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241.
Jaime Solís-Guzmán Madelyn Marrero Maria Victoria Montes-Delgado Antonio Ramírez-de-Arellano 《Waste management (New York, N.Y.)》2009,29(9):2542-2548
Currently, construction and demolition waste (C&D waste) is a worldwide issue that concerns not only governments but also the building actors involved in construction activity. In Spain, a new national decree has been regulating the production and management of C&D waste since February 2008. The present work describes the waste management model that has inspired this decree: the Alcores model implemented with good results in Los Alcores Community (Seville, Spain). A detailed model is also provided to estimate the volume of waste that is expected to be generated on the building site. The quantification of C&D waste volume, from the project stage, is essential for the building actors to properly plan and control its disposal. This quantification model has been developed by studying 100 dwelling projects, especially their bill of quantities, and defining three coefficients to estimate the demolished volume (CT), the wreckage volume (CR) and the packaging volume (CE). Finally, two case studies are included to illustrate the usefulness of the model to estimate C&D waste volume in both new construction and demolition projects. 相似文献
242.
Ram Kumar Dhaked Padma Singh Lokendra Singh 《Waste management (New York, N.Y.)》2010,30(12):2490-2496
The biomethanation of organic matter represents a long-standing, well-established technology. Although at mesophilic and thermophilic temperatures the process is well understood, current knowledge on psychrophilic biomethanation is somewhat scarce. Methanogenesis is particularly sensitive to temperature, which not only affects the activity and structure of the microbial community, but also results in a change in the degradation pathway of organic matter. There is evidence of psychrophilic methanogenesis in natural environments, and a number of methanogenic archaea have been isolated with optimum growth temperatures of 15–25 °C. At psychrophilic temperatures, large amounts of heat are needed to operate reactors, thus resulting in a marginal or negative overall energy yield. Biomethanation at ambient temperature can alleviate this requirement, but for stable biogas production, a microbial consortium adapted to low temperatures or a psychrophilic consortium is required. Single-step or two-step high rate anaerobic reactors [expanded granular sludge bed (EGSB) and up flow anaerobic sludge bed (UASB)] have been used for the treatment of low strength wastewater. Simplified versions of these reactors, such as anaerobic sequencing batch reactors (ASBR) and anaerobic migrating blanket reactor (AMBR) have also been developed with the aim of reducing volume and cost. This technology has been further simplified and extended for the disposal of night soil in high altitude, low temperature areas of the Himalayas, where the hilly terrain, non-availability of conventional energy, harsh climate and space constraints limit the application of complicated reactors. Biomethanation at psychrophilic temperatures and the contribution made to night-soil degradation in the Himalayas are reviewed in this article. 相似文献
243.
Parents adjust care in response to weather conditions and egg dehydration in a Neotropical glassfrog
Jesse R. J. Delia Aurelio Ramírez-Bautista Kyle Summers 《Behavioral ecology and sociobiology》2013,67(4):557-569
Parental hydration of terrestrially developing eggs has evolved repeatedly among frogs and is thought to buffer embryos from environmental variation. While many anurans offer relevant opportunities to study parental care, research on how parents respond to environmental variation and offspring conditions are lacking. In this study, we investigated the interrelationships of weather, embryo hydration demands, and parental provisioning in a wild population of the glassfrog Hyalinobatrachium (‘Centrolenella’) fleischmanni in Oaxaca, Mexico. We determined whether males modify parental behavior in response to changes in weather conditions that effect embryo dehydration, how variation in both weather and parental hydration affect egg water balance and embryonic mortality, and whether parental provisioning is related to the hydration levels of egg clutches. We found that male H. fleischmanni compensate for environmental variation in offspring conditions by adjusting the frequency of parental care in response to both weather and egg dehydration. Using a male removal experiment, we examined the function of paternal care and made comparisons with previous research, finding that both the adaptive value of parental care and flexibility in parental behavior are impacted by spatial and temporal conditions. We present observations that indicate a direct conflict between providing parental care and multiple matings. In summary, this research demonstrates that the variable frequency of paternal care in H. fleischmanni is a response to the fluctuating nature of the climate and resulting hydration requirements of embryos in combination with the allocation of effort to parental care versus mating activity. 相似文献
244.
245.
Although polycyclic aromatic hydrocarbons (PAHs) are common pollutants in snow, there is little quantitative data about their rates of photodegradation in this environment. To begin to address this gap, we have measured the degradation kinetics of phenanthrene, pyrene, and fluoranthene on ice, as these are the most abundant PAHs in arctic snow. Frozen aqueous solutions of individual PAHs, with and without added hydrogen peroxide (HOOH) as a source of hydroxyl radical (OH), were illuminated with simulated sunlight. For all three PAHs, direct photodecay is the main mechanism of degradation, while OH-initiated indirect photodegradation is a minor sink. Rate constants (±1 SE) for direct photodegradation extrapolated to midday, surface snow conditions at Summit, Greenland on the summer solstice are 3.8 (±0.8) × 10?5, 28 (±3) × 10?5, and 1.4 (±0.7) × 10?5 s?1 for phenanthrene, pyrene, and fluoranthene, respectively. Apparent quantum efficiencies for photodegradation with simulated sunlight were 3.8 (±0.8) × 10?3, 4.3 (±0.5) × 10?4, and 2 (±1) × 10?5, respectively. Calculated PAH lifetimes in surface snow under Summit conditions are 1–19 h during mid-summer, but increase to >100 days in the dark winter. While the short photodegradation lifetimes in the summer suggest that there should be no appreciable PAH levels in this season, past measurements at Summit sometimes show significant levels of these PAHs in summer surface snow. This discrepancy is likely due to differences in PAH location between lab samples (where the PAHs are probably in quasi-liquid layers) and real snow (where PAHs are likely primarily associated with particulate matter). 相似文献
246.
Biodiversity conservation and management of natural resources are the best options to restore and increase productivity of
degrading pastureland in dry areas. Hence, arthropod abundance, organic matter, respiration, and dehydrogenase activity were
measured in canopy zone soil of Prosopis cineraria (PC), Acacia nilotica (AN), Zizyphus nummularia (ZN), Capparis decidua (CD), and Acacia senegal (AS) associated with grasses with a view to establish interrelation for productivity enhancement of pastureland. Pure grass
bock outside tree canopy was control plot. Acari, Myriapoda, Coleoptera, Isoptera, Collembola, and other soil arthropods were
the major soil faunal groups. Integration of tree in pastureland enhanced population of soil arthropod by 9–65-fold in May
2001 and 8–13-fold in August/September as compared with control. The trends of changes in soil organic matter (SOM), soil
respiration (SR), and dehydrogenase activity (DHA) were similar to the changes in soil arthropod population, indicating the
role of soil fauna in facilitating biochemical processes and soil fertility. Two, eight, and nine times greater SOM, SR, and
DHA, respectively, in silvipastoral system than the values in control suggest the beneficial effects of trees on improvement
in biochemical processes and thus biodiversity in pastureland, as supported by negative values of relative tree effects (RTE).
Microbial activities were highest in the ZN system, which had highest abundance of soil arthropods. In the other systems,
CD and AS systems showed greater soil arthropod abundance and biological activities than with the PC and AN systems. Therefore,
Z. nummularia-, C. decidua-, and A. senegal-based silvipastoral systems and related soil fauna may be promoted for enhancement of biological activity and productivity
of pastureland in desert. The strategy may be adopted for developing a sustainable pedoecosystem in a region of the world
where agriculture is notoriously difficult. 相似文献
247.
This article assesses the role of local institutions in managing irrigation water use. Fifty irrigation systems in each country
were studied in Nepal and Thailand to compare the influence of local institutions on performance of irrigation systems amid
changes in external policy and market pressures. Nepal’s new irrigation policy after the re-instatement of multiparty democracy
in 1990 emphasized participatory irrigation management transferring the management responsibility from state authorities to
water users. The water user associations of traditional farmer-managed irrigation systems were formally recognized by requiring
registration with related state authorities. In Thailand also government policies encouraged people’s participation in irrigation
management. Today water users are directly involved in management of even some large irrigation systems at the level of tertiary
canals. Traditional communal irrigation systems in northern Thailand received support for system infrastructure improvement
but have faced increased interference from government. In Thailand market development supported diversification in farming
practices resulting in increased areas under high water-demanding commercial crops in the dry season. In contrast, the command
areas of most irrigation systems in Nepal include cereal-based subsistence farming with only one-third having commercial farming.
Cropping intensities are higher in Nepal than in Thailand reflecting, in part, differences in availability of land and management.
In both countries local institutions play an important role in maintaining the performance of irrigation systems as external
drivers and local contexts change. Local institutions have provided alternative options for irrigation water use by mediating
external pressures. 相似文献
248.
Ines Dombrowsky Ram Almog Nir Becker Eran Feitelson Simone Klawitter Stefan Lindemann Natalie Mutlak 《Environmental management》2010,45(5):1112-1126
The basin scale has been promoted universally as the optimal management unit that allows for the internalization of all external
effects caused by multiple water uses. However, the basin scale has been put forward largely on the basis of experience in
temperate zones. Hence whether the basin scale is the best scale for management in other settings remains questionable. To
address these questions this paper analyzes the economic viability and the political feasibility of alternative management
options in the Kidron/Wadi Nar region. The Kidron/Wadi Nar is a small basin in which wastewater from eastern Jerusalem flows
through the desert to the Dead Sea. Various options for managing these wastewater flows were analyzed ex ante on the basis
of both a cost benefit and a multi-criteria analysis. The paper finds that due to economies of scale, a pure basin approach
is not desirable from a physical and economic perspective. Furthermore, in terms of political feasibility, it seems that the
option which prompts the fewest objections from influential stakeholder groups in the two entities under the current asymmetrical
political setting is not a basin solution either, but a two plant solution based on an outsourcing arrangement. These findings
imply that the river basin management approach can not be considered the best management approach for the arid transboundary
case at hand, and hence is not unequivocally universally applicable. 相似文献
249.
250.
Fuentes D Disante KB Valdecantos A Cortina J Ramón Vallejo V 《Environmental pollution (Barking, Essex : 1987)》2007,145(1):316-323
We investigated the response of Pinus halepensis seedlings to the application of biosolids enriched with Cu, Ni and Zn on three Mediterranean forest soils under semiarid conditions. One-year-old seedlings were planted in lysimeters on soils developed from marl, limestone and sandstone which were left unamended, amended with biosolids, or amended with biosolids enriched in Cu, Ni and Zn. Enriched biosolids increased plant heavy metal concentration, but always below phytotoxic levels. Seedlings receiving unenriched biosolids showed a weak reduction in Cu and Zn concentration in needles, negatively affecting physiological status during drought. This effect was alleviated by the application of enriched sludge. Sewage sludge with relatively high levels of Cu, Zn and Ni had minor effects on plant performance on our experimental conditions. Results suggest that micronutrient limitations in these soils may be alleviated by the application of biosolids with a higher Cu, Zn and Ni content than those established by current regulations. 相似文献