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551.
Dennis A. Wentz Ian R. Waite Frank A. Rinella 《Environmental monitoring and assessment》1998,51(3):673-693
During 1992–93, 27 organochlorine compounds (pesticides plus total PCB) and 17 trace elements were analyzed in bed sediment and aquatic biota from 20 stream sites in the Willamette Basin as part of the U.S. Geological Survey's National Water-Quality Assessment Program. Data from each medium were compared to evaluate their relative effectiveness for assessing occurrence (broadly defined as documentation of important concentrations) of these constituents. Except for Cd, Hg, Se, and Ag, trace element concentrations generally were higher in bed sediment than in biota. Conversely, although frequencies of detection for organochlorine compounds in biota were only slightly greater than in bed sediment, actual concentrations in biota (normalized to lipid) were as much as 19 times those in sediment (normalized to organic carbon). Sculpin (Cottus spp.) and Asiatic clams (Corbicula fluminea), found at 14 and 7 sites, respectively, were the most widespread taxa collected during the study. Concentrations of trace elements, particularly As and Cu, were typically greater in Asiatic clams than in sculpin. In contrast, almost half of the organochlorine compounds analyzed were found in sculpin, but only DDT and its degradation products were detected in Asiatic clams; this may be related to the lipid content of sculpin, which was about three times higher than for clams. Thus, the medium of choice for assessing occurrence depends largely on the constituent(s) of interest. 相似文献
552.
Mike Hutchins Carlo Fezzi Ian Bateman Paulette Posen Amelie Deflandre-Vlandas 《Environmental management》2009,44(2):256-267
A case study of the Yorkshire Derwent (UK) catchment is used to illustrate an integrated approach for assessing the viability
of policy options for reducing diffuse nitrate losses to waterbodies. For a range of options, modeling methods for simulating
river nitrate levels are combined with techniques for estimating the economic costs to agriculture of modifying those levels.
By incorporating spatially explicit data and information on catchment residence times (which may span many decades particularly
in areas of groundwater discharge) a method is developed for efficient spatial targeting of measures, for example, to the
most at-risk freshwater environments. Combining hydrological and economic findings, the analysis reveals that, in terms of
cost-effectiveness, the ranking of options is highly sensitive to both (i) whether or not specific stretches of river within
a catchment are regarded as a priority for protection, and (ii) the criterion of nitrate concentration deemed most appropriate
as an indicator of the health of the environment. Therefore, given the focus under European legislation upon ecological status
of freshwaters, these conclusions highlight the need to improve understanding of mechanistic linkages between the chemical
and biological dynamics of aquatic systems. 相似文献
553.
Biomonitoring with Gammarus pulex at the Meuse (NL), Aller (GER) and Rhine (F) rivers with the online Multispecies Freshwater Biomonitor 总被引:1,自引:0,他引:1
Gerhardt A Kienle C Allan IJ Greenwood R Guigues N Fouillac AM Mills GA Gonzalez C 《Journal of environmental monitoring : JEM》2007,9(9):979-985
Biological early warning systems represent a set of tools that may be able to respond to certain chemical monitoring requirements of recent European legislation, the Water Framework Directive (WFD2000/60/EC), that aims to improve and protect water quality across Europe. In situ biomonitoring was performed along the rivers Meuse (NL), Aller (GER) and Rhine (F) within the frame of the European Union-funded Project SWIFT-WFD. Gammarus pulex was used as a test organism during the evaluation of the Multispecies Freshwater Biomonitor(R) (MFB), an online biomonitor to quantitatively record different behaviour patterns of animals. At the river Meuse G. pulex reacted to pulse exposure of either a mixture of trace metals or of several organic xenobiotics, by showing up to 20% decreased locomotory activity (already at the 1st pulse) and increased mortality (at 2nd or 3rd pulse only). G. pulex deployed within the MFB system were observed to survive well at the monitoring station on the Aller (100%) and monitoring did not result in the measurement of chemical irregularities. In contrast, deployment at the monitoring station on the Rhine river demonstrated that the test organism was able to detect chemical irregularities by up to 20% decreased locomotory activity in the animals. The MFB proved to be an alert system for water quality monitoring at sensitive sites and sites with accidental pollution. 相似文献
554.
A steady state model is developed to describe the bioaccumulation of organic contaminants by 14 species in a Baltic food web including pelagic and benthic aquatic organisms. The model is used to study the bioaccumulation of five PCB congeners of different chlorination levels. The model predictions are evaluated against monitoring data for five of the species in the food web. Predicted concentrations are on average within a factor of two of measured concentrations. The model shows that all PCB congeners were biomagnified in the food web, which is consistent with observations. Sensitivity analysis reveals that the single most sensitive parameter is log K(OW). The most sensitive environmental parameter is the annual average temperature. Although not identified amongst the most sensitive input parameters, the dissolved concentration in water is believed to be important because of the uncertainty in its determination. The most sensitive organism-specific input parameters are the fractional respiration of species from the water column and sediment pore water, which are also difficult to determine. Parameters such as feeding rate, growth rate and lipid content of organism are only important at higher trophic levels. 相似文献
555.
556.
Male pine engravers, Ips pini (Coleoptera: Scolytidae), assist their mates during reproduction by removing the debris that accumulates while females excavate
oviposition tunnels in the phloem tissue of host tree bark. Although duration of paternal care and male reproductive success
are positively correlated, large males leave their mates and brood sooner than small males. We address two hypotheses to
explain the earlier departure of larger males from their breeding galleries: (1) females oviposit most rapidly when paired
with large males, thereby reducing the length of time that paternal care increases male reproductive success, (2) larger males
have better prospects for future reproduction, and thus leave their galleries in search of new breeding opportunities sooner
than smaller males. Contrary to the first hypothesis, when females were paired either with large or small males, there was
no effect of male size on their rate of oviposition. Consistent with the second hypothesis, males that initiated breeding
galleries were larger than males from the general population. In addition, large males flew farther and faster on flight mills
than small males, which may indicate that large males have an advantage in locating suitable breeding sites. Thus, we suggest
that large male pine engravers leave their galleries earlier than small males because large individuals have better prospects
for future reproduction.
Received: 30 November 1997 / Accepted after revision: 23 May 1998 相似文献
557.
The frequently observed positive correlation between species diversity and community biomass is thought to depend on both the degree of resource partitioning and on competitive dominance between consumers, two properties that are also central to theories of species coexistence. To make an explicit link between theory on the causes and consequences of biodiversity, we define in a precise way two kinds of differences among species: niche differences, which promote coexistence, and relative fitness differences, which promote competitive exclusion. In a classic model of exploitative competition, promoting coexistence by increasing niche differences typically, although not universally, increases the "relative yield total", a measure of diversity's effect on the biomass of competitors. In addition, however, we show that promoting coexistence by decreasing relative fitness differences also increases the relative yield total. Thus, two fundamentally different mechanisms of species coexistence both strengthen the influence of diversity on biomass yield. The model and our analysis also yield insight on the interpretation of experimental diversity manipulations. Specifically, the frequently reported "complementarity effect" appears to give a largely skewed estimate of resource partitioning. Likewise, the "selection effect" does not seem to isolate biomass changes attributable to species composition rather than species richness, as is commonly presumed. We conclude that past inferences about the cause of observed diversity-function relationships may be unreliable, and that new empirical estimates of niche and relative fitness differences are necessary to uncover the ecological mechanisms responsible for diversity-function relationships. 相似文献
558.
A stand-level optimisation problem formulated to determine a set of efficient thinning regimes satisfying two objectives, i.e. value production for sawlog harvesting and volume production for a pulpwood market, was demonstrated for a Eucalyptus fastigata trial in Kaingaroa Forest, New Zealand. Genetic algorithms were used to estimate the set of efficient thinning regimes (i.e. regimes that occur when it is not possible to increase the achievement of one objective without reducing another) known as a Pareto frontier. Each thinning regime specified a unique combination of initial planting density; frequency, timing and intensity of thinning; final crop number; and rotation length. Specifications for the “best” regime in the Pareto set (i.e. the one that satisfied a balanced trade-off between value and volume production) were similar to those recommended through professional judgment based on pooled long-term field observations from different eucalypt species grown throughout New Zealand. The advantage of Pareto optimality was the ability of not only identifying a unique thinning regime, but equally efficient regimes each providing a different combination of value and volume production. Research on this approach has the potential of being applied to other forest sites, providing there is sufficient re-measurement data to reflect stand growth dynamics. 相似文献
559.
Introduction
The concept of knowledge translation as defined by the Canadian Institutes for Health Research and the Knowledge to Action Cycle, described by Graham et al (Graham et al., 2006), are used to make a case for the importance of using a conceptual model to describe moving knowledge into action in the area of falls prevention.Method
There is a large body of research in the area of falls prevention. It would seem that in many areas it is clear what is needed to prevent falls and further syntheses can determine where the evidence is sufficiently robust to warrant its implementation as well as where the gaps are that require further basic research.Conclusion
The phases of the action cycle highlight seven areas that should be paid attention to in order to maximize chances of successful implementation. 相似文献560.