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231.
D. López-Veneroni 《Atmospheric environment (Oxford, England : 1994)》2009,43(29):4491-4502
The sources and distribution of carbon in ambient suspended particles (PM2.5 and PM10) of Mexico City Metropolitan Area (MCMA) air were traced using stable carbon isotopes (13C/12C). Tested potential sources included rural and agricultural soils, gasoline and diesel, liquefied-petroleum gas, volcanic ash, and street dust. The complete combustion of LP gas, diesel and gasoline yielded the lightest δ13C values (?27 to ?29‰ vs. PDB), while street dust (PM10) represented the isotopically heaviest endmember (?17‰). The δ13C values of rural soils from four geographically separated sites were similar (?20.7 ± 1.5‰). δ13C values of particles and soot from diesel and gasoline vehicle emissions and agricultural soils varied between ?23 and ?26‰. Ambient PM samples collected in November of 2000, and March and December of 2001 at three representative receptor sites of industrial, commercial and residential activities had a δ13C value centered around ?25.1‰ in both fractions, resulting from common carbon sources. The predominant carbon sources to MCMA atmospheric particles were hydrocarbon combustion (diesel and/or gasoline) and particles of geological origin. The significantly depleted δ13C values from the industrial site reflect the input of diesel combustion by mobile and point source emissions. Based on stable carbon isotope mass balance, the carbon contribution of geological sources at the commercial and residential sites was approximately 73% for the PM10 fraction and 54% for PM2.5. Although not measured in this study, biomass-burning emissions from nearby forests are an important carbon source characterized by isotopically lighter values (?29‰), and can become a significant contributor (67%) of particulate carbon to MCMA air under the prevalence of southwesterly winds. Alternative sources of these 13C-depleted particles, such as cooking fires and municipal waste incineration, need to be assessed. Results show that stable carbon isotope measurements are useful for distinguishing between some carbon sources in suspended particles to MCMA air, and that wind direction has an impact on the distribution of carbon sources in this basin. 相似文献
232.
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
233.
234.
The objective of this study was to assess the effects of dredging on the structure and composition of diatom assemblages from a lowland stream and to investigate whether the response of diatom assemblages to the dredging is also influenced by different water quality. Three sampling sites were established in Rodríguez Stream (Argentina); physico-chemical variables and benthic diatom assemblages were sampled weekly in spring 2001. Species composition, cell density, diversity and evenness were estimated. Diatom tolerance to organic pollution and eutrophication were also analyzed. Differences in physico-chemical variables and changes in benthic diatom assemblages were compared between the pre- and post-dredging periods using a t-test. Data were analyzed using Principal Components Analysis (PCA), non-metric multidimensional scaling (MDS) ordination and cluster analysis. The effects of dredging in the stream involve two types of disturbances: (i) in the stream bed, by the removal and destabilization of the substrate and (ii) in the water column, by generating chemical changes and an alteration of the light environment of the stream. Suspended solids, soluble reactive phosphorus and dissolved inorganic nitrogen were significantly higher in post-dredging periods. Physical and chemical modifications in the habitat of benthic diatoms produced changes in the assemblage; diversity and species numbers showed an immediate increase after dredging, decreasing at the end of the study period. Changes in the tolerance of the diatom assemblage to organic pollution and eutrophication were also observed as a consequence of dredging; in the post-dredging period sensitive species were replaced by either tolerant or most tolerant species. These changes were particularly noticeable in site 1 (characterized by its lower amount of nutrients and organic matter previous to dredging), which showed an increase in the amount of nutrients and oxygen demand as a consequence of sediment removal. However, these changes were not so conspicuous in sites 2 and 3, which already presented a marked water quality deterioration before the execution of the dredging works. 相似文献
235.
Sustainability assessment (SA) is a holistic and long-range strategic instrument capable of assisting policy-making in electing,
and deciding upon, future development priorities. The outcomes of an SA process become more relevant and strengthened when
conducted with multi-stakeholder engagement, which provides for multiple dialogues and perspectives. This was the object of
research of the SA team in the context of BioScene (Scenarios for Reconciling Biodiversity Conservation with Declining Agriculture Use in Mountain Areas in Europe), a three-year project (2002–2005) funded by the European Union 5th Framework Program, which aimed to investigate the implications
of agricultural restructuring and decline for biodiversity conservation in the mountain areas of Europe, using three distinct
methodological streams: the ecological, the socio-economic, and the SA approaches. The SA approach drew on the previous two
to assess the importance for biodiversity management of different scenarios of agri-environmental change and rural policy
in six countries (France, Greece, Norway, Slovakia, Switzerland, and the United Kingdom), develop causal chains, include stakeholder
views, and identify potential contributions for, or conflicts with, sustainability. This article tells how SA was used, what
sustainability meant in each study area through different objectives of sustainability considered, discusses the methods used
in SA, and the benefits arising. The SA was conducted by a team independent of any study area, who developed and oversaw the
application of the SA methodology, assisting national teams, and developing a cross-country understanding of the sustainability
of proposed scenarios in the different geographical and social contexts, and their implications for policy-making. Finally,
it reflects on the persistent challenges of interdisciplinary research, compounded by multi-cultural teams, and concludes
on the BioScene’s lessons for the further development and application of SA.
相似文献
William R. SheateEmail: |
236.
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
237.
Silvina Vargas Gil Analia Becker Claudio Oddino Mónica Zuza Adriana Marinelli Guillermo March 《Environmental management》2009,44(2):378-386
Soil microbial populations can fluctuate in response to environmental changes and, therefore, are often used as biological
indicators of soil quality. Soil chemical and physical parameters can also be used as indicators because they can vary in
response to different management strategies. A long-term field trial was conducted to study the effects of different tillage
systems (NT: no tillage, DH: disc harrow, and MP: moldboard plough), P fertilization (diammonium phosphate), and cattle grazing
(in terms of crop residue consumption) in maize (Zea mays L.), sunflower (Heliantus annuus L.), and soybean (Glycine max L.) on soil biological, chemical, and physical parameters. The field trial was conducted for four crop years (2000/2001,
2001/2002, 2002/2003, and 2003/2004). Soil populations of Actinomycetes, Trichoderma spp., and Gliocladium spp. were 49% higher under conservation tillage systems, in soil amended with diammonium phosphate (DAP) and not previously
grazed. Management practices also influenced soil chemical parameters, especially organic matter content and total N, which
were 10% and 55% higher under NT than under MP. Aggregate stability was 61% higher in NT than in MP, 15% higher in P-fertilized
soil, and also 9% higher in not grazed strips, bulk density being 12% lower in NT systems compared with MP. DAP application
and the absence of grazing also reduced bulk density (3%). Using conservation tillage systems, fertilizing crops with DAP,
and avoiding grazing contribute to soil health preservation and enhanced crop production. 相似文献
238.
André Torre 《Journal of Environmental Planning and Management》2009,52(1):1-24
The use of the theoretical tools provided by proximity economics to address environmental questions, and the emergence of analyses revitalising the role of the spatial dimension in environmental problems, date from the late 1990s. This paper first aims to provide a review of the research conducted in this field and second to suggest some future research directions concerning the respective roles of geographical proximity and organised proximity in the production and management of environmental problems. First, it deals with the topic of ‘geographical proximity and land-use conflicts’, a topic that is currently the most researched in this field. This is followed by a discussion of the role of organised proximity in the regulation of environmental problems. The paper then explores the relation between the uncertainty associated with environmental issues and relations of organised proximity. Next it outlines a few possible research directions, focusing more particularly on the roles of geographical proximity as a mode of regulation of environmental problems, and on the possible role of organised proximity in their production. The concluding section draws an overview of the departures and extensions that have resulted from taking into account environmental issues in the paradigm of proximity economics. 相似文献
239.
Vinicius F. Farjalla André M. Amado Albert L. Suhett Frederico Meirelles-Pereira 《Environmental science and pollution research international》2009,16(5):531-538
Background, aim, and scope Dissolved humic substances (HS) usually comprise 50–80% of the dissolved organic carbon (DOC) in aquatic ecosystems. From
a trophic and biogeochemical perspective, HS has been considered to be highly refractory and is supposed to accumulate in
the water. The upsurge of the microbial loop paradigm and the studies on HS photo-degradation into labile DOC gave rise to
the belief that microbial processing of DOC should sustain aquatic food webs in humic waters. However, this has not been extensively
supported by the literature, since most HS and their photo-products are often oxidized by microbes through respiration in
most nutrient-poor humic waters. Here, we review basic concepts, classical studies, and recent data on bacterial and photo-degradation
of DOC, comparing the rates of these processes in highly humic ecosystems and other aquatic ecosystems.
Materials and methods We based our review on classical and recent findings from the fields of biogeochemistry and microbial ecology, highlighting
some odd results from highly humic Brazilian tropical lagoons, which can reach up to 160 mg C L−1.
Results and discussion Highly humic tropical lagoons showed proportionally lower bacterial production rates and higher bacterial respiration rates
(i.e., lower bacterial growth efficiency) than other lakes. Zooplankton showed similar δ13C to microalgae but not to humic DOC in these highly humic lagoons. Thus, the data reviewed here do not support the microbial
loop as an efficient matter transfer pathway in highly humic ecosystems, where it is supposed to play its major role.
In addition, we found that some tropical humic ecosystems presented the highest potential DOC photo-chemical mineralization
(PM) rates reported in the literature, exceeding up to threefold the rates reported for temperate humic ecosystems. We propose
that these atypically high PM rates are the result of a joint effect of the seasonal dynamics of allochthonous humic DOC input
to these ecosystems and the high sunlight incidence throughout the year. The sunlight action on DOC is positive to microbial
consumption in these highly humic lagoons, but little support is given to the enhancement of bacterial growth efficiency,
since the labile photo-chemical products are mostly respired by microbes in the nutrient-poor humic waters.
Conclusions HS may be an important source of energy for aquatic bacteria in humic waters, but it is probably not as important as a substrate
to bacterial growth and to aquatic food webs, since HS consumption is mostly channeled through microbial respiration. This
especially seems to be the case of humic-rich, nutrient-poor ecosystems, where the microbial loop was supposed to play its
major role. Highly humic ecosystems also present the highest PM rates reported in the literature. Finally, light and bacteria
can cooperate in order to enhance total carbon degradation in highly humic aquatic ecosystems but with limited effects on
aquatic food webs.
Recommendations and perspectives More detailed studies using C- and N-stable isotope techniques and modeling approaches are needed to better understand the
actual importance of HS to carbon cycling in highly humic waters. 相似文献
240.
Cristiano V.M. Araújo Fernando R. Diz Irene Laiz Luís M. Lubián Julián Blasco Ignacio Moreno-Garrido 《Environment international》2009,35(6):831-841
This study consisted of the sediment toxicity assessment of the Bay of Cádiz based on two endpoints: growth inhibition for Cylindrotheca closterium (benthic microalgae) and fecundity inhibition for Tisbe battagliai (harpacticoid copepod). A new methodology to eliminate (but not as storage technique) the autochthonous biota present in the sediment samples by immersing them in liquid nitrogen (? 196 °C) was also assessed. Sediment toxicity data showed different toxicity levels for both organisms. In general, T. battagliai was more sensitive; however a good correlation (r = 0.75; p < 0.05) between sediment toxicity results for both species was found. Data in pore water (pH, redox potential, and toxicity for microalgae and copepod) and sediment (pH, redox potential, organic carbon, and metal concentrations) demonstrated that ultra-freezing did not alter sample characteristics; thus, this technique can be adopted as a pre-treatment in whole-sediment toxicity tests in order to avoid misleading results due to presence of autochthonous biota. Multivariate statistical analysis such as cluster and principal component analysis using chemical and ecotoxicological data were employed. Silt and organic matter percentage and lead concentration were found to be the factors that explain about 77% of sediment toxicity in the Bay of Cádiz. Assay methodology determined in this study for both assayed species is considered adequate to be used in sediment toxicity monitoring programs. Results obtained using both species show that the Bay of Cádiz can be considered a moderately polluted zone. 相似文献