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61.
62.
The increased availability of global datasets and technologies such as global hydrologic models and the Gravity Recovery and Climate Experiment (GRACE) satellites have resulted in a growing number of global‐scale assessments of water availability using simple indices of water stress. Developed initially for surface water, such indices are increasingly used to evaluate global groundwater resources. We compare indices of groundwater development stress for three major agricultural areas of the United States to information available from regional water budgets developed from detailed groundwater modeling. These comparisons illustrate the potential value of regional‐scale analyses to supplement global hydrological models and GRACE analyses of groundwater depletion. Regional‐scale analyses allow assessments of water stress that better account for scale effects, the dynamics of groundwater flow systems, the complexities of irrigated agricultural systems, and the laws, regulations, engineering, and socioeconomic factors that govern groundwater use. Strategic use of regional‐scale models with global‐scale analyses would greatly enhance knowledge of the global groundwater depletion problem. 相似文献
63.
64.
We report the first record of vertical rhizome growth in the temperate seagrass Zostera marina. In a population of Z. marina occurring on subtidal sand in the Novigrad Sea (Croatia), an area subject to episodic high sediment transport, collected plants of Z. marina showed vertical rhizomes with shorter and narrower inter‐nodes (mean length = 3.4 ± 1.5 SD mm, mean width = 1.9 ± 0.3 SD mm) than those recorded for horizontal rhizomes (mean length = 9.0 ± 3.5 SD mm, mean width = 2.8 ± 0.4 SD mm). Out of a sample of 1130 rhizome fragments, 288 (25.5%) were vertical. Repeated moderate burial events may have stimulated the production of vertical rhizomes, and the ability of Z. marina to produce vertical rhizomes may enable it to withstand moderate burial in this highly dynamic environment. 相似文献
65.
Redi Daniele Cannatelli Claudia Esposito Rosario Lima Annamaria Petrosino Paola De Vivo Benedetto 《Mineralogy and Petrology》2017,111(1):43-67
Mineralogy and Petrology - Clinopyroxene and olivine are ubiquitous phases in Somma-Vesuvius (SV) volcanics and for the first time they were systematically studied in several products younger than... 相似文献
66.
Ekaterina Vasyukova Wolfgang Uhl Fuad Braga Claudia Simões Tânia Baylão Klaus Neder 《Environmental Earth Sciences》2012,65(5):1587-1599
Drinking water production at three waterworks was evaluated with respect to variable weather conditions in the Brasília Distrito
Federal. Results of the investigation revealed that seasonal variations in rainfall play an important role in influencing
the quality of the surface water sources used for drinking water production in the district. In most surface sources, particles
and apparent colour are likely to originate from erosion during rain events. This represents the primary challenge facing
waterworks, notably when the raw water qualities of the sources to be treated at one facility differ by one order of magnitude,
as well significantly varying from one season to the next. Treatment efficiencies in terms of turbidity, apparent colour and
dissolved organic carbon (DOC) removal were evaluated. Drinking water quality was found to be significantly influenced by
raw water quality at all considered treatment plants. With regard to DOC removal, treatment was most efficient in waterworks
which treated raw water with high percentages of biopolymers and humics. Most dissolved organics were removed by coagulation.
Finally, conclusions are drawn on how to better cope with challenges facing drinking water production in a tropical climate.
The first of these recommendations is the introduction of online turbidity and dissolved organic matter monitoring in order
to optimise the coagulation process for the removal of these two parameters. A combination of different coagulants could also
be considered for this process. Additional more sophisticated improvements to process stability, such as determination of
floc characteristics, introduction of artificial neural networks or the eventual upgrade of the treatment train using membrane
filtration, are also suggested. 相似文献
67.
Rodrigo de Freitas Lagoon, located in the Rio de Janeiro City, receives several types of polluted discharges. The knowledge of the sediment microfauna correlated with heavy metal and organic matter concentrations could supply important data about the conditions of the lagoon. The benthic foraminiferal assemblage presented larger diversity and more abundant samples in the lagoon entrance than in the inner area. The Ammonia tepida - Elphidiumexcavatum foraminiferal assemblage is characterized by dwarf, corroded and weak organisms. Agglutinated species were found only near the entrance. Low abundance values and sterility of five samples in the inner area (north/northeast) can be caused by high levels of heavy metals and organic matter. A. tepida shows negative correlation with increasing heavy metals values. PAHs and coprostanol high indexes, and the absence or low presence of microfauna in samples around the lagoon margin confirm illegal flows from gas stations and domestic sewage. 相似文献
68.
We describe a methodology for identifying complex rift zones on recent or active volcanoes, where structures hidden by recent
deposits and logistical conditions might prevent carrying out detailed fieldwork. La Réunion island was chosen as a test-site.
We used georeferenced topographic maps, aerial photos and digital terrain models to perform a statistical analysis of several
morphometric parameters of pyroclastic cones. This provides a great deal of geometric information that can help in distinguishing
the localisation and orientation of buried magma-feeding fractures, which constitute the surface expression of rift zones.
It also allowed the construction of a complete GIS database of the pyroclastic cones. La Réunion is a perfect example where
past and active volcanic rift zones are mostly expressed by clusters of monogenic centres. The data has been validated in
the field and compared and integrated with the distribution and geometry of dyke swarms. Results show the presence of several
main and secondary rift segments of different ages, locations and orientations, whose origin is discussed considering regional
tectonics, local geomorphology, and volcano deformation. 相似文献
69.
The dual-beam mini-DOAS technique—measurements of volcanic gas emission,plume height and plume speed with a single instrument 总被引:2,自引:0,他引:2
Mattias Johansson Bo Galle Yan Zhang Claudia Rivera Deliang Chen Klaus Wyser 《Bulletin of Volcanology》2009,71(7):747-751
The largest error in determining volcanic gas fluxes using ground based optical remote sensing instruments is typically the
determination of the plume speed, and in the case of fixed scanning instruments also the plume height. We here present a newly
developed technique capable of measuring plume height, plume speed and gas flux using one single instrument by simultaneously
collecting scattered sunlight in two directions. The angle between the two measurement directions is fixed, removing the need
for time consuming in-field calibrations. The plume height and gas flux is measured by traversing the plume and the plume
speed is measured by performing a stationary measurement underneath the plume. The instrument was tested in a field campaign
in May 2005 at Mt. Etna, Italy, where the measured results are compared to wind fields derived from a meso-scale meteorological
model (MM5). The test and comparison show that the instrument is functioning and capable of estimating wind speed at the plume
height. 相似文献
70.
With the development of high-resolution multibeam echosounder systems (MBES) for surveying shallow-water areas a new tool is available to monitor rapid changes in seabed morphology as, e.g., caused by the dumping of dredge spoil in coastal waters. In this study, four data sets of repeated bathymetric surveys with a MBES were processed and analyzed. The data were collected in a 1.94-km2 dumping site in the outer Weser Estuary (German Bight). Between June and December 1998, 2.6 million m3 of dredged sediment were deposited there. The bathymetric maps generated in the course of this study reveal features such as subaqueous dunes, scour holes, and mounds of dumped dredge spoil. The mean water depth decreased by about 1 m during the dumping period. Furthermore, difference grids showing changes in sediment volume allowed a calculation of the sediment budget for the monitored area. After a time period of only 5 months, 0.5 million m3 of the originally dumped 2.6 million m3 of dredge spoil had already been removed from the dumping site. 相似文献