基于Albedo-NDVI特征空间的玛曲县荒漠化时空动态监测

开展荒漠化时空动态监测是荒漠化防治的一项重要基础工作。以地处青藏高原东北缘的甘肃省玛曲县为例,以该县2001年、2005年、2010年的TM影像和2015年的HJ-1影像为数据来源,利用Albedo-NDVI特征空间法,从整体到局部,分别对该县全区域及其黄河沿岸地区不同尺度区域近15年的土地荒漠化进行了监测和时空动态分析。研究结果表明：Albedo-NDVI特征空间法能便捷、有效、精确地对荒漠化信息进行提取和分级,有利于荒漠化的定量分析与监测;玛曲县近15年来实施的生态恢复工程效果显著,该县荒漠化状况有所改善,荒漠化土地的面积持续减小,程度不断降低,主要发生“轻度荒漠化土地向非荒漠化土地”的转移;但是由于沙源丰富、人口密集以及过度放牧等原因,玛曲县黄河沿岸5 km带状区域荒漠化以“非荒漠化土地向轻度荒漠化土地”转移为主,荒漠化状况较全县整体水平严重,并且仍有不断恶化的趋势。     

Geochemistry of organic matter and elements of black shale during weathering in Northern Guizhou,Southwestern China: Their mobilization and inter-connection

Different from previous studies on effect of weathering upon geochemical variation along a single weathered profile, this paper provides a new methodology validated by comparing a weathered outcrop samples and their stratigraphic counterpart un-weathered core samples in a nearby shallow borehole. This outcrop and borehole penetrated the Ordovician-Silurian Wufeng–Longmaxi shales, located in the same anticline structure in the northern part of Guizhou Province, Southern China. The mineral composition, major, trace and rare earth elements (REEs) composition and Rock-Eval parameters of outcrop and core samples were analyzed and compared. Organic matter (OM) was observed in the microscope and extracted for elements analysis. The results show that short-term weathering still has significant influence on OM, mineral and elemental composition of black shales. The elements composition shows the outcrop profile was moderately weathered. The REEs compositions do not alter much during weathering process and the REEs composition and their relative ratios still are valid for rock origin determination. The OM, mainly composed by graptolite and bitumen, even entering the highly-over thermal maturity, is still sensitive to the weathering with a systematic loss 30–50% of TOC along the outcrop profile, which suggests that the OM consumption is predominantly controlled by weathering duration and the distance from the weathering surface. In turn, OM has significant influence on the trace elements transportation behavior during weathering. Some trace elements associated with the OM such as V, Cr, Th, U, Ni and Co, change significantly in their absolute concentration during weathering, but their relative ratios do not necessarily change too much and might be still reliable proxies for paleo-environmental determination. The mobility of shale minerals during weathering is in the following order: plagioclase?>?potassium feldspar and dolomite >pyrite and OM. Short-term weathering can also result in considerable transportation of elements and significant variation of minerals content in black shale, which may pose potentially high environmental and engineering risk in the regions rich in black shale.     

Sustainable groundwater development in the coastal Tra Vinh province in Vietnam under saltwater intrusion and climate change

Three-dimensional transient groundwater flow and saltwater transport models were constructed to assess the impacts of groundwater abstraction and climate change on the coastal aquifer of Tra Vinh province (Vietnam). The groundwater flow model was calibrated with groundwater levels (2007–2016) measured in 13 observation wells. The saltwater transport model was compared with the spatial distribution of total dissolved solids. Model performance was evaluated by comparing observed and simulated groundwater levels. The projected rainfalls from two climate models (MIROC5 and CRISO Mk3.6) were subsequently used to simulate possible effects of climate changes. The simulation revealed that groundwater is currently depleted due to overabstraction. Towards the future, groundwater storage will continue to be depleted with the current abstraction regime, further worsening in the north due to saltwater intrusion from inland trapped saltwater and on the coast due to seawater intrusion. Notwithstanding, the impact from climate change may be limited, with the computed groundwater recharge from the two climate models revealing no significant change from 2017 to 2066. Three feasible mitigation scenarios were analyzed: (1) reduced groundwater abstraction by 25, 35 and 50%, (2) increased groundwater recharge by 1.5 and 2 times in the sand dunes through managed aquifer recharge (reduced abstraction will stop groundwater-level decline, while increased recharge will restore depleted storage), and (3) combining 50% abstraction reduction and 1.5 times recharge increase in sand dune areas. The results show that combined interventions of reducing abstraction and increasing recharge are necessary for sustainable groundwater resources development in Tra Vinh province.

     

WV-3遥感数据在滇西矿产资源开发与地质灾害调查中的应用

选择云南三江中南段高黎贡山之南作为研究对象,利用WorldView-3卫星数据高空间分辨率的特点,基于Skyline软件构建三维模拟场景,从不同视域范围、远近尺度、方位视角对解译目标进行全方位展示,获取了不同矿山开发及地质灾害的典型识别标志,进行矿产资源开发状况精细识别及地质灾害详细信息提取,解译出区内建筑石料用灰岩等5种非金属矿以及滑坡等3种类型地质灾害,为矿山管理及地质灾害调查提供快速精准的目标,提升工作效率和质量。     

LCR-G型重力仪周期误差的研究

分析了LCR-G型重力仪周期误差的产生机制,讨论了周期误差标定的基本原理和方法,结合LCR-G920和LCR-G922在灵山重力基线场上的3次标定,对LCR-G型重力仪的周期误差进行了较为深入的研究,得出了一些有益的结论。     

华南沿海全新世海岸带碳酸盐胶结岩的分类及其研究意义

华南沿海的全新世海岸带碳酸盐胶结岩研究在成因、分类方面一直存有许多争议,并导致了对古海平面、构造升降、古气候等研究意义的诸多争议。本文通过成岩特征研究,将华南沿海的全新世海岸带碳酸盐胶结岩分为四类:海滩岩、砂丘岩、贝壳堤岩和硬壳灰岩,并对深圳西冲海滩岩、汕头广澳砂丘岩、韩江三角洲贝壳堤岩和海山岛硬壳灰岩等4个典型露头进行详细研究。在此基础上对这四类海岸带碳酸盐胶结岩的意义进行讨论,认为海滩岩在古海平面、海岸带演化和古气候方面具有重要研究意义,贝壳堤岩也具有古海平面(在某些条件下)和海岸线变迁的研究意义,而砂丘岩和硬壳灰岩在这些方面的研究意义较弱。     

Study on inelastic displacement ratio spectra for near-fault pulse-type ground motions

In displacement-based seismic design, inelastic displacement ratio spectra (IDRS) are particularly useful for estimating the maximum lateral inelastic displacement demand of a nonlinear SDOF system from the maximum elastic displacement demand of its counterpart linear elastic SDOF system. In this study, the characteristics of IDRS for near-fault pulse-type ground motions are investigated based on a great number of earthquake ground motions. The in? uence of site conditions, ratio of peak ground velocity (PGV) to peak ground acceleration (PGA), the PGV, and the maximum incremental velocity (MIV) on IDRS are also evaluated. The results indicate that the effect of near-fault ground motions on IDRS are signifi cant only at periods between 0.2 s - 1.5 s, where the amplifi cation can approach 20%. The PGV/PGA ratio has the most signifi cant in? uence on IDRS among the parameters considered. It is also found that site conditions only slightly affect the IDRS.     

Mutagenetic action of ethyl methanesulfonate on Spirulina platensis

In the present experiments, ethyl methanesulfonate (EMS) is used to treat blue-green alga Spirulina platensis. Results show that the chemical is a very effective mutagen on the species and some genetic changes, including morphological variation, different growth rate and greater resistance to low temperature, have been found, which may offer an efficient method for the strain breeding of Spirulina platensis.