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51.
To unravel the mystery of the relationship between evaporates, Ca–Cl brines and accumulations of oil and N2 in the basins of ancient cratons, their N2, CH4 and He concentration ratios, as well as the isotopic composition (δ15N, δ13C and 3He/4He) were compared within the Volga-Ural basin. The study allowed subsalt fluids from Volga-Ural Basin to divide into two genetic groups. The first one is found within the basin's platform area. It includes Ca–Cl brines, high-viscosity heavy oil, bitumen and N2, which has concentrations higher than that of CH4 and positive values of δ15N. The second one is tied to the edge of the platform, the Ural Foredeep and Peri-Caspian Depression. In this group, only the oil and gas reservoirs, which have more CH4 than N2, and possibly negative values of δ15N, were discovered. Interaction of gas components in compared fluids indicates great role of degassing in the formation of their composition. It is suggested that the fluids of the first group (N2 > CH4) is what remains, and the second group (N2 < CH4) is what is disappears from the rocks during their metamorphism and degassing. 相似文献
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While many harmful algal blooms have been associated with increasing eutrophication, not all species respond similarly and the increasing challenge, especially for resource managers, is to determine which blooms are related to eutrophication and to understand why particular species proliferate under specific nutrient conditions. The overall goal of this brief review is to describe why nutrient loads are not changing in stoichiometric proportion to the "Redfield ratio", and why this has important consequences for algal growth. Many types of harmful algae appear to be able to thrive, and/or increase their production of toxins, when nutrient loads are not in proportion classically identified as Redfield ratios. Here we also describe some of the physiological mechanisms of different species to take up nutrients and to thrive under conditions of nutrient imbalance. 相似文献
54.
The ratio of nitrogen/phosphorus (N/P) is known to affect cell proliferation of some marine micro algae. We evaluated the effect of N/P ratios on the proliferation and succession of phytoplankton using five marine micro algae species. We used two sources of nitrogen, NH4Cl (N1) and urea (N2), and a single source of phosphorous, NaH2PO4(P). The optimal N/P ratio that differed among the five species was affected by the source of nitrogen, being as follows (N1/P, N2/P in order): Thalassiosira sp. (30/1, 20/1),... 相似文献
55.
Application of stable isotope techniques in studies of carbon and nitrogen biogeochemical cycles of ecosystem 总被引:1,自引:1,他引:0
Zhigao Sun Xiaojie Mou Xinhua Li Lingling Wang Hongli Song Huanhuan Jiang 《中国地理科学(英文版)》2011,21(2):129-148
Stable isotope techniques have been proved useful as tools for studying the carbon (C) and nitrogen (N) biogeochemical cycles of ecosystem. This paper firstly introduced the basic principles and the distribution characteristics of stable isotope, then reviewed the recent advances and applications of stable isotope in the C and N biogeochemical cycles of ecosystem. By applying the 13 C natural abundance technique, ecologists are able to understand the photosynthetic path and CO 2 fixation of plants, the CO 2 exchange and C balance status of ecosystem, the composition, distribution and turnover of soil organic C and the sources of organic matter in food webs, while by using the 13 C labeled technique, the effects of elevated CO 2 on the C processes of ecosystem and the sources and fate of organic matter in ecosystem can be revealed in detail. Differently, by applying the 15 N natural abundance technique, ecologists are able to analyze the biological N 2 -fixation, the N sources of ecosystem, the N transformation processes of ecosystem and the N trophic status in food webs, while by using the 15 N labeled technique, the sources, transformation and fate of N in ecosystem and the effects of N input on the ecosystem can be investigated in depth. The applications of both C and N isotope natural abundance and labeled techniques, combined with the elemental, other isotope ( 34 S) and molecular biomarker information, will be more propitious to the investigation of C and N cycle mechanisms. Finally, this paper concluded the problems existed in current researches, and put forward the perspective of stable isotope techniques in the studies on C and N biogeochemical cycles of ecosystem in the future. 相似文献
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57.
D.O. Otieno H. MirzaeiM.Z. Hussain Y.L. LiM.W.T. Schmidt M. Wartinger E. Jung N. RibeiroJ.S. Pereira J. Tenhunen 《Journal of Arid Environments》2011,75(3):231-238
Nitrogen (N) content in the soil and in the herbaceous biomass were monitored during spring of 2004-2006 to determine how the herbaceous layer development influences soil N availability in the montado ecosystem of southern Portugal. Highest (246.6 ± 52.7 g m−2) and lowest (123.2 ± 89.5 g m−2) peak biomass occurred in 2006 and 2005 respectively. Total soil N within the top 20 cm soil profile ranged between 0.2 ± 0.1% in February and 0.41 ± 0.2% in May, while available soil N was lowest (5 ± 2 μg g−1soil) in February but increased three-to-five fold in March and was >17.5 μg g−1soil at senescence in May. Significant (p < 0.001) increase in total N in the aboveground pool occurred between February and May. There was however, no decay in soil N content. Instead, the herbaceous vegetation enhanced soil N input and N retention in the ecosystem. Most of the herbaceous plants were annuals with large reserves of organic N at senescence, which returned to the soil as detritus. The herbaceous vegetation is a critical component of the montado that contributes to N recharge and cycling within the ecosystem. 相似文献
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59.
城市化进程对氮循环格局及动态的影响研究进展 总被引:5,自引:0,他引:5
氮循环是全球生物地球化学循环的重要组成部分,随着城市化进程的不断加快,高强度的人类活动和城市景观格局的改变不仅影响了氮的循环过程,而且加重了氮污染的程度,对城市生态环境造成了严重的影响。城市尺度的氮循环研究不仅是全球关注的氮研究热点,而且也是城市生态学和城市地理学研究的前沿。本文基于城市生态系统的氮循环特征,综述了城市化进程对城市氮污染物来源、沉降、输移和累积影响研究的国内外大量研究成果,介绍了卫星遥感、稳定同位素、物质流模型等分析方法在城市氮循环研究中的应用,针对未来几十年活性氮增加可能带来的不利影响,提出对活性氮的减缓策略,以有效抑制活性氮对环境的影响。未来城市氮循环研究需要开展长期系统监测、深化城市氮循环机理研究、创新研究范式和研究方法,并将研究成果与城市规划和城市发展研究相结合,提升城市氮管理能力。 相似文献
60.
利用2002年5~7月对杭州湾淡化对虾养殖虾池水环境中氮磷营养盐的调查资料,分析了该养殖水环境中氮磷营养盐的存在形态与行为,结果表明:(1)在该养殖水环境中,IP含量随时间变化不大,相对较稳定;(2)IN含量的变化主要受生物活动控制,在养殖过程中变化较大,NO3-N为IN的主要存在形态,但在养殖后期,NO2-N含量有所增加;(3)该养殖水环境中氮磷营养盐含量均超过富营养化阈值,因而已无法判断浮游植物生长的限制因子;(4)叶绿素a与IN含量成显著负相关,而与IP含量的相关性不显著。 相似文献