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651.
Rodrigo Seguel A. Raúl G.E. Morales S. Manuel A. Leiva G. 《Atmospheric environment (Oxford, England : 1994)》2009,43(13):2125-2131
High concentration of fine airborne particulates is considered one of the major environmental pollutants in Santiago, the Chilean Capital city, which in 1997 was declared a PM10 saturated zone. To date there is no control of the amounts of fine and coarse aerosols concentrations and the source and chemical characterizations of the PM2.5 particulates in the carbonaceous fractions are not well known even though this fraction could be represented almost the 50% in mass of the PM2.5.In this work, we present for the first time determinations of primary organic aerosol (POA) and secondary organic aerosol composition (SOA) fractions of the total mass of PM2.5 particulates collected in the urban atmosphere of Santiago City. Our purpose is to know the anthropogenic contributions to the formation of SOA. To accomplish this we used the elemental carbon (EC) and organic carbon (OC) determinations developed by automatic monitoring stations installed in the city during the period 2002–2005, with a particular analysis of the summer time occurred in February 2004. Based on the EC tracer method, we have estimated the POA and SOA fraction and our data permit us to estimate the SOA reaching up to 20% of total organic aerosol matter, in good agreement to other measurements observed in large cities of Europe and U.S.A. 相似文献
652.
Landscape-fragmentation change due to recent agricultural expansion in the Brazilian Savanna,Western Bahia,Brazil 总被引:1,自引:0,他引:1
653.
The giant Amazon river turtle (Podocnemis expansa) nests on extensive sand bars on the margins and interior of the channel during the dry season. The high concentration of nests in specific points of certain beaches indicates that the selection of nest placement is not random but is related to some geological aspects, such as bar margin inclination and presence of a high, sandy platform. The presence of access channels to high platform points or ramp morphology are decisive factors in the choice of nesting areas. The eroded and escarped margins of the beaches hinder the Amazon river turtle arriving at the most suitable places for nesting. Through the years, changes in beach morphology can alter nest distribution. 相似文献
654.
The structure, diversity and temporal distribution of the infaunal polychaetes associated with Cymodocea nodosa meadows were studied in Tenerife (Canary Islands). The samples were collected monthly throughout a year, to depths of 13–16 m. The sediment was extracted by means of PVC cores, in which four layers were separated (i.e. 0–5 cm, 5–10 cm, 10–20 cm and 20–30 cm). A total of 1,167 polychaete specimens, belonging to 69 taxa were collected, representing one of the most dominant groups in the benthic assemblage throughout the entire year. The most common families were Syllidae, Paraonidae and Spionidae, both in terms of abundance and species richness. The dominant species were Streptosyllis bidentata, Aricidea assimilis and Exogone parahomoseta mediterranea, representing also the only constant species throughout the year. The highest values of species richness, diversity, equitability and abundance of polychaetes occurred in September. The multifactorial analysis of abundances (i.e. cluster analysis and non-metric, multi-dimensional scaling) indicated temporal segregation of the samples from July, August and September (i.e. the warmest months) with respect to those from the rest of the year, due to structural differences in the assemblage. Polychaete species have been found to a depth of up to 30 cm in the sediment. Nevertheless, most of them (89%) occurred in the upper 5 cm of the sediment, with an increase of specimens in deeper layers in February (i.e. due to sporadic episodes of higher hydrodynamics). To compare the vertical distribution of polychaetes, additional core samples were collected in two seagrass meadows (i.e. C. nodosa and Ruppia cirrhosa) at Ebros Delta (NW Mediterranean); these were separated into five layers (i.e. 0–5 cm, 5–10 cm, 10–15 cm, 15–20 cm, 20–25 cm). The results obtained for the R. cirrhosa meadow (98% of the polychaetes within the upper 5 cm) agree with those for the Canarian C. nodosa meadow, while the polychaetes reached up to 15 cm depth in the Mediterranean C. nodosa meadow (i.e. ~39% between 0 and 5 cm, ~41% between 5 and 10 cm, ~20% between 10 and 15 cm). Our results indicated that the structural characteristics of the assemblages appeared to be more strongly controlled by the combined characteristics of the sediment (i.e. lack of oxygen, granulometry and degree of compaction) than by the seagrass species building the meadow.Communicated by O. Kinne, Oldendorf/Luhe 相似文献
655.
Santana Antônio H. Araújo José A. S. Bento Amanda M. S. Santos Ana R. Santos Leocácia G. Gomes Hiago de O. da Costa José Galberto M. Menezes Jorge Marcell C. Coutinho Henrique Douglas Melo Filho Francisco José de P. Teixeira Raimundo Nonato P. 《Environmental geochemistry and health》2021,43(4):1583-1597
Environmental Geochemistry and Health - The contamination of bodies of water by potentially hazardous elements has in recent decades become an environmental problem that poses serious risks to... 相似文献
656.
We analyze data from a complex repeated measures experiment directed at the evaluation of the response to an electric stimulus
applied to mussel nerves under 5 different salinity levels. We discuss the form of the relation between the response and the
different salinity levels, as well as the choice of an adequate within subjects covariance structure that includes random
effects and autoregressive models. 相似文献
657.
Gavin M. Jones Berry Brosi Jason M. Evans Isabel G. W. Gottlieb Xingwen Loy Mauricio M. Núñez-Regueiro Holly K. Ober Elizabeth Pienaar Rajeev Pillay Kathryn Pisarello Lora L. Smith Robert J. Fletcher Jr. 《Conservation biology》2022,36(3):e13872
International demand for wood and other forest products continues to grow rapidly, and uncertainties remain about how animal communities will respond to intensifying resource extraction associated with woody bioenergy production. We examined changes in alpha and beta diversity of bats, bees, birds, and reptiles across wood production landscapes in the southeastern United States, a biodiversity hotspot that is one of the principal sources of woody biomass globally. We sampled across a spatial gradient of paired forest land-uses (representing pre and postharvest) that allowed us to evaluate biological community changes resulting from several types of biomass harvest. Short-rotation practices and residue removal following clearcuts were associated with reduced alpha diversity (−14.1 and −13.9 species, respectively) and lower beta diversity (i.e., Jaccard dissimilarity) between land-use pairs (0.46 and 0.50, respectively), whereas midrotation thinning increased alpha (+3.5 species) and beta diversity (0.59). Over the course of a stand rotation in a single location, biomass harvesting generally led to less biodiversity. Cross-taxa responses to resource extraction were poorly predicted by alpha diversity: correlations in responses between taxonomic groups were highly variable (−0.2 to 0.4) with large uncertainties. In contrast, beta diversity patterns were highly consistent and predictable across taxa, where correlations in responses between taxonomic groups were all positive (0.05–0.4) with more narrow uncertainties. Beta diversity may, therefore, be a more reliable and information-rich indicator than alpha diversity in understanding animal community response to landscape change. Patterns in beta diversity were primarily driven by turnover instead of species loss or gain, indicating that wood extraction generates habitats that support different biological communities. 相似文献
658.
José Eduardo Volponi Lúcia Helena Innocentini Mei Derval dos Santos Rosa 《Journal of Polymers and the Environment》2004,12(1):11-16
The widespread use of polymeric materials in many applications requires polymers that are weather resistant. The aim of this study is to examine the usefulness of oxidation onset temperature measurements as a tool for evaluating oxidative degradation of isotatic polypropylene. Differential scanning calorimetry was used to measure the oxidation onset temperature in formulations of isotatic polypropylene containing different concentrations of light and thermal stabilizers after aging in a Weather-Ometer. Oxidation onset temperature gave better results than oxidation induction time for evaluating the degradation of isotatic polypropylene during aging in a Weather-Ometer. However, both tests showed a poor correlation with the appearance of cracks seen by optical microscopy. 相似文献
659.
da Silva Barbosa Ferreira Eduardo Luna Carlos Bruno Barreto Siqueira Danilo Diniz Araújo Edcleide Maria de França Danyelle Campos Wellen Renate Maria Ramos 《Journal of Polymers and the Environment》2022,30(2):541-554
Journal of Polymers and the Environment - PLA has aroused industrial and scientific interest in recent years, mainly due to its biodegradable character. However, PLA is brittle and displays low... 相似文献
660.
Individual-level variation in resource use occurs in a broad array of vertebrate and invertebrate taxa and may have important
ecological and evolutionary implications. In this study, we measured the degree of individual-level variation in prey preference
of the hunting wasp Trypoxylon albonigrum, which inhabits the Atlantic Forest in southeastern Brazil. This wasp captures several orb-weaving spider genera to provision
nests. Individuals consistently specialized on a narrow subset of the prey taxa consumed by the population, indicating the
existence of significant individual-level variation in prey preferences. The population niche was broader in the wet season
in terms of both prey size and taxa. In the case of prey size, the population niche expansion was achieved via increased individual
niche breadths, whereas in the case of prey taxa, individual niches remained relatively constrained, and the population niche
expanded via increased interindividual variation. The observed pattern suggests the possibility of functional trade-offs associated
with the taxon of the consumed prey. The nature of the trade-offs remains unknown, but they are likely related to learning
in searching and/or handling prey. We hypothesize that by specializing on specific prey taxa, individuals increase foraging
efficiency, reducing foraging time and ultimately increasing reproductive success. 相似文献