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81.
本文通过对近年来在盐湖开采和试验过程中采卤设备以及输卤管、渠结盐实例的分析,得出如下结论:控制卤水结盐的主要因素是卤水的水化学类型以及矿化度、Na~+/Mg~(++)、Na~+/SO_4~=系数和CaCl_2的含量,其中Na~+/Mg~(++)系数是控制各类型卤水结盐的关键。并提出用回灌老卤的措施来解决卤水结盐问题。 相似文献
82.
《青海省东昆仑1:50万区化扫面项目》执行过程中,在取得分析成果后立即进行异常筛选,确定待查目标,进而安排异常检查,并做到了当年检查,当年见矿。不仅缩短了工作周期,也取得了较好的找矿效果。本文以某锑金矿为例,介绍了异常确认和野外实施检查等一系列工作方法,旨在与同仁们交流。 相似文献
83.
Guangyong You Yiping Zhang Yuhong Liu Qinghai Song Zhiyun Lu Zhenghong Tan Chuansheng Wu Youneng Xie 《水文研究》2013,27(18):2676-2682
Negative trends of measured pan evaporation are widely reported. Studies of the factors that underlie this reduction in pan evaporation have not reached a consensus about the controlling factors. Most studies employ statistical analysis (correlation analysis or stepwise regression) to identify the controlling climatic variables; in contrast, few studies have employed physical‐based theories. In addition, observations of pan evaporation and related climatic variables are reported to be influenced by anthropogenic activities. Consequently, the observed trends of climatic variables in a nature reserve would be useful for understanding regional climate change. The present study site is located in Ailaoshan National Nature Reserve, SW China, which is free of anthropogenic activity. In this study, we firstly applied the adjusted PenPan model to estimate the pan evaporation. Then, using this physical‐based model, we identified a positive trend in pan evaporation, with a much larger increase in the dry season than in the wet season. The model results indicate that the change in the aerodynamic component is larger than that in the radiative component. In contrast to the reduction in wind speed and sunshine hours that has been reported in previous studies at various sites, we found that wind speed and sunshine hours have increased in recent decades, thereby explaining the increase of the pan evaporation rate. Wind speed made the greatest contribution to the change in pan evaporation, followed by sunshine duration. This study indicates that the potential evaporation has increased at this site despite the widely reported reduction in measured pan evaporation. During the dry season, the availability of water for agriculture and agroforestry could be threatened. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
84.
近10余年来,中国对非洲直接投资的增长势头令人瞩目。与此同时,西方对中国在非投资的非议也甚嚣尘上,他们以"资源诅咒"命题为理论根据,宣扬中国在非投资活动是所谓的"新殖民主义"。对中国在非直接投资的主要行业、特征和"资源诅咒"命题的科学性进行了考察,认为"资源诅咒"命题本身存在很多缺陷,并不足以作为分析评价中国在非投资活动的理论基础,探究了西方把"资源诅咒"命题作为理论根据的根源和中国在非投资对非洲的真实影响,提出了建议。 相似文献
85.
全新世呼伦湖区植被和气候变化的孢粉记录 总被引:2,自引:1,他引:1
文章详细分析了内蒙古呼伦湖HL06岩芯沉积的孢粉组合,基于AMS 14C年代标尺,恢复了全新世湖区植被演变过程;并根据我国北方和蒙古表土孢粉数据和气象资料,建立了孢粉-气候参数转换函数,定量重建了呼伦湖区降水和气温的变化历史.结果表明,11000~8000aB.P.,湖区植被以蒿、藜占优,为干草原景观,气候暖干;8000~6400aB.P.,湖区禾本植物扩张,山地桦林发育,降水显著增加,气温逐渐降低;6400~4400aB.P.,湖区早生草本植物增加,降水减少,气温继续下降;4400~3350aB.P.,耐旱藜科植物大量生长,湖区荒漠化,气候极端干旱;3350~2050aB.P.,湖区草原植被有所恢复,降水略有增加,气温有所回升;2050~1000aB.P.,湖区蒿属植物减少,山地松林发育,气温降至全新世最低;最近1000年,藜科、禾本科等伴人植物大量出现,反映出人类活动对湖区自然环境的影响.全新世呼伦湖区气温变化在轨道尺度上受控于北半球太阳辐射量的变化,而在亚轨道尺度上可能与东亚夏季风强度有关.距今8000年前湖区降水较弱可能因为早全新世北半球高纬残存冰盖抑制了东亚季风雨带的北上,季风降水的千年-百年尺度波动与热带西太平洋海气相互作用密切相关. 相似文献
86.
Xiaozhong HUANG Gang ZHOU Yanlin MA Qinghai XU Fahu CHEN 《Frontiers of Earth Science》2010,4(2):174-180
The interpretation of the pollen records from lake sediments is always hampered by a lack of information relating to different
pollen production, transportation, deposition, and preservation. It is important to understand the modern process of pollen
sedimentation and its climatic implications. This paper presents results from a palynological study on 61 surface sediments
samples from Bosten Lake, the largest inland freshwater lake in China. Our results suggest that Chenopodiaceae and Artemisia dominate the modern pollen assemblages and have stable percentages at most sites of the lake basin except for the estuary
area. Pollen Artemisia/Chenopodiaceae ratio is about 0.5, indicating the dry climate of the region. Principle Components Analysis (PCA) of pollen
data can identify the pollen samples as several ecological groups from different parts of the lake. Pollen transportation
dynamics and the mixing effect of lake currents and waves on pollen deposition have affected the pollen assemblages. The distribution
of Typha pollen seems to be affected by the location where the parent plants grow. Picea pollen has higher percentages at estuary area, suggesting fluvial transport. Pollen concentration has high values at the
central part of the lake basin due to the sedimentation focusing process effect. Our results suggest that the pollen assemblages
of the sediment core from the central part of the lake can potentially record the regional vegetation history. 相似文献
87.
O,H, and Sr isotope evidences of mixing processes in two geothermal fluid reservoirs at Yangbajing,Tibet, China 总被引:1,自引:1,他引:0
The Yangbajing geothermal field with the highest reservoir temperature among Chinese hydrothermal systems is located about
90 km northwest to Lhasa City, capital of Tibet, where high temperature geothermal fluids occur in two reservoirs: a shallow
one at a depth of 180–280 m and a deep one at 950–1,850 m. In this study, Oxygen-18 and deuterium isotope compositions as
well as 87Sr/86Sr ratios of water samples collected from geothermal wells, cold springs and surface water bodies were characterized to understand
the genesis of geothermal fluids at Yangbajing. The results show that the deep geothermal fluid is the mixing product of both
magmatic and infiltrating snow-melt water, whereas the shallow geothermal fluid is formed by the mixing of deep geothermal
fluid with cold groundwater. Using a binary mixing model with deep geothermal fluid and cold groundwater as two endmembers,
the mixing ratios of the latter in most shallow geothermal water samples were calculated to be between 40 and 50%. The combined
use of O, H, and Sr isotopes proves to be an effective approach to depict the major sources of geothermal fluids and the mixing
processes occurring in two reservoirs at Yangbajing. 相似文献
88.
1856年黔江小南海地震初探 总被引:1,自引:0,他引:1
对小南海地震发生的地质背景、成因机制、地震灾害及其遗迹进行了论述,作为自然遗产应得到充分地保护。 相似文献
89.
90.
柴达木盆地北缘鱼卡河岩群的地质特征和时代 总被引:5,自引:3,他引:5
柴达木盆地北缘的鱼卡河岩群是在最近几年区域地质调查和研究的基础上新建立的构造岩石单位,主要分布于绿梁山—锡铁山—沙柳河—带,由石榴白云石英片岩、石榴(蓝晶)白云片岩、二云片岩、黑云变粒岩、黑云角闪片岩、榴辉岩、石榴斜长角闪岩及大理岩等组成,以含馏辉岩为特征。在绿梁山地区,鱼卡河岩群呈不同规模的残块产于花岗闪长质—二长花岗质片麻岩之中。野外观察和变质作用特点显示,至少有一部分榴辉岩的原岩是鱼卡河岩群表壳岩的组成部分,在早占生代遭受了高压变质再造。根据从鱼卡河岩群及花岗片麻岩中获得的同位素年龄,结合两者的野外地质关系,初步确定鱼卡河岩群形成于中元古代。 相似文献