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Marie Trydeman Knudsen Qiao Yu-Hui Luo Yan Niels Halberg 《Journal of Cleaner Production》2010,18(14):1431-1439
Growing global trade with organic products has increased the demand for environmental impact assessments during both production and transport. Environmental hotspots of organic soybeans produced in China and imported to Denmark were identified in a case study using a life cycle assessment approach. Furthermore, environmental impacts of organic and conventional soybeans at farm gate were compared in the case study. The total global warming potential (GWP) per ton organic soybeans imported to Denmark revealed that 51% came from transportation and 35% from the farm level. Comparing organic and conventional soybean at farm gate showed that GWP, non-renewable energy use, acidification and eutrophication was lower per ton organic soybeans, whereas land use was slightly higher. 相似文献
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Dedecker AP Goethals PL D'heygere T Gevrey M Lek S De Pauw N 《Environmental monitoring and assessment》2005,111(1-3):223-241
This study aimed at analysing the relationship between river characteristics and abundance of Gammarus pulex. To this end, four methods which can identify the relative contribution and/or the contribution profile of the input variables
in neural networks describing the habitat preferences of this species were compared: (i) the ‘PaD‘ (‘Partial Derivatives‘)
method consists of a calculation of the partial derivatives of the output in relation to the input variables; (ii) the ‘Weights‘method
is a computation using the connection weights of the backpropagation Artificial Neural Networks; (iii) the ‘Perturb‘method
analyses the effect of a perturbation of the input variables on the output variable; (iv) the ‘Profile‘ method is a successive
variation of one input variable while the others are kept constant at a fixed set of values. The dataset consisted of 179
samples, collected over a three-year period in the Zwalm river basin in Flanders, Belgium. Twenty-four environmental variables
as well as the log-transformed abundance of Gammarus pulex were used in this study. The different contribution methods gave similar results concerning the order of importance of the
input variables. Moreover, the stability of the methods was confirmed by gradually removing variables. Only in a limited number
of cases a shift in the relative importance of the remaining input variables could be observed. Nevertheless, differences
in sensitivity and stability of the methods were detected, probably as a result of the different calculation procedures. In
this respect, the ‘PaD‘method made a more severe discrimination between minor and major contributing environmental variables
in comparison to the ‘Weights‘, ‘Profile‘ and ‘Perturb‘ methods. From an ecological point of view, the input variables ‘Ammonium‘
and to a smaller extent ‘COD‘, were selected by these methods as dominant river characteristics for the prediction of the
abundance of Gammarus pulex in this study area. 相似文献
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Dorothe Ehrich Niels M. Schmidt Gilles Gauthier Ray Alisauskas Anders Angerbjrn Karin Clark Frauke Ecke Nina E. Eide Erik Framstad Jay Frandsen Alastair Franke Olivier Gilg Marie-Andre Giroux Heikki Henttonen Birger Hrnfeldt Rolf A. Ims Gennadiy D. Kataev Sergey P. Kharitonov Siw T. Killengreen Charles J. Krebs Richard B. Lanctot Nicolas Lecomte Irina E. Menyushina Douglas W. Morris Guy Morrisson Lauri Oksanen Tarja Oksanen Johan Olofsson Ivan G. Pokrovsky Igor Yu. Popov Donald Reid James D. Roth Sarah T. Saalfeld Gustaf Samelius Benoit Sittler Sergey M. Sleptsov Paul A. Smith Aleksandr A. Sokolov Natalya A. Sokolova Mikhail Y. Soloviev Diana V. Solovyeva 《Ambio》2020,49(3):786-800
Lemmings are a key component of tundra food webs and changes in their dynamics can affect the whole ecosystem. We present a comprehensive overview of lemming monitoring and research activities, and assess recent trends in lemming abundance across the circumpolar Arctic. Since 2000, lemmings have been monitored at 49 sites of which 38 are still active. The sites were not evenly distributed with notably Russia and high Arctic Canada underrepresented. Abundance was monitored at all sites, but methods and levels of precision varied greatly. Other important attributes such as health, genetic diversity and potential drivers of population change, were often not monitored. There was no evidence that lemming populations were decreasing in general, although a negative trend was detected for low arctic populations sympatric with voles. To keep the pace of arctic change, we recommend maintaining long-term programmes while harmonizing methods, improving spatial coverage and integrating an ecosystem perspective. 相似文献
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Twenty-four congeners of polychlorinated biphenyls (PCBs) were measured in 83 air samples and 20 elastic sealants samples of apartments with PCB-containing sealants. In addition, PCBs were measured in 21 air samples from reference apartments located in an uncontaminated section of the same estate. The PCBtot levels in the air of the contaminated section were 168-3843 ng m−3 (mean: 1030 ng m−3), while the mean levels in the reference apartments were 6.03 ng m−3. The sum of the 24 measured PCB congeners in sealants from the contaminated section was 187-221 680 mg kg−1. Principal component analysis revealed four groups among the sealant samples with different congener compositions, only two of which were clearly similar to known PCB mixtures, while two were not. Significant correlations and intercorrelations were observed between the lower chlorinated congeners in air and sealant, e.g. for PCB 28air and 28seal (p = 0.04) and for PCB 28air and 52air, 52seal. However, no correlation was observed between the lower chlorinated congeners and the sums of PCB (∑PCB6 or ∑PCB24) or the higher chlorinated congeners. Analysis of air concentrations in relation to questionnaire data indicated that the indoor air levels could be reduced by increased cleaning and airing frequencies. 相似文献