泥河湾保护区地貌特征与地质灾害

根据泥河湾保护区实地调查,黄土台地、黄土沟梁和河谷地貌是发育在“泥河湾层”及其覆地层上的主要地貌类型,其形态特征和形态测量反映了该区流水地貌的现代演化特征。伴随流水地质作用与地貌演化发生的水土流失、泥石流、崩塌和地面塌陷等地质灾害危及保护区的地层剖面。笔者认为该区域地质灾害是多种致灾因素造成的,其中的主导因素是气候、植被和人为因素,通过控制植被因素可以改变目前的地质环境状况。     

延河流域生态环境动态监测系统与应用

以遥感 (RS)、地理信息系统 (GIS)、全球定位系统 (GPS)为核心技术 ,采用 ETM/ TM卫星数据、航空机载对地观测数据 ,结合地面测试和综合调查方法 ,完成了延河流域面积 10 0 15 .797km₂的生态环境本底调查 ,建立了 1990～2 0 0 0年的生态环境动态监测系统。查明了区内主要物种和植被分布 ,土地利用 /土地覆盖现状及其动态变化 ,划分出 5个生态区 ,2 5个生态系统 ,提出了延河流域生态建设.     

地图印前计算机辅助设计软件系统研究与实践

介绍地图印前系统在我国产业部门应用概况及计算机图形辅助设计软件用于地图印前系统的三个共性问题。以计算机图形辅助设计软件MicroStation95为例,详细探讨该软件用于地图印前制作所涉及的技术要点。并以《南京市教育地图》为例,对用该软件进行彩色地图编制与出版的优点与局限性进行了探讨。     

Type III burst pair

We present a special solar radio burst detected on 5 January 1994 using the multi-channel (50) spectrometer (1.0–2.0 GHz) of the Beijing Astronomical Observatory (BAO). Sadly, the whole event could not be recorded since it had a broader bandwidth than the limit range of the instrument. The important part was obtained, however. The event is composed of a normal drift type III burst on the lower frequency side and a reverse drift type III burst appearing almost simultaneously on the high side. We call the burst type III a burst pair. It is a typical characteristic of two type III bursts that they are morphologically symmetric about some frequency from 1.64 GHz to 1.78 GHz on the dynamic spectra records, which indicates that there are two different electron beams from the same acceleration region travelling simultaneously in opposite directions (upward and downward). A magnetic reconnection mode is a nice interpretation of type III burst pair since the plasma beta 0.01 is much less than 1 and the beams have velocity of about 1.07×10⁸ cm s^–1 after leaving the reconnection region if we assume that the ambient magnetic field strength is about 100 G.     

陕西二台子铜金床钠长石碳酸（角砾）岩类特征及形成构造背景分析

从岩石学、矿物学、岩石化学、地球化学、稀土元素等方面研究了二台子铜金矿内长石炭酸（角砾）岩类地质地球化学特征。晚泥盆世－石炭纪,在区域幔羽构造作用下,深部热流体沿先存在构造通道上升进入镇安二台子三级热水沉积盆地之中,形成了石英重晶石炭酸角砾岩、碳酸角砾岩、复成分角砾岩、钠长岩、钠长石碳酸岩,受同性断裂及层位控制明显,并构成了金的矿源层及普遍金矿化。燕山期,具有幔源特征的深部含矿热流体在北东、北西向     

Biological mechanisms driving the seasonal changes in the internal loading of phosphorus in shallow lakes

Because of the obvious importance of P as a nutrient that often accelerates growth of phytoplankton (including toxic cyanobacteria) and therefore worsens water quality, much interest has been devoted to P exchange across the sediment-water interface. Generally, the release mode of P from the sediment differed greatly between shallow and deep lakes, and much of the effort has been focused on iron and oxygen, and also on the relevant environmental factors, for example, turbulence and decomposition, but a large part of the P variation in shallow lakes remains unexplained. This paper reviews experimental and field studies on the mechanisms of P release from the sediment in the shallow temperate (in Europe) and subtropical (in the middle and lower reaches of the Yangtze River in China) lakes, and it is suggested that pH rather than DO might be more important in driving the seasonal dynamics of internal P loading in these shallow lakes, i.e., intense photosynthesis of phytoplankton increases pH of the lake water and thus may increase pH of the surface sediment, leading to enhanced release of P (especially iron-bound P) from the sediment. Based on the selective pump of P (but not N) from the sediment by algal blooms, it is concluded that photosynthesis which is closely related to eutrophication level is the driving force for the seasonal variation of internal P loading in shallow lakes. This is a new finding. Additionally, the selective pump of P from the sediment by algal blooms not only explains satisfactorily why both TP and PO₄-P in the hypereutrophic Lake Donghu declined significantly since the mid-1980s when heavy cyanobacterial blooms were eliminated by the nontraditional biomanipulation (massive stocking of the filter-feeding silver and bighead carps), but also explains why TP in European lakes decreased remarkably in the spring clear-water phase with less phytoplankton during the seasonal succession of aquatic communities or when phytoplankton biomass was decreased by traditional biomanipulation. Compared with deep lakes, wax and wane of phytoplankton due to alternations in the ecosystem structure is also able to exert significant influences on the P exchange at the sediment-water interface in shallow lakes. In other words, biological activities are also able to drive P release from sediments, and such a static P release process is especially more prominent in eutrophic shallow lakes with dense phytoplankton.     

Changes in the patterns of inorganic nitrogen and TN/TP ratio and the associated mechanism of biological regulation in the shallow lakes of the middle and lower reaches of the Yangtze River

The changes of NH₃-N, NO₃-N, NO₂-N and TN/TP were studied during growth and non-growth season in 33 subtropical shallow lakes in the middle and lower reaches of the Yangtze River. There were significant positive correlations among all nutrient concentrations, and the correlations were better in growth season than in non-growth season. When TP>0.1 mgL^?1, NH₃-N increased sharply in non-growth season with increasing TP, and NO₃-N increased in growth season but decreased in non-growth season with TP. These might be attributed to lower dissolved oxygen and low temperature in non-growth season of the hypereutrophic lakes, since nitrification is more sensitive to dissolved oxygen and temperature than antinitrification. When 0.1 mgL^?1>TP>0.035 mgL^?1, TN and all kinds of inorganic nitrogen were lower in growth season than in non-growth season, and phytoplankton might be the vital regulating factor. When TP<0.035 mgL^?1, inorganic nitrogen concentrations were relatively low and NH₃-N, NO₂-N had significant correlations with phytoplankton, indicating that NH₃-N and NO₂-N might be limiting factors to phytoplankton. In addition, TN/TP went down with decline in TP concentration, and TN and inorganic nitrogen concentrations were obviously lower in growth season than in non-growth season, suggesting that decreasing nitrogen (especially NH₃-N and NO₃-N) was an important reason for the decreasing TN/TP in growth season. The ranges of TN/TP were closely related to trophic level in both growth and non-growth seasons, and it is apparent that in the eutrophic and hypertrophic state the TN/TP ratio was obviously lower in growth season than in non-growth season. The changes of the TN/TP ratio were closely correlated with trophic levels, and both declines of TN in the water column and TP release from the sediment were important factors for the decline of the TN/TP ratio in growth season.     

Biological mechanisms driving the seasonal changes in the internal loading of phosphorus in shallow lakes

Because of the obvious importance of P as a nutrient that often accelerates growth of phytoplankton (including toxic cyanobacteria) and therefore worsens water quality, much interest has been devoted to P exchange across the sediment-water interface. Generally, the release mode of P from the sediment differed greatly between shallow and deep lakes, and much of the effort has been focused on iron and oxygen, and also on the relevant environmental factors, for example, turbulence and decomposition, but a large part of the P variation in shallow lakes remains unexplained. This paper reviews experimental and field studies on the mechanisms of P release from the sediment in the shallow temperate (in Europe) and subtropical (in the middle and lower reaches of the Yangtze River in China) lakes, and it is suggested that pH rather than DO might be more important in driving the seasonal dynamics of internal P loading in these shallow lakes, i.e., intense photosynthesis of phytoplankton increases pH of the lake water and thus may increase pH of the surface sediment, leading to enhanced release of P (especially iron-bound P) from the sediment. Based on the selective pump of P (but not N) from the sediment by algal blooms, it is concluded that photosynthesis which is closely related to eutrophication level is the driving force for the seasonal variation of internal P loading in shallow lakes. This is a new finding. Additionally, the selective pump of P from the sediment by algal blooms not only explains satisfactorily why both TP and PO4-P in the hypereutrophic Lake Donghu declined significantly since the mid-1980s when heavy cyanobacterial blooms were eliminated by the nontraditional biomanipulation (massive stocking of the filter-feeding silver and bighead carps), but also explains why TP in European lakes decreased remarkably in the spring clear-water phase with less phytoplankton during the seasonal succession of aquatic communities or when phytoplankton biomass was decreased by traditional biomanipulation. Compared with deep lakes, wax and wane of phytoplankton due to alternations in the ecosystem structure is also able to exert significant influences on the P exchange at the sediment-water interface in shallow lakes. In other words, biological activities are also able to drive P release from sediments, and such a static P release process is especially more prominent in eutrophic shallow lakes with dense phytoplankton.     

南羌塘盆地扎仁古油藏白云岩储层特征及成因研究

根据薄片、铸体薄片、压汞、阴极发光等研究,详细描述了南羌塘盆地扎仁古油藏白云岩的储层特征,并对白云岩成因作了初步研究。认为该白云岩在沉积期后变化中经历了多种成岩作用改造,其中影响白云岩储集性的作用主要有白云石化作用、溶蚀作用、重结晶作用和构造应力作用,对白云岩孔渗改善起了积极作用。白云岩主要储集空间为晶间孔、晶间溶孔,储集物性良好。广泛发育的白云石环边结构等淡水成因标志表明,该区白云岩是通过大气水-海水孔隙混合流体交代灰岩所形成的。     

粤北花岗岩型铀矿找矿潜力及找矿方向

深部构造环境、长期活动的深大断裂和成群成组的成矿构造带、多期次构造岩浆活动和蚀变叠加、多期次地幔流体和成矿流体的频繁活动，以及花岗岩丰富的铀源、良好的还原条件和封闭成矿环境等优越的成矿条件，使粤北成为得天独厚的花岗岩型铀矿矿集区。通过分析下庄矿田330南西地区“群脉型”、中洞地区“交点型”铀矿化，以及南雄矿田坪下水地区、棉花坑-书楼丘地区“硅化碎裂岩型”铀矿化等成矿条件好、找矿线索明显的地区，表明区内有较大的铀资源潜力和找矿潜力，为下一步的工作指出了方向。