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Melisa Daiana Fernández Severini María Elizabeth Carbone Diana Mariel Villagran Jorge Eduardo Marcovecchio 《Environmental Earth Sciences》2018,77(10):393
Cadmium, chromium, nickel, and lead were evaluated in the particulate fraction at one of the most industrialized estuaries at the Southwestern Atlantic Ocean, through Geographic Information System (GIS). Concentrations were analyzed at 21 stations during 2008–2010. The highest metal concentrations (Cd: 8,9; Cr: 256,49; Ni: 27,02; Pb: 78,43 µg g??1 d. w.) were recorded at the stations located near industrial and urban discharges situated along the estuary. In addition, Pb presented a different seasonal and spatial behavior in comparison with Cd, Cr and Ni. Winter and spring presented the higher concentrations of Pb, and the inner stations presented the higher values. The estuary is considered a moderate to strongly polluted and significantly polluted according to the Index of geoaccumulation (Igeo) and the Enrichment Factor of Cd, respectively. The Multidimensional Scaling plot showed three groups of stations: the inner, associated to low levels of metals (G1), middle stations (G2) with intermediate levels and the outer (G3) with the highest ones. In addition, this work reveals the usefulness of the GIS-mapping techniques in the distribution of pollutants along an estuarine environment and the environmental quality assessment of estuarine systems. 相似文献
34.
Marc H. Taylor Jorge Tam Vernica Blaskovic Pepe Espinoza R. Michael Balln Claudia Wosnitza-Mendo Juan Argüelles Erich Díaz Sara Purca Noemi Ochoa Patricia Ayn Elisa Goya Dimitri Gutirrez Luis Quipuzcoa Matthias Wolff 《Progress in Oceanography》2008,79(2-4):366
The Northern Humboldt Current Ecosystem is one of the most productive in the world in terms of fish production. Its location near to the equator permits strong upwelling under relatively low winds, thus creating optimal conditions for the development of plankton communities. These communities ultimately support abundant populations of grazing fish such as the Peruvian anchoveta, Engraulis ringens. The ecosystem is also subject to strong inter-annual environmental variability associated with the El Niño Southern Oscillation (ENSO), which has major effects on nutrient structure, primary production, and higher trophic levels. Here our objective is to model the contributions of several external drivers (i.e. reconstructed phytoplankton changes, fish immigration, and fishing rate) and internal control mechanisms (i.e. predator-prey) to ecosystem dynamics over an ENSO cycle. Steady-state models and time-series data from the Instituto del Mar del Perú (IMARPE) from 1995 to 2004 provide the base data for simulations conducted with the program Ecopath with Ecosim. In simulations all three external drivers contribute to ecosystem dynamics. Changes in phytoplankton quantity and composition (i.e. contribution of diatoms and dino- and silicoflagellates), as affected by upwelling intensity, were important in dynamics of the El Niño of 1997–98 and the subsequent 3 years. The expansion and immigration of mesopelagic fish populations during El Niño was important for dynamics in following years. Fishing rate changes were the most important of the three external drivers tested, helping to explain observed dynamics throughout the modeled period, and particularly during the post-El Niño period. Internal control settings show a mix of predator–prey control settings; however a “wasp-waist” control of the ecosystem by small pelagic fish is not supported. 相似文献
35.
The heightening scale of urban tourism and the fast-growing number of “floating” city users raise new challenges to understand contemporary urban change – namely for internationally open, heritage-rich medium-sized cities. Discussing the case of Porto at a time when the contested notion of gentrification infuses local politics, we highlight the transnational drivers of this process in Portugal´s second city. While acknowledging perils and benefits, we argue that more than simply leaving a footprint to be solved with taxation, internationally-driven gentrification may endanger city diversity and identity, raising implications for urban policy and for our understanding of local development as a whole. 相似文献
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Ice core evidence for secular variability and 200-year dipolar oscillations in atmospheric circulation over East Antarctica during the Holocene 总被引:3,自引:0,他引:3
Barbara Delmonte Jean Robert Petit Gerhard Krinner Valter Maggi Jean Jouzel Roberto Udisti 《Climate Dynamics》2005,24(6):641-654
Two Holocene ice core records from East Antarctica (Vostok and EPICA-Dome C) were analysed for dust concentration and size
distribution at a temporal resolution of 1 sample per ~50 years. A series of volcanic markers randomly distributed over the
common part of the ice cores (from 9.8 to 3.5 kyear BP) ensures accurate relative dating (±33 years). Dust-size records from
the two sites display oscillations structured in cycles with sub-millennial and secular scale frequencies that are apparently
asynchronous. The power spectra of the composite sum (Σ) of the two dust-size records display spectral energy mostly for 150-
to 500-year periodicities. On the other hand, the 200-year band is common to both records and the 200 year components of the
two sites are out-of-phase (100-year lead or lag) over ~5.5 kyear, a phenomenon also reflected by a significant (>99% conf.
lev.) band in the power spectra of the composite difference (Δ) of the two size records. During long-range transport, mineral
dust originating from the Southern Hemisphere continents is graded to a variable extent depending on the altitude and duration
of atmospheric transport. Relatively coarse dust is associated with air mass penetration from the middle–lower troposphere
and conversely relatively fine dust with upper troposphere air masses or the influence of subsidence over the Antarctic plateau,
a hypothesis already proposed for the changes that occurred during the Last Glacial Maximum to Holocene transition (Delmonte
et al. 2004b). Moreover, we assume that the overall fluctuation of air mass advection over Antarctica depends on the meridional pressure
gradient with respect to low latitudes, i.e. the Antarctic Oscillation (AAO). We therefore suggest a regional variability
in atmospheric circulation over East Antarctica. The 150–500 year power spectrum of the composite (Σ) parameter represents
the long term variability of the AAO, imprinted by secular internal oscillations probably related to the southern ocean-climatic
system. On the other hand, the Δ dust composite parameter suggests a persistent atmospheric dipole over East Antarctica delivering
coarser (finer) dust particles alternatively to Vostok and Dome C regions with a bi-centennial periodicity. Indeed, a seesaw
phenomenon in dust size distribution was already observed at three East Antarctic sites during the last deglaciation (Delmonte
et al. 2004b) and was interpreted as a progressive reduction of the eccentricity of the polar vortex with respect to the geographic south
pole. Interestingly, the Δ parameter shows a pronounced 200-year oscillation mode, throwing new light on the unresolved question
of a possible relationship between climate and solar activity. 相似文献
38.
Coastal processes and environmental hazards: the Buenos Aires (Argentina) and Venetian (Italy) littorals 总被引:1,自引:0,他引:1
Jorge Pousa Luigi Tosi Eduardo Kruse Dardo Guaraglia Maurizio Bonardi Andrea Mazzoldi Federica Rizzetto Enrique Schnack 《Environmental Geology》2007,51(8):1307-1316
The Buenos Aires (Argentina) and Venice (Italy) coastlands have experienced significant saltwater contamination of the phreatic
aquifer, coastal erosion, hydrodynamic changes and relative sea level rise processes due to natural and man-induced factors.
These factors expose coastal areas to morpho-hydro-geological hazards, such as soil desertification, frequency and degree
of flooding, littoral erosion, and the silting of river mouths and channels. Man-made interventions and actions, such as beach
mining, construction of coastal structures and exploitation of aquifers without an adequate knowledge of the hydrology setting
and an adequate management program, worsen these natural hazards. Uncontrolled human activity induces environmental damage
to the overall coastal plains. The coastal plains play an important role in the social/economic development of the two regions
based on land use, such as agriculture, horticulture, breeding, and tourism, as well as industry. Results of investigations
on saltwater contamination, sea level rise and morphological changes recently performed in these two coastal areas are presented
here. 相似文献
39.
This article points out some particular features conditioning seismic hazard assessments (SHA) in Spain, a region with low–moderate
seismicity. Although sized earthquakes occurred in the past, as evidenced by historical documents and neotectonic studies,
no large events occurred during the last decades. The absence of strong motion records corresponding to earthquakes with magnitude
larger than 5.5 is an important obstacle for the development of ground motion models constrained by local data, with the consequent
difficulty in SHA studies. In this paper, some recent developments aiming at providing solutions to these difficulties are
presented. Specifically, a strong motion databank containing a massive collection of accelerograms and response spectra from
different configurations source-path-site corresponding to earthquakes all over the world is introduced, together with software
utilities for its management. A first application of this databank is the development of specific ground motion models for
Spain and for the Mediterranean region that predict peak ground accelerations as a function of several definitions of magnitude,
distance and soil class. The predictive power of these ground motion models is tested by contrasting their estimates with
recently recorded ground motions. The comparison between our ground-motion models with others proposed in the literature for
other areas reveals a regular overestimation of the expected ground motions at Spanish sites by the non-local models. Consequently,
SHA studies based in external models may overestimate the predicted hazard at the Iberian sites. In the last part of the paper
a method for checking whether the response spectra proposed in the Spanish Building Code (NCSE-02) are consistent with actual
accelerometric data from recent low magnitude earthquakes is applied. The spectral shapes of the Spanish Building Code NCSE-02
are compared with the response spectral shapes deduced from the available accelerograms by normalising the response spectra
with the recorded PGA. It is appreciated that the NCSE-02 spectral shapes are exceeded by a large number of actual spectral
shapes for short periods (around 0.2 s), a result to be taken into account in further revisions of the NCSE-02 code. The issues
tackled in this work constitute not only an improvement for ground-motion characterisation in Spain, but also provide guidelines
of general interest for potential applications in other regions with similar seismicity. 相似文献
40.