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111.
112.
Analysis of polycyclic aromatic hydrocarbons in wastewater treatment plant effluents using hollow fibre liquid-phase microextraction 总被引:3,自引:0,他引:3
A simple and efficient method for the enrichment of low molecular weight polycyclic aromatic hydrocarbons (PAHs) in effluents originating from wastewater treatment plants is presented here. The proposed protocol couples the recently introduced hollow fibre liquid-phase microextraction (LPME) method with gas chromatography-mass spectrometry. Method parameters were controlled and the optimised experimental conditions were: 5 ml aqueous samples, containing 2.5% NaCl w/v, stirred at 1000 rpm, extracted with toluene for 15 min. The developed protocol yielded a linear calibration curve in the concentration range from 0.5 to 50 microg l(-1) for all target analytes (namely acenaphthene, phenanthrene, fluoranthene and pyrene) and limits of detection in the low microg l(-1) level (0.005-0.011 microg l(-1)). The repeatability and inter-day precision of the method varied between 2.7% and 11.3% and 7.9% and 14.4% respectively. The relative recoveries from different types of natural water samples revealed that matrix had a small effect on the hollow fibre LPME process. The developed method was then applied for the determination of PAHs contamination in effluent samples taken from two major municipal wastewater treatment plants. The results were compared with those obtained with solid-phase microextraction. The ability of both microextraction methods to concentrate organic analytes was demonstrated as both methods confirmed the presence of PAHs as well as of phthalates in the examined effluent samples. 相似文献
113.
Guélat J Jaquiéry J Berset-Brändli L Pellegrini E Moresi R Broquet T Hirzel AH Perrin N 《Ecology》2008,89(7):2033-2042
Recent developments in metacommunity theory have raised awareness that processes occurring at regional scales might interfere with local dynamics and affect conditions for the local coexistence of competing species. Four main paradigms are recognized in this context (namely, neutral, patch-dynamics, species-sorting, and mass-effect), which differ according to the role assigned to ecological or life-history differences among competing species, as well as to the relative time scale of regional vs. local dynamics. We investigated the patterns of regional and local coexistence of two species of shrews (Crocidura russula and Sorex coronatus) sharing a similar diet (generalist insectivores) over four generations, in a spatially structured habitat at the altitudinal limit of their distributions. Local populations were small, and regional dynamics were strong, with high rates of extinction and recolonization. Niche analysis revealed significant habitat differentiation on a few important variables, including temperature and availability of winter resting sites. In sites suitable for both species, we found instances of local coexistence with no evidence of competitive exclusion. Patterns of temporal succession did not differ from random, with no suggestion of a colonization-competition trade-off. Altogether, our data provide support for the mass-effect paradigm, where regional coexistence is mediated by specialization on different habitat types, and local coexistence by rescue effects from source sites. The strong regional dynamics and demographic stochasticity, together with high dispersal rates, presumably contributed to mass effects by overriding local differences in specific competitive abilities. 相似文献
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Ton Snelder Doug Booker Nicolas Lamouroux 《Journal of the American Water Resources Association》2011,47(4):828-840
Snelder, Ton, Doug Booker, and Nicolas Lamouroux, 2011. A Method to Assess and Define Environmental Flow Rules for Large Jurisdictional Regions. Journal of the American Water Resources Association (JAWRA) 47(4):828‐840. DOI: 10.1111/j.1752‐1688.2011.00556.x Abstract: Hydrological rules of thumb are used across jurisdictional regions to set minimum flows and allocation limits that apply by default (i.e., when more detailed site‐scale studies have not been carried out). Uniform rules do not account for spatial variation in environmental characteristics, resulting in inconsistent consequences for the protection of ecosystems, and the reliability of water resources. We developed a method for assessing hydrological rules of thumb that describes their consequences for protection of the ecosystem (in terms of retention of physical habitat) and the reliability of the water resource. The method links regionalized flow duration curves, at‐station hydraulic geometry, and generalized physical habitat models to make assessments at many locations across a region. The method estimates, for a given set of rules, the retained physical habitat for specified taxa/life stages and the proportion of the time abstractions are restricted. We applied the method to assess a set of rules that are proposed as default minimum flows and allocation limits for New Zealand rivers. The assessment showed that the minimum flow rules had variable consequences. The method could be used to quantify the tradeoff between environmental protection and water resources availability and reliability. 相似文献
118.
Julie E. Elie Nicolas Mathevon Clémentine Vignal 《Behavioral ecology and sociobiology》2011,65(12):2197-2208
Same-sex sexual behaviors are well documented in both captive and wild animals. In monogamous species, these behaviors are
often exclusive, each individual having only one same-sex partner. A bias in sex ratio has been proposed as a social context
yielding same-sex pair-bonding, but this hypothesis has rarely been tested. Focusing on a life-long pair-bonding songbird,
the zebra finch Taeniopygia guttata, we tested whether same-sex pairing results from a shortage of individuals of the opposite sex. By experimentally skewing
the sex ratio towards members of one sex, we observed a greater proportion of same-sex pair-bonds of that sex. Moreover, we
assessed whether the quality and stability of social interactions were equivalent in same-sex and male–female pairs. Male–male
and female–female same-sex bonds display the same behavioral characteristics as male–female ones: they are intense, highly
selective, and stable affinitive relationships involving the same behavioral displays already described in wild birds. Moreover,
same-sex male bonds were sufficiently strong not to split up when individuals were given the opportunity to reproduce with
females. Because the pair-bond in socially monogamous species represents a partnership that may give advantages for survival
(e.g., resources defense, fighting against predators, etc.), we propose that same-sex pairing in the zebra finch may result
from the pressure to find a social partner. 相似文献
119.
Photoreactivation of microorganisms following UV inactivation is a well-known, but complex, phenomenon. It is affected by several factors, including UV fluence, wavelength, light intensity, and exposure time to photoreactivating light. The effect on photoreactivation of a combined peracetic acid (PAA)/UV process has not been investigated. Accordingly, this study compared the degree of photoreactivation, under both sunlight and artificial lights, following UV and combined PAA/UV inactivation of fecal coliforms. Effluent samples from the Montreal Wastewater Treatment Plant (MWTP) (Quebec, Canada) were exposed, for 3 hours, to both low- and high-intensity artificial lights and sunlight. All resulted in similar photoreactivation levels. However, average photoreactivation for UV-treated wastewater samples was 1.2 logs, compared with 0.1 log for the combined PAA/UV treatment. Hence, the use of PAA in combination with UV can significantly reduce the potential for photoreactivation. To simulate the photoreactivation conditions of the MWTP effluent (which passes through a 4-km outfall tunnel with approximately 3 hours detention time), UV-treated samples were kept in the dark for 3 hours before photoreactivating light exposure. After this period, photoreactivation levels were close to zero. Hence, the effects of photoreactivation may be diminished by use of a combined disinfection scheme and/or by delaying exposure of the disinfected wastewater to light. 相似文献
120.
Studies of the influence of parasites on host fitness generally conclude that parasites have a strong negative effect on their
hosts. In this study, we have investigated experimentally the role of Polymorphus minutus, an acanthocephalan parasite, on the salinity tolerance of the freshwater amphipod Gammarus roeseli, one of its intermediate hosts. Unexpectedly, P. minutus-infected gammarids were more tolerant to salinity stress than uninfected ones. The mean lethal salt concentrations for 50%
mortality of hosts tested were 17.3 (infected) and 9.7 g/L (uninfected). The parasitic load (one or two parasites per host)
did not affect the result. The size of hosts had no significant influence on the salinity tolerance of either infected or
uninfected gammarids. The mobility of all types of gammarid decreased when the salinity exceeded 9.0 g/L, but there was no
significant difference between infected and uninfected gammarids. We discuss the higher salinity tolerance of infected amphipods
in relation to O2 consumption and osmoregulation. Finally, we demonstrate that the salinity tolerance is enhanced in the parasitized amphipod
but without a significant change in behavior or an osmoregulatory adjustment. 相似文献