Lacustrine sedimentological and geochemical records for the last 170 years of climate and environmental changes in southeastern China

Reconstruction of modern climate and environmental changes in east Asia using inland natural climate archives can provide valuable insights on decadal–multidecadal climate and environmental patterns that are probably related to both natural and anthropogenic forcing. Here we investigated an 89‐cm‐long sediment core (TH1) from Tian Lake, southeastern China, for sedimentological, physical and geochemical parameters in order to understand climate and environmental changes for the latest two centuries. ¹³⁷Cs‐ and ²¹⁰Pb‐based age models show that the fine sand–coarse silt‐dominated core contains ~170 years (c. AD 1842–2011) of continuous sedimentation. Sediments with fine sands, low MS values, high water content, high TOC content and a high C:N ratio from c. AD 1842 to 1897 suggest intense hydrological conditions and strong runoff in the catchment, probably because of a humid climate. From AD 1897 to 1990, sediments with very fine sand and coarse silt, high MS values, low water content and unchanged TOC and C:N ratios indicate normal hydrological conditions and in‐lake algae‐derived organic matter. During this interval, the chemical weathering indicators show stronger weathering conditions compared with sediments deposited during AD 1842–1897, supporting the dominance of weathered surface soil input in the earlier interval and physical erosion dominance in the later period, respectively. Since AD 1990, the continuous decrease of geochemical proxies suggests human‐interacted Earth surface processes in the catchment of Tian Lake. A PCA revealed four dominant geochemical controlling factors – detrital input, trophic status, grain size and early diagenesis –, accounting for 26, 20, 18 and 16% of total variance, respectively. This study for the first time provides lacustrine geochemical evidence for the most recent two centuries of climate and environmental changes in coastal southeastern China, a region that is currently undergoing an inversion of critical zone, i.e. an overturning of its soil profile, owing to swift modernization.     

Strength anisotropy of granular material consisting of perfectly round particles

The strength anisotropy of granular materials deposited under gravity has mostly been attributed to elongated particles' tendency to align long axes along the bedding plane direction. However, recent experiments on near‐spherical glass beads, for which preferred particle alignment is inapplicable, have exhibited surprisingly strong strength anisotropy. This study tests the hypothesis that certain amount of fabric anisotropy caused by the anisotropic stress during deposition under gravity can be locked in a circular‐particle deposit. Such locked‐in fabric anisotropy can withstand isotropic consolidation and leads to significant strength anisotropy. 2D discrete element method simulations of direct shear tests on circular‐particle deposits are conducted in this study, allowing for the monitoring of both stress and fabric. Simulations on both monodispersed and polydispersed circular‐particle samples generated under downward gravitational acceleration exhibit clear anisotropy in shear strength, thereby proving the hypothesis. When using contact normal‐based and void‐based fabric tensors to quantify fabric anisotropy in the material, we find that the intensity of anisotropy is discernible but low prior to shearing and is dependent on the consolidation process and the dispersity of the sample. The fact that samples with very low anisotropy intensity measurements still exhibit fairly strong strength anisotropy suggests that current typical contact normal‐based and void‐based second‐order fabric tensor formulations may not be very effective in reflecting the anisotropic peak shear strength of granular materials. Copyright © 2017 John Wiley & Sons, Ltd.     

Sediment deposition and overland flow hydraulics in simulated vegetative filter strips under varying vegetation covers

Vegetative filter strips (VFSs) can effectively trap sediment in overland flow, but little information is available on its performance in controlling high‐concentration sediment and the runoff hydraulics in VFS. Flume experiments were conducted to investigate the sediment deposition, hydraulics of overland flow and their relationships in simulating VFS under a great range of sediment concentrations with four levels of vegetation cover (bare slope and 4%, 11% and 17%) and two flow rates (15 and 30 L min^?1). Sediment concentrations varied from 30 to 400 kg m^?3 and slope gradient was 9°. Both the deposited sediment load and deposition efficiency in VFS increased as the vegetation cover increased. Sediment concentration had a positive effect on the deposited load but no effect on deposition efficiency. A lower flow rate corresponded to greater deposition efficiency but had little effect on deposited load. Flow velocities decreased as vegetation cover increased. Sediment concentration had a negative effect on the mean velocity but no effect on surface velocity. Hydraulic resistance increased as the vegetation cover and sediment concentration increased. Sediment deposition efficiency had a much more pronounced relationship with overland flow hydraulics compared with deposited load, especially with the mean flow velocity, and there was a power relationship between them. Flow regime also affected the sediment deposition efficiency, and the efficiency was much higher under subcritical than supercritical flow. The results will be useful for the design of VFS and the control of sediment flowing into rivers in areas with serious soil erosion. Copyright © 2015 John Wiley & Sons, Ltd.     

Shiyang River streamflow since AD 1765, reconstructed by tree rings,contains far‐reaching hydro‐climatic signals over and beyond the mid‐latitude Asian continent

In this study, the regional tree‐ring chronology of Picea crassifolia was used to estimate annual (September to August) streamflow of the Shiyang River for the period from AD 1765 to 2010. The linear regression model was stable and could explain 41.5% of the variance for the calibration period of 1955–2005. According to the streamflow reconstruction, dry periods with below average streamflow occurred in AD 1775–1804, 1814–1823, 1831–1856, 1862–1867, 1877–1885, 1905–1910, 1926–1932, 1948–1951, 1960–1963 and 1989–2002. Periods of relatively wet years are identified for AD 1765–1774, 1805–1813, 1824–1830, 1857–1861, 1868–1876, 1886–1904, 1911–1925, 1933–1947, 1952–1959, 1964–1988 and 2003–2010. Comparisons with the precipitation reconstructions from surrounding areas supplied a high degree of confidence in our reconstruction. Our reconstructed streamflow is significantly correlated with sea surface temperature in the eastern equatorial Pacific Ocean and the North Atlantic Ocean. The Multitaper spectral and correlation analyses also suggested that the reconstructed streamflow variation in the Shiyang River could be associated with large‐scale atmospheric‐oceanic variability, such as El Niño‐Southern Oscillation (ENSO). The linkages among the streamflow reconstruction, NAO and ENSO suggest the connection of regional streamflow variations to the Asian monsoon and westerlies circulations. Copyright © 2016 John Wiley & Sons, Ltd.     

京津渤地区的水资源及开发利用中的环境问題

作者初步估算了京津渤地区的水资源,全区水资源总量多年平均为129.67亿立方米,可供水资源为87.13亿立方米.进而讨论水资源开发利用中的几个环境问题:供需矛盾突出、旱涝频繁、地面沉降和水源污染.并就如何合理利用水资源和保护水资源问题提出了建议.     

The dynamo theory of plasma turbulence wave in rotating celestial bodies

The various modes of plasma turbulence waves (including MHD waves) are easily excited under cosmic circumstances. In this paper, if we consider that the celestial bodies rotate, there is a source term generated for the magnetic induced equation by the excited plasma turbulence waves. If we expand the turbulent field in the Fourier series and include rotation velocity, the dynamo equation for turbulent waves is obtained. We have also obtained the solutions of various wave forms corresponding to different rotation velocities and then we significantly discuss the magnetic fields in the Sun, planets, and other celestial bodies.     

Spatial distribution and luminosity function of OH/IR maser sources

In this paper, we study the galactic distribution and luminosity function of OH/IR maser sources. All the selected OH/IR sources have optical or infrared identification. Most of them are associated with late-type (>M5) Mira variables. Their derived density distribution shows a steep peak at a galactocentric distance of r₀-7.5 kpc and decreases rapidly at smaller and larger R₀. The FWHM of the distribution curve is 2.1 kpc. This is similar to the galactic distribution of Mira variables investigated by Glass et al.

We also derive the luminosity function of the identified OH/IR maser sources from their distances, their detection probabilities, and their corrected OH radio peak flux densities. The luminosity function ρ(L) varies as L_OH^−1.79. This is similar to that of unidentified maser sources. The range of luminosity of identified OH/IR sources is approximately from 0.16 Jy · kpc² to 1000 Jy · kpc². It is quite different from that of unidentified OH sources.

Finally, we discuss some differences and relations between identified and unidentified OH/IR maser sources.     

泌阳断陷东南缘深断裂特征及其与油藏分布关系研究

泌阳断陷断块圈闭、滚动背斜及其与砾岩体复合圈闭油藏的形成，与断陷东南缘由多条断层组成的具下道上正呈断阶状的深断裂带的演化有关。本文首先研究了泌阳断陷区域构造背景，对典型地震测线的原始采集资料进行了处理和解释。在此基础上，对断陷东南缘深断裂特征及其与油藏分布关系进行了研究。