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1.
Gebauer Radek Lehman Liliana Monsees Hendrik Rennert Bernhard Mráz Jan Kloas Werner 《Aquaculture International》2022,30(4):2043-2058
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.
相似文献2.
Dissolved organic matter (DOM) is involved in many important biogeochemical processes in soil. As its collection is laborious, very often water‐soluble organic matter (WSOM) obtained by extracting organic or mineral soil horizons with a dilute salt solution has been used as a substitute of DOM. We extracted WSOM (measured as water‐soluble organic C, WSOC) from seven mineral horizons of three forest soils from North‐Rhine Westphalia, Germany, with demineralized H2O, 0.01 M CaCl2, and 0.5 M K2SO4. We investigated the quantitative and qualitative effects of the extractants on WSOM and compared it with DOM collected with ceramic suction cups from the same horizons. The amounts of WSOC extracted differed significantly between both the extractants and the horizons. With two exceptions, K2SO4 extracted the largest amounts of WSOC (up to 126 mg C kg–1) followed by H2O followed by CaCl2. The H2O extracts revealed by far the highest molar UV absorptivities at 254 nm (up to 5834 L mol–1 cm–1) compared to the salt solutions which is attributed to solubilization of highly aromatic compounds. The amounts of WSOC extracted did not depend on the amounts of Fe and Al oxides as well as on soil organic C and pH. Water‐soluble organic matter extracted by K2SO4 bore the largest similarity to DOM due to relatively analogue molar absorptivities. Therefore, we recommend to use this extractant when trying to obtain a substitute for DOM, but as WSOM extraction is a rate‐limited process, the suitability of extraction procedures to obtain a surrogate of DOM remains ambiguous. 相似文献
3.
As floodplain soils are often contaminated, we studied the release of trace metals from three topsoil horizons in column experiments with variable flow interruptions and flow velocities, compared it with that in batch leaching tests and evaluated the column data by inverse simulations. Only small proportions (<1%) of trace metals present in the neutral and humic soils were mobilised by the batch leaching tests and the column experiments. Release of Cr, Cu, Ni and Zn in the column experiments was rate-limited, as detected by increased concentrations after flow interruptions. A combination of linear equilibrium and non-equilibrium isotherms reflected the Ni and Zn elution data, with Zn release being slower. Simulated values for initially bound metals available for release are in the same order of magnitude as those determined by the batch leaching tests. However, the consistency of both experimental approaches decreases with increasing rate limitation, as detected here for Zn. 相似文献
4.
Kai U. Totsche Thilo Rennert Martin H. Gerzabek Ingrid Kögel‐Knabner Kornelia Smalla Michael Spiteller Hans‐Jörg Vogel 《植物养料与土壤学杂志》2010,173(1):88-99
Soil, the “Earth's thin skin” serves as the delicate interface between the biosphere, hydrosphere, atmosphere, and lithosphere. It is a dynamic and hierarchically organized system of various organic and inorganic constituents and organisms, the spatial structure of which defines a large, complex, and heterogeneous interface. Biogeochemical processes at soil interfaces are fundamental for the overall soil development, and they are the primary driving force for key ecosystem functions such as plant productivity and water quality. Ultimately, these processes control the fate and transport of contaminants and nutrients into the vadose zone and as such their biogeochemical cycling. The definite objective in biogeochemical‐interface research is to gain a mechanistic understanding of the architecture of these biogeochemical interfaces in soils and of the complex interplay and interdependencies of the physical, chemical, and biological processes acting at and within these dynamic interfaces in soil. The major challenges are (1) to identify the factors controlling the architecture of biogeochemical interfaces, (2) to link the processes operative at the individual molecular and/or organism scale to the phenomena active at the aggregate scale in a mechanistic way, and (3) to explain the behavior of organic chemicals in soil within a general mechanistic framework. To put this in action, integration of soil physical, chemical, and biological disciplines is mandatory. Indispensably, it requires the adaption and development of characterization and probing techniques adapted from the neighboring fields of molecular biology, analytical and computational chemistry as well as materials and nano‐sciences. To shape this field of fundamental soil research, the German Research Foundation (DFG) has granted the Priority Program “Biogeochemical Interfaces in Soil”, in which 22 individual research projects are involved. 相似文献
5.
Iron-cyanide complexes in soil under varying redox conditions: speciation, solubility and modelling 总被引：1，自引：0，他引：1
The distribution of iron‐cyanide complexes between ferrocyanide, [FeII(CN)6]4–, and ferricyanide, [FeIII(CN)6]3–, in soils on contaminated sites depends on the redox potential, EH. We carried out microcosm experiments in which ferrocyanide (20 mg l?1) was added to an uncontaminated moderately acidic subsoil (pH 5.2), and varied the EH of the soil suspension between 200 and 700 mV over up to 109 days. Ferrocyanide and ferricyanide were analysed by capillary isotachophoresis. At redox potentials ranging from 400 to 700 mV, small amounts of iron‐cyanide complexes were adsorbed, and ferrocyanide was almost completely oxidized to ferricyanide. Decreasing EH to 200 mV led to nearly complete removal of iron‐cyanide complexes from solution, and the complexes were not mobilized after subsequent aeration (EH > 350 mV). Under weakly to moderately reducing conditions (EH ≈ 200 mV), iron‐cyanide complexes were removed from solution by precipitation, which occurred, presumably in the form of e.g. Fe2[FeII(CN)6], Fe4[FeII(CN)6]3 or Mn2[FeII(CN)6], after reductive dissolution of Mn and Fe oxides. Four different sets of geochemical model calculations were carried out. The species distribution between ferrocyanide and ferricyanide in solution was predicted reliably under varying pH and redox conditions when iron‐cyanide complex concentrations and Fe concentrations, excluding Fe bound in iron‐cyanide complexes, were used in model calculations. In model calculations on the fate of iron‐cyanide complexes in soil, adsorption reactions must be considered, especially under oxidizing conditions. Otherwise, the calculated iron‐cyanide complex concentrations are larger than those actually measured. 相似文献
6.
The iron‐cyanide complexes ferrocyanide, [FeII(CN)6]4–, and ferricyanide, [FeIII(CN)6]3–, are anthropogenic contaminants in soil. We investigated their sorption on goethite, α‐FeOOH, in batch experiments in a time range from 1 d to 1 yr, their desorption by phosphate and chloride as well as their surface complexes on goethite by Fourier‐transform infrared spectroscopy (FTIR). The sorption of both complexes continued over the whole time range. Percent desorption of ferricyanide by phosphate decreased, whereas that of ferrocyanide increased until it amounted to approximately 87% for both complexes. By FTIR spectroscopy inner‐sphere complexation of both complexes on the goethite surface was indicated. With both complexes, a Berlin‐Blue‐like layer (Fe4[Fe(CN)6]3) was formed initially on the goethite surface which disappeared with increasing reaction time. After at least 30 d reaction time, ferricyanide was the only sorbed iron‐cyanide complex detected even when ferrocyanide was initially added. This resulted from slow oxidation of ferrocyanide, most probably by dissolved oxygen. Based on all results, we propose that ferricyanide forms monodentate inner‐sphere complexes on the goethite surface. 相似文献
7.
Iron‐cyanide complexes are present in soils on sites of former gas plants and coke ovens. We have studied the sorption of the complexes ferricyanide, [Fe(CN)6]3–, and ferrocyanide, [Fe(CN)6]4–, on goethite in batch experiments, including the effects of concentration, time, ionic strength, pH, and the extent of reversibility. The sorption of ferricyanide showed features of both outer‐sphere and inner‐sphere complexation: its extent decreased with increasing pH; it depended on ionic strength; it was quickly and completely reversible; and it induced a change in surface electric potential. In contrast, sorption of ferrocyanide depended on pH to a lesser extent and was not affected by ionic strength at different pHs. The desorption was slower and incomplete. For ferrocyanide we conclude that sorption involves inner‐sphere complexation and precipitation of a Berlin‐Blue‐like phase on the goethite surface. 相似文献
8.
Avoiding chemical and physical artifacts during sampling is crucial for realistic analyses of mineral and other colloids in soil. We developed a sampler, which allows for the in situ collection of Fe oxides that precipitate in their natural environment in a Bg horizon of a Calcaric Gleysol. Simultaneous measurements of redox‐sensitive parameters confirmed temporal changes from Fe‐reducing to Fe‐oxidizing conditions on site. 相似文献
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10.
T. Rennert M. Händel C. Höschen J. Lugmeier M. Steffens K. U. Totsche 《European Journal of Soil Science》2014,65(5):684-692
The development of Stagnosols is the consequence of perched water tables, which induce periodic oxidizing and reducing conditions. These cause the spatial distribution of iron (Fe) and manganese (Mn) between the soil matrix and ferromanganese concretions or nodules. Since oxides of these metals may interact with organic matter, we studied their spatial distribution in bulk material from the Bg horizon of a Stagnosol and in a nodule separated from the horizon. We used wet‐chemical analyses and X‐ray diffractometry together with microscopic techniques and nano‐scale secondary ion mass spectrometry (NanoSIMS), the latter allowing for a submicrometre‐scale spatial resolution. X‐ray diffractometry revealed the presence of quartz, clay minerals, micas and feldspars as the dominant minerals and indicated the presence of lepidocrocite. Relative to the bulk horizon material, the nodule was strongly enriched in organic C (by a factor of 31) and pedogenic (dithionite‐extractable) Fe and Mn (by factors of 2.2 and 62). We selected two regions on a thin section of the nodule for NanoSIMS investigations after studying the element distribution by scanning‐electron microscopy (SEM): one was located in an almost closed pore, the other one along an elongated pore. The NanoSIMS measurements allowed a clearer distinction of Fe‐ and Mn‐accumulation zones than SEM‐EDS. The evaluation of the NanoSIMS measurements by unsupervised classification revealed that zones containing silicates and Mn oxides and the transitional zones between Fe and Mn oxides were particularly enriched in soil organic matter, while, with one exception, the pure Fe‐accumulation zones did not indicate the presence of soil organic matter. 相似文献