黄河源生态环境变化与成因分析

以７０年代、８０年代和９０年代３个时期的卫星影像资料为基础,结合野外调查,对７０年代以来黄河源区生态环境演变过程及趋势进行了对比分析,并依据时期的气候变化、人为活动强度分析,对该区域生态环境变化的产生原因进行探讨,研究结果表明,与７０年代相比,８０年代和９０年代以高寒沼泽草甸、高寒草罗和高山草原化草甸为代表的主要生态体系均呈明显退化,尤其９０年代中期以来,高寒草原与高寒草甸植被退化剧烈,荒漠化发展     

半导体多相光催化氧化技术在环境保护中的应用研究进展

简单介绍了半导体多相光催化氧化的原理及其在降解污染物和环境保护中的应用和一些新型反应装置, 提出了提高光催化剂催化活性的方法, 讨论了影响光催化氧化反应速率的因素和提高光催化氧化反应速率的方法, 同时对光催化氧化技术今后的研究方向和工作重点提出了一些设想      

海洋粉质粘土在波浪荷载作用后的不排水抗剪强度衰化特性

通过对南海重塑粉质粘土土样的大量动三轴试验结果分析,得到此种土在波浪荷载作用后不捧水抗剪强度衰化同动载作用引起的动应变幅及平均累积孔压之间的相互关系和预估公式;并通过与超固结土样的静三轴剪切试验结果的比较,发现动、静三轴两种试验结果具有很好的吻合关系。建议可用超固结土样的静三轴剪切试验同时结合部分动三轴试验来预估土样在波浪荷载作用后不排水抗剪强度衰化与平均累积孔压之间的关系。     

Use of soil horizons for assessing soil degradation and reconstructing chronology of degradation processes: the case of Mwisanga Catchment, Kondoa, central Tanzania

This paper analyses the use of soil horizons for mapping soil degradation intensity and reconstructing chronology of degradation processes. Through “Pedogenetic Baseline Approach”, the catchment was classified into two categories: the erosional and depositional zones. The eroded soils were reconstructed even in those areas where there had been total soil stripping. Profiles of the undegraded soil provided a reference mark (particularly the argillic B horizon of Lixisols). One specific criterion for determining the degree of soil degradation of a given map unit in the erosional zone was based on whether A or B horizons or both had been eroded. Another criterion for classifying the units in the depositional zone was based on relating the quality of the buried soil with the overlying young soil developed from the colluvium/alluvium. Hence, the study underscores the importance of being able to reconstruct soil properties of pre-eroded soil profiles with the view to determining erosion units. This will eventually help in developing appropriate land use and conservation strategies.     

Perceptions and realities of land degradation in arid Otjimbingwe, Namibia

We examined the perceptions and realities of land degradation in a communal ranching area, Otjimbingwe, in arid Namibia (in south-western Africa). It is commonly perceived that large-scale degradation of Otjimbingwe has occurred due to a mixture of improper pastoral practices and pressures induced by a high human population growth rate. We sought to determine whether the inhabitants perceived land degradation to have taken place and whether their perceptions were consistent with empirical data on environmental quality. Furthermore, we wished to determine whether these pastoralists had management strategies to help them withstand the harsh environmental conditions in which they live. All respondents in our surveys perceived that the environment had become degraded. The claimed source of this degradation, a decline in annual rainfall, is inconsistent with long-term rainfall records (there was neither change nor cyclicity in rainfall over time). There is also little evidence of a decline in plant cover and soil quality in spite of the very high stocking densities. No overall pastoral strategy exists in Otjimbingwe. Options for management are extremely limited due to a variety of external and internal pressures such as a high human population growth rate, high immigration into Otjimbingwe, restricted water availability due to dams constructed upstream, and limited movement opportunities for livestock in drought periods.     

APGIS文件与MAPCAD文件格式转换

本文论述了将MAPGIS文件格式“降级”为MAPCAD文件格式的方法技术 ,并提供了一个实用的QBASIC语言程序。这是对电脑数字制图中文件格式转换的一个完善与补充     

农药在土壤环境中迁移转化规律研究的现状与展望

农药的使用带来了严重的负效应,人们对农药在土壤环境中的迁移转化进行了大量研究.对国内外的有关工作进行了总结回顾并展望了今后的研究方向.     

Permafrost and climatic change in China

The permafrost area in China is about 2.15×10⁶ km², and is generally characterized by altitudinal permafrost. Permafrost in China can be divided into latitudinal and altitudinal types, the latter can be further divided into plateau and alpine permafrost. Altitudinal permafrost also can be divided into five thermal stability types. The permafrost environment has changed significantly since the Late Pleistocene. In northeastern China, the southern limit of permafrost extended to 41–42°N during the last glaciation maximum; in the Holocene megathermal, it retreated northward. The ice wedges and permafrost formed during the Late Pleistocene are still present in the northern part of the Da-Xing'anling Mountains. The inactive ice wedges at Yitulihe indicate a cooling and subsequent permafrost expansion during the Late Pleistocene. The lower limit of altitudinal permafrost in western China has elevated from 800 to 1500 m since the last glaciation maximum. Compared with that in northern Europe and North America, latitudinal permafrost in northeastern China is less sensitive to climatic warming, but altitudinal permafrost, especially permafrost on the Qinghai–Tibet Plateau (QTP), is sensitive to climatic warming. Since the early 20th century, significant permafrost degradation has occurred and is occurring in most permafrost regions in China. Due to the combined influence of climatic warming and increasing anthropogenic activities, substantial retreat of permafrost is expected on the QTP and in northeastern China during the 21st century. Permafrost degradation has and will cast great influence on engineering construction, water resources and environments in the cold regions of China. The wetlands in the cold regions of China emit significant amounts of CH₄ and N₂O to the atmosphere and uptake atmospheric CO₂ at a considerable rate, which might contribute to the global atmospheric carbon budget and feedback to climatic systems. However, uncertainties about permafrost changes, rates of changes and their environmental impacts are still large and call for intensive studying.     

西南喀斯特地区土壤退化过程与机理探讨

自1971年FAO提出“土壤退化”的概念并出版Land Degradation以来,土壤退化问题日益受到人们的关注。随着土壤退化及土壤质量下降对全球食物安全、环境质量及人畜健康影响的日益凸显,土壤退化的研究已成为全球环境变化研究的重要组成部分,尤其是土壤退化的发生过程、机理和演变动态是目前土壤退化研究的前沿和热点问题。中国西南喀斯特山区位于世界三大连片喀斯特发育区之一的东亚片区中心,喀斯特地貌广泛发育,地形条件复杂,生态环境脆弱,土壤侵蚀退化严重。结合西南喀斯特地区的地质地理背景、生态环境特性从生物、化学、物理等角度对西南喀斯特地区土壤退化的过程与机理进行了分析和探讨。西南喀斯特地区的环境脆弱性只是土壤严重侵蚀退化的前提或内因,日益尖锐的人地矛盾导致的植被破坏和退化才是喀斯特土壤侵蚀退化的关键驱动力。西南喀斯特山区土壤退化的过程即是土壤结构劣化、土壤质地和孔隙性变差、土壤水分性能退化、土壤贫瘠化的过程,以上各退化要素形成相互影响相互催化的正反馈循环,加剧土壤的迅速退化。其中,土壤水分和土壤肥力尤其是土壤水分是喀斯特地区土壤退化关键退化因子。     

土地质量发展趋势对我国土地整理研究的启示

人口增长与经济发展对土地资源的压力越来越大,并导致了不同程度的土地退化和耕地的持续减少,人们越来越关注土地资源质量的状况与耕地的保护及管理。土地整理在增加耕地面积、提高土地收益和改善生态环境方面发挥了重要作用。随着土地整理的全面推进,与之密切相关的土地质量问题日益受到人们的重视。借鉴吸收土地质量研究的热点和发展趋势,探索土地整理的土地质量研究体系,以从其根源入手寻求提高土地质量的对策,对促进土地资源管理由数量管护转变到质量和生态管护具有重要的理论与现实意义。文章分析了土地质量的概念与研究现状,提出土地质量的发展趋势主要有：①土地质量指标的综合反映与实际应用日趋紧密;②土地质量变化的过程机理与尺度效应研究不断加强;③土地质量评价中的土地利用格局与生态过程受到重视。根据国际上土地质量的研究及其发展趋势,结合土地整理的内在要求和科学内涵,从土地整理中土地质量指标体系的构建、土地质量评价与调查的技术方法和土地质量变化的过程与机理研究等3个方面探讨了土地整理中土地质量的研究框架。以期对我国土地整理的发展与深化研究有所裨益,促进土地整理事业的良性发展。