Nutrient maximums related to low oxygen concentrations in the southern Canada Basin   总被引：3，自引：1，他引：2  

JIN Mingming  SHI Jiuxin  LU Yong  CHEN Jianfang  GAO Guoping  WU Jingfeng  ZHANG Haisheng 《海洋学报(英文版)》2005,24(6):88-96

The phenomenon of nutrient maximums at 70～200 m occurred only in the region of the Canada Basin among the world oceans. The prevailing hypothesis was that the direct injection of the low-temperature high-nutrient brines from the Chukchi Sea shelf (＜50 m) in winter provided the nutrient maximums. However, we found that there are five problems in the direct injection process. Formerly Jin et al. considered that the formation of nutrient maximums can be a process of locally long-term regeneration. Here we propose a regeneration-mixture process. Data of temperature, salinity, oxygen and nutrients were collected at three stations in the southern Canada Basin during the summer 1999 cruise. We identified the cores of the surface, near-surface, potential temperature maximum waters and Arctic Bottom Water by the diagrams and vertical profiles of salinity, potential temperature, oxygen and nutrients. The historical 129Ⅰ data indicated that the surface and near-surface waters were Pacific-origin, but the waters below the potential temperature maximum core depth was Atlantic-origin. Along with the correlation of nutrient maximums and very low oxygen contents in the near-surface water, we hypothesize that, the putative organic matter was decomposed to inorganic nutrients; and the Pacific water was mixed with the Atlantic water in the transition zone. The idea of the regeneration-mixture process agrees with the historical observations of no apparent seasonal changes, the smooth nutrient profiles, the lowest saturation of CaCO3 above 400 m, low rate of CFC-11 ventilation and 3H-3He ages of 8～18 a around the nutrient maximum depths.  相似文献   

煤中有机质二次生烃迟滞性及其反应动力学机制   总被引：25，自引：1，他引：24       下载免费PDF全文

秦勇  张有生 《地球科学》2000,25(3):278-282

采用自然成熟度系列与其预热残渣系列样品相结合方式, 通过热解模拟方法, 对煤中有机质二次生烃迟滞性显现特征和化学反应动力学机制进行了探讨.结果表明: 二次生烃起始成熟度增高, 二次生烃峰位成熟度呈规律性后移, 二次生烃作用“死线”位于R_o=4.0 %左右; 二次生烃峰位成熟度与起始成熟度之差随起始成熟度的增高呈抛物线式演化, 二次生烃的绝对迟滞性和相对迟滞性均呈阶段性演化, 由此可对二次生烃迟滞深度进行预测; 二次生烃半峰宽随起始成熟度呈阶段性演化, 暗示二次生烃起始成熟度位于生油高峰附近的烃源岩, 其生烃量可能相对较大.同时, 原始样品平均活化能的演化经历了4个阶段, 它们与热解生烃量及二次生烃迟滞性的阶段性演化特征高度吻合, 揭示出二次生烃作用严格受控于反应动力学的地球化学机制.   相似文献   

Commercial scale invertebrate fisheries enhancement in Australia: Experiences,challenges and opportunities     

《Marine Policy》2015

Stock enhancement or “assisted recruitment” for fisheries management in Australia is at an experimental R&D phase. Development of the science has focused largely on finfish targeted by the recreational sector; however it is considered that high value invertebrates will be the best candidates for commercial scale fisheries enhancement. Three main ingredients are required; technical capacity, governance capability, and the ‘correct’ species. The technical capacity needed is in the area of hatchery production and wild release methodologies, whilst the governance capability needed is informed policy that accounts for the complexities and interdisciplinary nature of stock enhancement. In particular, the appropriate articulation of policy to support economic development and integration into wild fisheries is currently lacking. If successful stock enhancement is implemented, the nature of fisheries management changes because the recruitment side of the fisheries equation is under substantial control, rather than just the production side. Management responses will require significant innovation, with a renewed emphasis on understanding the stock, rather than policing the fishers. By way of illustration, recent initiatives and key challenges encountered in Australian invertebrate fisheries are investigated through case studies. An example of a commercially-viable enhancement fishery that reflects solutions to the key challenges is also presented. The review ends with an argument to re-establish the context of stock enhancement in the discipline of ecological enhancement. This is a crucial and positive step forward for it recognises that, in principle, any renewable aquatic ecosystem has the potential to be enhanced instead of just depleted.  相似文献   

人促天然更新米槠次生林与杉木人工林乔木层碳贮量分配特征比较     

李丽红 《亚热带资源与环境学报》2012,7(2)

以杉木人工林为对照,分析三明陈大人工促进天然更新形成的米槠次生林乔木层碳贮量及其随树种、径阶、高阶的分配特点．结果表明：米槠次生林乔木层物种丰富度高于杉木林,人促天然更新有利于保持乔木层的树种多样性．米槠次生林乔木层碳贮量为178．67t·hm^-2,高于杉木人工林（111．24t·hm^-2）．米槠次生林和杉木人工林均以单优树种碳贮量占绝对优势,但米槠次生林中大个体林木（大径阶、大高阶）的碳贮量远大于杉木人工林．与杉木人工林相比,米槠次生林呈现出异龄的林分结构,这可能是其能够保持高碳吸存和高树种丰富度的重要原因．  相似文献   

Bromide removal and recovery with layered double hydroxides as an adsorbent     

Liang LU Jing HE Xiangjun PAN 《中国地球化学学报》2006,25(B08):107-107

Grignard regents have been applied extensively in chemical industry, especially in pharmacy. A mass of bromide-containing wastewater was produced after reaction, and ozonation of these organic contaminants can produce bromate and other brominated pollutants. The US Environmental Protection Agency （EPA） has established a maximum contaminant level of 10 μg/L for bromate in finished water. Therefore, it is necessary and significant to remove the DBP （disinfection by-products） precursor - bromide. On the other hand, since the bromine is a valuable element, recovery of it from wastewater is significant. Bromide removal is important to control DBP （disinfection by-products） contaminant and an ion exchange process is one of several treatment processes for this purpose. Layered double hydroxides （LDHs） are useful as adsorbents for bromide removal because of theft ion exchange properties. In this study, the adsorption properties of LDHs for bromide and the method of regeneration of this material were examined. It has been found that the LDHs with Mg/Al molar ratio of 2 represented the highest capacity to remove bromide ion from aqueous solution at pH 6.0. The equilibrium isotherms of uptake of bromide by CLDH were well fitted by the Langmuir equation. Bromide adsorbed on the LDHs was effectively desorbed at 30% Na2CO3 solution and the LDHs were regenerated at the same time. The regenerated LDHs could be reused repeatedly for the bromide removal. Bromide in the exhausted desorption solution was recovered as bromine by oxidation using Cl2.  相似文献   

新疆塔里木河下游应急输水的生态效益   总被引：17，自引：14，他引：17  

郭英杰  许英勤  马彦华 《干旱区地理》2002,25(3):237-240

2000年5月中旬至7月中旬向塔里木河下游断流河段应急输水，历时60天，输水2亿m^3，其后对进水河段分5个断面考察了沿岸植被的生长发育、恢复状况、草本植物地表生物量，根系的分布与数量、植被的分布特点、土壤状况及地下水分布等，通过比较分析，初步结论如下：1、断流河道应急输水对沿岸植被恢复作用显著，其中草本植物效果明显，灌木次之，乔木较差；2、非风积土壤效果更佳；3、应急输水加人工保护与更新则效果更好。  相似文献   

沈阳铁西区社区弹性特征与成因分析   总被引：2，自引：2，他引：0  

陈玉洁  张平宇 《地理科学》2018,38(11):1847-1854

基于问卷数据,运用统计分析、地理探测器,分析沈阳铁西区不同社区弹性差异、影响因素及其成因。研究发现：① 商品房社区社会弹性、制度弹性、社区资本分值高于单位社区;单位社区的经济弹性、物质弹性分值高于商品房社区。② 物质弹性、制度弹性对社区资本影响作用较为显著,社会弹性、经济弹性影响作用较小。③ 从制度转型、地方政府、经济发展、社区服务和社会与个人5方面探讨了沈阳铁西区社区弹性成因。沈阳铁西区在搬迁改造、产业转型等冲击下,城市更新过程表现出较强的适应能力和较弱的学习能力,这是社会弹性、经济弹性、制度弹性、物质弹性共同作用的结果。  相似文献   

再生空心砌块砌体填充墙-钢管再生混凝土框架骨架曲线模型研究          下载免费PDF全文

孟二从  余亚琳  苏益声  陈宗平 《世界地震工程》2018,34(1):131-137

为研究再生空心砌块砌体填充墙-钢管再生混凝土框架的骨架曲线模型,设计制作了2榀试件并对其进行低周反复加载试验,获取其滞回及骨架曲线。在此基础之上,对试件的骨架曲线模型进行相关的理论分析,建立了再生空心砌块砌体填充墙—钢管再生混凝土框架的四折线骨架曲线模型。研究表明:试件的滞回曲线呈现为饱满的梭形,表现出了良好的抗震耗能性能;通过相关理论分析建立的四折线骨架曲线模型与试验实测骨架曲线吻合良好,可为该类结构在地震作用下的弹塑性地震反应分析提供相关参考。  相似文献   

Beyond the spectacle of property windfalls in Singapore: Lefebvrian spaces of home against profit-making     

John Lowe 《Singapore journal of tropical geography》2020,41(2):209-225

In Singapore, owners of private housing estates reaping windfalls through collective sales have been subject to the news media's sensational coverage of the topic. While collective sales will give rise to new developments that regenerate the country's landscape to reflect the image and identity of an entrepreneurial city, efforts to resist this wealth generating urbanism are subject to erasure. Instances of minority owners disinterested in profit-making using the courts to save their homes from the collective sale juggernaut are certainly emblematic of the inherent tension between one's home as housing and home as investment repository. Drawing upon ethnographical experiences from a housing estate built for public officials in Singapore, this article's use of the Lefebvrian theory of spatial production sheds light on how minority owners unmotivated by monetary windfalls (re)produce spaces of their homes that are overtly inimical to the impulses of majority owners to monetize their homes at high premiums.  相似文献   

二次生烃机理在中下扬子高演化烃源岩评价中的应用   总被引：1，自引：0，他引：1  

林小云  刘建 《海洋地质与第四纪地质》2007,27(5):99-104

在野外地质观察、油气地球化学和样品分析的基础上,通过总结二次生烃特征和生烃机理,将其应用到中下扬子区海相高演化烃源岩生烃潜力的评价。模拟实验结果表明,二次生烃具有明显的迟缓现象,也仍具有相对的生烃高峰,二次生烃量与一次生烃量的总和小于连续热演化的生烃量,这些特征都与一次生烃的演化程度密切相关,初始演化程度成为评价高演化烃源岩二次生烃潜力的关键因素。中下扬子区中—古生界发育的6套烃源岩中,下二叠统、下志留统和下寒武统烃源岩具有较强的生烃能力,是主要的烃源层。下古生界烃源岩进入生烃时间较早,在强烈的构造运动背景下,生成的油气难以保存;上古生界烃源岩热演化程度相对较低,燕山—喜山期的再次沉降地区成为二次生烃的供源区。因此,下古生界台地相区和上古生界烃源岩具有一定的二次生烃潜力。  相似文献