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11.
Sebastiaan W. Rampen Stefan Schouten Enno Schefuß Jaap S. Sinninghe Damst 《Organic Geochemistry》2009,40(11):1124-1131
Long chain 1,14-diols and 12-hydroxy methyl alkanoates are biomarker lipids for Proboscia diatoms and occur widely in Quaternary sediments. To determine the effect of temperature on the lipid composition of these algae, a new Proboscia sp. culture grown at 8 °C and Proboscia indica cultures grown at 18, 21, 24 and 27 °C were examined. The results were combined with lipid data from a P. indica culture and a Proboscia alata culture, grown at 20 and 2 °C, respectively, from previous studies. The data showed a strong relationship between long chain diol and 12-hydroxy methyl alkanoate composition and growth temperature, i.e. the chain length increases and the degree of unsaturation of long chain 1,14-diols decreases with increasing growth temperature. To determine the effect of temperature on Proboscia lipid compositions in natural environments, we also analyzed fossil long chain 1,14-diols and 12-hydroxy methyl alkanoates in surface sediments derived from Proboscia diatoms living in the water column of the eastern South Atlantic. The results indicate a significant relationship between sea surface temperature and chain length distribution of saturated long chain diols, but also suggest that the relative abundances of unsaturated long chain diols and 12-hydroxy methyl alkanoates in sediments are predominantly determined by factors other than temperature. 相似文献
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Chunyan Zhu Leicheng Guo Dirk Sebastiaan van Maren Bo Tian Xianye Wang Qing He Zheng Bing Wang 《地球表面变化过程与地形》2019,44(12):2319-2332
The morphology of the Yangtze Estuary has changed substantially at decadal time scales in response to natural processes, local human interference and reduced sediment supply. Due to its high sediment load, the morphodynamic response time of the estuary is short, providing a valuable semi-natural system to evaluate large-scale estuarine morphodynamic responses to interference. Previous studies primarily addressed local morphologic changes within the estuary, but since an overall sediment balance is missing, it remains unclear whether the estuary as a whole has shifted from sedimentation to erosion in response to reduced riverine sediment supply (e.g. resulting from construction of the Three Gorges Dam). In this paper we examine the morphological changes of two large shoals in the mouth zone (i.e. the Hengsha flat and the Jiuduan shoal) using bathymetric data collected between 1953 and 2016 and a series of satellite images. We observe that the two shoals accreted at different rates before 2010 but reverted to erosion thereafter. Human activities such as dredging and dumping contribute to erosion, masking the impacts of sediment source reduction. The effects of local human intervention (such as the construction of a navigation channel) are instantaneous and are likely to have already resulted in new dynamic equilibrium conditions. The morphodynamic response time of the mouth zone to riverine sediment decrease is further suggested to be >30 years (starting from the mid-1980s). Accounting for the different adaptation time scales of various human activities is essential when interpreting morphodynamic changes in large-scale estuaries and deltas. © 2019 John Wiley & Sons, Ltd. 相似文献
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Damage to residential buildings due to flooding of New Orleans after hurricane Katrina 总被引：1，自引：1，他引：0
This article analyzes the direct damage to residential buildings caused by the flooding of New Orleans after hurricane Katrina
in the year 2005. A public dataset has been analyzed that contains information on the economic damage levels for approximately
95,000 residential buildings in the flooded area. The relationship between the flood characteristics and economic damage to
residential buildings has been investigated. Results of hydrodynamic flood simulations have been used that give insight in
water depths and flow velocities in the study area. In general, differences between the three polders in the observed distributions
of damage estimates are related to differences in flood conditions. The highest damage percentages and structural damage mainly
occurred in areas where higher flow velocities occurred, especially near the breaches in the Lower 9th Ward neighborhood.
Further statistical analysis indicated that there is not any strong one-to-one relationship between the damage percentage
and the water depth or the depth–velocity product. This suggests that there is considerable uncertainty associated with stage-damage
functions, especially when they are applied to individual structures or smaller clusters of buildings. Based on the data,
a more general approach has been proposed that could be used to distinguish different damage zones based on water depth and
flow velocity for an area that is affected by flooding due to breaching of flood defenses. Further validation of existing
damage models with the dataset and further inclusion of information on building type in the analysis of damage levels is recommended. 相似文献
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Jasper van Vliet Andries F. Hof Angelica Mendoza Beltran Maarten van den Berg Sebastiaan Deetman Michel G. J. den Elzen Paul L. Lucas Detlef P. van Vuuren 《Climatic change》2014,123(3-4):559-569
While most long-term mitigation scenario studies build on a broad portfolio of mitigation technologies, there is quite some uncertainty about the availability and reduction potential of these technologies. This study explores the impacts of technology limitations on greenhouse gas emission reductions using the integrated model IMAGE. It shows that the required short-term emission reductions to achieve long-term radiative forcing targets strongly depend on assumptions on the availability and potential of mitigation technologies. Limited availability of mitigation technologies which are relatively important in the long run implies that lower short-term emission levels are required. For instance, limited bio-energy availability reduces the optimal 2020 emission level by more than 4 GtCO2eq in order to compensate the reduced availability of negative emissions from bioenergy and carbon capture and storage (BECCS) in the long run. On the other hand, reduced mitigation potential of options that are used in 2020 can also lead to a higher optimal level for 2020 emissions. The results also show the critical role of BECCS for achieving low radiative forcing targets in IMAGE. Without these technologies achieving these targets become much more expensive or even infeasible. 相似文献
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Sebastiaan W. Rampen Stefan Schouten Ben Abbas Anna A.M. Noordeloos Jan A.J. Geenevasen 《Geochimica et cosmochimica acta》2009,73(2):377-492
Analysis of the sterol composition of more than 100 diatom cultures, representing all major marine diatom orders, indicates that this group of algae may be an important source for 4-desmethyl-23,24-dimethyl steroids in sediments and petroleum, as their precursors, i.e. 4-desmethyl-23,24-dimethyl sterols, were present in 22 of the cultures. The phylogenetic positions of diatom species that produce 4-desmethyl-23,24-dimethyl sterols show that, within the centric diatoms, only a specific group of diatoms is able to produce these sterols, while within the pennate diatoms, a phylogenetic relationship between 4-desmethyl-23,24-dimethyl sterol-producing diatoms is less apparent. Based on the phylogenetic relationship, it is suggested that diatoms inherited the ability of producing these sterols from a single common ancestor, which originated between 150 and 100 Ma ago. Co-injection of an authentic 23R,24R-dimethyl-5α-cholestane standard with extracts confirmed its presence in sediments. We also tentatively identified three other 4-desmethyl-23,24-dimethyl sterane isomers having different side-chain stereo-configurations and observed that some of the isomers co-elute with other steranes including 24-ethyl-5α-cholestane. 相似文献
18.
Sebastiaan W. Rampen Stefan SchoutenJaap S. Sinninghe Damsté 《Organic Geochemistry》2011,42(5):572-574
Long chain 1,14-diols have been reported in diatoms of the genus Proboscia and applied as specific biomarker lipids for such algae. We report here the presence of saturated C28, C30 and C32 1,14-diols in a culture of the marine heterokont alga Apedinella radians (Class Dictyochophyceae, order Pedinellales). Apedinella species occur globally, although predominantly in estuarine waters, so the finding has potential implications for the use of long chain 1,14-diols as biomarkers of Proboscia diatoms and as an indicator of upwelling. 相似文献
19.
Vnia Freitas Joana F.M.F. Cardoso Sílvia Santos Joana Campos Jan Drent Sofia Saraiva Johannes IJ. Witte Sebastiaan A.L.M. Kooijman Henk W. Van der Veer 《Journal of Sea Research》2009,62(2-3):75
Required assimilated energy to support observed growth was reconstructed for four common bivalve species (Mya arenaria, Cerastoderma edule, Mytilus edulis and Macoma balthica) from various Northeast Atlantic coastal areas, along the species distributional range. The approach applied was based on the Dynamic Energy Budget (DEB) theory whereby observed growth patterns in the field, in combination with prevailing temperatures, were used to reconstruct the average food intake experienced in the field scaled to the maximum possible. For all species, results suggest food limitation over the range of locations. In general, reconstructed food intake indicated better conditions for C. edule compared to the other species, while M. edulis presented the lowest food conditions in all the areas. Despite the indications for a latitudinal trend in primary production, no clear pattern or relationship between reconstructed food conditions and latitude was observed suggesting that any trend may be overruled by local conditions. 相似文献
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The impact of silt trapping in large reservoirs on downstream morphology: the Yangtze River 总被引：2，自引：0，他引：2
The sediment load of the Yangtze River (China) is decreasing because of construction of dams, of which the Three Gorges Dam (TGD) is the best known example. The rate of the decline in sediment load is well known, but changes in the sediment grain size distribution have not been given much attention. The TGD mostly traps sand and silt while clay is flushed through the reservoir. A large amount of sand is available in the Yangtze River downstream of the reservoir, and therefore the pre-dam sand concentration is not substantially reduced. The availability of silt on the Yangtze River bed is limited, and it is expected that most silt will be removed from the riverbed within one to two decades. In order to evaluate the impact of the change in grain size distribution on the tidal flats of the Yangtze Estuary, a highly schematized tidal flat model is setup. This model broadly reveals that the observed deposition rates are exceptionally large because of the high sediment concentration, the abundance of silt, the seasonal dominance of waves (shaping a concave profile), and the offshore tidal asymmetry. The model further suggests that deposition rates will be limitedly influenced by reductions in clay or fine silt but strongly impacted by reductions in median to coarse silt. The response of the downstream morphology to reservoir sedimentation therefore strongly depends on the type of trapped sediment. As a consequence, silt-dominated rivers, such as the Yangtze River and the Yellow River may be more strongly impacted than sand-dominated systems. 相似文献