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501.
502.
D. Briassoulis 《Journal of Polymers and the Environment》2004,12(2):65-81
The mechanical behavior of various types of biodegradable materials depends, mainly, on their chemical composition and the application conditions. Various additives are added into the bioblends to improve their properties, which sometimes even reach the levels of the conventional plastics. It is well known that the environmental conditions during production, storage, and usage of these materials influence their mechanical properties. Ageing during the useful lifetime also causes great losses in the elongation. In the present paper, the overall mechanical behavior of biodegradable films, which may be considered suitable for agricultural applications, but also of partially biodegradable films, is reviewed and analyzed. Selected critical mechanical properties of films before their exposure to biodegradation are investigated and compared against those of conventional agricultural films. 相似文献
503.
As one of a series of studies concerning the relationship between the higher-order structure and the biodegradability of a biodegradable plastic, the effects of the crystal structure of the plastic on microbial degradation were investigated. Bacterial poly(d-(–)-3-hydroxybutyrate) (PHB) films which had a wide range of crystallinity were prepared by the melt-quenching method. Results of the microbial degradation indicated that the development of crystallinity evidently depressed the microbial degradability. From scanning electron microscopy (SEM) observations, it is suggested that the microbial degradation proceeded in at least two manners. One was preferential degradation of the amorphous region leaving the crystalline lamellae intact, which was considered to be a homogeneous enzymatic degradation over the surface. The other was nonpreferential spherical degradation on the surface. The SEMs indicate that the spherical holes were the result of colonization by degrading bacteria. The holes varied in size and number with the change of crystal structure. Therefore, it is considered that the crystal structure of PHB also influenced the physiological behavior of the degrading bacteria on the PHB surface. 相似文献
504.
Irina Herzon Johan Ekroos Jukka RintalaJuha Tiainen Tuomas SeimolaVille Vepsäläinen 《Agriculture, ecosystems & environment》2011,143(1):3-7
The set-aside obligation under the Common Agricultural Policy (CAP) brought widespread benefits for wild farmland species. Shortly after it was abolished in 2008, the national political process in Finland replaced it with a targeted agri-environment scheme for environmental fallow. Though potentially highly valuable, the value of the current scheme for securing biodiversity is yet to be confirmed. This study evaluates the importance of set-asides established under CAP to all birds of open farmland based on national monitoring data from 2001 to 2006. The set-aside fields supported 25-40% more species and held 60-105% more pairs of birds typical of open farmland in comparison with cereal fields within a similar landscape setting. The estimated effect of set-aside presence in farmland on the studied bird species is large enough to trigger considerable changes in bird populations on the national scale. The relevance of the results to the novel agri-environment scheme is discussed. 相似文献
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506.
David J.T. Douglas Juliet A. Vickery Tim G. Benton 《Agriculture, ecosystems & environment》2010,135(1-2):127-131
Managing arthropod populations on farmland for conservation purposes, such as food resources for declining farmland birds, requires information on the way distributions vary between crop types, for example under varying sowing regimes. In this study arthropods were sampled during one summer from fields of winter-sown and spring-sown barley. The relative timing of crop development had a strong influence on arthropod abundance between crop types, with winter barley supporting significantly higher abundance of total counts and many individual orders in early summer, but the reverse being the case in late summer. Fields of both crop types that received higher herbicide inputs showed reduced arthropod counts. 相似文献
507.
电子废弃物资源循环是一系统问题,除电子废弃物收集计划与物流、政策措施外,电子废弃物资源流程结构的建立和资源回收技术是保证。全面分析了电子垃圾中的资源结构,论述了从电子废物中回收材料的各种可行方法,尤其是从电子废物中回收玻璃、塑料和金属的各种再循环技术。如玻璃,讨论了从玻璃—玻璃和从玻璃—铅的再循环技术;如塑料,分析了化学再循环、机械再循环和热量再循环方法;如金属,讨论了铜、铅,以及贵重金属如银、金、铂和钯的回收过程与程序,最后对生物技术在电子垃圾金属回收中的应用这一环境友好的新技术做了介绍。 相似文献
508.
509.
碱法制浆造纸废水生物膜法达标排放技术 总被引:2,自引:0,他引:2
本文介绍了一种适用于碱法麦草制浆造纸废水达标排放处理工艺-生物膜法。在对四个示范工程的前期试验试验研究中证实了生物膜法在碱法麦草浆造纸废水处理的技术和经济可行性。 相似文献
510.
Portillo MC Reina M Serrano L Saíz-Jiménez C González JM 《Environmental geochemistry and health》2008,30(2):165-170
The Doñana National Park contains highly complex microbial communities that play critical roles in the bioavailability and biogeochemical cycling of elements. In this study, we analyzed the formation of Fe-rich films on the surface of shallow waters at Doñana National Park as a model for future applications in bioremediation. Phytoplankton composition and abundance, physicochemical measurements, culture enrichments, and molecular detection of microorganisms were determined during this study. Natural samples were incubated in the laboratory and enrichments producing similar phenomena were obtained. Bacteria belonging to the genera Enterobacter were the major participants in surface Fe-film formation in laboratory enrichments. Film formation was dependent on wind exposure and only those sites protected from the direct influence of wind developed these films. A higher concentration of euglenophytes was found in the proximity of film-covered waters. Available iron (Fe2+) and total Fe concentrations were high (18.8 and 46.6 mg/L, respectively) underneath the surface film, and higher than in film-free waters and pore-sediment water. The concentration of phosphate and its availability were higher in the iron-rich film sediment, as 61% of total P was bound to iron oxy-hydroxides. Our results provide evidence of the link between P and Fe biogeochemical cycling in aquatic systems on sandy soils at the Doñana National Park. In addition, they provide significant insights into the bioavailability of these elements with potential interest in the role of microorganisms for metal sequestration in natural environments and utilization in bioremediation processes. 相似文献