第四纪华容隆起构造活动、成因及动力机制

第四纪华容隆起位于江汉—洞庭盆地中部。通过地表观察和第四系钻孔对华容隆起及周缘地貌、第四纪断裂和沉积进行调查,恢复华容隆起构造升降特征与过程,进而探讨华容隆起的成因及其构造活动的动力机制。研究表明:早更新世-中更新世中期华容隆起与周缘凹陷一道沉降,同时前者受周边正断裂控制相对后者有抬升,中更新世晚期一道抬升,晚更新世—全新世构造稳定或弱沉降。第四纪期间华容隆起总体表现为明显的构造沉降。以上表明第四纪华容隆起主要由前第四纪盆—山地貌分异造成,其次与第四纪期间相对周缘凹陷抬升有关。上述地质特征以及区域第四纪地质资料,表明早更新世-中更新世中期江汉—洞庭盆地为断陷盆地,中更新世晚期—全新世转变为坳陷盆地。就华容隆起第四纪构造活动的动力机制进行了探讨并提出:1)早更新世-中更新世中期江汉—洞庭盆地断陷沉降与地幔上隆背景下的深部物质迁出有关。2)中更新世晚期以来的构造活动可能与深部物质蠕移运动的回返以及板块尺度的物质运动和挤压作用有关。3)江汉—洞庭盆地的整体性沉降导致盆地中部的华容隆起以沉降为主;华容隆起特殊的地壳物质结构可能导致深部物质更难向外迁移,使其相对周缘凹陷有抬升。     

Using comprehensive and sequential vegetation classification system to predict the influence of climate change on vegetation succession of alpine grassland of Qinghai Plateau

Distribution of grassland vegetation is highly associated with climatic conditions and varied with climatic change. The tendency of climatic changes on Qinghai Plateau was analyzed, based on the meteorological data from 1961 to 2007 collected from 50 meteorological stations distributed throughout the whole plateau. The vegetation distribution of alpine grassland under past and future climatic change was estimated by using the approach of Comprehensive and Sequential Classification system. Results show that the climate varied greatly before and after 1987. The temperature increased 0.16°C/10a before 1987 and 0.64°C/10a after 1987. The precipitation increased 0.14 mm/10a before 1987 and 3.92 mm/10a after 1987. There were 12 types of grassland vegetation between 1961 and 1987, while there were 11 types of grassland vegetation between 1988 and 2007 on the Plateau. When climatic warming continued with CO₂ doubling in the future, the vegetation of alpine grassland will shrink into nine types.     

Contamination and potential mobility assessment of heavy metals in urban soils of Hangzhou,China: relationship with different land uses

Concentration and distribution of heavy metals (Cd, Cu, Pb and Zn) in urban soils of Hangzhou, China, were measured based on different land uses. The contamination degree of heavy metals was assessed on the basis of pollution index (PI), integrated pollution index (IPI) and geoaccumulation index (I _geo). The 0.1 mol l⁻¹ HCl extraction procedure and gastric juice simulation test (GJST) were used to evaluate the potential mobility and environmental risk of heavy metals in urban soils. The average concentration of Cd, Cu, Pb and Zn in urban soils was measured at 1.2 (with a range of 0.7–4.6), 52.0 (7.4–177.3), 88.2 (15.0–492.1) and 206.9 (19.3–1,249.2) mg kg⁻¹, respectively. The degree of contamination increased in the order of industrial area (IA) > roadside (RS) > residential and commercial areas (RC) > public park and green areas (PG). The PIs for heavy metals indicated that there is a considerable Cd, Cu, Pb and Zn pollution, which originate from traffic and industrial activities. The IPI of these four metals ranged from 1.6 to 11.8 with a mean of 3.5, with the highest IPI in the industrial area. The assessment results of I _geo also supported that urban soil were moderately contaminated with Cd and to a lesser extent also with Cu, Pb and Zn. The IP and I _geo values reveal the pollution degree of heavy metal was the order of Cd > Pb > Zn ≈ Cu. It was shown that mobility and bioavailability of the heavy metals in urban soils increased in the order of Cd > Cu > Zn ≈ Pb. Owing to high mobility of Cd and Cu in the urban soils, further investigations are needed to understand their effect on the urban environment and human health. It is concluded that industrial activities and emissions from vehicles may be the major source of heavy metals in urban contamination. Results of this study present a rough guide about the distribution and potential environmental and health risk of heavy metals in the urban soils.     

High Flare Activity in the Late Declining Phase of Cycle 23

In the declining phase of the current solar cycle (23), a large number of major flares were produced. In this cycle, the monthly sunspot number continuously remained below 100 since October 2002. However, during four epochs since then, flare activity became very high. Compared to this, each of cycles 21 and 22 produced only one epoch of high activity in the declining phase. In the declining phase of cycle 20, similarly to this cycle, there were four epochs of high flare activity. During 2003 and 2004, the distribution of flare sizes measured in GOES classes was much harder (i.e., proportionately more energetic flares) than during the maximum years. Such pronounced hardening of the size distribution was not observed in the previous cycles. It is of theoretical interest to understand why some cycles are very active in the declining phase, and the high level of activity in the declining phase has practical implications for planning solar observations and forecasting space weather.     

东昆仑东段加里东造山旋回侵入岩特征研究

新一轮区调填图所获资料表明,加里东期花岗岩成因类型复杂多样,有岛弧花岗岩、同碰撞花岗岩及少量陆内造山花岗岩等,说明东昆仑东段在加里东时期经历了复杂的洋—陆俯冲、陆陆碰撞的动力学过程。     

DYNAMICS OF SANDY DESERTIFICATION AND ITS DRIVING FORCES IN WESTERN JILIN PROVINCE

By establishing the interpreting elements, and applying supervised classification, the sandy desertification was interpreted and the desertified land areas of the counties in the western Jilin Province in 1986 and in 2000 were obtained. Taking Tongyu and Qian‘an as examples, the natural driving forces and man-made driving forces were analyzed. The paper comes the conclusions that the material sources and the warming and dry climate are the internal causes of potential land descrtification: the irrational human activities, such as destroying forest and reclaiming the grassland, are the external causes of potential land desertification; while more rational human activities, such as planting trees and restoring grassland can reverse the land desertification. Furthermore, the countermeasures and suggestions for the development of agriculture and animal husbandry in the western Jilin Province are put forward.     

Some issues in diagnostics of solar chromospheric magnetic fields with the Mg b2 line

Up to now, exact measurements of chromospheric magnetic fields have not been as successful as those done in the photosphere. We are currently engaging in diagnostics of chromospheric magnetic fields with the Mg b2 line by employing the Multi-Channel Solar Telescope at Huairou Solar Observing Station. Therefore, how to improve accuracy in the measurement is the main issue of our present study. To this end, we first study linear calibration coefficients for longitudinal and transverse components of chromospheric fields, which vary with wavelength, in the case of a weak field assumption. Then the polarization crosstalk introduced by instruments is analyzed in detail with two numerical simulation methods. Comparisons of the po- larization signals between cases with and without correction are presented. The result indicates that polarization accuracy is greatly improved after crosstalk correction.     

珠江源区生态地质环境安全体系构建研究

珠江源区森林生态系统严重退化,湿地遭到破坏,导致石漠化和水土流失严重,水旱灾害频繁。生态地质环境问题制约了该区经济和社会的发展,影响了整个珠江流域。应在加强全民教育的基础上,坚持科技引导,推进制度建设,以退耕还林为切入点,调整产业结构,改善农村能源结构,建立生态地质环境监测网,以此构建一个珠江源区生态地质环境安全体系。