民勤绿洲农田生态系统能值空间分异特征

利用能值分析方法对2011年民勤绿洲18个乡镇农田生态系统的环境资源条件、投入产出结构和可持续性进行了系统分析,构建了反映民勤绿洲农田生态系统综合水平的能值指标体系,运用主成分分析方法对其进行了综合评价和排序。结果表明：民勤绿洲农田生态系统可持续性强的是夹河乡,其他乡镇农田生态系统为消费型生态经济系统,可持续性弱;民勤绿洲农田生态系统能值综合水平存在着明显的地域差异,呈现东北片高于西南片、绿洲边缘带高于中心带的地理分布特征;民勤绿洲农田生态系统总体上不具有可持续性,不协调发展型区域和极不协调发展型区域农田面积占民勤绿洲农田总面积的73.68%,强、中、弱协调发展型区域只占26.32%。因此,目前民勤绿洲农田生态系统面临的不可持续性应当引起相关部门的高度重视。     

夏季金塔边界层风、温度和湿度结构特征的初步分析

利用2004年6～7月在河西走廊金塔陆-气相互作用试验的观测资料,分析了该地区夏季夜间和中午风、温、湿的垂直结构特征,结果表明：夏季夜间,当地面风较小时,金塔绿洲高空可能为偏西风气流,夜间稳定层高度大致在100～190m。夏季中午,当低空为偏东风时,风速随高度的变化比较复杂。总的来说,存在着东风急流,急流高度在1000-4000m之间,大气边界层顶盖（即逆温层底）约在3000-3600m高度,在500-800m高度以下存在绿洲内边界层;当低空为偏北风或西北风时,高空都为偏西风或西北风气流,低空风速随高度的变化比较平缓,风速有时存在极大值,大气边界层顶盖（即逆温层底）在3500m左右,在1200m以下可能存在绿洲内边界层,绿洲内边界层高度有时会很低。     

民勤县2000-2009年来水资源生态环境压力分析

 民勤县面临的水资源危机已经受到人们的普遍关注。水资源生态环境压力是指为了保护人类生存发展的生态环境、以维持整个社会经济活动的正常运行,而对水资源造成的数量和质量上的压力,简称水资源压力。通过从人口、经济和生态3个方面选取多个指标建立水资源压力指数,对民勤近10 a来水资源压力问题进行分析。结果表明,民勤水资源压力较高,属于重度缺水,人口和经济发展挤占生态需水,引起生态环境恶化。多年来通过采取节水、调水、分水等措施,水资源压力指数由2000年的0.627降到2009年0.329,虽然水资源压力有所减缓,但地下水超采和生态环境缺水严重、水资源短缺问题仍未缓解。     

1999-2013年民勤绿洲地下水埋深年际变化动态及影响因素

为探究内陆河下游绿洲地下水动态变化规律,以民勤绿洲1999-2013年实测数据,在对绿洲地下水年际尺度埋深动态及潜在影响因素进行描述性统计分析的基础上,运用主成分分析法提取12个影响地下水埋深的主要因素,并采用灰色关联度方法分析了地下水埋深对各影响因子的敏感程度。结果表明：（1）绿洲地下水埋深总体呈逐年增加趋势,且不同区域、不同时期有明显差异;（2）民勤绿洲地下水埋深动态对12个因子的敏感程度依次为化肥使用量 >农膜覆盖面积 >年平均气温 >年末耕地总面积 >人口规模 >经济作物种植面积 >有效灌溉面积 >森林面积 >降水量 >蒸发量 >生产用电度数 >大牲畜年存栏量。     

对民勤绿洲生态退化问题的探讨

针对位于河西走廊东北部、石羊河流域最下游的民勤绿洲近40a生态环境逐渐退化的现象,从土地荒漠化、植被死亡等方面分析了民勤绿洲退化的特点;从气候变化和人类活动等方面分析了民勤绿洲退化的原因;最后针对保护石羊河流域生态环境提出几点建议。     

疏勒河绿洲系统气候变化的特征分析

概述了疏勒河流域绿洲系统的基本气候特点及近5O年来的气候演变特征,分析了疏勒河绿洲上游产流区和中下游绿洲开发区的主要气候要素的年际、年代际变化规律。指出在有限水资源条件下,中游人工绿洲的过度开发可能导致下游自然生态环境的恶化。     

绿洲型城市生态经济系统持续发展仿真研究

本文从限制绿洲型城市发展的水、土因素出发，分析了自然资源、环境条件与社会经济发展之间的相互关系，运用系统动力学方法建立了绿洲型城市生态经济系统持续发展的动态仿真模型，并以新疆自治区奎屯市为例，对该模型作了模拟调试及多方案的仿真实验，有关结果对绿洲型城市发展提供了科学依据。     

Study of Sediments in the Yutian-Hotan Oasis, South Xinjiang, China

Based on investigation of sediments in the Yutian-Hotan Oasis at the southern margin of the Tarim basin, 14C ages and grain-size and chemical element analyses, the following views are put forward in this paper.(1) Sediments in the Yutian-Hotan Oasis are composed chiefly of "oasis soil", similar to the recent oasis soil, i.e. brown desert soil, which was formed due to pedogenesis after aeolian sand (sandy loam) and dust (loess) of 3.32-6.64 were deposited.(2) The ancient Yutian-Hotan Oasis represented by oasis soil was formed at 13000 a B.P. During the cold period of the past 13000 years, this region is characterized mainly by accumulation of sand and dust storms, and sandy oasis soil was developed in this region due to pedogenesis in an oasis environment; during the warm period, dust falls predominated along with certain current concomitants (lacustrine facies), and silty oasis soil was formed by pedogenesis. Owing to fluctuations of cold and warm climates since 13000 a B.P., sandy oasis soil was deposi     

绿洲防护林系统的最优控制模式及其应用研究

以河西地区绿洲防护林系统为研究对象，分析了防护林资源分布的时空特征及建群种的增长动态，运用生物控制理论，构建了防护林区生物资源管理的最大持续产量模型、生态经济意义下的最优控制模型及多资源种群控制模型。根据有关模型和试验观测结果，确定了防护林建群种的资源保护指标、生态经济意义下的最优种群水平和人工调控措施。该防护林主要建群种二白杨胸径的保护指标为 k/2＝18．22cm，在不同成本与价格比下计算了主要建群种二白杨胸径指标的个最优控制量。估算了防护林系统的生态需水量，其中农田生态需水量为 1 796 m³/hm²，固沙林和阻沙防护林生态需水量为57 100m³/hm²，并提出了相应的持续发展对策。     

Uranium isotopic evidence for the origin of the Bahariya iron deposits, Egypt

The economic iron ore deposits of Egypt are located at Bahariya Oasis in the Lower Middle Eocene limestone. The main iron minerals are goethite, hematite, siderite, pyrite, and jarosite. Manganese minerals are pyrolusite and manganite. Gangue minerals are barite, glauconite, gibbsite, alunite, quartz, halite, kaolinite, illite, smectite, palygorskite, and halloysite. Geochemical comparison between the ore and the Nubia sandstone showed that the ore is depleted in the residual elements (Al, Ti, V, and Ni) and enriched in the mobile elements (Fe, Mn, Zn, Ba, and U) which indicates that the Bahariya iron ore is not a lateritic deposit despite the deep weathering in this area. On the other hand, the Nubia sandstone showed depletion in the mobile elements, which demonstrates the leaching process in the Nubia Aquifer. The presence of such indicator minerals as jarosite, alunite, glauconite, gibbsite, palygorskite, and halloysite indicate that the ore was deposited under strong acidic conditions in fresh water.Isotopic analyses of the uranium in the amorphous and crystalline phases of the ore, in the country rocks, and dissolved in the Nubia Aquifer water, all support the conclusion that U and Fe were precipitated together from warm ascending groundwater. U and Fe display strong co-variation in the ore, and the ²³⁴U/²³⁸U activity ratio of the newly precipitated U in the country rock and the leached component of U in the groundwater are identical. There is only slightly more uranium in the amorphous phase than in the crystalline and only a slightly lower ²³⁴U/²³⁸U activity ratio, suggesting that the iron in the two phases have a similar origin. Comparison of the excess ²³⁴U in the water and in the total ore leads to the conclusion that the precipitation of the U, and by inference the iron, occurred within the last million years. However, that both precipitation and leaching of U have occurred over the last 300,000 years is evidenced by the extreme ²³⁰Th/²³⁴U disequilibria observed in some of the samples. Some of the amorphous depositional events have been very recent, perhaps within the last 10,000 years.