Nitrogen recovery in a decoupled aquaponic system with lamellar settler and trickling biofilter: implications for system management

Careful nitrogen (N) management will be needed to nourish the growing human population while minimizing adverse environmental impacts. Aquaponic systems (AS) have a great potential to become a sustainable technology making further use of N-rich aquaculture wastewater. In the present study, we observed the N retention and losses in a running prototype of decoupled AS with Nile tilapia (Oreochromis niloticus) and tomatoes (Solanum lycopersicum) over 24 days. N losses amounted to 32.5% of feed N input and were observed in the recirculating aquaculture system (RAS) of the AS. Fish retained 21.1% of N input while 25.2% of N input accumulated in the RAS water. About 14.1% of the loss of N was caused probably by anaerobic denitrification processes in the lamellar settler (LS). In addition, 18.4% of N input was discharged during the three cleanings of LS. In the hydroponic unit of the AS that has been due to space limitations much smaller than an optimized AS could be (only about 20% of the optimal size relative to fish biomass), the tomato plants, including fruits, leaves, and stems, recovered 3.1% of N input with water uptake of 1700 L. The fish culture management, system design, and environmental management in the greenhouse affect the N recovery in the decoupled AS.

     

益生素可改善肠道微生物平衡和饲料卫生

肠道菌群与宿主动物间的关系是微妙的 ,而且二者间的应激作用对生产不利。即使在现代生产条件下 ,环境卫生改善 ,饲料配制合理 ,饲料中添加促生长剂、药物、口服疫苗 ,二者间的平衡也可能出现紊乱。随着对细菌性感染的了解 ,人们开始用饲料添加剂影响生物调节过程和通过稳定肠道菌群降低腹泻次数或消除腹泻。益生素与抗生素是有区别的 ,其微生物分类如下 :1母猪乳中细菌 :乳酸片球菌 ,嗜酸乳杆菌1 ,鼠李糖乳杆菌 ,胚芽乳杆菌 ,粪肠球菌。 2活酵母 :酿酒酵母。3产芽孢菌 :枯草芽孢杆菌 ,蜡状芽孢杆菌 ,地衣芽孢杆菌。 4其它 :米曲霉。益生素…     

Historical Contaminated Sediments and Soils at the River Basin Scale

Background, Aims, and Scope  

Data from the Elbe River and its tributaries indicate, despite extensive improvement in water quality during the last 15 years, that the respective sediment situation of many priority pollutants has not reached an acceptable level. For the coming decades, risks for downstream sites and stakeholders will persist, mainly due to secondary sources originating from historical pollution of soils and sediments in the catchment area. In practice, a catchment-wide assessment of historical contaminated soil and sediment should apply a three-step approach: (i) Identification of substances of concern (s.o.c.) and their classification into ’hazard classes of compounds’; (ii) identification of areas of concern (a.o.c.) and their classification into ‘hazard classes of sites’; (iii) identification of areas of risk (a.o.r.) and their assessment relative to each other with regard to the probability of polluting the sediments in the downstream reaches. The conversion of this concept has to consider the underlying philosophy of the EU Water Framework Directive, particularly with respect to the analysis and monitoring of priority substances in solid matrices. However, major deficiencies are still in the assessment and prognosis of resuspension processes, and potential approaches to fill this gap are described both in theory and from examples of the Elbe River.     

Wechselwirkungen zwischen Boden-Huminstoffen und Metall-Ionen I. Isolierung und Charakterisierung der Boden-Huminstoffe

Interactions between soil humic substances and metal ions I. Isolation and characterization of the soil humic substances From two horizons of a podzol humic acids and fulvic acids were isolated by two different methods. The obtained samples were characterized by elemental analysis, the determination of the ash and moisture content, functional group analysis as well as FTIR-, ¹H-NMR-, and ¹³C-NMR-spectroscopic examinations. In spite of the different isolation methods humic and fulvic acids show great similarities. A higher oxidized state and a lower content of aromatic structural features are clearly observed in the fulvic acids in contrast to humic acids. Besides aromatic structural elements, distinct aliphatic sections were detected in the investigated samples, which showed a lower concentration in the less transformed fractions of the Ahe-horizon.     

Wechselwirkungen zwischen Boden-Huminstoffen und Metall-Ionen II. Untersuchung von Boden-Huminstoffen mit der Gel-Permeations-Chromatographie und der Dampfdruck-Osmometrie

Interaction between soil humic substances and metal ions. II. Investigation of soil humic substances by gel permeation chromatography and vapour pressure osmometry By gel permeation chromatography and vapour pressure osmometry average molar masses of soil fulvic and soil humic acids from two horizons of a podzol were determined. For the fulvic acids average molar masses of 9000 g/mol were obtained by the chromatographic method, while 5000 g/mol were obtained by the osmometric method. In contrast to these results for the humic acids values were measured which are 3 - 4 times larger when measured by gel permeation chromatography and 2 - 3 times smaller when measured by vapour pressure osmometry. The average molar masses found show that the applied methods of isolation and purification as well as the different determination methods with the experimental conditions attached to them have a considerable influence on the molecular size of the isolated humic substances.     

Vertikaler Wasser- und Nitrattransport in tiefere Bodenschichten süddeutscher Ackerstandorte

Vertical water and nitrate movement into deeper soil layers on fields located in the south of Germany In Southern Bavaria, selected fields from deep loess and sandy sediments were sampled to a depth of maximum 10 m every 4 months, in order to determine the basic processes of water and nitrate movement in the course of the year. The downward movement of water and nitrate followed the principle of piston flow only in the intermediate vadose zone of loess soils with a leaching distance amounting 0.8 m per year. On the other hand, an accelerated as well as a delayed transport was observed in the zone of evapotranspiration of loess soils and in the whole profile of sandy soils, not being in accordance with the simple simulation model FLOTRA based on the classic theories of transport (Darcy flow, convection-dispersion-equation). Preferential flow led to the leaching of nitrate from the top soil to the lower boundary of the evapotranspiration zone of loess soils in 2 m depth, in winter and spring. In sandy soils nitrate was leached to the groundwater table in 4–6 m depth after extensive rainfall.     

Axonal neuregulin-1 regulates myelin sheath thickness

In the nervous system of vertebrates, myelination is essential for rapid and accurate impulse conduction. Myelin thickness depends on axon fiber size. We use mutant and transgenic mouse lines to show that axonal Neuregulin-1 (Nrg1) signals information about axon size to Schwann cells. Reduced Nrg1 expression causes hypomyelination and reduced nerve conduction velocity. Neuronal overexpression of Nrg1 induces hypermyelination and demonstrates that Nrg1 type III is the responsible isoform. We suggest a model by which myelin-forming Schwann cells integrate axonal Nrg1 signals as a biochemical measure of axon size.     

Nitrite, an electron donor for anoxygenic photosynthesis

We report a previously unknown process in which anoxygenic phototrophic bacteria use nitrite as an electron donor for photosynthesis. We isolated a purple sulfur bacterium 98% identical to Thiocapsa species that stoichiometrically oxidizes nitrite to nitrate in the light. Growth and nitrate production strictly depended on both light and nitrite. This is the first known microbial mechanism for the stoichiometric oxidation of nitrite to nitrate in the absence of oxygen and the only known photosynthetic oxidation in the nitrogen cycle. This work demonstrates nitrite as the highest-potential electron donor for anoxygenic photosynthesis known so far.