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101.
Introduced Pacific oysters (Crassostrea gigas) have shown rapid expansion in the Oosterschelde estuary, while stocks of native bivalves declined slightly or remained stable.
This indicates that they might have an advantage over native bivalve filter feeders. Hence, at the scale of individual bivalves,
we studied whether this advantage occurs in optimizing food intake over native bivalves. We investigated feeding current characteristics,
in which potential differences may ultimately lead to a differential food intake. We compared feeding currents of the invasive
epibenthic non-siphonate Pacific oyster to those of two native bivalve suspension feeders: the epibenthic siphonate blue mussel
Mytilus edulis and the endobenthic siphonate common cockle Cerastoderma edule. Inhalant flow fields were studied empirically using digital particle image velocimetry and particle tracking velocimetry.
Exhalant jet speeds were modelled for a range of exhalant-aperture cross-sectional areas as determined in the laboratory and
a range of filtration rates derived from literature. Significant differences were found in inhalant and exhalant current velocities
and properties of the inhalant flow field (acceleration and distance of influence). At comparable body weight, inhalant current
velocities were lower in C. gigas than in the other species. Modelled exhalant jets were higher in C. gigas, but oriented horizontally instead of vertically as in the other species. Despite these significant differences and apparent
morphological differences between the three species, absolute differences in feeding current characteristics were small and
are not expected to lead to significant differences in feeding efficiency. 相似文献
102.
‘Value of Time’ (VOT) is a key parameter in economics and policy. This paper presents an alternative method to estimate VOT by analyzing an hourly dataset on drivers speeding behavior as a function of the gasoline price. Our identification strategy is novel as it is based on the intensive margin. In comparison, previous studies reveal VOT on the extensive margin, but choice alternatives have multiple attributes thereby potentially confounding estimates. Consistent with the range of the prior literature, we find a VOT of about 50% of the wage rate and analyze sources of bias from accidents and traffic tickets. These bias functions suggest that previous stated preference VOT estimates are likely downward whereas previous revealed preference estimates are likely upward biased. 相似文献
103.
Mette Mikkelsen Mikkel Jørgensen Frederik C. Krebs 《International Journal of Greenhouse Gas Control》2010,4(3):452-458
The synthesis of three amine-based carbon dioxide fixing reagents is presented. The reagents were designed so that they would be able to bind CO2 reversibly through the formation of the well known carbamates that was stabilized through forming a zwitterion. CO2 fixing experiments were performed with 13CO2 labeling and medium pressure NMR. The experiments showed that two of the three reagents were able to form carbamates and thus bind CO2. In addition we investigated this particular class of molecules for the possible formation of neutrally charged spiro compounds and we show that these did not form under the conditions studied. 相似文献
104.
Debbie Eraly Frederik Hendrickx Lieven Bervoets 《Environmental pollution (Barking, Essex : 1987)》2010,158(6):2124-2131
Both local adaptation and acclimation in tolerance mechanisms may allow populations to persist under metal pollution. However, both mechanisms are presumed to incur (energetic) costs and to trade-off with other life-history traits. To test this hypothesis, we exposed Pardosa saltans (Lycosidae) spiderlings originating from metal-polluted and unpolluted sites to a controlled cadmium (Cd) treatment, and compared contents of metal-binding metallothionein-like proteins (MTLPs), internal metal concentrations, and individual survival and growth rates with a reference treatment. While increased MTLP concentrations in offspring originating from both polluted and unpolluted populations upon exposure indicates a plastic tolerance mechanism, survival and growth rates remain largely unaffected, independent of the population of origin. However, MTLP and Cd concentrations were not significantly correlated. We suggest that MTLP production may be an important mechanism enabling P. saltans populations to persist in ecosystems polluted with heavy metals above a certain level. 相似文献
105.
Sholtz RI McLaughlin KR Cirillo PM Petreas M Park JS Wolff MS Factor-Litvak P Eskenazi B Krigbaum N Cohn BA 《Environment international》2011,37(4):709-714
Conserving irreplaceable, archived serum samples may sometimes conflict with the objective of minimizing measurement error due to laboratory effects. We sought to determine whether we could successfully combine assay results for DDT-related compounds and polychlorinated biphenyls (PCBs) in serum from the same birth cohort obtained from different laboratories over time. Using the Child Health and Development Studies (CHDS) serum archive, we compared variability for assays of a quality control pool to variability for assays of subject serum. The quality control pool was created from native archived serum samples that were pooled, then aliquoted, blinded and inserted pair-wise into assay batches along with the subject serum for 5 studies using CHDS samples conducted over a 13year period by three different laboratories. We found that the variability between laboratory and over time within laboratory was small relative to inter-individual variability for p,p'-DDT (1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane), p,p'-DDE (1,1'-dichloro-2,2'-bis(p-chlorophenyl)ethylene) and o,p'-DDT (1,1,1-trichloro-2-(p-chlorophenyl)-2-(o-chlorophenyl)-ethane). Results were also consistent for most PCB congeners which were detectable in 85% or more of samples. Our results suggest that it is possible to combine assays for DDT and PCB congeners measured at positive levels as they are accumulated for cohort subjects without risking meaningful misclassification due to variation stemming from laboratory or time period. This has significant implications for future study costs, conservation of irreplaceable archived samples and for leveraging past investments for future research. For PCB congeners with very low levels, findings caution against pooling of assays without further exploration. 相似文献
106.
REACH (Registration, Evaluation, Authorisation and Restriction of Chemicals) is the new European chemical legislation which aims to assess risk or safety of tens of thousands of chemicals to improve the protection of human health and the environment. The chemical safety assessment process is of an iterative nature. First, an initial, worst-case assessment is conducted after which refinements are made until no risk has been estimated or the risk is adequately controlled. Wasting time and resources on additional testing and implementing risk management measures with low effect on risk conclusions should be avoided as much as possible. This paper demonstrates the usefulness of an intelligent data collection strategy based on a sensitivity (and uncertainty) analysis on the risk assessment model EUSES to identify and order the most important "within-EU-TGD-reducible" input parameters influencing the local and regional risk characterisation ratios. The ordering can be adjusted for the costs involved in additional testing (e.g. ecotoxicity, physico-chemical properties, emission estimates, etc.). The risk refinement tool therefore reduces the resources needed to obtain a realistic risk estimate (both less conservative and less uncertain) as efficient as possible. 相似文献
107.
Wim J. Wolff 《Conservation biology》2000,14(3):876-885
Abstract: The various causes of extirpation of marine and estuarine species were investigated for the Dutch Wadden Sea to gain an impression of their relative importance. I obtained data from geological, archaeological, historical, and biological publications. At least 10 species of algae, 10 invertebrates, 13 fishes, 5 birds, and 4 marine mammals became extinct during the past 2000 years. Habitat destruction played a part in at least 26 cases, overexploitation in at least 17, and pollution in at least 3. Causes of the disappearance of two species are unknown. Introduction of exotic marine species was not involved in any of the extirpations. I compared this pattern of extinction to that of worldwide extinctions of marine and estuarine species, which have been attributed to overexploitation, habitat destruction, and in two cases to the introduction of terrestrial predators to the breeding habitats of marine birds. The results imply that conservation of marine species should address overexploitation and habitat destruction as the main causes of extinction. 相似文献
108.
109.
George T. Wolff 《Journal of the Air & Waste Management Association (1995)》2013,63(9):935-938
This report summarizes the important results which were presented at an international symposium on particulate elemental carbon in the atmosphere. The “Particulate Carbon: Atmospheric Life Cycle” symposium was sponsored by General Motors Research Laboratories on October 12–14, 1980. Supplemental background data are included. 相似文献
110.
George T. Wolff Carrie M. Stroup David P. Stroup 《Journal of the Air & Waste Management Association (1995)》2013,63(8):746-750
The technique to measure the coefficient of haze (COH) was developed in 1953 and was widely employed as a surrogate technique to measure total suspended particulate matter (TSP) in the 1960s. Because of the physical design of the sampler (known as the AISI Tape Sampler) used to measure COH, it was postulated that COH was directly related to the mass of fine elemental carbon particles (EC) with diameters less than 2.5 μm. To test the hypothesis, simultaneous samples of COH and EC were collected and analyzed during the 1981 Summer Study in Detroit. Regression analysis indicates that the two quantities are linearly related over the concentration range observed. Additional analyses indicate that COH is not related to TSP, fine particle mass, or light-scattering aerosol. Calculation of specific light absorption coefficients for EC from the COH data support the hypothesis that the tape sampler responds only to fine EC. A brief examination of historical COH data from Detroit suggests that the EC concentration has declined since 1972. This should be regarded as a preliminary assessment, however, until further verification of the COH-EC connection can be made. 相似文献