Sorption influenced transport of ionizable pharmaceuticals onto a natural sandy aquifer sediment at different pH

The pH-dependent transport of eight selected ionizable pharmaceuticals was investigated by using saturated column experiments. Seventy-eight different breakthrough curves on a natural sandy aquifer material were produced and compared for three different pH levels at otherwise constant conditions. The experimentally obtained K_OC data were compared with calculated K_OC values derived from two different log K_OW-log K_OC correlation approaches. A significant pH-dependence on sorption was observed for all compounds with pK_a in the considered pH range. Strong retardation was measured for several compounds despite their hydrophilic character. Besides an overall underestimation of K_OC, the comparison between calculated and measured values only yields meaningful results for the acidic and neutral compounds. Basic compounds retarded much stronger than expected, particularly at low pH when their cationic species dominated. This is caused by additional ionic interactions, such as cation exchange processes, which are insufficiently considered in the applied K_OC correlations.     

Investigation of NiO/NiAl2O4 oxygen carriers for chemical-looping combustion produced by spray-drying

Chemical-looping combustion is a novel combustion technology with inherent separation of the greenhouse gas CO₂. The technology uses circulating oxygen carriers to transfer oxygen from the combustion air to the fuel. In this paper, oxygen carriers based on commercially available NiO and α-Al₂O₃ were prepared using the industrial spray-drying method, and compared with particles prepared by freeze-granulation. The materials were investigated under alternating oxidizing and reducing conditions in a laboratory fluidized bed, thus simulating the cyclic conditions of a chemical-looping combustion system. The particles produced by spray-drying displayed a remarkable similarity to the freeze-granulated oxygen carriers, with high reactivity when the bed was fluidized and similar physical properties when sintered at the same temperature. This is an important result as it shows that the scaling-up from a laboratory production method, i.e. freeze-granulation, to a commercial method suitable for large-scale production, i.e. spray-drying, did not involve any unexpected difficulties. A difference noticed between the spray-dried and freeze-granulated particles was the sphericity. Whereas the freeze-granulated particles showed near perfect sphericity, a large portion of the spray-dried particles had hollow interiors. Defluidization was most likely to occur for highly reduced particles, at low gas velocities. The apparent density and crushing strength of the oxygen carriers could be increased either by increasing the sintering temperature or by increasing the sintering time. However, the fuel conversion was fairly unchanged when the sintering temperature was increased but was clearly improved when the sintering time was increased.     

Evaluation of the forest growth simulator SILVA on dominant trees in mature mixed Silver fir–Norway spruce stands in South-West Germany

Forest growth simulators go beyond a mere tabulation of empirical measurements by employing biometric models that functionally describe the dependence of forest growth of the initial forest structure, growth conditions and management regime. This makes them very flexible and allows predicting growth reactions for unknown and/or complex forest growth scenarios. When simulation outcomes are to be used in silvicultural strategic planning, the results are of direct and delicate importance, and the correct simulator performance must be ascertained. This is especially so when the considered forest situation differs from the forest data used to parameterise the model (e.g. different geographical region).In this article, the forest growth simulator SILVA (version 2.2) was validated for 55 long-term experimental plots of mature mixed Silver fir–Norway spruce stands in southwest Germany (Picea abies, Abies alba). The evaluation was restricted to the upper canopy trees during the survey period 1989–2004. Following the general evaluation criteria for ecological models from [Vanclay, J.K., Skovsgaard, J.P., 1997. Evaluating forest growth models. Ecol. Mod. 98, 1–12], a specific methodology was developed to evaluate the simulated height and diameter growth on the basis of forest growth principles.The qualitative analysis proved the SILVA growth algorithms to be in accordance with physiologically based standard growth equations. The quantitative evaluation was limited by incomplete knowledge of the site conditions. To overcome this problem, the experimental plots were regarded as a “heterogeneous growth series” which allows analysing the growth behaviour in a more general way. It could be shown that for the given data set, the SILVA simulations produced an overestimation of height growth (median: +61% spruce, +12% fir), and an underestimation of diameter growth and competition sensitivity (median: ?16% spruce, ?70% fir). The errors partially compensated in the volume growth resulting in an overall over-/underestimation of +9% for spruce and ?58% for fir (median).The unbalanced height and diameter growth cannot be compensated by a change in the site conditions because this affects both height and diameter growth either positive or negative. Hence, an adjustment of selected parameterisation values appears to offer the best solution to adapt SILVA to the considered forest situation. This approach of adaptive parameterisation is discussed against a more general background of deductive vs. inductive forest growth modelling.     

Erprobung und Erfolgskontrolle eines Phytoremediationsverfahrens zur Sanierung Sprengstoff-kontaminierter Böden

The final article of a series of three evaluates the in situ-remediation of TNT(trinitrotoluene)-contaminated soil from ‘Werk Tanne’. The multidisciplinary approach allows a differentiated assessment. Grading with large-scale machinery leads to a depletion of TNT for almost 90% within the first 6 months, while ADNT(amino-dinitrotoluene)-content decreases more or less steadily over 1,5 years. Grading reduces the heterogenous distribution of the contamination only slightly. Results from field-monitoring and biotest-battery indicate residual toxicities of ecotoxicological relevance and a reduced capacity for biological regeneration, in comparison with the uncontamined site. Mycorrhized plants safe-guard the site and improve the soilecological conditions. Their role in reducing lower level residual toxicity requires further investigation. There is need for future research (1) on the dynamics and mechanisms of the initial decrease of TNT followed by stagnation, (2) on the fate of the primary metabolites, (3) on long-term effects of the phytoremediation, and (4) on the establishment of the complex monitoring for routine work.     

Identifying pathways to visions of future land use in Europe

Regional Environmental Change - Plausible scenarios of future land use derived from model projections may differ substantially from what is actually desired by society, and identifying such...     

The scent of sun worship: basking experience alters scent mark composition in male lizards

Signals used in female choice should honestly advertise the benefits that males can provide, with direct benefits often argued as being more important than indirect benefits. However, the nature of direct benefits in species without paternal care or nuptial gifts is poorly understood. Previous studies on lizards suggest that females decide where to settle and assumedly who to mate with based on information contained in scent marks from territorial males. Access to high-quality thermal resources is crucial for female reproductive success. Females may therefore be able to detect and exploit thermal-induced variation in the chemical composition of male scent marks when assessing the quality of his territory. We show that the amount of time male wall lizards (Podarcis muralis) are allowed to bask significantly alters the chemical composition of their femoral secretions used in scent marking. The direction of the change is consistent with adaptive plasticity to maintain signalling efficacy under warm conditions that increase evaporation of femoral secretions. The compounds affected by basking experience included those previously associated with male quality or shown to mediate male–male competition in lizards. However, whilst female lizards could discriminate between scent marks of males that had experienced different basking conditions, they did not preferentially associate with the scent from males from high-quality thermal conditions. These results highlight the potential importance of a previously neglected environmental effect on chemical signalling. We suggest thermal effects may have significant consequences for scent-mark composition in variable environments, with potential repercussions on olfactory communication in lizards.     

Effects of high atmospheric CO2 concentration on root hydraulic conductivity of conifers depend on species identity and inorganic nitrogen source

We examined root hydraulic conductivity (L_p) responses of one-year-old seedlings of four conifers to the combined effects of elevated CO₂ and inorganic nitrogen (N) sources. We found marked interspecific differences in L_p responses to high CO₂ ranging from a 37% increase in P. abies to a 27% decrease in P. menziesii, but these effects depended on N source. The results indicate that CO₂ effects on root water transport may be coupled to leaf area responses under nitrate (NO₃⁻), but not ammonium (NH₄⁺) dominated soils. To our knowledge, this is the first study that highlights the role of inorganic N source and species identity as critical factors that determine plant hydraulic responses to rising atmospheric CO₂ levels. The results have important implications for understanding root biology in a changing climate and for models designed to predict feedbacks between rising atmospheric CO₂, N deposition, and ecohydrology.     

Deforestation and cattle expansion in the Paraguayan Chaco 1987–2012

Regional Environmental Change - The dry forests of Latin America are among the most dynamic deforestation frontiers in the world and are important carbon and biodiversity reservoirs. Our knowledge...     

Chemical-looping with oxygen uncoupling for combustion of solid fuels

Chemical-looping with oxygen uncoupling (CLOU) is a novel method to burn solid fuels in gas-phase oxygen without the need for an energy intensive air separation unit. The carbon dioxide from the combustion is inherently separated from the rest of the flue gases. CLOU is based on chemical-looping combustion (CLC) and involves three steps in two reactors, one air reactor where a metal oxide captures oxygen from the combustion air (step 1), and a fuel reactor where the metal oxide releases oxygen in the gas-phase (step 2) and where this gas-phase oxygen reacts with a fuel (step 3). In other proposed schemes for using chemical-looping combustion of solid fuels there is a need for an intermediate gasification step of the char with steam or carbon dioxide to form reactive gaseous compounds which then react with the oxygen carrier particles. The gasification of char with H₂O and CO₂ is inherently slow, resulting in slow overall rates of reaction. This slow gasification is avoided in the proposed process, since there is no intermediate gasification step needed and the char reacts directly with gas-phase oxygen. The process demands an oxygen carrier which has the ability to react with the oxygen in the combustion air in the air reactor but which decomposes to a reduced metal oxide and gas-phase oxygen in the fuel reactor. Three metal oxide systems with suitable thermodynamic properties have been identified, and a thermal analysis has shown that Mn₂O₃/Mn₃O₄ and CuO/Cu₂O have suitable thermodynamic properties, although Co₃O₄/CoO may also be a possibility. However, the latter system has the disadvantage of an overall endothermic reaction in the fuel reactor. Results from batch laboratory fluidized bed tests with CuO and a gaseous and solid fuel are presented. The reaction rate of petroleum coke is approximately a factor 50 higher using CLOU in comparison to the reaction rate of the same fuel with an iron-based oxygen carrier in normal CLC.