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991.
Stuart G. Wakeham Cindy Lee Michael L. Peterson Zhanfei Liu Jennifer Szlosek Isabel F. Putnam Jianhong Xue 《Deep Sea Research Part II: Topical Studies in Oceanography》2009,56(18):1437-1453
The transfer of material through the twilight zone of the ocean is controlled by sinking particles that contain organic matter (OM) and mineral ballast. During the MedFlux field program in the northwestern Mediterranean Sea in 2003, sinking particulate matter was collected in time series (TS) and settling velocity (SV) traps and analyzed for amino acids, lipids, and pigments (along with ballast minerals) [Lee, C., Armstrong, R.A., Wakeham, S.G., Peterson, M.L., Miquel, J.C., Cochran, J.K., Fowler, S.W., Hirschberg, D., Beck, A. Xue, J., 2009b. Particulate matter fluxes in time series and settling velocity sediment traps in the northwestern Mediterranean Sea. Deep-Sea Research II, this volume [doi:10.1016/j.dsr2.2008.12.003]]. The goal was to identify how organic chemical compositions of sinking particles varied as a function of their in-situ settling velocity. The TS record was used to define the biogeochemical character and temporal pattern in flux during the period of SV trap deployment. Temporal variations in organic and mineral compositions are consistent with particle biogeochemistry being driven by the seasonal succession of phytoplankton. Spring diatom bloom conditions led to a high flux of rapidly sinking aggregates and zooplankton fecal matter; summer oligotrophy followed and was characterized by a higher proportion of slowly sinking phytoplankton cells. Bacterial degradation is particularly important during the low-flux summer period. Settling velocity traps show that a large proportion of particulate organic matter sinks at 200–500 m d−1. Organic compositions of this fast-sinking material mirrors that of fecal pellets and aggregated material that sinks as the spring bloom terminates. More-slowly sinking OM bears a stronger signature of bacterial degradation than do the faster-sinking particles. The observation that compositions of SV-sorted fractions are different implies that the particle field is compositionally heterogeneous over a range of settling velocities. Thus physical and biological exchange between fast-sinking and slow-sinking particles as they pass down the water column must be incomplete. 相似文献
992.
This paper outlines a methodology to assess the seismic drift of reinforced concrete buildings with limited structural and geotechnical information. Based on the latest and the most advanced research on predicting potential near-field and far field earthquakes affecting Hong Kong, the engineering response spectra for both rock and soil sites are derived. A new step-by-step procedure for displacement-based seismic hazard assessment of building structures is proposed to determine the maximum inter-storey drift demand for reinforced concrete buildings. The primary information required for this assessment is only the depth of the soft soil above bedrock and the height of the building. This procedure is further extended to assess the maximum chord rotation angle demand for the coupling beam of coupled shear wall or frame wall structures, which may be very critical when subjected to earthquake forces. An example is provided to illustrate calibration of the assessment procedure by using actual engineering structural models. 相似文献
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近年来,平阴县国土资源局充分发挥部门职能,按照“保护资源,保障发展,维护权益,服务社会”的工作目标,完成土地开发整理项目95个,建设规模0.90万hm^2,实现新增耕地面积0.24万hm^2;完成旧村改造31个,整治面积573.33hm^2;治理破损山体26座,治理面积205.9万m^2。改善了平阴县农村的生产生活条件和居住环境,有力促进了农村发展、农业增效和农民增收。下一步,该局要在“开发整理、示范区建设、土地经营、依法行政”4个方面管好用好土地资源,全力支持和服务新农村建设。 相似文献
995.
Slope-confined submarine canyons in the Baiyun deep-water area,northern South China Sea: variation in their modern morphology 总被引:1,自引:0,他引:1
X. S. Li Q. J. Zhou T. Y. Su L. J. Liu S. Gao S. W. Zhou 《Marine Geophysical Researches》2016,37(2):95-112
On the basis of newly collected multibeam bathymetric data, chirp profiles and existing seismic data, we presented a detailed morphological interpretation of a series of slope-confined canyons in water depths of 300–2000 m in the Baiyun deep-water area, northern margin of the South China Sea. Although these canyons are commonly characterized by regular spacing and a straight-line shape, they vary in their lengths, starting and ending water depths, canyon relief, slope gradients, wall slope gradients and depth profiles along the axis. The eastern canyons (C1–C8) have complex surface features, low values in their slope gradient, canyon relief and wall slope gradient and high values in their length and starting and ending depth contrasting to the western ones (C9–C17). From the bathymetric data and chirp profiles, we interpret two main processes that have controlled the morphology and evolution of the canyons: axial incision and landsliding. The western part of the shelf margin where there were at least four stages of submerged reefs differs from the eastern part of the shelf margin where sedimentary undulations occurred at a water depth of ~650 m. We consider that the variation in morphology of submarine canyons in the study area is the result of multiple causes, with the leading cause being the difference in stability of the upper slope which is related to the submerged reefs and sedimentary undulations. 相似文献
996.
陆地水储量是赋存在陆地上各种形式水的综合体现,研究其时空变化对认识区域水循环过程和水资源调控等具有重要意义。然而现有陆地水储量变化数据实际分辨率较低,限制了其在中小流域或地区中的应用。针对这一问题,本文基于GRACE重力卫星和其后续卫星GRACE-FO反演的陆地水储量变化数据,首先采用随机森林模型,分别基于格点、区域(流域)和区域(全国)3种空间降尺度思路将GRACE数据降尺度至0.25°×0.25°,后结合GLDAS模型数据,基于水量平衡原理计算得到地下水储量变化数据,最后基于降尺度模型模拟效果和实测地下水位数据评估3种降尺度思路在全国的适用性。结果表明:随机森林模型能够较好地模拟驱动数据(降水、气温、植被条件指数和土壤水储量)与GRACE数据的统计关系,验证期格点降尺度思路的平均相关系数总体在0.6左右,区域降尺度思路的平均纳什效率系数、相关系数和均方根误差分别>0.5、>0.75和<6.6 cm,3种空间降尺度思路的模拟精度均满足基本要求;2003—2021年间,GRACE数据、格点降尺度、区域降尺度(流域)和区域降尺度(全国)得到的我国陆地水储量亏缺量分别约为... 相似文献
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Lin HJ Dai XX Shao KT Su HM Lo WT Hsieh HL Fang LS Hung JJ 《Marine environmental research》2006,62(1):61-82
Tapong Bay, a eutrophic and poorly flushed tropical lagoon, supports intensive oyster culture. Using the Ecopath approach and network analysis, a mass-balanced trophic model was constructed to analyze the structure and matter flows within the food web. The lagoon model is comprised of 18 compartments with the highest trophic level of 3.2 for piscivorous fish. The high pedigree index (0.82) reveals the model to be of high quality. The most-prominent living compartment in terms of matter flow and biomass in the lagoon is cultured oysters and bivalves, respectively. The mixed trophic impacts indicate that phytoplankton and periphyton are the most-influential living compartments in the lagoon. Comparative analyses with the eutrophic and well-flushed Chiku Lagoon and non-eutrophic tropical lagoons show that high nutrient loadings might stimulate the growth and accumulation of phytoplankton and periphyton and therefore support high fishery yields. However, net primary production, total biomass, fishery yields per unit area, and mean transfer efficiency of Tapong Bay were remarkably lower than those of Chiku Lagoon. The lower transfer efficiency likely results from the low mortality of cultured oysters and invasive bivalves from predation or the lower density of benthic feeders constrained by the hypoxic bottom water as a result of poor flushing. This might therefore result in a great proportion of flows to detritus. However, the hypoxic bottom water might further reduce the recycling of the entering detritus back into the food web. In contrast to many estuaries and tropical lagoons, poor flushing of this eutrophic tropical lagoon might induce a shift from detritivory to herbivory in the food web. 相似文献
1000.
SUQin CAOYou-hui LINBing-yao 《中国地理科学(英文版)》2005,15(1):70-79
Based on the questionnaire investigation, the authors make a comparative study on local residents‘ perception of tourism impacts in Xidi, Zhouzhuang and Jiuhua Mountain. The result shows that residents of the three places tend to have strong and consistent perception of its positive economic, socio-cultural and environmental impacts, but distinctly diverse ones of its negative impacts. Residents in Xidi and Zhouzhuang also have noticeable perception of its negative environmental impacts while those in Jiuhua Mountain have weaker perception of them.The research confirms the fact that residents are more liable to have positive perceptions at the early stage of the life cycle of the tourist places. The authors conclude that there exists a nonlinear relationship between residents‘ perception and tourism development stages, and that tourism socio-cultural impact may appear at an early stage of tourism development instead of being no universal. 相似文献