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Thomas Backhaus Rolf Altenburger sa Arrhenius Hans Blanck Michael Faust Antonio Finizio Paola Gramatica Matthias Grote Marion Junghans Wiebke Meyer Manuela Pavan Tobias Porsbring Martin Scholze Roberto Todeschini Marco Vighi Helge Walter L. Horst Grimme 《Continental Shelf Research》2003,23(17-19):1757
Freshwater and marine ecosystems are exposed to various multi-component mixtures of pollutants. Nevertheless, most ecotoxicological research and chemicals regulation focus on hazard and exposure assessment of individual substances only, the problem of chemical mixtures in the environment is ignored to a large extent. In contrast, the assessment of combination effects has a long tradition in pharmacology, where mixtures of chemicals are specifically designed to develop new products, e.g. human and veterinary drugs or agricultural and non-agricultural pesticides. In this area, two concepts are frequently used and are thought to describe fundamental relationships between single substance and mixture effects: Independent Action (Response Addition) and Concentration Addition. The question, to what extent these concepts may also be applied in an ecotoxicological and regulatory context may be considered a research topic of major importance, as the concepts would allow to make use of already existing single substance toxicity data for the predictive assessment of mixture toxicities. Two critical knowledge gaps are identified: (a) There is a lack of environmental realism, as a huge part of our current knowledge about the applicability of the concepts is restricted to artificial situations with respect to mixture composition or biological effect assessment. (b) The knowledge on what exactly is needed for using the concepts as tools for the predictive mixture toxicity assessment is insufficient. Both gaps seriously hamper the necessary, scientifically sound consideration of mixture toxicities in a regulatory context.In this paper, the two concepts will be briefly introduced, the necessity of considering the toxicities of chemical mixtures in the environment will be demonstrated and the applicability of Independent Action and Concentration Addition as tools for the prediction and assessment of mixture toxicities will be discussed. An overview of the specific aims and approaches of the BEAM project to fill in the identified knowledge gaps is given and first results are outlined. 相似文献
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Solutions for chaotic dynamos driven by thermal convection in a rotating spherical shell are obtained numerically for different Prandtl numbers. The influence of this parameter which is usually suppressed in the magnetostrophic approximation is emphasized in the present analysis. 相似文献
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摘要: 泰国东北部新生代硅化木十分丰富且保存完好。经对23 件木化石标本研究,已鉴定出真双子叶植物6 科7 属约13 种,包括Canarium sp． ( Burseraceae) ; Terminalia sp． vel Combretum sp． ,Terminalia sp． ( Combretaceae) ; cf． Irvingia sp． ( Irvingiaceae) ; Cynometroxylon holdeni,Cynometroxylon sp． ,cf． Cynometroxylon spp． ,cf． Millettia spp． ( Leguminosae) ; Careya spp. ( Lecythidaceae) ; Azadirachta sp． ( Meliaceae) ; 以及其他4 个分类群( 分类位置待定) 。这些高度分化的古植物群显示出与泰国东北部现存的混合落叶林、干旱阔叶林和干旱常绿林非常相似的特征,反映了该地区当时的古气候是近于湿润的热带疏林草原气候( 热带干湿气候) 。 相似文献
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A manual SPME method is presented for the analysis of organic compounds in industrial wastewater. 24 compounds commonly found in the wastewater of a chemical plant in northern Germany have been selected as reference compounds. Precision, linearity, and detection limits have been determined. Moreover, the effect of methanol content, pH value, salt content, and an excess of compounds on the extraction process have been studied. Several compounds have been investigated for their applicability as internal standards to quantify the compounds of interest. Since the method will later be transferred to a fully automated SPME-GC system, which will be operated directly on-site at an industrial wastewater purification plant, special attention has been paid to the analysis of real wastewater samples. In this context, the fibre stability has been studied by performing 53 extraction/desorption cycles from one wastewater sample. Neither a decrease in fibre performance nor in precision has been observed indicating that the proposed method is suitable for the analysis of real wastewater. 相似文献
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Grote Reber 《Astrophysics and Space Science》1995,224(1-2):93-96
The study of star forming regions (SFR) allows us to observe many young stellar objects with both the same metallicities and distances but with different masses. Because of its close distance ( 140pc) Taurus-Auriga is one of the best studied SFR with more than 100 well-studied, low-mass, pre-main sequence stars, T Tauri stars (TTS). A motivation for studying X-ray emission of T associations is to understand the origin of X-rays and coronal activity. The large sample observed with the ROSAT All-Sky Survey (RASS) also enables us to compare different types of young stars. Other primary goals include star formation efficiency and the interaction of young stars with their intermediate environment (probed by absorption of X-rays). RASS detection rates are comparable withEinstein Observatory results: 43 out of 65 (66%) weak-lined TTS (WTTS) and 9 out of 79 (11%) classical TTS (CTTS) exhibit X-ray emission above RASS detection limit. A strong correlation between X-ray surface flux and stellar rotation indicates that WTTS are intrinsically more X-ray active than CTTS, because WTTS rotate faster. However, rotation is not the only parameter that determines X-ray activity. Also, we compare Taurus-Auriga TTS with TTS of southern SFR like ScoCen, Lupus, Chamaeleon, and CrA. A new result is that CTTS and WTTS can be discriminated reliably by their X-ray spectral hardness ratios. X-ray emission of CTTS appears to be harder, partly because of circumstellar absorption. Spectral fits give results consistent with Raymond-Smith spectra and emission temperatures of 1.0 keV for both WTTS and CTTS. However, we find that CTTS and WTTS have significantly different X-ray luminosity functions. Medians of absorption corrected X-ray luminosities (logL
X
in cgs units) are 29.701 ± 0.045 for WTTS and 29.091 ± 0.032 for CTTS. WTTS are intrinsically more luminous than CTTS, most likely because WTTS rotate on average faster than CTTS and are less absorbed. This paper concentrates on differences between CTTS and WTTS and indirect clues to be drawn from X-ray absorption and hardness ratios about circumstellar material around TTS. 相似文献
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