Changes in the area of inland lakes in arid regions of central Asia during the past 30 years

Inland lakes are major surface water resource in arid regions of Central Asia. The area changes in these lakes have been proved to be the results of regional climate changes and recent human activities. This study aimed at investigating the area variations of the nine major lakes in Central Asia over the last 30 years. Firstly, multi-temporal Landsat imagery in 1975, 1990, 1999, and 2007 were used to delineate lake extents automatically based on Normalized Difference Water Index (NDWI) threshold segmentation, then lake area variations were detailed in three decades and the mechanism of these changes was analyzed with meteorological data and hydrological data. The results indicated that the total surface areas of these nine lakes had decreased from 91,402.06 km² to 46,049.23 km² during 1975?C2007, accounting for 49.62% of their original area of 1975. Tail-end lakes in flat areas had shrunk dramatically as they were induced by both climate changes and human impacts, while alpine lakes remained relatively stable due to the small precipitation variations. With different water usage of river outlets, the variations of open lakes were more flexible than those of other two types. According to comprehensive analyses, different types of inland lakes presented different trends of area changes under the background of global warming effects in Central Asia, which showed that the increased human activities had broken the balance of water cycles in this region.     

NDVI indicated characteristics of vegetation cover change in China��s metropolises over the last three decades

How urban vegetation was influenced by three decades of intensive urbanization in China is of great interest but rarely studied. In this paper, we used satellite derived Normalized Difference Vegetation Index (NDVI) and socioeconomic data to evaluate effects of urbanization on vegetation cover in China??s 117 metropolises over the last three decades. Our results suggest that current urbanization has caused deterioration of urban vegetation across most cities in China, particularly in East China. At the national scale, average urban area NDVI (NDVI_u) significantly decreased during the last three decades (P?<?0.01), and two distinct periods with different trends can be identified, 1982?C1990 and 1990?C2006. NDVI_u did not show statistically significant trend before 1990 but decrease remarkably after 1990 (P?<?0.01). Different regions also showed difference in the timing of NDVI_u turning point. The year when NDVI_u started to decline significantly for Central China and East China was 1987 and 1990, respectively, while NDVI_u in West China remained relatively constant until 1998. NDVI_u changes in the Yangtze River Delta and the Pearl River Delta, two regions which has been undergoing the most rapid urbanization in China, also show different characteristics. The Pearl River Delta experienced a rapid decline in NDVI_u from the early 1980s to the mid-1990s; while in the Yangtze River Delta, NDVI_u did not decline significantly until the early 1990s. Such different patterns of NDVI_u changes are closely linked with policy-oriented difference in urbanization dynamics of these regions, which highlights the importance of implementing a sustainable urban development policy.     

First observation of different diffusion coefficients for two conformers in a neat liquid

 Self-diffusion coefficients were studied for the highly polar liquid N-methylformamide at pressures up to 200 MPa between the melting pressure curves and 420 K by the spin-echo method. N-Methylformamide exists as a mixture of two conformers in the neat liquid. These conformers have large differences at lower temperatures in their dynamic and structural properties. The self-diffusion coefficient of the cis-conformer being 17% lower than that of the trans-conformer at the same T and p. This is the first observation of such an effect. The experimental study is supported by Monte Carlo (MC) calculations which show that the first neighbors around a cis conformer are arranged differently than in an all trans liquid. The difference leads in the simulations to a much lower dielectric constant for the trans-cis mixture and might also explain the retardation of diffusion for the cis conformer. Received: 15 November 1999 / Accepted in revised form: 28 February 2000     

外生菌根对欧洲赤松苗(Pinussylvestris)Cu、Zn积累和分配的影响

通过测定２种不同施锌和施铜水平下苗木和离体菌丝中铜锌含量研究了接种外生菌根（Ｓｕｉｌｌｕｓｂｏｖｉｎｕｓ）对欧洲赤松（Ｐｉ－ｎｕｓｓｙｌｖｅｓｔｒｉｓ）苗生长和微量元素积累和分配的影响． 结果表明菌丝的侵染增加了苗木生长同时也增加了植物体内重金属的含量．然而菌根植物中的重金属大部分分布在根部在铜处理中菌根植物地下部分的铜含量是无菌根植物的２．６倍在锌处理中锌是无菌根植物的１．３ 倍． 说明菌丝侵染使植物将过量的重金属滞留在根部从而增加了植物对过量重金属的抗性．通过进一步测定培养在过量重金属中的离体菌丝的重金属含量结果显示随着外界重金属浓度的增加菌丝分泌物内重金属含量比菌丝内重金属含量增加快说明滞留在根部的重金属可能并没有进入根系而是以某种形态滞留在菌丝分泌物和菌丝内．     

应用DNDC模型估算区域农业土壤N2O释放通量和释放量——以贵州省为例

根据ＤＮＤＣ模型能较好地拟合贵州省玉米－油菜轮作田、大豆－冬小麦轮作田和休耕地的N₂O释放通量及其影响因子的季节变化模式,采用ＤＮＤＣ模型估算了以县为空间分辨尺度的贵州省农业土壤１９９５ 年N₂O释放通量和释放量;定量评估了施肥和耕作农业活动对该地区N₂O释放量的贡献． 本工作将为准确估算我国农业土壤的N₂O释放量和提出科学的减排措施提供研究基础和方法参考．     

柴达木盆地水资源承载力研究

提出了以期望人口为核心的水资源承载力指标体系,并应用于柴达木盆地水资源承载力的实际研究． 用柴达木盆地水资源承载力系统动力学仿真模型（ＳＤＳＭＷＲＳＣＣＢ）计算了人口等承载力指标的预测值,把期望值和预测值进行了深入分析比较,推断出柴达木盆地水资源承载力．     

农田生态系统管理与非点源污染控制

随着化肥和农药大量使用,农业非点源污染已经成为全球水污染的主要来源．不同农田管理措施,如免耕、少耕、传统耕作方式,化肥和农药的使用量、使用方式以及使用季节,灌溉的不同方式,如沟灌、淹灌和喷灌等与农业非点源污染形成之间均有密切的关系,通过农田景观设计来控制非点源污染,可望在控制农业非点源污染方面起到指导作用．     

厂房、办公楼租赁、转让的环境保护问题

随着市场经济的迅速发展，大量厂房办公楼租赁、转让产生新类型的环境问题。由于其具有突发性、隐蔽性、难追究、治理难的特点，因而应将合同(契约)等重要经济环节纳入环境约束，加强管理，切实实施。     

活性炭水处理技术应用

本文综述了活性炭水处理的特点，主要影响因素，活性炭的再生及活性炭吸附法在水处理中的应用，从而论证了活性炭吸附法应用于水处理的可行性和有效性。     

昆明市废弃食用油脂污染及其管理

本文通过对昆明市废弃食用油的去向对环境污染和人体危害的调查，提出了加强管理的措施及处理工艺。以达到对其有效治理和合理运用的目的。