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A crucial challenge for including biophysical photosynthesis–transpiration models into complex crop growth models is to integrate the plasticity of photosynthetic processes that is related to factors like nitrogen (N) content, age, and rank of leaves, or to the adaptation of plants to growth temperature (Tg). Here we present a new version of the combined photosynthesis-stomatal conductance model LEAFC3-N [Müller, J., Wernecke, P., Diepenbrock, W., 2005. LEAFC3-N: a nitrogen sensitive extension of the CO2 and H2O gas exchange model LEAFC3 parameterised and tested for winter wheat (Triticum aestivum L.). Ecological Modelling 183, 183–210.] that was revised, extended and completely re-parameterised for barley (Hordeum vulgare L.) with special regard for these factors to facilitate the use of the model in ecophysiological studies and in crop modelling. The analysis is based on novel comprehensive data on photosynthetic CO2 and light response curves measured at two oxygen concentrations and different temperatures on leaves of barley (H. vulgare L.) differing in leaf N and chlorophyll content. Plants were grown in climatic chambers or in the field at different N and Tg.We thoroughly revised the existing and introduced new nitrogen relations for key model parameters that account for a linear increase with leaf N of Vmax, Jmax, Tp, and Rdmax (maximum rates of carboxylation, electron transport, triose phosphate export, and mitochondrial respiration), a saturation-type increase of φ (quantum yield of electron transport), and a non-linear decrease of θ and m (curvature of the light dependence of electron transport rate, scaling factor of the stomata model). The adaptation of photosynthetic characteristics to Tg was included into the model by linear relations that were observed between Tg and the activation energy ΔHa of the temperature response characteristics of Vmax, Jmax, and Tp as well as of the nitrogen dependency of these characteristics. Based on an analysis of diurnal time courses of gas exchange rates it was found necessary including not only the relation between leaf water potential (Ψ) and stomatal conductance as used originally in LEAFC3, but additional effects on Vmax and Jmax. With the above-listed extensions, the model was capable to reproduce the observed plasticity and the recorded diurnal time courses of gas exchange rates fairly well. Thus, we conclude that the new model version can be used under a broad range of conditions, both for ecophysiological studies and as a submodel of crop growth models. The results presented here for barley will facilitate adapting photosynthesis models like LEAFC3-N to other C3-species as well. The modelling of the effects of drought stress should be further elaborated in future based on more specific experiments. 相似文献
276.
van Elteren JT Slejkovec Z Arcon I Glass HJ 《Environmental pollution (Barking, Essex : 1987)》2006,139(3):477-488
During the later stages of hard-rock mining in Cornwall, UK, widespread processing and refining of arsenic in purpose-built calciners resulted in severe, localized contamination of soils with arsenic. Several physical-chemical techniques were applied to characterize arsenic in a calciner residue dump: X-ray powder diffraction (XRD), sequential extraction combined with hyphenated speciation methods, and X-ray absorption spectroscopic (XAS) methods such as XANES (X-ray absorption near-edge structure) and EXAFS (extended X-ray absorption fine structure). Arsenic was predominantly present in pentavalent form, bound to amorphous or poorly-crystalline hydrous oxides of Fe (probably alpha-hematite). A small amount of a non-classified crystalline iron arsenate phase was found, viz. Fe2(As(AsO4)3). There was also evidence for the presence of some arsenate bound to quartz (alpha-SiO2). The overall results make us believe that the normally assumed relative safety, from a mobility point of view, is questionable since only a small fraction of arsenic is found in a crystalline iron arsenate form. 相似文献
277.
Johannes Tintner Ena Smidt Katharina Böhm Lydia Matiasch 《Waste management (New York, N.Y.)》2012,32(12):2418-2425
Risk assessment of two sections (I and II) of an old landfill (ALH) in Styria (Austria) in terms of reactivity of waste organic matter and the related potential of gaseous emissions was performed using conventional parameters and innovative tools to verify their effectiveness in practice. The ecological survey of the established vegetation at the landfill surface (plant sociological relevés) indicated no relevant emissions over a longer period of time. Statistical evaluation of conventional parameters reveals that dissolved organic carbon (DOC), respiration activity (RA4), loss of ignition (LOI) and total inorganic carbon (TIC) mostly influence the variability of the gas generation sum (GS21). According to Fourier Transform Infrared (FT-IR) spectral data and the results of the classification model the reactivity potential of the investigated sections is very low which is in accordance with the results of plant sociological relevés and biological tests. The interpretation of specific regions in the FT-IR spectra was changed and adapted to material characteristics. Contrary to mechanically–biologically treated (MBT) materials, where strong aliphatic methylene bands indicate reactivity, they are rather assigned to the CH vibrations of plastics in old landfill materials. This assumption was confirmed by thermal analysis and the characteristic heat flow profile of plastics containing landfill samples. Therefore organic carbon contents are relatively high compared to other stable landfills as shown by a prediction model for TOC contents based on heat flow profiles and partial least squares regression (PLS-R). The stability of the landfill samples, expressed by the relation of CO2 release and enthalpies, was compared to unreactive landfills, archeological samples, earthlike materials and hardly degradable organic matter. Due to the material composition and the aging process the landfill samples are located between hardly degradable, but easily combustible materials and thermally resistant materials with acquired stability. 相似文献
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279.
Formation of chlorinated and brominated dioxins and other organohalogen compounds at the pilot incineration plant VERONA 总被引:5,自引:0,他引:5
Experiments were conducted at the VERONA pilot plant, an incineration plant with stationary grate and separate post-combustion chamber, using wood and propane as basic combustible materials and with controlled dosage of various bromine-, chlorine- and copper-containing compounds. The behaviour of the following compounds was studied in the combustion chamber, after the post-combustion chamber and after the heat exchanger: polychlorinated phenols (PCPh), polybrominated phenols (PBrPh), polychlorinated benzenes (PCBz), polybrominated benzenes (PBrBz), polychlorinated dioxins and furans (PCDD/F) and polybrominated dioxins and furans (PBDD/F). The bromine co-incineration leaded to very high bromophenol concentrations after the post-combustion chamber. The formation of brominated and mixed-halogenated phenols and the further reaction to halogenated dioxins is apparently a relevant reaction mechanism for dioxin formation in processes involving bromine. This assumption is supported by the high formation rates of PBDD/F found in the heat exchanger, which were 4-20 times higher than those of PCDD/F. Moreover, the strong correlations found between the formation rates of PCPh, PCBz and PCDD/F in the heat exchanger indicate that in addition considerable new formation of dioxins takes place through de novo synthesis. Experiments involving the variation of primary operational parameters and fuel properties have shown that the quality of post-combustion plays a much greater role than the other parameters. Furthermore, it became apparent that the congeners of the chlorophenols and of the chlorobenzenes, measured in various incineration stages, do not correlate closely with the dioxin concentrations after the heat exchanger. 相似文献
280.
Andreani-Aksoyoglu Sebnem Keller Johannes Dommen Josef Prévôt André S. H. 《Water, Air, & Soil Pollution: Focus》2003,3(5-6):289-305
The three-dimensional Eulerian model CAMx (Comprehensive Air QualityModel with Extensions) was applied for the first time to simulate bothgaseous and particulate photochemical air pollution in Switzerland during July 28–30, 1993. The meteorological input data were prepared using the Systems Applications International Mesoscale Model (SAIMM). The CAMx model results were compared with the measurements carried out at ground level andfrom airborne measuring platforms within the frame of the Swiss POLLUMET research programme. In general, the CAMx performance for gaseous species wasfound to be better than that of the previously used Urban Airshed Model (UAM)and the Variable Grid Urban Airshed Model (UAM-V). The most significant improvement for the gaseous species is in the prediction of HNO3 concentrations, due to the inclusion of aerosol chemistry. Aerosol species such as NO3
-, NH4
+, SO4
2-, and secondary organic aerosols were calculated in one particle size range (0.04–2.5 m) and compared with a few measurements available. Although July 29 was reasonably well simulated, overestimated wind speeds by SAIMM for July 30 caused a too fast transport of pollutants. Similarly to measurements, significant spatial correlation of the secondarily formed aerosols with ozone and formaldehyde is found in the afternoon. 相似文献