排序方式： 共有22条查询结果，搜索用时 15 毫秒
1.
Abstract. Photosynthesis and growth rates in samples of two green seaweeds ( Ulva and Enteromorpha ) were monitored in the laboratory. The macroalgae were collected every 15 days from four coastal embayments in Galicia (NW Spain). Ulva samples were found to be nutritionally limited, particularly in summer. The physiological activity of Enteromorpha did not appear to be as affected by nutrient scarcity, although it may have suffered from phosphorus limitation. The subsistence quotas, critical concentrations and storage capacity for N and P in Ulva were comparable to those obtained by other investigators in similar studies. The trace metals analysed apparently did not negatively affect the macroalgae at the measured concentrations; one explanation is that many of these metals function as essential micronutrients. The complex physiological interactions between metals and nutrients, however, may complicate interpretation of the results. 相似文献
2.
Jan Klimeš Miroslava Benešová Vít Vilímek Petr Bouška Alejo Cochachin Rapre 《Natural Hazards》2014,71(3):1617-1638
In April 2010, an ice/rockfall into Lake 513 triggered a glacial lake outburst flood (GLOF) along the Chucchun River in the Cordillera Blanca of Peru. This paper reconstructs the hydrological characteristics of this as yet undocumented event using a 1D flood model prepared with HEC-RAS. The principle model inputs were obtained during detailed field surveys of surface characteristics and topography within the river and across the adjacent floodplain; a total of 120 cross-sections were surveyed. These inputs were refined further by eyewitness accounts and additional geomorphological observations. The flood modelling has enabled us to constrain the extent of the water surface and its elevation at each cross-section in addition to defining the peak discharge (580 m3 s?1). These modelling results show good agreement with other information about the flood including: flood marks and minimum flood levels; the lake displacement wave height; the extent of the flooded area; and the travel time from Lake 513 to the confluence with the Santa River. This demonstrates that the model offers a reliable reconstruction of the basic hydrological characteristics of the GLOF. It provides important information about the flood intensity and significantly improves our ability to model future flood scenarios along both the studied river and within neighbouring catchments. The flood hazard, defined by the flood depth during peak discharge, shows that the majority of the damaged infrastructure (houses, bridges, and a drinking water treatment plant) was only subjected to low or medium flood intensities (defined by a maximum water depth of less than 2 m). These low flood intensities help to explain why the flooding caused comparatively minor damage despite the significant public attention it attracted. 相似文献
3.
J. Angel Fernández Angela Ares Ana Rey-Asensio Alejo Carballeira Jesus R. Aboal 《Journal of Atmospheric Chemistry》2009,63(1):1-11
The effects of growth of autoirrigated, shaded transplants of Pseudoscleropodium purum on the quantification of tissue concentrations of Cd, Cu, Hg, V and Zn, were investigated in 4 exposure periods, each of
56 days, at 7 sampling sites (contaminated and uncontaminated). Concentrations of the elements in the basal portions of the
moss shoots were compared with the concentrations in the portions of the shoots that grew during the exposure period. Mercury
and V were present at lower concentrations in the new portions of the shoots than in the basal portions, whereas the opposite
was true for Cd, Cu and Zn. The magnitude of error introduced by growth was not negligible, and in some cases was higher than
40%, relative to the results obtained by analysis of the whole shoot. Devitalization of moss prior to its use as transplant
material is recommended to avoid growth of the plant during the exposure period. 相似文献
4.
This article analyses the implementation of emissions trading systems (ETSs) in eight jurisdictions: the EU, Switzerland, the Regional Greenhouse Gas Initiative (RGGI) and California in the US, Québec in Canada, New Zealand, the Republic of Korea and pilot schemes in China. The article clarifies what is working, what isn’t and why, when it comes to the practice of implementing an ETS. The eight ETSs are evaluated against five main criteria: environmental effectiveness, economic efficiency, market management, revenue management and stakeholder engagement. Within each of these categories, ETS attributes ? including abatement cost, stringency of the cap, improved allocation practices over time and the trajectory of price stability ? are assessed for each system. Institutional learning, administrative prudence, appropriate carbon revenue management and stakeholder engagement are identified as key ingredients for successful ETS regimes. Recent implementation of ETSs in regions including California, Québec and South Korea indicates significant institutional learning from prior systems, especially the EU ETS, with these regions implementing more robust administrative and regulatory structures suitable for handling unique national and sub-national opportunities and constraints. The analysis also shows that there is potential for a ‘double dividend’ in emissions reductions even with a modest carbon price, provided the cap tightens over time and a portion of the auctioned revenues are reinvested in other emissions-reduction activities. Knowledge gaps exist in understanding the interaction of pricing instruments with other climate policy instruments and how governments manage these policies to achieve optimum emissions reductions with lower administrative costs.Key policy insights
Countries are learning from each other on ETS implementation.
Administrative and regulatory structures of ETS jurisdictions appear to evolve and become more robust in every ETS analysed.
A ‘double dividend’ for emissions reductions may also exist in cases where mitigation occurs as a result of the ETS policy and when auction revenues are reinvested in other emissions-reduction activities.
5.
6.
Seasonal monitoring of the levels of carbon, nitrogen and phosphorus in two green macroalgae (Ulva and Enteromorpha) was carried out at 22 sampling sites in four embayments (rías) on the northwest coast of Spain. Sediments were also analysed to determine the concentrations of these elements as well as organic matter, organic carbon, iron and texture. In addition, accumulations of Ulva were monitored. Nitrogen levels in algae were similar to those found in comparable studies, whereas carbon concentrations were generally higher and those of phosphorus were lower. As a result the macroalgae were relatively enriched by carbon and nitrogen compared with phosphorus. Seasonal variations in algal tissue nitrogen and phosphorus followed the usual pattern for temperate zones, with minimum levels in summer and maximum levels in winter. Variations in carbon concentrations were much less accentuated. The low levels of P in the algae appear to indicate limitation by this element, however, comparison of the monthly changes in nitrogen and phosphorus in Ulva with the critical concentrations of these elements suggests dual nutrient limitation in this alga in summer. By contrast, the sediments were more enriched by phosphorus; high retention of this element by the sediment may explain the low levels in algae. The highest accumulations of Ulva occurred in spring and summer; hydrodynamic factors appeared to be important in determining the extent of these accumulations. 相似文献
7.
Zulema Varela J. A. Fernández J. R. Aboal C. Real A. Carballeira 《Journal of Atmospheric Chemistry》2010,65(1):37-48
The aim of the present study was to determine the optimal size of the sampling area that should be used in the moss biomonitoring
technique, in relation to the spatial variation in the concentrations of contaminants determined in samples collected within
short distances (<30 m). For this, the spatial structure in the concentrations of various metals and metalloids was explored
by use of semivariograms calculated by use of a robust estimator of the variance. In each of the 3 sampling sites considered
in the study (one sampled on two occasions), 50 samples of the moss Pseudoscleropodium purum were collected and the tissue concentrations of As, Cd, Cu, Hg, K, Ni, Pb, Se and Zn were determined. The results obtained
show that in most cases (25 out of 32), there was no spatial structure in the concentrations of the elements and that the
semivariograms were subject to the nugget effect. For those elements for which spatial independence or a linear spatial structure
was observed, the size of the sampling area did not affect the results, and the dimensions were irrelevant within the range
studied. The existence of spatial structure, which can be fitted to a spherical model, enabled a range of autocorrelation
to be defined, which corresponded to an area of diameter >16 m. The proposed method must be applied to other species and in
other regions, in order to standardize the size of the sampling sites in the moss biomonitoring technique. 相似文献
8.
With the aim of studying the interspectific differences in the bioaccumulation of a series of elements in six species of estuarine
macrophytes, we measured the concentrations of various metals (Co, Cr, Cu, Fe, Mn, Ni, Pb, and Zn), as well as C and N, in
several species of macroalgae and one species of seagrass in estuaries in northwest Spain. To facilitate the interpretation
of the results, we also determined the concentrations of the same metals in sediments. Contamination by particulate metal
did not appear to be important. The levels of Cu in the different species were generally high in comparison with those found
in similar studies; in contrast, the concentrations of Pb and Zn were relatively low. The metal concentrations showed greater
variability and a distibution that was further from normal than those of C and N. In general the highest concentrations of
elements were found inEnteromorpha spp. andZostera noltii, and the lowest occurred inUlva spp. There were several significant positive correlations among tissue concentrations of Cr, Cu, and Ni. There were also
significant correlations between tissue concentrations of N and Zn, suggesting possible synergetic effects between them. Cluster
analysis clearly revealed that the chemical composition ofZ. noltii differed from that of the macroalage. Macroalgae were not grouped according to their taxonomic position, therefore it appears
that the concentrations of the elements depended more on the ecological traits of the macroalgal species rather than on any
possible, physiological differences among different taxonomic groups. Of the species studied,Ascophyllum nodosum andEnteromorpha spp. appeared to be the best biomonitors of metal contamination. 相似文献
9.
Sea urchin embryo-larval development (ELD) and fertilization tests have been widely used in ecotoxicity studies and are included in regulatory frameworks. Biological processes occur naturally within a range of salinity that depends on the species considered. In an attempt to determine the optimum range of salinity, ELD and fertilization bioassays were performed at different salinities (15-40.5‰) with two species of Atlantic sea urchin: Arbacia lixula and Paracentrotus lividus. In the ELD assay, the optimum range of salinity was wider for A.?lixula (29-35.5‰) than for P.?lividus (29-33‰). In the fertilization assay with P.?lividus as a bioindicator species, the highest percentage of fertilization (90%) was obtained at salinities of between 29 and 33‰. More research on A.?lixula is required, since the fertilization success was below 60%. The results of the present study demonstrate that salinity may be a confounding factor in interpreting ELD test results. 相似文献
10.
Water Resources - This study assessed the applicability of Climate Hazards Group Infrared Precipitation with Stations (CHIRPS) as rainfall input in watershed modeling using the Soil and Water... 相似文献