The exposure to benzene, toluene, xylenes and total hydrocarbons among 25 individuals exposed to exhaust from a snowmobile equipped with a two-stroke engine has been evaluated. Sampling was performed by pumped and diffusive sampling in parallel. There was a relatively bad agreement between the two air-sampling methods. The bad agreement can in part be explained by back diffusion of the substances from the samplers, a high face velocity, and deposition of droplets of unburned gasoline onto or in the vicinity of the samplers.
The levels of benzene ranged from not detectable (0.01 mg m−3) to 2.5 mg m−3. For toluene, xylenes and total hydrocarbons the exposure was 0.10–12.0, 0.05–13.0 and 0.90–273 mg m−3 respectively. The result from two measurements on individuals travelling on an open sleigh at the rear of the vehicle indicated higher levels of benzene, 0.7–0.8 mg m−3. Children are often riding as a passenger on a sledge and may thus have a higher exposure than their parents. This study indicates that spare time driving a snowmobile may cause a considerable exposure to benzene. Using a four-stroke engine equipped with a catalyst could reduce the exposure. To reduce the exposure for the passenger on a sleigh an extension of the exhaust pipe may be effective. 相似文献
The bioaccumulation of buried polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) added to specific depths in sediment (2.0-2.5, 5.0-5.5 and 10.0-10.5 cm) was studied in two infaunal species with similar feeding habits (surface deposit-feeders) but different bioturbation modes. The deep-burrowing polychaetes Marenzelleria spp. (Mz) displayed up to 36 times higher tissue concentrations of buried (spiked) contaminants than the surface-dwelling biodiffusing amphipod Monoporeia affinis. The differences in bioaccumulation were most pronounced for less hydrophobic contaminants due to the bioirrigating activity of Mz. Contaminants buried at shallow depths displayed higher accumulation than more deeply buried contaminants. In contrast, the bioaccumulation of unspiked (native) contaminants with a uniform vertical distribution in the sediment was similar between the species. For Mz, the BSAFs increased with increased KOW for the uniformly distributed contaminants, but decreased for the buried contaminants, which indicates that the dominant uptake routes of the buried contaminants can differ from the uniformly distributed contaminants. The surface sediment concentration of buried contaminants increased in Mz treatments, showing that Mz bioturbation can remobilize historically buried contaminants to the biologically active surface layer and increase the exposure for surface-dwelling species. 相似文献
Sex allocation theory predicts that whenever the relative fitness of sons and daughters differ, females should invest more
in the sex with the greatest fitness return. In this study, we evaluated the influence of various ecological factors on the
brood sex ratio (BSR) of Savi’s warblers (Locustella luscinioides) across several breeding seasons. There was a slight but significant female production bias at the population level, which
is consistent with the ‘local resource competition’ hypothesis, as the breeding density is very high and females are more
prone to disperse. We found that there was a significant decline in BSR during the breeding season, but no influence of male
size, female size, social status nor extra-pair paternity were detected. The seasonal decline in BSR was further evaluated
by assessing the within- and between-female effects, which indicated that multiple factors were operating simultaneously in
our study population. First, there was a significant within-female decline in BSR, which was consistent with the decline in
female condition due to the reproductive effort associated with multiple brooding (supporting the Trivers and Willard hypothesis).
Second, a significant decline in BSR with the laying date of first clutches of different pairs indicated that male and/or
female qualities are also associated with the seasonal variation in BSR. Finally, a comparison between the sex of the youngest
nestling with the remaining ones did not suggest any bias, indicating that females do not compensate for the increased mortality
of the last nestling (caused by asynchronous hatching) by producing a male from the last laid egg. 相似文献
There is a need to reduce the amount of fossil energy used for transport, both because of the easily available fossil fuel is becoming sparser and because of climate concerns. In this article, the concept of “peak oil” is briefly presented. Second, a practical approach to reduction of fossil fuel use for transport elaborated by two British commissions is presented. A key feature is the introduction of electric cars. This raises the third issue covered in this article: namely, how battery technology is going to meet the increasing needs posed by the transport sector. 相似文献
Many cities today face challenges related to urban growth. This is also the case in Oslo, currently one of the fastest growing capitals in Europe. In order to prepare for the population growth, a new municipal master plan has been prepared. In this, sustainable development is a prominent concept, and the urban district is going to be densified as part of the strategy. This paper examines some obstacles of turning planning theory into practice. There is a lack of coherence between municipal goals and the actual outcome. The analysis indicates that the official strategy is not able to cater for social sustainability partly due to institutional constraints. Moreover, there is no concise understanding of what sustainability means, which in turn hampers the ability to operationalise the concept in urban planning. 相似文献
The external phosphorus (P) loading has been halved, but the P content in the water column and the area of anoxic bottoms in Baltic proper has increased during the last 30 years. This can be explained by a temporary internal source of dissolved inorganic phosphorus (DIP) that is turned on when the water above the bottom sediment becomes anoxic. A load-response model, explaining the evolution from 1980 to 2005, suggests that the average specific DIP flux from anoxic bottoms in the Baltic proper is about 2.3 g P m−2 year−1. This is commensurable with fluxes estimated in situ from anoxic bottoms in the open Baltic proper and from hydrographic data in the deep part of Bornholm Basin. Oxygenation of anoxic bottoms, natural or manmade, may quickly turn off the internal P source from anoxic bottoms. This new P-paradigm should have far-reaching implications for abatement of eutrophication in the Baltic proper.
Electronic supplementary material
The online version of this article (doi:10.1007/s13280-013-0441-3) contains supplementary material, which is available to authorized users. 相似文献
Life-cycle assessments are normally made without quantitative estimations of their uncertainty. More interest has been focused on sensitivity analysis. In ISO 14040, LCA standard and SETAC's ‘code of practice’ sensitivity and uncertainty analysis are recommended or even requested. In the EPS system, an analysis of significance and sensitivity has been carried out for several years. The article describes this procedure in ISO terms and generalises it for other types of life-cycle assessments. 相似文献