胡焕庸线的学术思想源流与地理分界意义   总被引：4，自引：2，他引：2  

丁金宏  程晨  张伟佳  田阳 《地理学报》2021,76(6):1317-1333

20世纪早期,中国面临内忧外患、人地关系矛盾空前剧烈,地理学家对于中国人口国情、西北开发及国内移民等关乎国运问题的思考与探索,孕育了中国的人口地理学.1935年胡焕庸发表的"中国人口之分布"是中国人口地理学走向成熟的标识,文中提出的"瑷珲-腾冲线"即"胡焕庸线",是中国人口地理的重要分界线.胡焕庸线的存在性与稳定性被人...  相似文献   

黄骅坳陷中区中生代构造演化   总被引：2，自引：0，他引：2  

楼达  李三忠  金宠  周永刚  刘博  许淑梅  戴黎明  周立宏  高振平 《海洋地质与第四纪地质》2008,28(3)

渤海湾盆地地区中生代构造演化与样式始终不明朗,特别是对燕山期变形始终存在争议,故选择黄骅坳陷中区中生界作为重点剖析对象,通过大量地震剖面的解释和平衡剖面技术复原古构造演化的研究,并结合前人研究成果和区域构造背景,提出黄骅坳陷中区中生代演化过程可大致分为4个阶段:印支晚期东西向宽缓褶皱及后期逆冲构造变形期、燕山早期挤压走滑构造变形期、燕山中期继承性挤压与右旋张扭构造变形期、燕山晚期—喜山期区域性伸展构造变形期。  相似文献   

Extension of a qualitative model on nutrient cycling and transformation to include microtidal estuaries on wave-dominated coasts: Southern hemisphere perspective     

S. Taljaard  L. van NiekerkW. Joubert 《Estuarine, Coastal and Shelf Science》2009

Estuaries are dynamic transition zones acting as filters and transformers of nutrients passing from catchments to the sea. We propose an extension to an existing southern hemisphere model on nutrient dynamics in estuaries to include the relatively constricted, microtidal estuaries located along wave-dominated coasts in the region, specifically focusing on the limiting macronutrients nitrogen (N) and phosphorus (P) and on key processes, including physical (e.g. flushing, mixing and sedimentation), geochemical (e.g. flocculation), biochemical (e.g. remineralisation) and biological (e.g. primary production) processes. A simplified model of the physical states (primarily controlled by hydrological characteristics) is used as the basis for the qualitative model, where these are defined in terms of characteristic salinity-induced stratification of the water column, flushing time and the mouth condition. Four physical states are identified: a freshwater-dominated state, freshwater pulsed/recovery state, marine-dominated state and the closed mouth state. The states and their physical characteristics largely resemble that of the earlier model, except that the extended model reflects the dynamics of restricted inlets and introduces the closed mouth state. This model specifically explores the variation within southern African estuarine systems to better inform research and management programmes on the appropriate trophic, temporal and spatial scales at which uncertainties in ecosystem functioning need resolving. It can also be applied to other regions in the southern hemisphere, and even the northern hemisphere, with similar hydrological and estuarine geomorphological characteristics (e.g. the Mediterranean coast, the west coasts of North and South America, and the south-west and south-eastern coasts of Australia).  相似文献   

Trace element and molecular markers of organic carbon dynamics along a shelf–basin continuum in sediments of the western Arctic Ocean     

Laura L. Belicka  Robie W. Macdonald  H. Rodger Harvey 《Marine Chemistry》2009,115(1-2):72-85

Molecular organic biomarkers together with trace element composition were investigated in sediments east of Barrow Canyon in the western Arctic Ocean to determine sources and recycling of organic carbon in a continuum from the shelf to the basin. Algal biomarkers (polyunsaturated and short-chain saturated fatty acids, 24-methylcholesta-5,24(28)-dien-3β-ol, dinosterol) highlight the substantial contribution of organic matter from water column and sea-ice primary productivity in shelf environments, while redox markers such as acid volatile sulfide (AVS), Mn, and Re indicate intense metabolism of this material leading to sediment anoxia. Shelf sediments also receive considerable inputs from terrestrial organic carbon, with biomarker composition suggesting the presence of multiple pools of terrestrial organic matter segregated by age/lability or hydrodynamic sorting. Sedimentary metabolism was not as intense in slope sediments as on the shelf; however, sufficient labile organic matter is present to create suboxic and anoxic conditions, at least intermittently, as organic matter is focused towards the slope. Basin sediments also showed evidence for episodic delivery of labile organic carbon inputs despite the strong physical controls of water depth and sea-ice cover. Principal components analysis of the lipid biomarker data was used to estimate fractions of preserved recalcitrant (of terrestrial origin) and labile (of marine origin) organic matter in the sediments, with ranges of 12–79%, 14–45%, and 37–66% found for the shelf, slope, and basin cores, respectively. On average, the relative preserved terrestrial organic matter in basin sediments was 56%, suggesting exchange of organic carbon between nearshore and basin environments in the western Arctic.  相似文献   

地幔不均一性与地幔循环的多维表征和原因思考     

郑建平  刘为先  王伟  马强  吴树成  戴宏坤 《地质学报》2024,98(3):662-679

地幔早先经核- 幔- 壳分异形成,后受不同尺度对流和循环的影响,因而具有不均一性特征。近三十年来,地幔化学通过研究大洋玄武岩发现了多样地幔端元和非放射性同位素证据并证明了地幔不均一性,逐渐建全了地幔地球化学体系。然而,地幔不均一性如何对应于时空尺度的地幔循环,以及地球演化如何影响地幔不均一性等,仍不清楚。此外,地球物理研究显示,岩石圈厚度差异、中下地幔的波速异常体以及俯冲板片形态的观测为纵横向对流系统提供了空间不均一性证据支持。联合地球化学和地球物理手段对研究地幔不均一性至关重要,用好透视地幔成分与结构的“双目镜”已成为共识。本文从地幔不均一性结合地球化学场、地球物理的不同表现形式,以及现今及历史时期的洋陆格局的对比,多维度联系地幔循环和演化,思考了超大陆旋回与地幔不均一化的内在逻辑。强调了从全球演化角度看地幔不均一性的重要性和提出多手段联合建立地幔循环驱动模型的展望。  相似文献   

济阳坳陷孤西负反转断层形成演化定量研究及其油气地质意义   总被引：1，自引：0，他引：1  

雷超  任建业  吴梅莲  祁鹏  胡德胜 《大地构造与成矿学》2008,32(4)

以高精度三维地震资料和钻井资料为基础,对研究区断裂构造进行精细解释,确定孤西断层为"薄底型"的、且表现为北段缓而南段陡、并向西倾的负反转构造;通过回剥技术和平衡剖面等定量分析技术对垂直穿越孤西断层的典型地震剖面研究揭示,孤西断层在J3-K1时期断层性质发生改变,由逆断层反转变为正断层,且在印支、J3-K1和Ek-Es4时期剖面拉伸率分别为-4%,17.2%和18.5%;沿孤西断层走向方向不同位置计算其断层活动速率表明该断层整体经历了负反转运动。以上述分析为基础,论文从烃源岩、圈闭、储集岩和油气运移角度,探讨了孤西负反转断层在孤岛潜山油气成藏方面的重要意义。  相似文献   

Factors controlling the solubility of aerosol trace metals in the atmosphere and on mixing into seawater     

Lucinda J. Spokes  Tim D. Jickells 《Aquatic Geochemistry》1995,1(4):355-374

Previous work has shown that the type and pH history of an aerosol governs trace metal solubility in rainwater. This study concentrates on the crustal elements Al, Fe and Mn and identifies additional processes which affect dissolution not only in the atmosphere but also on mixing into seawater. Aerosol dissolution experiments (at aerosol concentrations of about 30 mg 1^–1) show manganese exhibiting high solubility at the low pH values typical of clouds (54±2.5% at pH 2, with results expressed in mole percent units) with 85% of this increase occurring within 6 hours of acidification. The percentage dissolution decreases to 50% at pH values representative of rainwater (pH 5.5) and to 26±4% at pH 8, typical of seawater. No such dramatic solution phase removal occurs at pH 8 in the presence of inorganic anions (to a final solubility of 44±2%). Thus the extent of manganese dissolution depends strongly on whether aerosols are cycled through acidic environments and on subsequent inorganic complexation once rainwater mixes into sea. Aluminium shows highest dissolution (7.1±0.6%) at low pH with 78% of this increase occurring within 6 hours of acidification. Rapid solution phase removal occurs on increasing the pH to that representative of rainwater (to 0.9±0.4% with 87% of this decrease occurring within 15 min). As a consequence of acid cycling and aluminium's amphoteric nature, solubility is enhanced at seawater pH (2.3±0.3%) over that in rain. Iron shows a strong pH-solubility relationship with highest solubility at low pH (4.7±0.2%), 70% of this value being reached within 6 hours of acidification, and decreasing rapidly to 0.17% as pH is raised to 8. Addition of inorganic anions at pH 8 to simulate mixing into seawater causes a further decrease in solubility, perhaps due to anion induced colloid destabilisation. Photochemical reduction also effects solubility under low pH conditions with Fe(II) comprising 1% of the total iron in the Saharan Aerosol used and 8.4% in an Urban material at a pH of 2. This element shows rapid solution phase removal with increasing particulate load which is tentatively rationalised in terms of a simple Kd approach.  相似文献   

The Effect of Organic Carbon-Iron Oxide Association on the Preservation of Sedimentary Organic Carbon in Marine Environments   总被引：1，自引：0，他引：1  

Zhao Bin  Yao Peng  Yu Zhigang 《地球科学进展》2016,31(11):1151-1158

Understanding the mechanisms responsible for long-term storage of organic carbon (OC) in marine environment is important for studying the marine carbon cycling and predicting how the global carbon cycle will respond to climate change. It is estimated that more than 20% of the OC in marine sediments is associated with iron oxides and thus these complexes are one of the most important factors in the long-term storage of OC. The OC-iron oxide (OC-Fe) association can be formed through either adsorption or co-precipitation, but the dominant mechanism of OC-Fe association in marine environments is co-precipitation. The combination of OC from different sources with iron oxides is selective. Iron oxides preferentially combine with marine OC in most marine environments, but in estuarine delta regions they prefer terrestrial OC. Due to large inputs of terrestrial materials, high primary production and frequent re-suspension, estuarine and marginal seas are suitable sites for OC-Fe association studies, which should be emphasized in the future.  相似文献   

海洋沉积物中氮的形态及其生态学意义     

吕晓霞  宋金明 《海洋科学集刊》2003,(45):101-111

海洋沉积物作为生源要素氮的重要源与汇，在其生物地球化学循环中起着至关重要的作用。该项研究旨在查清海洋沉积物中氮的存在形态及其生态学意义。氮是生物生命活动必需的营养要素，海洋中的氮往往是海洋初级生产力的限制因子，氮的吸收与再生释放在估算海洋新生产力和生源要素的生物地球化学循环率上也有重要贡献。海洋沉积物中的氮作为海水中氮的重要供给源是海洋生物赖以生存的重要物质基础，对维持海洋生态平衡、修复失衡的海洋生态环境具有重要意义。但由于不同海区海洋沉积物的来源和环境不同，氮的形态和含量亦不相同，可被生物吸收和利用的数量就不相同，因此造成了不同海区生物种群和环境不同，进而影响生态环境。因此，研究海洋沉积物中氮的形态，了解各个形态与沉积物中生物种群及与环境的关系，确定其生物和化学活性，査清氮不同形态的生态学功能，对于深入探讨海洋生物资源可持续利用的方法和策略具有重要意义。本文主要阐述海洋沉积物中氮的存在形式与分布、氮的早期成岩和去营养化作用、硝化和反硝化作用以及氮与生物特定种群的关系等，探讨了影响海洋沉积物中的氮循环的主要因素，并分析了海洋沉积物中的氮与生态系的关系，以期对研究氮的海洋生物地球化学过程有所帮助。  相似文献   

Nutrient Cycling and a Stoichiometric Model in Epidavros, a Deep Basin in the Aegean Sea     

Nicholas  Friugos 《Marine Ecology》1986,7(1):43-57

Abstract. The nutrient cycling of Epidavros, a deep basin in the Saronikos Gulf, was studied in relation to various environmental factors during 1973–1976 at a station characterized by stagnant conditions. The regeneration of nutrients was related to the consumption of oxygen, and a seasonal nutrient cycle occurred with low nutrient concentrations in the spring and summer, followed by high nutrient levels in autumn and winter. In addition high values of nitrate and silicate were observed in the deeper waters, which tended to be anoxic, although the water masses were renewed during spring 1974. The distribution pattern of nutrients together with nutrient ratios were compared with previous studies of the same and neighbouring areas as well as of other isolated basins. A stoichiometric model indicates that plankton organisms in the Epidavros basin have approximate atomic ratios for C: N: P of 150: 14:1, while the ratio of change for nitrogen and phosphorus in the water is only 8.8:1 by atoms. This is probably because of the slow rate of regeneration of nitrogenous material and/or assimilation and regeneration in organic forms. The water/plankton relation in the Epidavros basin appears to be very similar to that in the Baltic Sea.  相似文献