher than the other species. M. aeruginosa and Chlamydomonas sp. had better total P removal efficiency than those of the other microalgal strains and removal rates were greater than 60%, and the second highest total P removal efficiency was by C. pyrenoidosa. Different types of microalgal strains had different absorption rates of different morphological nitrogen. M. aeruginosa and Chlamydomonas sp. had the highest nitrate nitrogen removal rate (approximately 70%). Chlamydomonas sp. had a fast and persistent removal rate of ammonia nitrogen, with the removal rate being as high as 100%. The removal efficiency of M. aeruginosa and C. pyrenoidosa were a little slower, and those of Scenedesmus obliquus, Synedra sp., and Navicula graciloides were the slowest. After 16 d, the removal rate reached more than 90%. Cryptomonas obovate and C. pyrenoidosa displayed the best removal rate of nitrite nitrogen, and the removal rate reached 80% on day 8, and the removal rate of C. obovata was more persistent. These results can provide scientific reference for the orientation and use of microalgae to remove pollutants in tailings water from shrimp aquaculture systems. © 2018 Science Press. All rights reserved.     

两种碳源对聚磷菌种群结构及除磷脱氮性能的影响

分别以乙酸钠和丙酸钠作为有机碳源,利用序批式反应器系统对聚磷菌进行富集培养,通过高通量测序技术和化学分析,研究两种碳源对聚磷菌种类及除磷脱氮性能的影响。结果表明：稳定状态下,两者均取得良好的除磷率（＞94%）,丙酸钠对除磷的促进作用优于乙酸钠,丙酸钠对脱氮的促进作用低于乙酸钠;在科和属的水平上,丙酸钠系统的聚磷菌丰度均高于乙酸钠系统。     

升钟湖水体叶绿素a动态特征及其影响因子分析

2011—2015年每月监测升钟湖湖区的4个代表性断面的水质指标,分析水体中叶绿素a时空分布特征、变化规律及影响水体水质状况的其他要素。结果表明:升钟湖的叶绿素a具有显著性的年际差异,表现为夏季高、冬季低且呈现逐年下降的变化趋势,总磷、总氮、氨氮、溶解氧、透明度监测指标同样表现为夏季高、冬季低的变化趋势,除溶解氧和透明度的监测指标逐年上升外,其他监测指标均逐年下降。构建了叶绿素a与总氮、总磷的多元回归方程模型,该模型可根据水体营养盐状态准确预测升钟湖叶绿素a的变化趋势。