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341.
El Miloud Maafi Fouad Malek Lan Tighzert Philippe Dony 《Journal of Polymers and the Environment》2010,18(4):638-646
Polyurethane (PU) based on polycaprolactone (PCL) and 4,4′ diphenyl methylene diisocyanate (MDI) was synthesized using a two-step
method. The PU obtained was then blended with various amounts of cellulose extracted from alfa stems to prepare composite
materials. The influence of cellulose on the thermal and mechanical properties of different composites was demonstrated by
means of several characterization techniques such as Fourier transform infrared spectroscopy (FTIR), differential scanning
calorimetry (DSC), scanning electron microscopy (SEM)… 相似文献
342.
Contamination by chromium (Cr) is widespread in agricultural soils and industrial sites. This heavy metal represents a risk to human health. In order to gain fundamental insights into the nature of the adaptation to Cr excess, the characterisation of physiological indices, including responses of photosynthetic gas exchange and chlorophyll a fluorescence along with changes in mineral nutrient contents and water status were studied in ray grass (Lolium perenne L.). Increased concentrations of Cr(VI) (0-500 microM Cr) in the Co?c and Lessaint nutrient solution were applied. The growth of Lolium perenne is decreased by chromium and the leaves have lost their pigments. Chromium accumulation was greater in roots than in leaves and reached 2450 and 210 microg g(-1) DW, respectively with 500 microM Cr(VI) in nutrient medium. The physiological parameters were severely reduced by this heavy metal. Cr induced toxicity arising from 100 microM Cr(VI) and resulted in a modification of mineral content in roots and leaves, especially for Ca, Mg and Fe. The chromium stress decreased CO2 assimilation rates mainly due to stomatal closure, which reduced water loss by transpiration without decreasing the cellular available CO2. The fluorescence parameters associated with photosystem II (PSII) activity and the photochemical activity are modified by chromium. Non-radiative energy dissipation mechanisms were triggered during stress since non-photochemical quenching was increased and efficiency of excitation capture by open centers was reduced. 相似文献
343.
Grath J Ward R Scheidleder A Quevauviller P 《Journal of environmental monitoring : JEM》2007,9(11):1162-1175
The establishment of high quality long-term monitoring programmes is essential if the implementation of the Water Framework Directive (WFD) is to be effective. It is recognised that monitoring can be very expensive and so guidance is needed to establish cost-effective, risk-based and targeted groundwater monitoring across Europe that enables WFD objectives to be met. In this context, the Groundwater Working Group (WGC) of the Common Implementation Strategy (CIS) of the WFD has developed recommendations aiming to implement consistent groundwater monitoring across Europe. This has been published on the internet in the form of a non-legally binding guidance document, which provides useful elements for the development and maintenance of networks at high standards and thereby provide the necessary information to assess (ground)water status, identify trends in pollutant concentrations, support establishment and assessment of programmes of measures and the effective targeting of economic resources. This paper presents this guidance document. 相似文献
344.
Influence of hydropower dams on the composition of the suspended and riverbank sediments in the Danube 总被引:1,自引:0,他引:1
Klaver G van Os B Negrel P Petelet-Giraud E 《Environmental pollution (Barking, Essex : 1987)》2007,148(3):718-728
Large hydropower dams have major impacts on flow regime, sediment transport and the characteristics of water and sediment in downstream rivers. The Gabcikovo and Iron Gate dams divide the studied Danube transect (rkm 1895-795) into three parts. In the Gabcikovo Reservoir (length of 40km) only a part of the incoming suspended sediments were deposited. Contrary to this, in the much larger Iron Gate backwater zone and reservoir (length of 310km) all riverine suspended sediments were deposited within the reservoir. Subsequently, suspended sediments were transported by tributaries into the Iron Gate backwater zone. Here they were modified by fractional sedimentation before they transgressed downstream via the dams. Compared with undammed Danube sections, Iron Gate reservoir sediment and suspended matter showed higher clay contents and different K/Ga and Metal/Ga ratios. These findings emphasize the importance of reservoir-river sediment-fractionation. 相似文献
345.
Sage M Coeurdassier M Defaut R Lucot E Barbier B Rieffel D Berny P Giraudoux P 《Environmental pollution (Barking, Essex : 1987)》2007,148(1):372-379
We aimed to evaluate whether environmental factors affect the persistence of bromadiolone in baits in field treatment. Baits were distributed in three soils according to two types of distribution: (1) artificial galleries conform to agricultural practices; (2) storage cavities to mimic bait storage by voles. Persistence was evaluated for 30 days in galleries and 80 days in storage cavities in autumn and spring. The decrease of bromadiolone concentrations was described by a first-order kinetic model. In galleries, the half-lives ranged from 3.0 to 5.1 days in autumn and from 5.4 to 6.2 days in spring. The half-lives were similar between soils and seasons but the pattern of persistence differed lightly for two soils between seasons. Half-lives in storage cavities, 42.7 and 24.6 days in autumn and spring respectively, were longer than in galleries. To conclude, both soil characteristics and climatic conditions weakly influence persistence, while bait storage lengthens it dramatically. 相似文献
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349.
Antonello Lobianco Philippe Delacote Sylvain Caurla Ahmed Barkaoui 《Environmental Modeling and Assessment》2016,21(3):391-405
Given the importance of anthropogenic determinants in forest ecosystems within Europe, the objective of this paper is to link the evidence arising from biological models to socio-economic determinants, where the expected returns of forest investments represent the main driver. A micro-economic area allocation module is therefore coupled with an inventory-based forest dynamics module and a partial-equilibrium market module in a national-level forest sector model for France (FFSM++). Running long-term scenarios (until 2100), we show the implication of an active management policy on forest composition: when the most profitable option drives forest investments, coniferous forests are generally preferred over broadleaved ones. This result is, however, reappraised when the risk aversion of forest owners is explicitly considered in the model, given the higher risk associated with the former. We further show the strong stability of forest ecosystems that, due to the very long cycles, undergoes very small variations in volume stocks, even in scenarios where the initial forest regeneration is strongly influenced. 相似文献
350.