867 resultados para global warming potential


Relevância:

80.00% 80.00%

Publicador:

Resumo:

Subsistence in Alaska is currently being impacted by naturally occurring factors such as global warming, species migration shifts, and the declination of fishery and wildlife populations. Not only are external factors pressuring the debate, management strategies from the dual management operation appear to have failed. The current national focus has been centered on federal policy changes regarding subsistence. This project extends the federal subsistence review process into the state management of subsistence and provides practical solutions for enhancing both policy programs.

Relevância:

80.00% 80.00%

Publicador:

Resumo:

Natural coral reefs are in a state of serious decline worldwide. The pressures of over fishing, recreational activities, environmental pollutants, and global warming have stressed these marine ecosystems to the breaking point. One of the oldest methods of augmenting natural reef systems is the implementation of artificial reefs. These projects are not as simple as dumping waste or scrap materials in offshore areas. Proper material selection is vital to produce a healthy artificial marine habitat that is completed on schedule and on budget. This Capstone Project will evaluate the most commonly used materials and provide a comparison of their strengths and weaknesses. This comparison provides a valuable tool for project managers as they begin the reef planning process.

Relevância:

80.00% 80.00%

Publicador:

Resumo:

In this work, batch and dynamic adsorption tests are coupled for an accurate evaluation of CO2 adsorption performance for three different activated carbons obtained from olives stones by chemical activation followed by physical activation with CO2 at varying times, i.e. 20, 40 and 60 h. Kinetic and thermodynamic CO2 adsorption tests from simulated flue-gas at different temperature and CO2 pressure are carried out both in batch (a manometric equipment operating with pure CO2) and dynamic (a lab-scale fixed-bed column operating with CO2/N2 mixture) conditions. The textural characterization of the activated carbon samples shows a direct dependence of both micropore and ultramicropore volume on the activation time, hence AC60 has the higher contribution. The adsorption tests conducted at 273 and 293 K showed that, when CO2 pressure is lower than 0.3 bar, the lower the activation time the higher CO2 adsorption capacity and a ranking ωeq(AC20)>ωeq(AC40)>ωeq(AC60) can be exactly defined when T= 293 K. This result can be likely ascribed to a narrower pore size distribution of the AC20 sample, whose smaller pores are more effective for CO2 capture at higher temperature and lower CO2 pressure, the latter representing operating conditions of major interest for decarbonation of a flue-gas effluent. Moreover, the experimental results obtained from dynamic tests confirm the results derived from the batch tests in terms of CO2 adsorption capacity. It is important to highlight that the adsorption of N2 on the synthesized AC samples can be considered negligible. Finally, the importance of a proper analysis of characterization data and adsorption experimental results is highlighted for a correct assessment of CO2 removal performances of activated carbons at different CO2 pressure and operating temperature.

Relevância:

80.00% 80.00%

Publicador:

Resumo:

With global warming becoming one of the main problems our society is facing nowadays, there is an urgent demand to develop materials suitable for CO2 storage as well as for gas separation. Within this context, hierarchical porous structures are of great interest for in-flow applications because of the desirable combination of an extensive internal reactive surface along narrow nanopores with facile molecular transport through broad “highways” leading to and from these pores. Deep eutectic solvents (DESs) have been recently used in the synthesis of carbon monoliths exhibiting a bicontinuous porous structure composed of continuous macroporous channels and a continuous carbon network that contains a certain microporosity and provides considerable surface area. In this work, we have prepared two DESs for the preparation of two hierarchical carbon monoliths with different compositions (e.g., either nitrogen-doped or not) and structure. It is worth noting that DESs played a capital role in the synthesis of hierarchical carbon monoliths not only promoting the spinodal decomposition that governs the formation of the bicontinuous porous structure but also providing the precursors required to tailor the composition and the molecular sieve structure of the resulting carbons. We have studied the performance of these two carbons for CO2, N2, and CH4 adsorption in both monolithic and powdered form. We have also studied the selective adsorption of CO2 versus CH4 in equilibrium and dynamic conditions. We found that these materials combined a high CO2-sorption capacity besides an excellent CO2/N2 and CO2/CH4 selectivity and, interestingly, this performance was preserved when processed in both monolithic and powdered form.

Relevância:

80.00% 80.00%

Publicador:

Resumo:

Las grandes emisiones de CO2 procedentes de la combustión de combustibles fósiles están provocando un calentamiento global en nuestro planeta. Estos problemas medioambientales están obligando a los diferentes gobiernos a buscar soluciones que permitan reducir esas emisiones y mitigar sus efectos adversos. Una de las soluciones más prometedoras consiste en la captura selectiva de CO2 en efluentes industriales mediante el uso de materiales adsorbentes porosos (zeolitas, carbón activado y materiales híbridos MOFs) que combinen una elevada capacidad de adsorción y una adecuada selectividad a CO2 frente al resto de gases del proceso industrial, además de una adecuada regeneración.

Relevância:

80.00% 80.00%

Publicador:

Resumo:

The present work aims to develop the Life Cycle Assessment study of thermo-modified Atlanticwood® pine boards based on real data provided by Santos & Santos Madeiras company. Atlanticwood® pine boards are used mainly for exterior decking and cladding facades of buildings. The LCA study is elaborated based on ISO 14040/44 standard and Product Category Rules for preparing an environmental product declaration for Construction Products and Construction Services. The inventory analysis and, subsequently, the impact analysis have been performed using the LCA software SimaPro8.0.4. The method chosen for impact assessment was EPD (2013) V1.01. The results show that more than ¾ of ‘Acidification’, ‘Eutrophication’, ‘Global warming’ and ‘Abiotic depletion’ caused by 1 m3 of Atlanticwood® pine boards production is due to energy consumption (electricity + gas + biomass). This was to be expected since the treatment is based on heat production and no chemicals are added during the heat treatment process.

Relevância:

80.00% 80.00%

Publicador:

Resumo:

We present the first circum-East Antarctic chronology for the Holocene, based on 17 radiocarbon dates generated by the accelerator method. Marine sediments from around East Antarctica contain a consistent, high-resolution record of terrigenous (ice-proximal) and biogenic (open-marine) sedimentation during Holocene time. This record demonstrates that biogenic sedimentation beneath the open-marine environment on the continental shelf has been restricted to approximately the past 4 ka, whereas a period of terrigenous sedimentation related to grounding line advance of ice tongues and ice shelves took place between 7 and 4 ka. An earlier period of open-marine (biogenic sedimentation) conditions following the late Pleistocene glacial maximum is recognized from the Prydz Bay (Ocean Drilling Program) record between 10.7 and 7.3 ka. Clearly, the response of outlet systems along the periphery of the East Antarctic ice sheet during the mid-Holocene was expansion. This may have been a direct consequence of climate warming during an Antarctic 'Hypsithermal'. Temperature-accumulation relations for the Antarctic indicate that warming will cause a significant increase in accumulation rather than in ablation. Models that predict a positive mass balance (growth) of the Antarctic ice sheet under global warming are supported by the mid-Holocene data presented herein.

Relevância:

80.00% 80.00%

Publicador:

Resumo:

The Palaeocene/Eocene thermal maximum represents a period of rapid, extreme global warming approx ~55 million years ago, superimposed on an already warm world (Zachos et al., 2003, doi:10.1126/science.1090110; Bowen et al., 2004, doi:10.1038/nature03115; Thomas et al., 2002, doi:10.1130/0091-7613(2002)030<1067:WTFFTF>2.0.CO;2). This warming is associated with a severe shoaling of the ocean calcite compensation depth **4 and a >2.5 per mil negative carbon isotope excursion in marine and soil carbonates (Zachos et al., 2003, doi:10.1126/science.1090110; Bowen et al., 2004, doi:10.1038/nature03115; Thomas et al., 2002, doi:10.1130/0091-7613(2002)030<1067:WTFFTF>2.0.CO;2; Zachos et al., doi:10.1126/science.1109004). Together these observations indicate a massive release of 13C-depleted carbon (Zachos et al., doi:10.1126/science.1109004) and greenhouse-gas-induced warming. Recently, sediments were recovered from the central Arctic Ocean (Backman et al., 2006, doi:10.2204/iodp.proc.302.2006), providing the first opportunity to evaluate the environmental response at the North Pole at this time. Here we present stable hydrogen and carbon isotope measurements of terrestrial-plant- and aquatic-derived n-alkanes that record changes in hydrology, including surface water salinity and precipitation, and the global carbon cycle. Hydrogen isotope records are interpreted as documenting decreased rainout during moisture transport from lower latitudes and increased moisture delivery to the Arctic at the onset of the Palaeocene/Eocene thermal maximum, consistent with predictions of poleward storm track migrations during global warming (Backman et al., 2006, doi:10.2204/iodp.proc.302.2006). The terrestrial-plant carbon isotope excursion (about ~4.5 to ~6 per mil) is substantially larger than those of marine carbonates. Previously, this offset was explained by the physiological response of plants to increases in surface humidity (Bowen et al., 2004, doi:10.1038/nature03115). But this mechanism is not an effective explanation in this wet Arctic setting, leading us to hypothesize that the true magnitude of the excursion - and associated carbon input - was greater than originally surmised. Greater carbon release and strong hydrological cycle feedbacks may help explain the maintenance of this unprecedented warmth.of this unprecedented warmth.

Relevância:

80.00% 80.00%

Publicador:

Resumo:

The Paleocene/Eocene Thermal Maximum (PETM) was a transient interval of global warming ~55 m.y. ago associated with transformation of ecosystems and changes in carbon cycling. The event was caused by the input of massive amounts of CO2 or CH4 to the ocean-atmosphere system. Rapid shoaling of the lysocline and calcite compensation depth (CCD) is a predicted response of CO2 or CH4 input; however, the extent of this shoaling is poorly constrained. Investigation of Ocean Drilling Program (ODP) Sites 1209-1212 at Shatsky Rise, which lies along a depth transect, suggests a minimum lysocline shoaling of ~500 m in the tropical Pacific Ocean during the PETM. The sites also show evidence of CaCO3 dissolution within the sediment column, carbonate "burn-down" below the level of the carbon isotope excursion, and a predicted response to a rapid change in deepwater carbonate saturation. Close examination of several foraminiferal preservation proxies (i.e., fragmentation, benthic/planktonic foraminiferal ratios, coarse fraction, and CaCO3 content) and observations of foraminifers reveal that increased fragmentation levels most reliably predict intervals with visually impoverished foraminiferal preservation as a result of dissolution. Low CaCO3 content and high benthic/planktonic ratios also mirror intervals of poorest preservation.