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391.
国外土壤风蚀的研究历史与特点 总被引:14,自引:7,他引:14
根据国外土壤风蚀的发展和研究成果,本文将土壤风蚀研究历史划分为四个阶段。第一阶段大致在本世纪二十年代以前,为土壤风蚀研究的萌芽阶段,以土壤风蚀现象的认识和描述为主;本世纪三十年代到六十年代中期,为土壤风蚀科学研究大发展阶段,实现了由定性描述到定量研究的突破;六十年代中期到八十年代中期,为土壤风蚀研究理论的检验与完善阶段。自本世纪八十年代中期之后,土壤风蚀研究进入了全球性研究阶段。 相似文献
392.
大气气溶胶吸湿性质国内外研究进展 总被引:14,自引:1,他引:13
大气气溶胶的吸湿性质是联系气溶胶微物理、化学参数的桥梁和纽带之一,更是气溶胶基本光学性质的决定性参数之一,因此研究气溶胶吸湿性质在整个大气气溶胶科学研究中处于基础地位。对气溶胶吸湿性质的研究意义、研究方法与技术、主要研究结论做了系统回顾,并指出该研究领域存在的不足并对未来的研究方向做出展望。众多研究者从实验室分析、外场实验、数值模拟3个方面来研究颗粒物的吸湿性质,研究表明大气气溶胶的吸湿性质对研究大气能见度、大气辐射强迫具有重要影响。国内对大气气溶胶吸湿性质的研究数量偏少,研究方法单一,在国内广泛开展气溶胶吸湿性质的研究非常必要。 相似文献
393.
The Field Research Center (FRC) including five contaminated sites and a clean background area was established in Oak Ridge,
Tennessee, as a part of the U.S. Department of Energy’s Natural and Accelerated Bioremediation Research (NABIR) program. This
study investigates the mineralogy and mineralogical pathways of saprolite at the FRC background site to provide a fundamental
basis for the remediation strategy for contaminated sites. The background site is underlain interbedded shales, siltstones,
and limestones with nearly identical characteristics to the contaminated sites. Bulk samples of saprolite were collected by
hand picking approximately at 1 m depth (C horizon) from the soil surface. The soil pH of 4.3 and cation exchange capacity
(CEC) of 10.5 cmol/kg measured are in the range of the typical shallow depth saprolite layer in this area. Total Fe by citrate-bicarbonate-dithionate
(CBD) and ammonium oxalate extractable (amorphous) were 17.6 and 0.61 g/kg, respectively. Total Mn extracted by NH2OH·HCl was 0.17 g/kg. X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses indicate that quartz, illite,
and microcline (K-feldspar) are the dominant minerals, occupying 95% of mineral composition. The saprolite samples analyzed
have shown characteristics of oxic conditions overall, and the degrees of weathering for three sampling locations were various,
most for S1 and least for S3, likely influenced either by the flow channels developed through saprolite or by seasonal fluctuation
of the groundwater table. The source of the manganese oxide that observed from the site is likely to be Mn-rich muscovite
in the shale or Mn-rich biotite in the blackish band in the limestone. The results such as abundant Mn and Fe contents identified
encouraging prospects for conducting remediation projects in FRC sites. 相似文献
394.
The thermoelastic parameters of Ca3Cr2Si3O12 uvarovite garnet were examined in situ at high pressure up to 13 GPa and high temperature up to 1100 K by synchrotron radiation energy-dispersive X-ray diffraction within a 6-6-type multi-anvil press apparatus. A least-square fitting of room T data to a third-order Birch–Murnaghan (BM3) EoS yielded K0 = 164.2 ± 0.7 GPa, V0 = 1735.9 ± 0.3 Å3 (K’0 fixed to 4.0). P–V–T data were fitted simultaneously by a modified HT-BM3 EoS, which gave the isothermal bulk modulus K0 = 163.6 ± 2.6 GPa, K’0 = 4.1 ± 0.5, its temperature derivative (?K0,T/?T)P = –0.014 ± 0.002 GPa K?1, and the thermal expansion coefficients a0 = 2.32 ± 0.13 ×10?5 K?1 and b0 = 2.13 ± 2.18 ×10?9 K?2 (K’0 fixed to 4.0). Our results showed that the Cr3+ enrichment in natural systems likely increases the density of ugrandite garnets, resulting in a substantial increase of mantle garnet densities in regions where Cr-rich spinel releases chromium through a metasomatic reaction. 相似文献
395.
Saskia Erdmann Rucheng Wang Fangfang Huang Bruno Scaillet Kai Zhao Hongsheng Liu Yan Chen Michel Faure 《Comptes Rendus Geoscience》2019,351(8):551-561
Constraining crystallization pressure and thus intrusion depth of granites in various geodynamic settings remains challenging, yet important to further our understanding of magma system and crustal evolution. We propose that titanite, which is a common accessory in metaluminous and weakly peraluminous granites, can be used as a barometer if it crystallized in magmatic, near-solidus conditions and in equilibrium with amphibole, plagioclase, K-feldspar, quartz, biotite, and magnetite ± ilmenite. Titanite Al2O3 increases with pressure (P) according to: P (in MPa) = 101.66 × Al2O3 in titanite (in wt%) + 59.013 (R2 = 0.83) with estimated uncertainties of ~±60 to ~±100 MPa for crystallization between ~150 and 400 MPa. We highlight that the current calibration dataset is limited, and that systematic experimental studies are needed to rigorously quantify the relation. The most important use of this empirical barometer will be for rocks in which amphibole is present but significantly altered, or in combination with amphibole barometry, as titanite can be easily dated by LA-ICP-MS. 相似文献
396.
表层岩溶带及其水循环的研究进展与发展方向 总被引:19,自引:7,他引:12
表层岩溶带是现代岩溶学一个很重要的概念,表层岩溶水对于解决西南岩溶山区居民的干旱缺水问题具有重要意义。近年来,不但揭示了表层岩溶带的特征、形成的动力条件机理及其含水层特征、开展了表层岩溶的自动化监测、研究了表层岩溶水与生态环境的相关性,还对西南表层岩溶水资源进行了初步评价。今后一段时期内表层岩溶水的主要研究方向是开展表层岩溶水与管道水的耦合关系研究、生态环境调蓄表层岩溶水的功能研究及表层岩溶水资源评价。 相似文献
397.
Six years of quasi-meridional crossings of the Antarctic Ocean from Antarctica to southern Africa between 4°W and 16°E longitude are analyzed, with emphasis on temperature and salinity distributions. Data are sparse, but (particularly in the southern part of the sections) adequate to show significant variations in the latitude/depth distributions and T-S characteristics of the principal water masses. In particular, the cross-sectional area occupied by Warm Deep Water (Weddell Deep Water) dropped by about one third in 1968. Positions of major features associated with the Antarctic Divergence varied by up to 5 degrees of latitude. The surface temperature gradient often observed at the Antarctic Divergence appears to be the surface expression of a shallow (possibly seasonal) thermocline which sometimes slopes upward to intersect the sea surface. There is a clear need for more closely spaced and consistently planned data from Antarctic cruises, particularly those on which physical oceanography is an ancillary activity. As a bare minimum, much more closely spaced surface temperature (and if possible also salinity) measurements would be useful. 相似文献
398.
This paper analyses the experiences acquired through several research projects on the history of water and sanitation services by two multidisciplinary teams. Challenges have been faced in identifying feasible objectives, realistic resources, time allocations and unexpected external factors. Water history can preserve cultural heritage, promote reputation management, record vanishing knowledge, and discover new facts. 相似文献
399.
多环芳烃来源与分布及迁移规律研究概述 总被引:14,自引:0,他引:14
概述了多环芳烃的来源,就近年来多环芳烃(PAHs)在大气、土壤、植被和水体沉积物中分布与迁移规律的研究成果进行了综述,并展望了未来PAHs研究方向。 相似文献
400.