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81.
Youneng Tang Michal Ziv-El Chen Zhou Jung Hun Shin Chang Hoon Ahn Kerry Meyer Daniel Candelaria David Friese Ryan Overstreet Rick Scott Bruce E. Rittmann 《Frontiers of Environmental Science & Engineering》2010,4(3):280-285
A long-term pilot-scale H2-based membrane biofilm reactor (MBfR) was tested for removal of nitrate from actual groundwater. A key feature of this second-generation pilot MBfR is that it employed lower cost polyester hollow fibers and still achieved high loading rate. The steady-state maximum nitrate surface loading at which the effluent nitrate and nitrite concentrations were below the Maximum Contaminant Level (MCL) was at least 5.9 g·N·(m2·d)?1, which corresponds to a maximum volumetric loading of at least 7.7 kg·N·(m3·d) ?1. The steady-state maximum nitrate surface area loading was higher than the highest nitrate surface loading reported in the first-generation MBfRs using composite fibers (2.6 g·N·(m2·d)?1). This work also evaluated the H2-utilization efficiency in MBfR. The measured H2 supply rate was only slightly higher than the stoichiometric H2-utilization rate. Thus, H2 utilization was controlled by diffusion and was close to 100% efficiency, as long as biofilm accumulated on the polyester-fiber surface and the fibers had no leaks. 相似文献
82.
Gabor Mezösi Burghard C. Meyer Wolfgang Loibl Christoph Aubrecht Peter Csorba Teodora Bata 《Regional Environmental Change》2013,13(4):797-811
The assessment of regional climate change impacts combined with the sensitivity of landscape functions by predictive modelling of hazardous landscape processes is a new fundamental field of research. In particular, this study investigates the effects of changing weather extremes on meso-regional-scale landscape vulnerability. Climatic-exposure parameter analysis was performed on a predicted climate change scenario. The exposure to climate change was analysed on the basis of the original data of the meso-scale IPCC A1B climate scenario from the REMO and ALADIN regional models for the periods of 2021–2050 and 2071–2100, and the regional types of climate change impacts were calculated by using cluster analysis. Selected climate exposure parameters of the REMO and ALADIN models were analysed, in particular, for extreme events (days with precipitation greater than 30 mm, heat waves, dry periods, wet periods) and for daily temperature and precipitation. The landscape functions impacted by climate change are proxies for the main recent and future problematic processes in Hungary. Soil erosion caused by water, drought, soil erosion caused by wind, mass movement and flash floods were analysed for the time periods of 1961–1990, 2021–2050 and 2071–2100. Based on the sensitivity thresholds for the impact assessments, the landscape functional sensitivity indicators were interpreted, and an integrative summary of the five indicators was made, differentiating the regions facing only a few or multiple sensitivities. In Central Hungary, the increasing exposure and sensitivity to droughts will be a serious problem when following the REMO scenario. In several regions, most indicators will change the sensitivity threshold from a tolerable risk to an increased or very high risk. 相似文献
83.
Across animal taxa, exclusive female offspring care has evolved repeatedly from biparental care, suggesting that the latter
becomes evolutionarily unstable under certain conditions. Both the attributes of a species and the environment it experiences
can help to predict shifts from one particular care mode to another. Nevertheless, factors inducing differences in care strategies
among closely related species, or seasonal variation within species, have been subject to surprisingly little empirical testing.
Here, we report the results of a field-based study that examined both among and within species variation in mate desertion
in five species of closely related Nicaraguan cichlid fish in the genera Amphilophus and Amatitlania. The results show a link between female body size and male involvement in offspring care. Specifically, the larger the species
the less often males were found to provide extended care. Furthermore, we found that solitary females became more common towards
the end of the breeding season. We discuss the implications of this finding in the context of previous theoretical and empirical
contributions regarding the frequency of offspring desertion by males. 相似文献
84.
Duester L Prasse C Vogel JV Vink JP Schaumann GE 《Journal of environmental monitoring : JEM》2011,13(5):1204-1211
The pore water transport of antimony and titanium, applied as nanoparticles (NPs), was studied by spiking stable suspensions of two different nanomaterials on the surface of an undisturbed floodplain soil. For preparation of stable dispersions, two different strategies were followed. (i) Comparable to those used in industrial applications: titanium dioxide nanoparticles, with an average diameter of 99 nm, were prepared by high-energy ball milling in water, whereas for (ii) antimony trioxide (Sb(2)O(3); average diameter 121 nm) a dispersing agent (sodium salt of poly[(naphthaleneformaldehyde)sulfonate] (pNFS) in water) was used. The upper 17 cm of a floodplain soil (river Rhine, Germany) was sampled using the minimally invasive sediment or fauna incubation experiment (SOFIE? two compartment cell; 3 l volume each), which preserved the pore system of the soil. The cells were equipped with 450 and 100 nm filter probes at different depths providing a non-invasive sampling of the pore water. The pore water was sampled at different times (T = 0, 24, 48, 96 and 196 h) and analysed by inductively coupled plasma quadrupole mass spectrometry (ICP-QMS). Sb and Ti were transported via the pore water of the floodplain soil to a depth of 14 cm, corresponding to the maximum cell depth. The highest Sb concentration in the pore water was detected after 24 h at a depth of 5.5-8 cm. Although the spiked concentration was higher for Ti than for Sb, the total Ti concentration in the pore water of the spiked cell was lower. This indicates a stronger agglomeration of TiO(2) NPs or a more intensive interaction of Ti with the solid matrix and a faster transport of Sb towards deeper soil layers. The results show that metal(loid)s from metal oxide NPs are transported in the soil pore water and, hence, have the potential to act as the source of contamination of deeper soil layers after soil surface contamination. 相似文献
85.
The discovery of a possibly invasive Proscoloplos species on the French Atlantic coast led to a detailed morphological and molecular investigation. Proscoloplos consists of three nominal species, but molecular analyses of the variable ITS1 and ITS2 region revealed no clade support
for samples from South Africa, France and Australia, representing at least two of these nominal species. We found no unambiguous
diagnostic characters for the three different species even with scanning electron microscopy. Two main characters—first appearance
of branchiae and hooks—that were used for species delineation show considerable intrapopulational variation and do not withstand
critical evaluation. The obtained data and the observed regenerative capabilities point to a cautious use of the position
of branchiae and hooked chaetae as taxonomic marker in Proscoloplos. After experimental bisection of animals, the recovery led to a phenotype without recognizable signs of regeneration, but
neither branchiae nor hooked chaetae reoccurred at the same initial segmental position. Summarising the molecular and morphological
data we suggest the synonymy of the known Proscoloplos species under the senior synonym Proscoloplos cygnochaetus Day, 1967. The enormous geographic range of this species comprises the temperate waters of the whole southern hemisphere
and includes the French population. We discuss a dispersal enabled through the effective anchorage on vessels using mucous
glands and chaetae possibly combined with architomic reproduction. 相似文献
86.
Rapid tissue reduction and recovery in the sponge <Emphasis Type="Italic">Aplysinella</Emphasis> sp.
We observed a pronounced, yet reversible tissue reduction in the tropical sponge Aplysinella sp. under non-experimental conditions in its natural habitat, after transfer into seawater tanks, as well as after transplantation
from deep to shallow water in the field. Tissue reduction resulted in the formation of small “reduction bodies” tightly attached
to the sponge skeleton. Although volume loss and gain were substantial, both tissue reduction and regeneration were often
remarkably rapid, occurring within few hours. Microscopic analysis of the reduction bodies revealed morphological similarities
to previously described sponge primmorphs, with densely packed archaeocytes and spherulous cells enclosed by a thin layer
of epithelial-like cells. Denaturing gradient gel electrophoresis (DGGE) revealed pronounced changes in the sponge-associated
microbial community upon tissue reduction during laboratory and field experiments and following changes in ambient conditions
after transplantation in the field. Generally, the microbial community associated with this sponge proved less stable, less
abundant, and less diverse than those of other, previously investigated Verongid sponges. However, one single phylotype was
consistently present in DGGE profiles of Aplysinella sp. This phylotype clustered with γ-proteobacterial sequences found previously in other sponge species of different taxonomic
affiliations and geographic provenances, as well as in sponge larvae. No apparent changes in the total secondary metabolite
content (per dry weight) occurred in Aplysinella sp. upon tissue reduction; however, comparative analysis of intact and reduced tissue suggested changes in the concentrations
of two minor compounds. Besides being ecologically interesting, the tissue reduction phenomenon in Aplysinella sp. provides an experimentally manipulable system for studies on sponge/microbe symbioses. Moreover, it may prove useful
as a model system to investigate molecular mechanisms of basic Metazoan traits in vivo, complementing the in vitro sponge
primmorph system currently used in this context. 相似文献
87.
Hawkins BA Diniz-Filho JA Bini LM Araújo MB Field R Hortal J Kerr JT Rahbek C Rodríguez MA Sanders NJ 《Ecology》2007,88(8):1898-1902
88.
A review is presented on trace gas exchange of CH4, CO, N2O, and NOx arising from agriculture and natural sources in the world's semiarid and arid zones due to soil processes. These gases are important contributors to the radiative forcing and the chemistry of the atmosphere. Quantitative information is summarized from the available studies. Between 5 and 40% of the global soil-atmosphere exchange for these gases (CH4, CO, N2O, and NOx) may occur in semiarid and arid zones, but for each of these gases there are fewer than a dozen studies to support the individual estimates, and these are from a limited number of locations. Significant differences in the biophysical and chemical processes controlling these trace gas exchanges are identified through the comparison of semiarid and arid zones with the moist temperate or wet/dry savanna land regions. Therefore, there is a poorly quantified understanding of the contribution of these regions to the global trace gas cycles and atmospheric chemistry. More importantly, there is a poor understanding of the feedback between these exchanges, global change, and regional land use and air pollution issues. A set of research issues is presented. 相似文献
89.
Skjøth CA Ellermann T Hertel O Gyldenkaerne S Mikkelsen MH 《Journal of the Air & Waste Management Association (1995)》2008,58(9):1158-1165
Releases of ammonia (NH3) to the atmosphere contribute significantly to the deposition of nitrogen to both terrestrial and aquatic ecosystems. This is the background for the national NH3 emission ceilings in Europe. However, in some countries the national legislation aims not only to meet these ceilings but also to reduce the atmospheric nitrogen deposition to local ecosystems. Such measures to reduce the load of nitrogen to local ecosystems were introduced in Denmark in 1994. In this paper we demonstrate that this regulation is reflected in the NH3 concentrations in Denmark. The Danish legislation forces farmers to applying manure to the fields during the crop-growing season. We have analyzed the seasonal variation in local NH3 concentrations over the time period of 1989-2003. During this period the seasonal variation has changed from having moderate spring and autumn concentration peaks to having a single and much more pronounced spring peak. In the analysis we apply an NH3 emission model to demonstrate that these changes in the seasonal variation are a result of the changes in the Danish legislation. The analysis demonstrates the strength of using a high-resolution emission model in the analysis of routine monitoring data. 相似文献
90.
Jacobsen CS van der Keur P Iversen BV Rosenberg P Barlebo HC Torp S Vosgerau H Juhler RK Ernstsen V Rasmussen J Brinch UC Jacobsen OH 《Environmental pollution (Barking, Essex : 1987)》2008,156(3):794-802
Pesticide mineralization and sorption were determined in 75 soil samples from 15 individually drilled holes through the vadose zone along a 28 km long transect of the Danish outwash plain. Mineralization of the phenoxyacetic acid herbicide MCPA was high both in topsoils and in most subsoils, while metribuzine and methyltriazine-amine was always low. Organic matter and soil pH was shown to be responsible for sorption of MCPA and metribuzine in the topsoils. The sorption of methyltriazine-amine in topsoil was positively correlated with clay and negatively correlated with the pH of the soil. Sorption of glyphosate was tested also high in the subsoils. One-dimensional MACRO modeling of the concentration of MCPA, metribuzine and methyltriazine-amine at 2 m depth calculated that the average concentration of MCPA and methyltriazine-amine in the groundwater was below the administrative limit of 0.1 μg/l in all tested profiles while metribuzine always exceeded the 0.1 μg/l threshold value. 相似文献