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1.
主要基于华北平原上93个钻孔中沉积物详细观测和分析数据,结合182组14C测年和埋深数据、参考前人黄河下游河道历史变迁及其他相关研究成果,估算出2600年以来黄河下游在602BC～11A.D.,11～1034A.D.,1034～1128A.D.,1128～1855A.D.和1855～1997A.D.等5个历史时期的年平均沉积量分别是3.89×108t/a,2.24×108t/a,6.63×108t/a,6.78×108t/a和8.47×108t/a。通过建立黄河下游有无堤防和决溢频率与泥沙输移比的关系,计算出5个时期黄河上中游的平均年输沙量分别是6.2×108t/a,6.8×108t/a,8.3×108t/a,11.5×108t/a和15.3×108t/a。进而探讨了黄河输沙量变化的主要原因,以及历史上王景治河后出现的600年安流时期的原因。 相似文献
2.
胶州湾沉积速率:多种分析方法的对比* 总被引：5，自引：0，他引：5
根据胶州湾内外海域采集的柱状岩芯样品的 210 Pb测试,结合物源分析方法,计算了1952年以来胶州湾的沉积物收支状况和胶州湾区域的平均沉积速率。结果表明,胶州湾百年尺度的沉积速率较高,达到了100mm/a量级(7.43mm/a),沉积通量为10-3g/mm2a量级(7.39×10-3g/mm2a),而胶州湾外邻近海区沉积速率略低(4.46mm/a)。这与其他学者获得的海图地形对比法的结果大致相当。与胶州湾内钻孔岩芯的14 C测年对比表明,万年尺度的沉积速率为10-1mm/a量级(0.25~0.92mm/a),比百年尺度的沉积速率约小一个数量级。分析结果表明,沉积体系的演化过程使沉积速率随时空尺度的不同而产生差异,这是导致不同分析方法所获结果之间存在复杂关系的主要因素。 相似文献
3.
贵阳市及邻近地区地表和地下水的化学与Sr同位素组成变化反映了典型喀斯特地区地表/地下水文系统的水-岩反应和城市污染特征:水体中的化学溶解物质主要来源于碳酸盐岩(石灰岩和白云岩)的风化作用和膏岩层的溶解,其次为人为污染物的输入;污染物以K+,Na+,Cl-,SO2-4,NO-3为主,枯水期因大气降水补给小而受人为活动影响较大;丰水期和枯水期地表/地下水的化学组成变化说明地表/地下水交换活跃,地下水环境容易受到人为活动影响。 相似文献
4.
冰岩芯研究与全球变化 总被引：2，自引：0，他引：2
冰岩芯研究是古气候、古环境研究的有力手段,它将为“全球变化研究”提供多方面的气候、环境信息。在冰岩芯研究中,通过稳定同位素(δ18O或δD)、放射性10Be、微粒含量变化、冰结构变化、CO2含量变化、CH4含量变化、各种化学元素含量的变化等多种手段建立了两极地区倒数第二次冰期以来气候、环境及大气成分演化的大概轮廓。 相似文献
5.
我国主要钼（铜）成矿带的铼-锇年龄及成矿时、空演化 总被引：1，自引：0，他引：1
本文将我国钼和铜,钼矿床归属子7个主要成矿带,并据其中典型矿床的辉钼矿Re-Os年龄,阐明所述矿带和矿床的时、空演化特征：东部隶属太平洋构造域的燕辽、东秦岭、长江中下游、赣东北和湘南成矿带的成矿高峰期为燕山期(189×106~106×l06 a);古亚洲构造域的多宝山矿带成矿时代为加里东期( 512×l06～40g×l06 a)。西部金沙江．红河成矿带主要是喜山期（36×l06 a左右）成矿。燕辽和东秦岭两个钼矿带的成矿作用分别有从燕山早期(189×l06~177×l06 a)到中晚期(148×106~134×106 a)和从148×l06～138×106 a的自东向西迁徙趋势;长江中下游铜-钼矿带的成矿作用自西北一东南呈燕山中晚期(141×106 a)一晚期(106×l06 a)的趋势。这同3个成矿带内与成矿有关花岗岩类侵位的相应先后次序大体相吻合。 相似文献
6.
选择位于长江下游的固城湖流域作为研究区域,基于分布式流域水文模型SWAT,采用数值模拟的手段,反演了1951～2000年流域农业非点源氮、磷的输移规律。模拟结果与实测值的一致性反映了模型的良好模拟能力。比较两个时段的模拟结果发现,1981～2000年,流域农业非点源氮、磷年平均浓度和输移量分别为:总氮0.82mg/L和411.88×103kg/a,总磷0.084mg/L和43.04×103kg/a;远高于1951～1960年的氮、磷年平均浓度和输移量分别为:总氮0.22mg/L和49.55×103kg/a,总磷0.036mg/L和7.67×103kg/a。模拟主要反映了流域下垫面条件和农作物耕作模式对农业非点源氮、磷浓度及输移量的影响。 相似文献
7.
测定了新疆罗布泊地区湖相沉积物CK-2钻孔样品的总有机碳含量（TOC）及其同位素组成、碳酸盐含量和C/N比值等环境代用指标,以及石膏矿物的质谱-铀系年龄。测试结果表明,20～9kaB.P.期间沉积物δ13Corg.在-23.4‰～-16.1‰之间波动且阶段性明显,与TOC呈现良好的相关关系,整体变化趋势同南极Dome C冰芯中记录的全球大气CO2浓度一致;C/N比值表明有机碳来源主要是陆生高等植物。因此大气CO2浓度变化是影响20～9kaB.P.期间罗布泊湖相沉积物δ13Corg.值变化的主导因素,周围山体上C3/C4植物相对生物量的变化则是另一重要因素。依据δ13Corg.的变化序列将此时间段湖区古环境的演化分成6个阶段:20.0～14.1kaB.P.期间受到末次盛冰期的影响,气温偏低,湖水丰沛;14.1～13.3kaB.P.是一个气候不稳定期,冷暖波动较频繁,但以暖为趋势;13.3～12.8kaB.P.期间经历了一段冷期,于12.8kaB.P.结束了末次冰期,随后气候开始转暖至11.8kaB.P.;其后气温再次变冷并维持到10kaB.P.;最后从10kaB.P.进入全新世暖期。δ13Corg.序列明显向偏负方向变化,表明该地区变暖的趋势相当明显。罗布泊地区日益干旱化是全球气候变化的结果,尤其是受到全球CO2浓度的不断升高所制约。 相似文献
8.
位于青藏高原与黄土高原过渡带的甘肃武都万象洞石笋WXSM51和WXSM52提供了MIS 5(118~79kaB.P.)高分辨率的δ18 O记录。研究表明, 万象洞石笋δ18 O值与夏季风强度呈负相关关系, 与我国西南部的贵州董歌洞石笋δ18 O记录有良好的对应关系, 并与高纬度的格陵兰NGRIP冰芯δ18 O记录和65°N太阳辐射强度有很好的一致性, 说明万象洞石笋δ18 O记录了118~79kaB.P.期间亚洲季风强度的变化, 同时也说明东亚季风强度的变化和全球气候变化同步, 而且主要受控于北半球太阳辐射强度的变化。同时它与地中海碳酸盐记录有很好的相似性, 和巴西石笋δ18 O记录在千年尺度上表现出相反的变化趋势, 说明东亚季风区、地中海地区以及巴西季风区之间存在密切的联系, 指示了南北半球气候在千年尺度上存在"跷跷板"(seesaw)现象。万象洞石笋δ18 O记录的MIS 5b与MIS 5a突发性转换, 与NGRIP冰芯δ18 O记录相似, 而与神农架记录存在差异, 说明万象洞地区对亚洲季风强度的响应更为敏感。 相似文献
9.
黑河中游水土资源开发利用现状及水资源生态环境安全分析 总被引：12，自引：1，他引：12
黑河流域水资源产生于南部祁连山区,主要消耗于中游农业灌溉区。对黑河流域水文资料分析计算发现,流域出山水资源量多年变化比较稳定,最枯年和最丰年水资源量之比为 1:2,丰枯变化幅度与长江以南丰水河流相当。多年平均水资源量为32．31×108 m3／a,近10年中游水资源开发利用量稳定在34×108 m3／a以上,仅中游地区对水资源的开发利用率达120％左右。目前国际上公认的人均水资源量紧缺线为 1000～1700 m3／a,黑河流域水资源开发利用具有反复转化多次重复利用的特点,用这个指标无法全面评价黑河流域水资源的安全状况。 相似文献
10.
成都市近地表大气尘铅分布特征及源解析 总被引：7，自引：1，他引：7
分析了成都市近地表大气尘样品铅及其同位素含量比的测定数据,铅含量变化范围为(119.76～1327.42)×10-6,均值为374.51×10-6,统计标准偏差为273.36,变异系数为0.73,说明成都市近地表大气尘铅含量变化大。燃煤飞灰的放射性成因铅明显高于汽油和柴油,可作为鉴别大气尘铅来源的证据。铅同位素含量数据表明成都市近地表大气尘的铅污染是复合污染源所致,其中,相对清洁区污染以建筑扬尘为主,中度污染区是汽车尾气和扬尘的叠加作用,重污染区是燃煤飞灰汽车尾气和工业污染源的综合表征。 相似文献
11.
地下水与环境变化研究 总被引：12，自引：2，他引：12
环境变化研究是当前国际地球科学和环境科学界最为活跃的研究领域之一。作为全球水循环的重要环节,地下水是全球环境变化的受体和信息载体。地下水及其沉积物的物理、化学指标,诸如地下水水位、宏量组分、微量组分、同位素、惰性气体等可以用作不同时间尺度上环境变化的指示剂。从地下水及其沉积物中识别和提取高分辨率的环境变化信息,实现对环境变化的预警功能是地下水科学向环境科学延伸的重要方向;而随着全球淡水资源紧缺形势不断恶化,全球环境变化、特别是全球气候变化对地下水资源的影响成为水文地质研究的新课题。 相似文献
12.
Hafnium isotopes of zircon represent a well-dated proxy for the evolution of magmatic systems through Earth history. Time series analysis on the hafnium isotopes of zircon reveals a hierarchy of statistically significant periodic signals spanning multiple orders of magnitude (106–109 year cycles). We attribute the hierarchy of cyclicity to organizing mechanisms of mantle and lithospheric convection at various time scales, ranging from short-term cycles in magmatism and subduction to long-term cycles related to oceans, supercontinents, and superoceans. A ∼600-Myr supercontinent cycle is the strongest signal in the global hafnium database and the phase relationship implies elevated mantle-derived magmatism during supercontinent tenure and elevated crustal reworking during plate reorganization, as expected. A half-supercontinent cycle (Wilson cycle) and a double-supercontinent cycle (superocean cycle) are also present, harmonic with the supercontinent cycle, and related to each other by amplitude modulation. Analysis of local magmatic systems of the circum-Pacific subduction girdle surrounding Pangaea reveal similar significant and harmonic cycles of ∼6 and ∼20 Myr attributed to magmatic cycles and ∼60, ∼120, and ∼240 Myr attributed to subduction cycles. All subduction systems reveal a prevalent ∼60 Myr cycle attributed to an upper mantle convective cycle that has two phase relationships, suggesting that advancing and retreating arc systems can be identified with time series analysis. The harmonic hierarchy of geodynamic cycles identified herein controlled by mantle convection on long time scales and lithospheric convection on short time scales arguably completes the picture of cyclicity in the Earth system, complimenting well-known orbital, oceanic, and astronomical cycles. 相似文献
13.
The integration of terrestrial carbonate δ13C chemostratigraphy and radiometric dates is opening a new window into the continental paleoclimate dynamics of the major carbon cycle perturbations of the Aptian-Albian interval. Results published to date by many researchers clearly show that there was a tight temporal coupling between Aptian-Albian marine, atmospheric, and terrestrial carbon pools that now permits refined global chemostratigraphic and chronostratigraphic correlations on time scales of 106 years or less. This development opens new opportunities to explore the Aptian-Albian Earth system by incorporating continental climate change dynamics in a developing global synthesis. In this paper, we present new U–Pb and U–Th/He age dates on a late Albian volcanic ash deposit in a stratigraphic section that fills a previous gap in in the terrestrial δ13C record. Here we also present, for the first time, coordinated δ13Ccarbonate, δ18Ocarbonate, and δ13Corganic data from stacked successions of paleosols in Aptian-Albian terrestrial strata of the Cedar Mountain Formation of Utah, USA. From the whole of this record, the late Aptian C10 C-isotope feature is especially noteworthy as an interval of major global change. Coordinated carbonate and organic carbon isotope data from this interval suggest that this positive carbon isotope excursion (CIE) was related to a buildup of atmospheric pCO2 to a peak level of about 1200 ppmV over a period of several million years duration, above earlier Aptian baseline levels of about 1000 ppmV. The C10 interval was immediately preceded and followed by drawdowns in pCO2 to levels of about 800 ppmV, and the entirety of the Aptian-Albian record from the Cedar Mountain Formation suggests a long-term fall of pCO2 levels from about 1000 down to 600 ppmV. We suggest that the late Aptian buildup likely is related to submarine volcanic activity in the Kerguelen Large Igneous Province in the southern Indian Ocean. Strata of the C-10 C-isotope feature are also associated with sedimentary evidence for an aridification event in the leeward rain shadow of the Sevier Mountains. On the basis of diagenetic studies of dolomitized calcretes in this C10 interval, we calculate that the precipitation-evaporation deficit intensified to the extent that 35–50% of the shallow groundwater system was lost to the atmosphere through evaporation. 相似文献
14.
《China Geology》2022,5(3):475-509
Global warming and the response to it have become a topic of concern in today’s society and are also a research focus in the global scientific community. As the world’s third pole, the global warming amplifier, and the starting region of China’s climate change, the Qinghai-Tibet Plateau is extremely sensitive to climate change. The permafrost on the Qinghai-Tibet Plateau is rich in natural gas hydrates (NGHs) resources. Under the background of global warming, whether the NGHs will be disassociated and enter the atmosphere as the air temperature rises has become a major concern of both the public and the scientific community. Given this, this study reviewed the trend of global warming and accordingly summarized the characteristics of the temperature increase in the Qinghai-Tibet Plateau. Based on this as well as the distribution characteristics of the NGHs in the permafrost on the Qinghai-Tibet Plateau, this study investigated the changes in the response of the NGHs to global warming, aiming to clarify the impacts of global warming on the NGHs in the permafrost of the plateau. A noticeable response to global warming has been observed in the Qinghai-Tibet Plateau. Over the past decades, the increase in the mean annual air temperature of the plateau was increasingly high and more recently. Specifically, the mean annual air temperature of the plateau changed at a rate of approximately 0.308–0.420°C/10a and increased by approximately 1.54–2.10°C in the past decades. Moreover, the annual mean ground temperature of the shallow permafrost on the plateau increased by approximately 1.155–1.575°C and the permafrost area decreased by approximately 0.34×106 km2 from about 1.4×106 km2 to 1.06×106 km2 in the past decades. As indicated by simulated calculation results, the thickness of the NGH-bearing permafrost on the Qinghai-Tibet Plateau has decreased by 29–39 m in the past 50 years, with the equivalent of (1.69 – 2.27)×1010–(1.12–1.51)×1012 m3 of methane (CH4) being released due to NGHs dissociation. It is predicted that the thickness of the NGH-bearing permafrost will decrease by 23 m and 27 m, and dissociated and released NGHs will be the equivalent of (1.34–88.8)×1010 m3 and (1.57–104)×1010 m3 of CH4, respectively by 2030 and 2050. Considering the positive feedback mechanism of NGHs on global warming and the fact that CH4 has a higher greenhouse effect than carbon dioxide, the NGHs in the permafrost on the Qinghai-Tibet Plateau will emit more CH4 into the atmosphere, which is an important trend of NGHs under the background of global warming. Therefore, the NGHs are destructive as a time bomb and may lead to a waste of efforts that mankind has made in carbon emission reduction and carbon neutrality. Accordingly, this study suggests that human beings should make more efforts to conduct the exploration and exploitation of the NGHs in the permafrost of the Qinghai-Tibet Plateau, accelerate research on the techniques and equipment for NGHs extraction, storage, and transportation, and exploit the permafrost-associated NGHs while thawing them. The purpose is to reduce carbon emissions into the atmosphere and mitigate the atmospheric greenhouse effect, thus contributing to the global goal of peak carbon dioxide emissions and carbon neutrality.©2022 China Geology Editorial Office. 相似文献
15.
地球系统科学是当今地球科学的研究前缘,早白垩时期全球气候经历了巨大的变化,前人为此做了大量的研究工作,但就铁矿形成与环境变化方面的研究还鲜见人提及。本文针对早白垩世大规模岩浆活动、铁矿成因、温室气体的释放及对气候变化的可能耦合关系做探索性的研究工作。本文主要通过大数据统计、整理分析、制图对比等科学手段,论证早白垩世各重要地质事件之间的耦合关系。发现早白垩世的大规模岩浆活动和铁矿爆发巅峰期、陆相红层的出现有着非常吻合的时间一致性。推测早白垩世时期大规模岩浆活动以及铁矿床的形成释放大量CO_2温室气体。大气中CO_2温室气体含量急剧增加导致大气环境温度升高,Fe~(2+)变成Fe~(3+)导致了大陆红层的形成;大气中CO_2温室气体含量急剧增加也导致了大气中氧气含量变低,致使后生生物为了适应这种极端环境气候个体趋向于小型化。因此,铁矿床爆发式成矿作用间接地导致了当时气候环境变化和生物演化方向。在当今面临的全球变暖的大环境下,我们更要加深了解和我们当代很相似的晚中生代时期,以便更加主动的应对以后的气候环境变化和生物发展。 相似文献
16.
Palaeoclimatic cycles, global environmental changes and new glacial periods induced by the impact of extraterrestrial bodies 总被引：1，自引：1，他引：0
In terms of Earth-Sun geometry, the Milankovitch theory has successfully explained most of the cyclic palaeoclimatic variations
during the history of the Earth, especially in the Quaternary. In this paper, the authors suggest that the impact of extraterrestrial
bodies on the Earth may be another mechanism to cause palaeoclimatic cycles, global environmental changes and new glacial
periods. Based on geological and geochemical records in the boundary layers produced by six huge Cenozoic bolide-impact events
(65, 34, 15, 2.4, 1.1, 0.73 Ma B.P.), including those at 34, 15, 1.1 and 0.73 Ma B. P. which are represented by four famous
tektite-strewn fields, the process and mechanics of palaeoclimatic cycles and global environmental catastrophes induced by
extraterrestrial impact are discussed in detail. Impact-generated dust, soot and aerosol floating in the stratosphere could
result in short-term (<1 year), rapid drop in temperature immediately after impact. Through self-regulation of the Earth’s
climate system, the temperature at the surface slowly went up within 100a and maintained stable for a long time at 250K. If
there were no other factors leading to the break-down of the newly-established equilibrium, a new glacial pound would be initiated.
Estimating from the thickness of δ13C and δ18O anomalies in sediments across the impact boundary layer and deposition rate, the duration of two stages of the palaeoclimate
cycle in the form of cold weather—greenhouse effect—normal weather was 104 – 105a, respectively. The conclusion deduced from the above model is supported by palaeotemperature change recorded by oxygen isotope
in sediments across the impact boundary layer.
The study was granted by the Scientific and Technological Bureau of Resources and Environment, Chinese Academy of Sciences
(KZ952-J1-031) and the National Natural Science Foundation of China. 相似文献
17.
Karst areas contain valuable groundwater resources and high biodiversity, but are particularly vulnerable to climate change and human impacts. Land-use change is the cause and consequence of global environmental change. The releases of the Climate Change Initiative-Land Cover (CCI-LC) and World Karst Aquifer Map (WOKAM) datasets have made it possible to explore global land-use changes in karst areas. This paper firstly analyses the global karst land-use distribution in 2020, as well as the land-use transition characteristics between 1992 and 2020. Then, two indicators, proportion of land-use change and dominant type of land-use change, are proposed to identify the spatial characteristics of land-use change in global karst areas. Finally, three examples of land-use change in karst areas are analyzed in detail. Land-use types and proportions of the global karst areas from large to small are as follows: forest (31.78%), bare area (27.58%), cropland (19.02%), grassland (10.87%), shrubland (7.21%), wetland (1.67%), ice and snow (1.16%) and urban (0.71%). The total area of global karst land-use change is 1.30 million km2, about 4.85% of global karst surface. The land-use change trend of global karst is dominated by afforestation, supplemented by scattered urbanization and agricultural reclamation. The tropical climate has a higher intensity of land-use change. Regions of agricultural reclamation are highly consistent with the population density. These results reflect the impact of human activities and climate change on land-use changes in global karst areas, and serve as a basis for further research and planning of land resource management.
相似文献18.
典型岩溶水系统碳汇通量估算 总被引：6，自引：1，他引：5
现代岩溶学研究成果表明,碳酸盐岩在全球碳循环中响应极其迅速,水循环过程中的碳汇效应显著。本研究选取广西桂林寨底地下河系统、广西环江大安地下河系统、重庆北碚青木关地下河系统三个典型岩溶地下水系统,利用各系统地下河的流量和HCO3-浓度的监测资料,采用简单化学平衡模式法估算碳汇通量(CO2)。结果显示,寨底地下河系统的单位面积年碳汇通量为68.82 t/(km2.a),大安地下河系统的单位面积年碳汇通量为81.18 t/(km2.a),青木关地下河系统的单位面积年碳汇通量为100.07 t/(km2.a)。分析认为同一个岩溶水系统的结构特征和环境条件基本上是稳定的;地下河的流量和HCO3-浓度是影响岩溶碳汇强度的关键因素,尤其是地下河流量的变化对碳汇强度的影响显著;不同岩溶水系统的碳汇通量不但受水化学条件和地下水动力条件的控制,同时受土地利用变化的影响。该研究对于改进碳循环模型和评价岩溶地质碳汇有重要意义。 相似文献
19.
中国全球变化研究的回顾与展望 总被引：20，自引：0，他引：20
文中简要回顾了中国全球变化研究的历史 ,指出 ,1986— 1990年是中国国际地圈生物圈计划(IGBP)研究的初期 ,围绕IGBP主要科学问题如古环境、气候和海平面变化以及地气相互作用方面开展了有计划、有组织的研究。1991— 1995年中国全球变化研究有了较大发展 ,研究范围扩展到陆地生态系统 ,全球气候变化预测、影响和对策 ,中国生存环境变化以及生物多样性保护和持续利用等领域。1996— 2 0 0 0年其研究进一步与社会可持续发展相结合 ,成功实施了一批以中国科学家领衔的国际研究计划。随着新世纪的来临 ,中国一系列全球变化大型研究计划相继启动 ,使全球变化研究进入了一个新的发展阶段 ,特别是集成研究方法的应用 ,在解决与公众利益密切相关的由环境恶化所带来的一系列重大问题 ,组织全球变化的区域响应以及全球变化适应性等研究方面得到了深化和加强。 相似文献
20.
Multidisciplinary research during the past 25 years has established that the Acraman impact structure in the 1.59 Ga Gawler Range Volcanics on the Gawler Craton, and an ejecta horizon found 240?–?540 km from Acraman in the ??580 Ma Bunyeroo Formation in the Adelaide Fold Belt and Dey Dey Mudstone in the Officer Basin, record a Late Neoproterozoic (Ediacaran) event of major environmental importance. Research since 1995 has verified Acraman as a complex impact structure that has undergone as much as 3?–?5 km of denudation and which originally had a transient cavity up to 40 km in diameter and a final structural rim possibly 85?–?90 km in diameter. The estimated impact energy of 5.2?×?106 Mt (TNT) for Acraman exceeds the threshold of 106 Mt nominally set for global catastrophe, and the impact probably caused a severe perturbation of the Ediacaran environment. The occurrence of the impact at a low palaeolatitude (12.5 +?7.1/???6.1°) may have magnified the environmental effects by perturbing the atmosphere in both hemispheres. These findings are consistent with independent data from the Ediacaran palynology of Australia and from isotope and biomarker chemostratigraphy that the Acraman impact induced major biotic change. Future research should seek geological, isotopic and biological imprints of the Acraman?–?Bunyeroo impact event across Australia and on other continents. 相似文献