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排序方式: 共有6201条查询结果,搜索用时 140 毫秒
201.
Gilles Billen Sabine Barles Josette Garnier Joséphine Rouillard Paul Benoit 《Regional Environmental Change》2009,9(1):13-24
Between the tenth and twentieth century the population of Paris city increased from a few thousand to near 10 million inhabitants.
In response to the growing urban demand during this period, the agrarian systems of the surrounding rural areas tremendously
increased their potential for commercial export of agricultural products, made possible by a surplus of agricultural production
over local consumption by humans and livestock in these areas. Expressed in terms of nitrogen, the potential for export increased
from about 60 kg N/km2/year of rural territory in the Middle Ages, to more than 5,000 kg N/km2/year from modern agriculture.
As a result of the balance between urban population growth and rural productivity, the rural area required to supply Paris
(i.e. its food-print) did not change substantially for several centuries, remaining at the size of the Seine watershed surrounding
the city (around 60,000 km2). The theoretical estimate of the size of the supplying hinterland at the end of the eighteenth
century is confirmed by the figures deduced from the analysis of the historical city toll data (octroi). During the second
half of the twentieth century, the ‘food-print’ of Paris reduced in size, owing to an unprecedented increase in the potential
for commercial export associated with modern agricultural systems based on chemical N fertilization. We argue that analysing
the capacity of territories to satisfy the demand for nitrogen-containing food products of local or distant urban population
and markets might provide new and useful insights when assessing world food resource allocation in the context of increasing
population and urbanization. 相似文献
202.
203.
Plaza C Xing B Fernández JM Senesi N Polo A 《Environmental pollution (Barking, Essex : 1987)》2009,157(1):257-263
Binding of two model polycyclic aromatic hydrocarbons (PAHs), phenanthrene and pyrene, by humic acids (HAs) isolated from an organic substrate at different stages of composting and a soil was investigated using a batch fluorescence quenching method and the modified Freundlich model. With respect to soil HA, the organic substrate HA fractions were characterized by larger binding affinities for both phenanthrene and pyrene. Further, isotherm deviation from linearity was larger for soil HA than for organic substrate HAs, indicating a larger heterogeneity of binding sites in the former. The composting process decreased the binding affinity and increased the heterogeneity of binding sites of HAs. The changes undergone by the HA fraction during composting may be expected to contribute to facilitate microbial accessibility to PAHs. The results obtained also suggest that bioremediation of PAH-contaminated soils with matured compost, rather than with fresh organic amendments, may result in faster and more effective cleanup. 相似文献
204.
Rodica Chiriac Jean Carré Yves Perrodin Hervé Vaillant Santiago Gasso Philippe Miele 《Atmospheric environment (Oxford, England : 1994)》2009,43(11):1926-1931
The dispersion of VOCs emitted by a municipal solid waste landfill was studied for a period of over one year. Sixteen VOCs were monitored: linear alkanes from C7 to C11, BTEX, trimethylbenzene, trichlorethylene, tetrachlorethylene, α and β-pinenes, limonene. The analytical procedure was first comprised of static long-term sampling of about 2 months using radial diffusion Radiello tubes containing activated carbon, followed by extraction by solvent (i.e. CS2) and GC/MS analysis. The results were initially analysed on the basis of the total concentration of the quantified VOCs, then by examining the concentrations of certain selected compounds. The influence of different parameters such as operating conditions, meteorological conditions and site morphology was highlighted on the basis of total VOC concentrations. In order to study the VOC's dispersion more closely, 5 compounds were chosen: toluene, benzene, limonene, and the sum trichlorethylene + tetrachlorethylene, as a “marker”, to verify the origin of the VOCs emitted. The results showed that the main source of VOCs is the open cell and lead to different hypotheses on interferences from neighbouring sources and to the proposal of solutions to limit the emission of VOCs and their dispersion. To our knowledge, this type of study has not been accomplished until this day. 相似文献
205.
Cécile Coeur-Tourneur Alexandre Tomas Angélique Guilloteau Françoise Henry Frédéric Ledoux Nicolas Visez Véronique Riffault John C. Wenger Yuri Bedjanian 《Atmospheric environment (Oxford, England : 1994)》2009,43(14):2360-2365
The formation of secondary organic aerosol from the gas-phase reaction of catechol (1,2-dihydroxybenzene) with ozone has been studied in two smog chambers. Aerosol production was monitored using a scanning mobility particle sizer and loss of the precursor was determined by gas chromatography and infrared spectroscopy, whilst ozone concentrations were measured using a UV photometric analyzer. The overall organic aerosol yield (Y) was determined as the ratio of the suspended aerosol mass corrected for wall losses (Mo) to the total reacted catechol concentrations, assuming a particle density of 1.4 g cm?3. Analysis of the data clearly shows that Y is a strong function of Mo and that secondary organic aerosol formation can be expressed by a one-product gas–particle partitioning absorption model. The aerosol formation is affected by the initial catechol concentration, which leads to aerosol yields ranging from 17% to 86%. The results of this work are compared to similar studies reported in the literature. 相似文献
206.
Oscar Pindado Rosa Ma Pérez Susana García Miguel Sánchez Pilar Galán Marta Fernández 《Atmospheric environment (Oxford, England : 1994)》2009,43(17):2796-2803
The results from a year-long study of the organic composition of PM2.5 aerosol collected in a rural area influenced by a highway of Spain are reported. The lack of prior information related to the organic composition of PM2.5 aerosol in Spain, concretely in rural areas, led definition of the goals of this study. As a result, this work has been able to characterize the main organic components of atmospheric aerosols, including several compounds of SOA, and has conducted a multivariate analysis in order to assign sources of particulate matter. A total of 89 samples were taken between April 2004 and April 2005 using a high-volume sampler. Features and abundance of n-alkanes, polycyclic aromatic hydrocarbons (PAHs), alcohols and acids were separately determined using gas chromatography/mass spectrometry and high performance liquid chromatography analysis. The Σn-alkane and ΣPAHs ranged from 3 to 81 ng m?3 and 0.1 to 6 ng m?3 respectively, with higher concentrations during colder months. Ambient concentrations of Σalcohols and Σacids ranged from 21 to 184 ng m?3 and 39 to 733 ng m?3, respectively. Also, several components of secondary organic aerosol have been quantified, confirming the biogenic contribution to ambient aerosol. In addition, factor analysis was used to reveal origin of organic compounds associated to particulate matter. Eight factors were extracted accounting more than 83% of the variability in the original data. These factors were assigned to a typical high pollution episode by anthropogenic particles, crustal material, plant waxes, fossil fuel combustion, temperature, microbiological emissions, SOA and dispersion of pollutants by wind action. Finally, a cluster analysis was used to compare the organic composition between the four seasons. 相似文献
207.
Bustamante J Pacios F Díaz-Delgado R Aragonés D 《Journal of environmental management》2009,90(7):2219-2225
We have used Landsat-5 TM and Landsat-7 ETM+ images together with simultaneous ground-truth data at sample points in the Doñana marshes to predict water turbidity and depth from band reflectance using Generalized Additive Models. We have point samples for 12 different dates simultaneous with 7 Landsat-5 and 5 Landsat-7 overpasses. The best model for water turbidity in the marsh explained 38% of variance in ground-truth data and included as predictors band 3 (630–690 nm), band 5 (1550–1750 nm) and the ratio between bands 1 (450–520 nm) and 4 (760–900 nm). Water turbidity is easier to predict for water bodies like the Guadalquivir River and artificial ponds that are deep and not affected by bottom soil reflectance and aquatic vegetation. For the latter, a simple model using band 3 reflectance explains 78.6% of the variance. Water depth is easier to predict than turbidity. The best model for water depth in the marsh explains 78% of the variance and includes as predictors band 1, band 5, the ratio between band 2 (520–600 nm) and band 4, and bottom soil reflectance in band 4 in September, when the marsh is dry. The water turbidity and water depth models have been developed in order to reconstruct historical changes in Doñana wetlands during the last 30 years using the Landsat satellite images time series. 相似文献
208.
Costa EA Campos VP da Silva Filho LC Greven HA 《Journal of environmental management》2009,90(2):1060-1068
In recent years, growing interest has focused on determining the performance of materials and evaluating the service life of structures exposed to various environmental forces. In this context, the determination of the aggressive potential of marine salts on mortars used as external renders is critical. The present study aimed to evaluate the spatial distribution of marine salts relative to distance from the sea. This was done by monitoring the deposition rate of chlorides and sulfates in wet candle sensors, located at nine stations scattered around the Metropolitan Region of Salvador, state of Bahia, Brazil. The study also determined the effectiveness of water-soluble salts at penetrating three different types of mortars of varying cement content via deposition and diffusion. The methodology employed enabled an evaluation of the efficiency of the monitoring sensors' measurement of the aggressiveness potential of local marine aerosol, and determination of the comparative performance of the three mortars tested, from the standpoint of resistance to salt penetration. The type and amount of salts captured both in solution and in powder samples extracted from the mortars were determined by ion chromatography. The analysis of the various types of mortars tested indicated which types are more resistant to the aggressive potential of the region's marine aerosol and the distance from the shore where local buildings are liable to be most strongly affected. 相似文献
209.
Miguel Delibes-Mateos Miguel ángel Farfán Jesús Olivero Ana Luz Márquez Juan Mario Vargas 《Environmental management》2009,43(6):1256-1268
Agricultural change has transformed large areas of traditional farming landscapes, leading to important changes in the species
community assemblages in most European countries. We suspect that the drastic changes in land-use that have occurred in Andalusia
(southern Spain) over recent decades, may have affected the distribution and abundance of game species in this region. This
article compares the distribution of the main game species in Andalusia during the 1960s and 1990s, using data from maps available
from the Mainland Spanish Fish, Game and National Parks Service and from recent datasets on hunting yield distributions, respectively.
Big-game and small-game species were significantly segregated in southern Spain during the 1990s, as two clearly independent
chorotypes (groups of species whose abundances are similarly distributed) were obtained from the classification analysis.
In contrast, big-game and small-game species were not significantly segregated several decades ago, when there was only one
chorotype consisting of small-game species and wild boar. The other three ungulates did not constitute a significant chorotype,
as they showed positive correlations with some species in the group mentioned above. These changes seem to be a consequence
of the transformations that have occurred in the Iberian Mediterranean landscape over the last few decades. The abandoning
of traditional activities, and the consequent formation of dense scrubland and woodland, has led to an expansion of big-game
species, and a decrease of small-game species in mountain areas. Moreover, agricultural intensification has apparently depleted
small-game species populations in some agricultural areas. On the other hand, the increasingly intensive hunting management
could be artificially boosting this segregation between small-game and big-game species. Our results suggest that the conservation
and regeneration of traditional agricultural landscapes (like those predominating in the 1960s) should be a priority for the
conservation of small-game species. 相似文献
210.
Use of Descriptors of Ecosystem Functioning for Monitoring a National Park Network: A Remote Sensing Approach 总被引:1,自引:0,他引:1
Baseline assessments and monitoring of protected areas are essential for making management decisions, evaluating the effectiveness
of management practices, and tracking the effects of global changes. For these purposes, the analysis of functional attributes
of ecosystems (i.e., different aspects of the exchange of matter and energy) has advantages over the traditional use of structural
attributes, like a quicker response to disturbances and the fact that they are easily monitored through remote sensing. In
this study, we described the spatiotemporal patterns of different aspects of the ecosystem functioning of the Spanish national
parks and their response to environmental changes between 1982 and 2006. To do so, we used the NOAA/AVHRR-GIMMS dataset of
the Normalized Difference Vegetation Index (NDVI), a linear estimator of the fraction of photosynthetic active radiation intercepted
by vegetation, which is the main control of carbon gains. Nearly all parks have significantly changed during the last 25 years:
The radiation interception has increased, the contrast between the growing and nongrowing seasons has diminished, and the
dates of maximum and minimum interception have advanced. Some parks concentrated more changes than others and the degree of
change varied depending on their different environmental conditions, management, and conservation histories. Our approach
identified reference conditions and temporal changes for different aspects of ecosystem functioning, which can be used for
management purposes of protected areas in response to global changes. 相似文献