Application of Digital Elevation Model in the geological mapping of the coastal plain of Tianjin

Tianjin coastal plain is flat and its landform is not easy to be divided. The grain size of the sediments is fine, with poor remote sensing interpretation accuracy and field identification, which leads to weak geological map expression effect by the traditional geological survey method. Digital Elevation Model (DEM) is a digital representation of the topographic surface and it has 3D visual information that cannot be expressed by the general topographic map, which can truly reflect the features of the landform. The authors divided the geomorphic units of shallow sediments during the geological mapping process of Tianjin coastal plain based on DEM and the geological survey of the route, the construction of the shallow groove drilling and the sample testing. The shallow sediments can be divided into three sedimentary systems: fluvial sedimentary system, transgression sedimentary systm and deltaic sedimentary system. The fluvial sedimentary system includes several genetic types of point bar, oxbow lake, crevasse splay, natural levee, flood basin and lake marsh. And the transgression sedimentary system can be divided into beach ridge, overland fan, high tide flat, residual lagoon, while the deltaic sedimentary system includes the delta front. DEM can fully make up for the shortage of remote sensing images after the comparative analysis with the results of remote sensing interpretation of different types. Besides, DEM can also be used for the detailed genetic classification of the shallow sediments and improve the cognition about shallow geological process, which will guide the field mapping. The application of high-precision DEM data to the geological mapping on the covered areas of quaternary system can greatly improve the mapping accuracy and efficiency, and provide basic geological support for urban ecological security, territorial space planning and industrial structure layout.     

Experimental study on unsaturated soil water diffusivity in different soils in Hebei Piedmont Plain

Horizontal soil column method was used to determine the horizontal diffusion rate of sandy loam, loam and clay loam under the same bulk density. The results showed that the migration rates of different lithological wet fronts were different. The sandy loam had the fastest migration rate, the loam followed, and the clay loam was the slowest, but the law of change is the same among the three lithologies. The volumetric water content affects the change of Boltzmann parameter λ. When the volumetric water content is between 0.35-0.45 cm3/cm3, λ approaches stability. When the volumetric water content is less than 0.35 cm3/cm3, the λ value decreases rapidly with the decrease of water content. The water diffusion rate is related to the volumetric water content and particle size. The greater the moisture content is, the greater the diffusion rate will be. The larger the particle size, the larger the diffusion rate. The diffusivity of sandy loam is 10-30 times larger than that of loam and clay loam. The relationship between water content and diffusion rate is in accordance with the exponential function.     

Palaeoenvironmental reconstruction of late Quaternary foraminifera and molluscs from the ENEA borehole (Versilian plain, Tuscany, Italy)

Foraminifera and molluscs from the 90 m deep ENEA borehole (Versilian plain, central Italy) were studied for paleoenvironmental purposes. Palaeontological analyses, integrated with U/Th and radiocarbon data, helped to recognize late Quaternary sea-level changes and supplied results on tectonic mobility of the area. The study highlighted four sedimentary phases. The first phase consists of a shore environment attributed to MIS 7.1. A hiatus corresponding to MIS 6 is hypothesized at the top of this interval. Recognition of the paleo-shoreline of MIS 7.1 at − 72.8 m signifies a vertical displacement due to the extensional tectonics of the Apennine orogenesis. The second phase consists of a transgressive succession with evidence of warm temperatures, which was interpreted as part of the transgression leading to the MIS 5.5 highstand. The third phase includes sub-aerial and lacustrine deposits. Radiocarbon dates and palaeoecological reconstruction led us to attribute this interval to MIS 4, MIS 3 and MIS 2. The fourth phase begins with a lagoon environment attributable to Holocene sea-level rise and ends with marsh episodes, signifying the progradation of the alluvial plain. This reconstruction confirms the hypothesis of tectonic stability for the Versilian area during the Holocene.     

鲁西平原地热水的化学特征及开发利用

鲁西平原地热水资源较丰富,属中低温地热,埋藏分布广,温度适中,开采潜力大。通过对鲁西平原地热水的水化学和冷水、海水的水化学进行对比分析,研究地热水的形成及水化学特征,根据地热水的水化学特征对地热水进行有针对性地开发利用。     

Arsenic enrichment in groundwater in the middle Gangetic Plain of Ghazipur District in Uttar Pradesh,India

Groundwater with high geogenic arsenic (As) is extensively present in the Holocene alluvial aquifers of Ghazipur District in the middle Gangetic Plain, India. A shift in the climatic conditions, weathering of carbonate and silicate minerals, surface water interactions, ion exchange, redox processes, and anthropogenic activities are responsible for high concentrations of cations, anions and As in the groundwater. The spatial and temporal variations for As concentrations were greater in the pre-monsoon (6.4–259.5 μg/L) when compared to the post-monsoon period (5.1–205.5 µg/L). The As enrichment was encountered in the sampling sites that were close to the Ganges River (i.e. south and southeast part of Ghazipur district). The depth profile of As revealed that low concentrations of NO₃⁻ are associated with high concentration of As and that As depleted with increasing depth. The poor relationship between As and Fe indicates the As release into the groundwater, depends on several processes such as mineral weathering, O₂ consumption, and NO₃⁻ reduction and is de-coupled from Fe cycling. Correlation matrix and factor analysis were used to identify various factors influencing the gradual As enrichment in the middle Gangetic Plain. Groundwater is generally supersaturated with respect to calcite and dolomite in post-monsoon period, but not in pre-monsoon period. Saturation in both periods is reached for crystalline Fe phases such as goethite, but not with respect to poorly crystalline Fe phases and any As-bearing phase. The results indicate release of arsenic in redox processes in dry period and dilution of arsenic concentration by recharge during monsoon. Increased concentrations of bicarbonate after monsoon are caused by intense flushing of unsaturated zone, where CO₂ is formed by decomposition of organic matter and reactions with carbonate minerals in solid phase. The present study is vital considering the fact that groundwater is an exclusive source of drinking water in the region which not only makes situation alarming but also calls for the immediate attention.     

菏泽黄泛平原地区浅层地下水资源可持续开发利用潜力分析

对菏泽黄泛平原地区浅层地下水资源潜力进行了分析,采用地下水开采潜力指数法来分析开采程度的强弱,判定其开采潜力。全区浅层地下水尚处于正均衡状态,属有开采潜力区。为保持区内地下水资源的可持续利用,将全区按照科学合理的采、补、控、改等原则分为增源区、增采区、节水区和咸水改造利用区分区。     

江汉平原湿地生态旅游发展对策研究

通过实地调查和发放调查问卷等方式开展江汉平原湿地生态旅游发展对策研究。结果表明,江汉平原湿地旅游资源丰富,具备开展湿地生态旅游的良好基础,在湿地资源开发的过程中应以可持续发展为基础,制定科学规划,明确开发时序,确定开发区域,开发特色生态旅游产品,完善生态化旅游基础设施建设,提高公众环境保护的意识,推动江汉平原湿地生态旅游的健康发展。     

Environmental evolution in the salt-water intru-sion area south of Laizhou Bay since late Pleisto-cene

The south coastal plain of Laizhou Bay is one of the typical salt-water intrusion areas in China, the occurrence and development of which was closely related with the pa-laeoenvironment evolution. Systematic analyses of pollen, foraminifera and grain size com-position based on 14C and luminescence dating from two sediment cores were performed for the purpose of understanding the salt-water intrusion in the coastal plain of Laizhou Bay from the perspective of environmental evolution since late Pleistocene. It could be classified into seven evolution stages since 120 kaBP: 120–85 kaBP was a transition period from cold to warm; 85–76 kaBP was a period with warm and wet climate having swamp lakes developed in the lower reaches of the Weihe River, south coastal plain of Laizhou Bay; 76–50 kaBP was characterized by grassland vegetation and coarse sediments in terrestrial environment, which was the early stage of Dali Ice-Age; 50–24 kaBP was a period with alternate sea deposition in the south coastal plain of Laizhou Bay; 24–10 kaBP was the late stage of Dali Ice-Age with coldest period of Quaternary, the south coastal plain of Laizhou Bay was dry grassland and loess deposition environment; 10–4 kaBP was another warm and wet climate period, sea level was high and regressed at 4 kaBP; and has been the modern sedimentary environment since 4 kaBP. Among the three warm stages, including 85–76 kaBP, 50–24 kaBP and 10–4 kaBP, corresponded to late Yangkou, Guangrao and Kenli seawater transgression respec-tively. The duration of the latter one in south coastal plain of Laizhou Bay was longer than that in west coast of Bohai Sea and east coast of Laizhou Bay. The three periods of seawater transgression formed the foundation of salt-water intrusion in this area.     

北京平原区新近沉积土基本工程地质特性分析

文章通过各种实验,分析了北京市新近沉积土的物质组成、化学成分、矿物成分及其基本的岩土工程特 性。结果表明,新近沉积土在总体上是工程地质性质较差的地层,一般来讲呈欠压密状态,具有较高的压缩性,强 度相对较低。但是对于新近沉积的砂质粉土而言,即当塑性指数Ip<7时,通过比较发现新近沉积土的实验数据则 接近于一般第四纪沉积土,并出现了交错,反映出新近沉积的砂质粉土与一般第四纪沉积的砂质粉土的力学性质 指标接近而不容易被区分。     

鲁北平原黄河古河道初步研究

鲁北平原黄河古河道可分为地面古河道(埋藏深度0—8m)和浅埋古河道(埋藏深度8—40m)。两类古河道部大致可分为三条古河道带,呈SW-NE向近平行展布,每带一般宽5—15km,最宽处可达20km。 古河道沉积层主要由细砂或粉砂组成,为古河床之曲流砂堤或天然堤沉积。各期古河道沉积层之顶、底板主要为粘土或亚粘土和淤泥层所构成,为古黄河泛滥相沉积物。 本区古河道按形成时间顺序可分为三期,下部第一期古河道大约形成于晚更新世晚期—全新世早期,中部第二期古河道形成于全新世早—中期,上部第三期古河道形成于全新世中—晚期。