Geochemical and organic petrological characterization of the organic matter of lacustrine Eocene oil shales (Prinz von Hessen,Germany): reconstruction of the depositional environment     

Peter?HofmannEmail author  Martina?Duckensell  Arkadi?Chpitsglous  Lorenz?Schwark 《Journal of Paleolimnology》2005,33(2):155-168

Optical and geochemical techniques were applied to sedimentary organic matter from the profundal area of the Eocene Lake Prinz von Hessen, which formed in a pull-apart basin on the Sprendlinger Horst, near Darmstadt, Germany. Variations in total sulphur content (S tot) and total organic carbon content (TOC), hydrogen index (HI), oxygen index (OI) and ¹³C values of the organic matter were used to reconstruct the lakes filling history. Following an initial rapid deepening phase, open lake conditions developed with HI reaching more than 500 mg HC/g TOC and TOC values up to 40%. The productivity of the lake was probably high and organic matter preservation was enhanced by a stratified water column. As the lake began to fill with sediment and became shallower, TOC and HI values declined, as the lake water was better oxygenated and preservation conditions declined. ¹³C values between –31 and –27 are controlled by the mixing of aquatic (algae and microbial mats) and terrigenous organic matter (wood, spores, pollen and cuticles). Following a rapid drop in lake level, shallow lake conditions alternated with swamp deposits (lignites) in the basin center. The organic matter preserved during this stage is strictly terrigenous in nature and experienced oxic degradation (HI 100 mg HC/g TOC). ¹³C values between –26 and –24 are typical for Eocene terrigenous matter. The inferred lake level fluctuations are interpreted to have been controlled by tectonic as well as climatic processes.  相似文献   

Sedimentary geochemical evidence for recent eutrophication of Lake Chenghai, Yunnan, China   总被引：7，自引：2，他引：5  

Wu Jinglu  Michael K. Gagan  Jiang Xuezhong  Xia Weilan  Wang Sumin 《Journal of Paleolimnology》2004,32(1):85-94

Geochemical anomalies and stable isotope ratios (¹⁸O, ¹³C) in authigenic carbonates and organic matter (¹³C) from a 660-year sediment core from Lake Chenghai, southern China, provide a continuous history of recent lake eutrophication. The multi-proxy geochemical and isotopic record can be divided into a three-part history of contrasting limnological development, including: (1) a clear-water, oligotrophic open lake system (1340 and 1690 AD); (2) an environmentally unstable, hydrologically closed, oligotrophic lake system (1690–1940 AD); and (3) an increasingly eutrophic, closed lake system marked by higher organic matter, nitrogen, CaCO₃, and pigment concentrations, and lower ¹⁸O and ¹³C values in authigenic calcite (1940–1999 AD). The unanticipated lowering of ¹⁸O and ¹³C of authigenic calcite during eutrophication is thought to be the result of disequilibrium water–carbonate fractionation of oxygen and carbon isotopes during periods of elevated primary production, pH, and [CO₃ ^2–] activities in the water column. The recent eutrophication of Lake Chenghai indicated by these geochemical proxies is essentially simultaneous with large-scale human migration and the application of agricultural fertilizers in the catchment area during the 20th century.  相似文献   

黑河流域植被净初级生产力的遥感估算   总被引：13，自引：2，他引：13  

卢玲  李新 《中国沙漠》2005,25(6):823-830

利用光能利用率模型C-FIX,高时空分辨率的SPOT/VEGETATION遥感数据,全球格网化气象再分析资料以及黑河流域土地利用图,估算了1998—2002年黑河流域不同生态系统净初级生产力(NPP)的年总量和平均生产力,输出了黑河流域NPP年累积量空间分布格局图、NPP季节动态图,分析了近5a来黑河流域NPP时空变化特征,评价了不同土地利用类型下的生态系统生产力水平差异。其结果表明,黑河流域陆地生态系统NPP空间分布及其季相变化特征是流域自然环境、地貌、气候以及人类生产活动长期共同作用和影响的结果,其中水分条件是控制黑河流域陆地生态系统NPP空间格局的决定因子。1998—2002年黑河流域山区高覆盖度草地和下游荒漠区净初级生产力持续下降,反映出这些地区生态环境恶化严重。这些研究结果可以为黑河流域的水-生态-经济系统的合理设计与有效实施提供科学数据集。  相似文献   

Productivity change and fleet restructuring after transition to individual transferable quota management     

《Marine Policy》2015

Productivity change after transition to an individual transferable quota (ITQ) management system is driven by exit of some vessels, entry of other vessels, and changes in productivity of existing vessels. Generally, it is thought that an ITQ system boosts productivity due to the exit of less productive vessels. However, ITQ management systems also create an additional barrier to entry, and more productive vessels may not be able to enter the fishery. This study constructs the Färe–Primont index to measure productivity change for the Mid-Atlantic surf clam and ocean quahog fishery over a 32 year time period, which includes both pre and post-ITQ time periods. The index is then combined with a biomass change index to arrive at a measure of biomass adjusted productivity change. Results show that when biomass changes are considered, positive productivity gains occurred throughout the time period. Further examination of contributions from entering and survivor vessels show that entering vessels had little impact on aggregate productivity, but on an individual basis, they eventually were equal in productivity to survivor vessels.  相似文献   

海水池塘混合施肥养殖台湾红罗非鱼的鱼产力和负荷力   总被引：2，自引：0，他引：2  

杨红生  李德尚  董双林  卢敬让  徐宁  张鸿雁 《海洋与湖沼》2000,31(2):117-122

于１９９５年７—９月,在烟台市黄海水产集团公司第二养虾场,采用围隔实验法研究了海水池塘混合施肥养殖台湾红罗非鱼的鱼产力、负荷力和最适放养量。实验中每个围隔面积为 ５ｍ×５ｍ,各设 １台 ９０Ｗ的搅水机（４ ８００ｒ／ ｈ）。每日施肥基准为：鸡粪干物质, ２５ｋｇ／ｈａ：氮肥, Ｎ０．１５× １０－６;磷肥,Ｐ０．０１５× １０－６。结果表明,静水海水池塘混合施肥的鱼产力为０．７９ｇ／（ｍ２·ｄ）,池塘对台湾红罗非鱼的负荷力为１７９６．０ｋｇ／ｈａ,鱼（体重７０ｇ／ｉｎｄ）的最适放养量约为８０００ｉｎｄ／ｈａ。  相似文献