基于AnnAGNPS模型的山美水库流域非点源氮控制研究

探索研究流域非点源氮污染控制的有效措施,对于治理改善水环境恶化具有重要的现实和长远意义。以山美水库流域为研究区域,建立AnnAGNPS氮污染模型,通过情景模拟技术分别模拟了河岸缓冲带、适量施肥、免耕、少耕、梯田和退耕还林等最佳管理措施的非点源氮污染削减效率。结果表明:(1)梯田与退耕还林对氮的削减率较高,均高于15%;免耕较低,为13%;少耕、合理施肥、河岸缓冲带削减效果有限,低于10%。(2)河岸缓冲带、少耕、免耕、梯田等措施的总氮削减率在不同月份的变化趋势与泥沙削减变化趋势一致,在7月和8月有较高的削减率;合理施肥与退耕还林的总氮削减率则与流域施肥状况相关性更高,在2—4月份有较高的削减率,因此山美水库流域水环境改善应结合非点源氮污染治理和流域水土流失治理。     

微量元素分析在判别沉积环境中的应用——以柴达木盆地西部锶矿区富锶地层为例

沉积岩中的微量元素对沉积环境水介质的变化较为敏感,是研究沉积物沉积时古气候、古环境的有效手段。选取了对沉积环境介质较为敏感的锶(Sr)、钡(Ba)、铜(Cu)、铀(U)、钒(V)、镍(Ni)、钍(Th)等元素作为判别指标,对柴达木盆地西部上新统油砂山组、狮子沟组和更新统七个泉组三套富锶岩层的古气候和古沉积环境特征进行了研究。结果表明,柴达木盆地西部从油砂山组到七个泉组沉积时总体上为干旱的气候环境;湖盆水体的盐度较高,表现为咸水环境,且从油砂山组到七个泉组随着地层变新,盐度有逐渐增大的趋势;油砂山组、狮子沟组和七个泉组沉积时湖盆水体均表现为中等分层、湖水循环较为顺畅的氧化环境。     

四川叠合盆地盆山耦合特征分析

四川叠合盆地三面环山,自东而西夹持于江南、秦岭与龙门山三大山系之间,位于古亚洲、环太平洋与特提斯三大构造域的结合部位;中生代以来,先后经历了海盆、煤盆、陆相广盆、残盆四个盆地世代;盆地沉积充填过程可概括为前陆、坳陷、再生前陆三种基本样式。系统的山盆构造样式及运动学、沉积充填过程分析结果表明盆地周缘造山带造山活动期与盆内古隆起发育期时间耦合;盆地周缘造山带造山活动期与盆地沉积环境转换期时间耦合;盆地周缘造山带构造轴线走向基本保持与盆内山前坳陷或前陆褶冲带构造轴线走向相耦合;盆地周缘造山带不同时期形成的褶冲构造轴线走向基本保持与其同期盆内产生的沉积或沉降中心构造轴线走向相耦合。     

中国叠合型盆地复合含油气系统的基本特征

中国叠合型含油气盆地具有演化历史漫长、多阶段构造演化、充填层系多的特点。所发育的含油气系统常具有油气混源、多储集层系、运聚方式组合多变与成藏期次多的特点 ,很难用Magoon和Dow( 1994 )的概念对其进行确切描述。文中从中国含油气系统的特点出发 ,提出了“复合含油气系统”的概念 ,并建立相应的划分及评价方法。中国复合含油气系统有叠置型、运聚变异型、相向汇聚型、断层贯通型、油气分异型、共盖型及改造型等 7种常见类型 ,每一叠合盆地含有上述 1种或多种类型。如中国中西部前陆克拉通叠合型盆地以冲断带断层贯通型与前陆斜坡不整合面运聚型为特色 ,而东部断陷坳陷叠合型盆地则以叠置型复合含油气系统为主 ,南方残留新生型叠合盆地则以改造型复合含油气系统占主导 ,因此每类盆地的复合含油气系统的特点与勘探手段并不一致。复合含油气系统描述是油气勘探战略选区的基础 ,油气运聚单元的划分与评价则是制定油气勘探方向的关键 ,现代勘探技术的综合配套应用是提高中国复合含油气系统勘探成效的根本保证。     

煤田资料的铀矿二次开发技术及其找矿意义——以二连盆地ZS煤田铀矿点的发现为例

在中国北方主要盆地铀矿地质调查工作中,煤田自然伽马异常作为主要矿化信息和找矿线索,为一系列铀矿床(点)的快速发现奠定了坚实基础。为进一步提高煤田资料铀矿二次开发的高效性和准确性,运用水成铀矿理论,以中国二连盆地ZS煤矿区典型铀矿点的发现为例,初步探讨了煤田资料的铀矿二次开发技术,提出了"异常筛选与选区分析、原位验证与环境判别、等时地层格架建立与沉积体系分析、综合分析与靶区定位"四位一体的煤矿区铀矿地质调查模式。这对中国北方含煤盆地铀矿地质调查工作提供了新的找矿思路和技术路线,具有较重要的指导意义。     

渤海湾西岸QX02孔Ⅱ海的识别及OSL年龄

以渤海湾沿海低地的QX02孔为研究对象,进行了沉积岩石学分析和底栖有孔虫统计,结合加速器质谱~(14)C测年和光释光(optically stimulated luminescence,OSL)测年,探讨了该孔记录的第Ⅱ海相层埋深和形成时代。第Ⅱ海相层厚度11.4m,记录相对海面高度-26.83~-15.43m。AMS~(14)C年龄表明,Ⅱ海形成于MIS 3早期、甚至更早。OSL年代学研究显示,Ⅱ海样品等效剂量离散度较高,并且主要集中在2个区间,计算得到新、老2个年龄阶段。基于OSL测年原理的常规判断,认为较老的83.5~62.6ka阶段系受曝光不充分组分的影响,通常采用较年轻的51.9~39.9ka阶段为QX02孔的Ⅱ海沉积年龄。但是,较老的一组年龄从新的视角,暗示了可能的原始沉积过程及相应的海侵发生时间,因而具有重要的年代学和沉积学意义。     

Coping with water scarcity in Kashafroud G-WADI Basin,Iran: climate change or growing demands?

This paper assesses the various factors contributing to climate change in the region of the Kashafroud G-WADI Basin in Iran; quantifies the local impacts of climate change, especially local water scarcity; and simulates and discusses several proposed methods to combat these impacts. Hydrologic and climatic data are statistically analyzed and VENSIM modeling is used for various simulations of water resources in the basin. Results show that the natural climate changes affecting Kashafroud Basin include increased temperature, less rainfall, more frequent droughts, and changes in rainfall patterns, all of which are local symptoms of climate change in recent years. However, the most important challenge in the basin is the overexploitation of surface and groundwater resources to meet the growing water demands, especially domestic needs. Changes in land use, reallocation of water uses, groundwater depletion, and degradation of the quality of surface waters have all contributed to significant changes in the environmental features of this basin, and are the main reason why water demands now exceed the renewal capacity of the basin. Proposed response measures include reallocation of resources among different uses, inter-basin water transfers, drawing water from six small dams on the Kashafroud River, reducing groundwater extraction, and replacing groundwater extraction for agriculture by reuse of urban wastewater. This study concludes that although changes in global climatic parameters have altered environmental features in the basin, local factors, such as water utilization beyond the renewable capacity of the basin, are more significant in worsening the impacts of climate change.     

塔西南新生代前陆盆地东段盆山结构与冲断带变形特征

塔西南新生代前陆盆地受西昆仑山造山带南北向挤压和帕米尔弧形构造带向北突进的影响,导致盆山结构与盆地冲断带构造变形在平行造山带方向表现出明显差异。本文通过地震资料解释,系统研究了塔西南新生代前陆盆地东段盆山结构与冲断带的构造变形特征,认为塔西南新生代前陆盆地东段盆山结构表现为西昆仑造山带向北大规模冲断,盆地区挠曲沉降,前陆地区发育宽的褶皱冲断带,冲断带前锋已扩展至捷得背斜一线,褶皱冲断带与前渊坳陷存在大范围重叠。盆地东段的褶皱冲断带在纵向上可以分为基底卷入变形带、滑脱变形带。山前第一排变形带受多期构造叠加影响,产生横向变形的分异:西段柯东段早期为构造楔形体变形形成的背斜构造,后期被甫沙–克里阳右行走滑断裂改造,剖面呈现复杂的变形特征;东段克里阳段构造变形以早期的逆冲推覆为主。结合生长地层与磁性地层分析,冲断带的变形总体表现出前展式的构造变形特征,上新世阿图什组沉积期开始形成柯东构造带;随后变形向北传播,在上新世早中期形成柯克亚构造带;至早中更新世晚期,构造变形扩展至固满–合什塔格构造带。     

An analytical study on three‐dimensional versus two‐dimensional water table‐induced flow patterns in a Tóthian basin

Although it has been increasingly acknowledged that groundwater flow pattern is complicated in the three‐dimensional (3‐D) domain, two‐dimensional (2‐D) water table‐induced flow models are still widely used to delineate basin‐scale groundwater circulation. However, the validity of 2‐D cross‐sectional flow field induced by water table has been seldom examined. Here, we derive the analytical solution of 3‐D water table‐induced hydraulic head in a Tóthian basin and then examine the validity of 2‐D cross‐sectional models by comparing the flow fields of selected cross sections calculated by the 2‐D cross‐sectional model with those by the 3‐D model, which represents the “true” cases. For cross sections in the recharge or discharge area of the 3‐D basin, even if head difference is not significant, the 2‐D cross‐sectional models result in flow patterns absolutely different from the true ones. For the cross section following the principal direction of groundwater flow, although 2‐D cross‐sectional models would overestimate the penetrating depth of local flow systems and underestimate the recharge/discharge flux, the flow pattern from the cross‐sectional model is similar to the true one and could be close enough to the true one by adjusting the decay exponent and anisotropy ratio of permeability. Consequently, to determine whether a 2‐D cross‐sectional model is applicable, a comparison of hydraulic head difference between 2‐D and 3‐D solutions is not enough. Instead, the similarity of flow pattern should be considered to determine whether a cross‐sectional model is applicable. This study improves understanding of groundwater flow induced by more natural water table undulations in the 3‐D domain and the limitations of 2‐D models accounting for cross‐sectional water table undulation only.     

旋回地层学理论基础、研究进展和展望

在过去30余年中旋回地层学研究得到了极大发展, 对理解和解决地球科学领域众多科学问题做出了很大贡献.旋回地层学(Cyclostratigraphy)已被定义为"对地层记录的(准)周期性旋回变化进行识别、描述、对比和成因解释, 并将其应用于地质年代学以提高地层年代框架的精度和分辨率, 实现地层高精度划分与对比的一门地层学分支学科".能够反映古气候变化的岩性、岩相、地球物理和地球化学参数(即古气候替代指标)均可用于旋回地层学分析.通过岩性组合识别、频谱分析、连续窗口频谱分析、小波分析、滤波和调谐等方法可进行识别米兰科维奇旋回信号和建立高精度天文年代标尺.中国学者在北方黄土剖面、南海新近纪海相沉积、古生代海相沉积和部分中新生代陆相沉积中获得了良好的旋回地层学研究成果.对中国东北松辽盆地陆相白垩系和华南海相二叠系乐平统—中三叠统开展旋回地层学研究有望取得重要突破.