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241.
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Frederick W. Kutz Donald G. Barnes Erich W. Bretthauer David P. Bottimore Helmut Greim 《毒物与环境化学》2013,95(1-4):99-109
The International Toxicity Equivalency Factor (I‐TEF) method of risk assessment is a revised interim procedure for assessing the risks associated with exposures to complex mixtures of chlorinated dibenzo‐p‐dioxins and dibenzofurans (CDDs and CDFs). This updated scheme was developed by a working group of the North Atlantic Treaty Organization's Committee on the Challenges of Modern Society and has been officially adopted by the U.S. Environmental Protection Agency (EPA), Canada, Ontario Ministry of the Environment, the Nordic countries, the Netherlands, and the United Kingdom. Prior to the development of the I‐TEF method, at least ten slightly different schemes had been used throughout the world which complicated communication among scientists and regulatory agencies concerning the toxicological significance of complex mixtures of CDDs and CDFs. The I‐TEF approach facilitates risk communication internationally by reducing large volumes of analytical data into a single number‐International Toxicity Equivalents (I‐TEQ). As a result, the I‐TEF method represents an improvement in an already useful risk assessment/regulatory tool. 相似文献
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Summary. Summary. Oilseed rape, Brassica napus L. (cv Express),
plants were grown under three different sulphur regimes:
sulphur-free (S0), normal sulphur (Sn, normal field concentration)
and a sulphur-rich (S+, 2 × concentration of Sn). We
performed dual choice oviposition assays with the diamondback
moth, Plutella xylostella, using real plants and,
for the first time with this insect, artificial leaves sprayed
with methanolic leaf-surface extracts. The results mirrored
those of a separate study of preferences for whole plants.
Females laid more eggs on surrogate leaves that were
treated with Sn extracts than on S0 plants, while only a
slight, not significant, difference was observed between
extracts of normal and sulphur-rich plants. This shows
that chemical compounds on the leaf surface mediate the
oviposition preference and that the female insect can
perceive the quality of the host-plants in terms of their
fertilisation status.Since leaf volatiles are known to be oviposition stimulants,
we investigated the effects of leaf-surface extracts on
insect olfactory responses using electroantennograms
(EAGs). In agreement with the behavioural data, we found
that extracts of sulphur-treated plants yielded higher EAG
amplitudes than the S0 extracts. Since the leaf content of the
volatiles isothiocyanates is influenced by sulphur nutrition,
we analysed the extracts for these compounds. Above the
detection threshold of our GC-MS system, no isothiocyanates
were found. Thus, other compounds present in the
surface extracts must be perceived by the antenna.However, the HPLC analysis revealed 11 different
glucosinolates. Progoitrin (2-Hydroxy-3-butenyl) and
gluconapoleiferin (2-Hydroxy-4-pentenyl), which belong to
the hydroxy-alkene class of glucosinolates, were the most
abundant compounds. The total glucosinolate content
sharply increased from S0 to Sn plants, whereas it was slightly
lower in n versus S+ plants. Since it is known that glucosinolates
can stimulate oviposition, it seems likely that the
increased content we observed was influencing the insect
preference in this study too. 相似文献
246.
The Science of Nature - 相似文献
247.
Germany seems to be one of the leading nations in solid waste management, especially in the case of packaging waste; success
stories about the ongoing increase in recycling strengthen this impression. However, enormous costs and questionable ecological
benefits are the result of Germany's packaging ordinance and the formation of the recycling organization Duales System Deutschland
(DSD). This article shows that similar progress in the reduction and recycling of packaging could have been realized without
the packaging ordinance and dual system, with lower costs. This regulatory impact analysis of the German packaging ordinance
covers all the effects on the different life-cycle stages of packaging, from production to recycling or disposal. The conclusion
is that a fragmentary solid waste management approach – one that is based, like the German packaging ordinance, more on ideology
than on facts – leads to enormous costs and questionable ecological benefits. To improve this situation, there is a need for
an integrated solid waste management approach, based on evaluation of the economic, environmental, and social effects of different
waste management options for the materials involved.
Received: February 4, 1999 / Accepted: April 30, 1999 相似文献
248.
A thermodynamic approach is used to model changes in the hydrate assemblage and the composition of the pore solution during the hydration of calcite-free and calcite-containing sulphate-resisting Portland cement CEM I 52.5 N HTS. Modelling is based on thermodynamic data for the hydration products and calculated hydration rates for the individual clinker phases, which are used as time-dependent input parameters. Model predictions compare well with the composition of the hydrate assemblage as observed by TGA and semi-quantitative XRD and with the experimentally determined compositions of the pore solutions. The calculations show that in the presence of small amounts of calcite typically associated with Portland cement, C-S-H, portlandite, ettringite and calcium monocarbonate are the main hydration products. In the absence of calcite in the cement, however, siliceous hydrogarnet instead of calcium monocarbonate is observed to precipitate. The use of a higher water-to-cement ratio for the preparation of a calcite-containing cement paste has a minor effect on the composition of the hydrate assemblage, while it significantly changes the composition of the pore solution. In particular, lower pH value and higher Ca concentrations appear that could potentially influence the solubility and uptake of heavy metals and anions by cementitious materials. 相似文献