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31.
Maud Leriche Didier Voisin Nadine Chaumerliac Anne Monod Bernard Aumont 《Atmospheric environment (Oxford, England : 1994)》2000,34(29-30)
A multiphase box model for a remote environment of the troposphere has been developed with an explicit chemistry for both gas and aqueous phase. The model applied to a set of measurements performed by Voisin et al. (2000) during the European CIME experiment for a cloud event on 13th December 1997 at the top of the Puy de Dôme (France). The results of the simulation are compared to the measurements in order to follow the evolution of the ambient chemical composition as a function of the pH and of the varying water content. After verifying that the model retrieves the main features observed in the behavior of species in the cloud droplets, a detailed analysis of the simulated chemical regime is performed. It essentially discusses the sources and sinks of radical in aqueous phase, the relative importance of the oxidation pathways of volatile organic compounds by the main radicals and the conversion of S(IV) into S(VI) which seems to be influenced by the presence of peroxonitric acid, HNO4, in aqueous phase in the environmental conditions that are considered with low H2O2. These numerical results are then compared with the theoretical study from Herrmann et al. (2000), who proposed a slightly different mechanism, including C2 chemistry and transition metal chemistry whereas they neglect some reaction pathways, such as the one involving OHCH2O2 radical. This double confrontation between model results and both real experimental data and numerical results from Herrmann et al. (1999c) underlines limitations of such modeling approach that does not include any dynamical or microphysical coupling but also demonstrates its capability to identify the main oxidants or reactants in aqueous phase in real environmental conditions more realistic than a purely theoretical approach. The originality of this study resides in the explicit and exhaustive ways the chemical reactions are treated in aqueous phase and in a first attempt to compare such a detailed chemical scheme to real environmental conditions. 相似文献
32.
Valente GF Santos Mendonça RC Pereira JA Felix LB 《Journal of environmental science and health. Part. B》2012,47(4):355-361
Iron electrodes were used for electrocoagulation (EC) treatment of wastewater from a dairy plant. Electrolysis time, pH, current density and distance between electrodes were considered to assess the removal efficiency of chemical oxygen demand (COD), total solids (TS) and their fractions and turbidity. Samples were collected from the effluent of a dairy plant using a sampling methodology proportional to the flow. The treatments were applied according to design factorial of half fraction with two levels of treatments and three repetitions at the central point. The optimization of parameters for treating dairy industry effluent by electrocoagulation using iron electrodes showed that electric current application for 15 minutes, an initial sample pH close to neutral (pH 7.0) and a current density of 50 A (.)(m-2) resulted in a significant reduction in COD by 58 %; removal of turbidity, suspended solids and volatile suspended solids by 95 %; and a final treated effluent pH of approximately 9.5. Negative consequences of the type of electrode used were the emergence of an undesirable color and an increase in the proportion of dissolved solids in the treated effluent. 相似文献
33.
Gerson Freitas Silva Valente Regina Célia Santos Mendonça José Antonio Marques Pereira Leonardo Bonato Felix 《Journal of environmental science and health. Part. B》2013,48(4):355-361
Iron electrodes were used for electrocoagulation (EC) treatment of wastewater from a dairy plant. Electrolysis time, pH, current density and distance between electrodes were considered to assess the removal efficiency of chemical oxygen demand (COD), total solids (TS) and their fractions and turbidity. Samples were collected from the effluent of a dairy plant using a sampling methodology proportional to the flow. The treatments were applied according to design factorial of half fraction with two levels of treatments and three repetitions at the central point. The optimization of parameters for treating dairy industry effluent by electrocoagulation using iron electrodes showed that electric current application for 15 minutes, an initial sample pH close to neutral (pH 7.0) and a current density of 50 A . m?2 resulted in a significant reduction in COD by 58 %; removal of turbidity, suspended solids and volatile suspended solids by 95 %; and a final treated effluent pH of approximately 9.5. Negative consequences of the type of electrode used were the emergence of an undesirable color and an increase in the proportion of dissolved solids in the treated effluent. 相似文献
34.
Maud C. Quinzin Jonathan Sandoval-Castillo Joshua M. Miller Luciano B. Beheregaray Michael A. Russello Elizabeth A. Hunter James P. Gibbs Washington Tapia Freddy Villalva Adalgisa Caccone 《Conservation biology》2019,33(6):1404-1414
Hybridization poses a major challenge for species conservation because it threatens both genetic integrity and adaptive potential. Yet, hybridization can occasionally offer unprecedented opportunity for species recovery if the genome of an extinct taxon is present among living hybrids such that selective breeding could recapture it. We explored the design elements for establishing a captive-breeding program for Galapagos tortoises (Chelonoidis spp.) built around individuals with admixed ancestry involving an extinct species. The target individuals were hybrids between the extinct species from Floreana Island, C. niger, and an extant species, C. becki, which were recently found in the endemic range of C. becki, from Wolf Volcano on Isabela Island. We combined genotypic data from 35 tortoises with high ancestry from C. niger with forward-in-time simulations to explore captive breeding strategies that maximized overall genetic diversity and ancestry from C. niger while accommodating resource constraints, species biology, and the urgency to return tortoises to Floreana Island for facilitating ecosystem restoration. Overall genetic diversity was maximized when in the simulation tortoises were organized in relatively small breeding groups. Substantial amounts of the C. niger genome were captured despite limited resources available for selectively breeding tortoises in captivity. Genetic diversity was maximized when captive-bred offspring were released to the wild rather than being used as additional breeders. Our results provide genetic-based and practical guidance on the inclusion of hybrids with genomic representation from extinct taxa into species restoration programs and informs the ongoing debate on the value of hybrids in biodiversity conservation. 相似文献
35.
36.
Maud C. O. Ferrari Terence Capitania-Kwok Douglas P. Chivers 《Behavioral ecology and sociobiology》2006,60(4):522-527
The supposition that prey animals respond to a predator with an intensity that matches the risk posed by the predator is known as the threat-sensitive predator avoidance hypothesis. Many studies have provided support for this hypothesis; yet, few studies have attempted to determine how such abilities are acquired by prey species. In this study, we investigated whether fathead minnows (Pimephales promelas) could learn to recognize an unknown predator (northern pike, Esox lucius) in such a way that they could match the intensity of their antipredator response with the threat posed by the predator. We exposed pike-naïve minnows to conspecific alarm cues paired with either a high or low concentration of pike odor. The following day, both groups were tested for a response to either high or low concentration of pike odor alone. We found that minnows conditioned with alarm cues paired with a given concentration of pike odor subsequently responded with a higher intensity to higher concentrations of pike odor, and with a lower intensity to lower concentrations of pike odor. These results demonstrate that during a single conditioning trial, minnows learn the identity of the predator in a threat-sensitive manner. Minnows use predator odor concentrations that they experience in subsequent interactions to adjust the intensity of their antipredator behavior. 相似文献
37.
Determination of organochlorine pesticide residue in sediment and water from the Densu river basin, Ghana 总被引:2,自引:0,他引:2
Kuranchie-Mensah H Atiemo SM Palm LM Blankson-Arthur S Tutu AO Fosu P 《Chemosphere》2012,86(3):286-292
The distribution of organochlorine pesticides in the aquatic ecosystem from the Densu river revealed varying levels of concentration in water and the sediment samples. Three locations were sampled along the river to evaluate the levels of organochlorine pesticide residue in the river. Sediment and surface water samples were extracted by soxhlet and liquid-liquid extraction respectively and analyzed using Gas Chromatograph coupled with electron capture detector. The detectable organochlorine pesticides were gamma-hexachlorocyclohexane (HCH), delta-hexachlorocyclohexane, heptachlor, aldrin and dieldrin. The other pesticides that were investigated are gamma-chlordane, alpha endosulfan, endosulfan sulfate, p,p′-DDT and its metabolite p,p′-DDE, methoxychlor, endrin and its metabolite endrin aldehyde and endrin ketone. The order of increasing frequency of detection of samples was higher in sediment than water. In sediment, the mean concentration ranged from 0.030 μg kg−1 dry weight (endrin) to 10.98 μg kg−1 dry weight (aldrin). The highest detected concentration of organochlorine in water was endosulfan sulfate with mean concentration of 0.185 μg L−1. Analysis of variance indicated significant differences for most organochlorine pesticide residue in the sediment sampled from the various locations. Some of the levels of organochlorine pesticides detected in water were relatively high compared to guideline values set by World Health Organization and Australia and thus could be harmful if the trend is not checked. 相似文献
38.
Marie Maud Bear Valérie Langlois Daniel Robic Richard Bourbouze Philippe Guerin 《Journal of Polymers and the Environment》1999,7(3):127-134
Design of optically active polymeric materials for temporary therapeutic and environmental applications requires the working-out of functionalized polymers with structures and properties adjusted to the considered applications. Biocompatibility of selected polymers is a required property in regard to the interactions between living organisms and macromolecular systems. It is therefore important to prepare highly optically active monomers and their corresponding hydrolyzable and biocompatible polymers. Bacterium Clostridium tetanomorphum is an useful source of enzymes for bioconversion and particularly in the chemoenzyrnatic route to optically active alkylmalolactonic acid esters and their optically pure stereoisomers. 3-Methylaspartase, involved in the glutamate fermentation pathway, is a very interesting enzyme, which can provide chiral precursors with high optically purity. This chemoenzymatic strategy can be used to prepare the four stereoisomers of 3-methylmalolaconic acid esters, by enzymatic resolution of natural and artificial stereoisomers of 3-methylaspartic acid. A series of 3-alkymalolactonic acid esters with alkyl equal to ethyl or isopropyl, have been also synthesized and transformed into corresponding optically active polyesters. 相似文献
39.
Maud C. O. Ferrari François Messier Douglas P. Chivers 《Behavioral ecology and sociobiology》2008,62(7):1079-1083
A prerequisite for prey to show adaptive behavioural responses to predators is that the prey has the ability to recognise
predators as threats. While predator recognition can be innate in many situations, learning is often essential. For many aquatic
species, one common way to learn about predators is through the pairing of a novel predator odour with alarm cues released
from injured conspecifics. One study with fish demonstrated that this mode of learning not only allows the prey to recognise
the predatory cues as a threat, but also mediates the level of threat associated with the predator cues (i.e. threat-sensitive
learning). When the prey is exposed to the novel predator with a high concentration of alarm cues, they subsequently show
a high intensity of antipredator response to the predator cues alone. When exposed to the predator with a low concentration
of alarm cues, they subsequently show a low-intensity response to the predator cues. Here, we investigated whether larval
mosquitoes Culex restuans have the ability to learn to recognise salamanders as a threat through a single pairing of alarm cues and salamander odour
and also whether they would learn to respond to salamander cues in a threat-sensitive manner. We conditioned individual mosquitoes
with water or a low, medium or high concentration of crushed conspecific cues (alarm cues) paired with salamander odour. Mosquitoes
exposed to salamander odour paired with alarm cues and subsequently exposed to salamander odour alone responded to the salamander
as a threat. Moreover, the intensity of antipredator response displayed during the conditioning phase matched the response
intensity during the testing phase. This is the first demonstration of threat-sensitive learning in an aquatic invertebrate. 相似文献
40.
Although the study of ecological interactions often takes into account functional variation between species, intraspecific variation is commonly ignored. Here, we investigate the importance of an intraspecific polymorphism in shaping interspecific interactions in a habitat-building species. Colonies of the social spider Anelosimus studiosus provide habitat for dozens of arthropod species, and colony members exhibit markedly polymorphic behavioral temperaments (BT): "aggressive" or "docile." We manipulated the phenotypic compositions of colonies (100% aggressive, 50% aggressive and 50% docile, 100% docile) and measured the nature and magnitude of interactions between A. studiosus and two heterospecific web associates, Larinioides cornutus and Agelenopsis emertoni. We found that BT composition significantly affected the outcome of interspecific interactions, changing the relationship between A. studiosus and its web associates from an ammensalism (where A. studiosus experiences reduced fecundity and survival) to a commensalism or mutualism. Our study successfully illustrates the potential of BTs to impact whole community dynamics, and conversely, for community structure to influence the maintenance of BTs. 相似文献