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991.
Víctor H. Marín Antonio Tironi Luisa E. Delgado Manuel Contreras Fernando Novoa Marcela Torres-Gómez René Garreaud Irma Vila Italo Serey 《Ecological modelling》2009
Contemporary shallow lakes theory proposes that these ecosystems may experience abrupt regime shifts due to small changes in controlling variables or triggers. So far, these triggers have been related mostly to nutrients as the immediate driver. During May 2004 the río Cruces wetland, a Ramsar site located in Southern Chile, underwent a major regime shift, from a clear water state, vastly dominated by the invasive macrophyte Egeria densa, to a turbid water state. In this article we show, through the analysis of long-term meteorological data that late fall 2004 was anomalous due to the presence of a high-pressure cell that persisted most of the month of May over Southern Chile. This climatic event caused an almost complete absence of precipitations and lower temperatures during this period, including several freezing nights. Eco-physiological experiments showed that 6 h exposure to desiccation kill the macrophyte. We developed a simple-biology dynamic model, under Stella Research 9.1, to show that the climatic anomaly of May 2004, plus the increased sedimentation of the wetland's floodplains, and the associated response of E. densa, explains its sudden disappearance from río Cruces wetland. 相似文献
992.
de Guzmán Báez A Villoria Sáez P del Río Merino M García Navarro J 《Waste management (New York, N.Y.)》2012,32(5):920-924
In the last years, the European Union (EU) has been focused on the reduction of construction and demolition (C&D) waste. Specifically, in 2006, Spain generated roughly 47million tons of C&D waste, of which only 13.6% was recycled. This situation has lead to the drawing up of many regulations on C&D waste during the past years forcing EU countries to include new measures for waste prevention and recycling. Among these measures, the mandatory obligation to quantify the C&D waste expected to be originated during a construction project is mandated. However, limited data is available on civil engineering projects. Therefore, the aim of this research study is to improve C&D waste management in railway projects, by developing a model for C&D waste quantification. For this purpose, we develop two equations which estimate in advance the amount, both in weight and volume, of the C&D waste likely to be generated in railway construction projects, including the category of C&D waste generated for the entire project. 相似文献
993.
Correlation analysis between sulphate content and leaching of sulphates in recycled aggregates from construction and demolition wastes 总被引:1,自引:0,他引:1
Barbudo A Galvín AP Agrela F Ayuso J Jiménez JR 《Waste management (New York, N.Y.)》2012,32(6):1229-1235
In some recycled aggregates applications, such as component of new concrete or roads, the total content of soluble sulphates should be measured and controlled. Restrictions are usually motivated by the resistance or stability of the new structure, and in most cases, structural concerns can be remedied by the use of techniques such as sulphur-resistant cements. However, environmental risk assessment from recycling and reuse construction products is often forgotten. The purpose of this study is to analyse the content of soluble sulphate on eleven recycled aggregates and six samples prepared in laboratory by the addition of different gypsum percentages. As points of reference, two natural aggregates were tested. An analysis of the content of the leachable amount of heavy metals regulated by European regulation was included. As a result, the correlation between solubility and leachability data allow suggest a limiting gypsum amount of 4.4% on recycled aggregates. This limit satisfies EU Landfill Directive criteria, which is currently used as reference by public Spanish Government for recycled aggregates in construction works. 相似文献
994.
Gotzon Gangoiti Milln M. Milln Rosa Salvador Enrique Mantilla 《Atmospheric environment (Oxford, England : 1994)》2001,35(36):2163
During the warm season (March–September), high ozone concentrations have been reported at the coastal and mountain monitoring stations of the eastern Iberia coast (Millán et al., J. Geophys. Res. 102 (D7) 8811, J. Appl. Meteorol. 4 (2000) 487). The vegetation protection threshold of current Directive 92/72/EEC and the World Health Organisation guideline for the protection of crops and semi-natural vegetation are systematically exceeded during the whole period. The main objective of the present study is to search for the origin of these chronic pollution levels: to search for the reason(s) for such high O3 concentrations during such a long period. A mesoscale model is used to reproduce the diurnal cycle of winds and stability/layering over the Western Mediterranean Basin (WMB), at a sufficient space/temporal resolution, under a typical recursive synoptic condition during the warm season: data from the flight tracks of the European Project—Regional Cycles of Air Pollution in the West-Central Mediterranean Area—are used to substantiate the model results. Times of residence and the final distribution of pollutants entering the WMB are estimated using single-particle Lagrangian trajectories and a multiple-particle dispersion model. Our results show that the marine boundary layer and the lower troposphere in the region between the Balearic Islands and eastern Iberia are subject to a flow regime that tends to accumulate pollutants within large circulations, covering the entire western basin. We have also shown a diurnal pulsation of the Tramontana/Mistral wind regime, which can transport new pollutants into the area (background concentrations of 50–65 ppb of O3 of continental European origin) that are added to local emissions and re-circulated within the coastal breezes at eastern Iberia for periods of more than five days. Local emissions and wind configuration contribute to increase the O3 concentrations up to 100 ppb and even more. 相似文献
995.
J M López-Gutiérrez M García-León C Schnabel M Suter H A Synal S Szidat 《Journal of environmental radioactivity》2001,55(3):269-282
Iodine-129 (T1/2 = 1.57 x 10(7) yr) concentrations have been determined by accelerator mass spectrometry in rainwater samples taken at Seville (southwestern Spain) in 1996 and 1997. This technique allows a reduction in the detection limits for this radionuclide in comparison to radiometric counting and other mass spectrometric methods such as ICP-MS. Typical 129I concentrations range from 4.7 x 10(7) 129I atoms/l (19.2%) to 4.97 x 10(9) 129I atoms/l (5.9%), while 129I depositions are normally in the order of 10(8)-10(10) atoms/m2d. These values agree well with other results obtained for recent rainwater samples collected in Europe. Apart from these, the relationship between 129I deposition and some atmospheric factors has been analyzed, showing the importance of the precipitation rate and the concentration of suspended matter in it. 相似文献
996.
The aim of this study was to evaluate the possible toxicity of the leachate produced by the residues generated in the process of recycling lead from waste batteries. These residues are slag, which once formed, is characterised by its content in ferrous sulphide, sodium carbonate as well as residual coke from the process. It also contains, as minor components, lead and other heavy metals. The slag was stored and watered periodically over a period of 6 months, its composition changing until finally becoming inert, with no exothermal activity. The slag was leached, and its ecotoxicity was determined by means of the bioluminescence test, along with its content in heavy metals. The results obtained indicate a greater degree of toxicity in the residues with a shorter storage period than the established one, and which were therefore still in the phase of decomposition. However, in the samples taken on completing 6 months of storage, the EC50 value of the leachate was found to be higher than 3000 mg/l. Hence, a storage period under suitable environmental conditions which leads to inactivity of the residue as well as a decrease in its ecotoxicity, is considered absolutely essential. At the same time, a direct relationship was observed between the lead content and the ecotoxicity value. 相似文献
997.
We call sexual selection the selection attributable only to the mating system, to distinguish it from other forms of selection (i.e. viability or fertility) which we call natural selection. We introduce a new continuous time model of sexual selection and we explore its relationship with natural selection. This model is an extension of the model proposed by Hoppensteadt [Hoppensteadt, F., 1977. Mathematical Theories of Populations: Demographics, Genetics and Epidemics. SIAM] and considers the three genotypes determined by two alleles in a locus, each with its own mortality and fertility rates, and the respective mating preferences. 相似文献
998.
Extractable atrazine and its metabolites (hydroxyatrazine, deethylatrazine and deisopropylatrazine) were evaluated in agricultural
soils from the temperate humid zone (Galicia, NW Spain) under laboratory conditions. The experiment was performed with five
soils with different properties (organic C, soil texture and atrazine application history), both unamended and treated with
atrazine at field application rate. Measurements of the atrazine compounds were made at different time intervals (1, 3, 6,
9 and 12 weeks) during a 3-month incubation period. Results showed that only hydroxyatrazine was detected in the extractable
fraction of the unamended soils, with values remaining relatively constant throughout the incubation period. Atrazine addition
notably increased the concentration of the parent compound and its degradation products; deisopropylatrazine and hydroxyatrazine
were the main metabolites detected in the extractable fraction of the treated soils, whereas deethylatrazine was not detected.
After 7 days incubation, values of total extractable residues, expressed as percentage of initially added atrazine, ranged
from 75 to 86% (25–68% of atrazine, 7–11% of hydroxyatrazine and 9–57% of deisopropylatrazine). The values decreased rapidly
during the first 3 weeks of incubation, showing values of 2–8% in soils with higher atrazine application and from 28 to 30%
in soils with lower application history. At the end of the incubation, 2–8% of total extractable residues were still detected
(0–4% of atrazine, 2–3% of hydroxyatrazine and 0–2% of deisopropylatrazine), indicating a residual effect of atrazine addition.
These variations in the extractable fraction indicated that most added atrazine was rapidly degraded, especially in soils
with higher application history. 相似文献
999.
Sjouke A. Kingma István Szentirmai Tamás Székely Veronika Bókony Maarten Bleeker András Liker Jan Komdeur 《Behavioral ecology and sociobiology》2008,62(8):1277-1288
Melanin-based ornaments are often involved in signaling aggression and dominance, and their role in sexual selection is increasingly
recognized. We investigated the functions of a melanin-based plumage ornament (facial ‘mask’) in male Eurasian penduline tits
Remiz pendulinus in the contexts of male–male aggression, mating success, and parental care. The penduline tit is a passerine bird with a
unique mating system in which both sexes may mate with several mates in a breeding season, and one (or both) parent deserts
the clutch. Our study revealed that mask size of males is more likely an honest signal used by females in their mate choice
decisions than a trait involved in male–male competition. First, mask size increased with both age and body condition, indicating
that the mask may signal male quality. Second, males with larger masks paired more quickly and had more mates over the breeding
season than males with smaller masks. Third, we found no evidence that male mask size signals male–male aggression or dominance
during competitive encounters. The increased mating success of large-masked males, however, did not translate into higher
reproductive success, as nestling survival decreased with mask size. Therefore, we conclude that there is either no directional
selection on male mask size or males with larger masks receive indirect, long-term benefits. 相似文献
1000.
Carlos César Martínez-Rivera H. Carl Gerhardt 《Behavioral ecology and sociobiology》2008,63(2):195-208
Senders and receivers influence dynamic characteristics of the signals used for mate attraction over different time scales.
On a moment-to-moment basis, interactions among senders competing for a mate influence dynamic characteristics, whereas the
preferences of receivers of the opposite gender exert an influence over evolutionary time. We observed and recorded the calling
patterns of the bird-voiced treefrog Hyla avivoca to assess how the dynamic characters of calls vary during interactions among groups of males in a chorus. This question was
also addressed using playback experiments with males. Playback experiments with females showed how changes in dynamic call
properties are likely to affect male mating success. Frogs calling in pairs, groups, or in response to playbacks produced
longer calls than did isolated males. During call overlap, males often increased the duration of the silent interval (gaps)
between the pulses of their calls so that the pulses of the calls of two neighbors interdigitated. This change resulted in
increased variability of pulse rate, a traditionally static acoustic property; however, males also produced high proportions
of non-overlapped calls in which variability in pulse rate was low and had species-typical values. Females preferred long
calls to short- and average-duration calls, and non-overlapped calls to overlapped calls. Given a choice between pairs of
overlapped calls, females preferred pairs in which the proportion of overlap was low and pairs in which the pulses of such
calls interdigitated completely. The observed patterns of vocal competition thus reflect the preferences of conspecific females,
which have influenced the evolution of the calling behavior of H. avivoca.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献