中昆仑山阿什库勒盆地地貌与第四纪环境问题

本文论述了阿什库勒盆地的地貌和沉积物的发育等问题。认为:(1)阿什库勒盆地的火山锥至少有11座,1号火山1951年不可能有岩浆喷发,火山泥石流体是不存在的;(2)黄土物质是全新世风积物,戈壁荒漠是其物源区;(3)阿什库勒湖与乌鲁克库勒湖均是火山堰塞湖,前者是18kaB.P.前熔岩流阻塞盆地东部出口而成;后者则是6.5kaB.P.新期火山喷发物拦截阿什库勒湖的部分水域所致。     

盐湖硼氯同位素地球化学研究进展

对与盐湖硼、氯同位素地球化学研究有关的样品中硼、氯的提取、分离纯化 ,硼、氯同位素质谱测定方法以及盐湖卤水、粘土沉积物和蒸发硼酸盐矿物的硼同位素地球化学和盐湖卤水与盐类矿物的氯同位素地球化学研究进展进行了系统总结。所总结的内容代表了世界范围内此领域研究的最新进展 ,其中很大部分内容是中国科学院青海盐湖研究所 VG35 4课题组的研究成果 ,反映了中国科学院青海盐湖研究所在此研究领域的水平。     

云南省重点湖库水体透明度和叶绿素a建议控制指标的探讨

为了控制云南省高原湖泊的富营养化,切实改善湖库的水环境质量,本文在通过调查统计云南省辖区内的典型湖库和国内外相关指标分析评价研究的基础上,提出了云南省重点保护湖库水中透明度、叶绿素a环境控制指标的标准限值:Ⅰ类5．0m、Ⅱ类2．5m、Ⅲ类为1．0m、Ⅳ类和Ⅴ类均为0．5m;叶绿素a为:Ⅰ类2μg／L、Ⅱ类10μg/L、Ⅲ类20μg/L、Ⅳ类40μg／L、Ⅴ类60μg／L.这两项控制指标能与国家标准有较好的衔接,可作为云南省执行GB3838-2002《地面水环境质量标准》时重点湖库的地方补充标准限值．     

南四湖流域1980-2015年土地利用变化及其对流域生境质量的影响

生境质量在一定程度上决定了区域生物多样性维持能力的高低,评估区域生境质量对土地利用/覆被变化的响应,可以间接衡量区域生物多样性维持功能的时空变化,为生物多样性保护提供定量参考.本文以南四湖流域为例,运用InVEST-Habitat Quality模型模拟评价1980-2015年流域生境质量的时空变化,定量评估湖区退耕还湿还林和丘陵地区退耕还林2种政策情景对区域生境质量改善的效果.结果表明：35 a间流域耕地、林地和草地大量转化为建设用地,城市建设用地增长40.23%,湖泊面积减少35.56%,主要转化为渔业坑塘;南四湖流域整体生境质量处于较低水平,近35 a来快速发展的工农业生产和不断扩张的城市用地使得流域生境质量呈现降低趋势,当前平均生境质量为历年最低（0.20）.环境保护力度和人类活动剧烈程度的差异导致生境质量在空间上呈现出西部平原区（0.19） < 东部丘陵山区（0.44） < 南四湖湖区（0.81）的分布特征.近35 a来生境稀有度（即生境保存完整性指数）较高的区域主要是湖区主体和流域东部丘陵山区,但部分边缘湖区生境稀有度指数却极低,受人类活动干扰剧烈,主要原因在于沿湖渔业养殖和农业活动.定量评估湖区退耕还林还湿和流域丘陵旱地退耕还林2种政策情景对生境质量的改善效果,结果表明湖区退耕还湿还林能使湖区生境质量上升9.21%,而丘陵旱地退耕还林可使流域平均生境质量提高16.75%.     

基于RS和GIS的城镇化与南四湖生态易损性关系

城镇建设与扩张是人类社会经济发展到一定阶段的必然过程,但城镇发展会对区域的生态系统产生不可忽视的影响,在脆弱敏感的湿地区域表现尤为突出。该文以山东省南四湖以及周边3个县域为研究对象,以遥感数据为基础,利用GIS技术,分析研究区1987—2010年间的地表覆被变化和生态易损性变化,并通过卫星遥感影像分析城镇景观的变化,探讨城镇化与区域生态易损性的关系。结果表明:1987—2010年间,城镇面积的增长占所有景观有效变化的60%以上,但区域内生态损失度变化最大的景观却是水域和绿地,生态易损性变化最明显的区域是南四湖湖滨地带。     

高原湖泊和平原湖泊遥感动态监测的对比分析——以洱海和鄱阳湖为例

湖泊及其动态变化在区域生态环境保护中占据极其重要的作用,监测并对比分析不同类型的湖泊动态变化对区域生态环境保护意义重大。应用Landsat TM遥感数据,基于ENVI遥感图像处理软件和Arc GIS空间分析软件,分别以洱海和潘阳湖为例,利用单波段阈值法、波段组合法等方法提取了湖泊水体现状信息;通过波段运算、波段替换等方法提取了湖泊的动态变化信息;对比分析了高原湖泊和平原湖泊两类湖泊动态变化信息提取监测效果。研究表明:应用波段组合法提取湖泊水体信息有较高的准确度,而缨帽变换法提取湖泊水体信息准确度偏低;受湖泊界限标准不统一、季节性水域变化,湖泊周边地理环境等影响,平原湖泊水体分布状况较高原湖泊水体分布状况复杂,多种遥感图像处理方法结合使用更适用于平原湖泊遥感动态监测。     

Wave grouping characteristics in nearshore Great Lakes

The recently advanced approach of wavelet transform is applied to the analysis of wave data measured in the nearshore areas of the Great Lakes. The conventional spectrum analysis of wave time series in the frequency domain can be readily generalized to the frequency and time domain using the wavelet transform. The traditional Fourier transform approach has not been able to directly assess the time localized nature of wave groups. With the application of wavelet transformation, the relatively unexplored wave grouping characteristics come to light as the predominant feature of wave processes.     

乌梁素海冰封期分层与混合特征及对氧代谢速率的影响

为探究寒旱区浅湖冰封期分层动态与其对湖泊新陈代谢速率的影响,于2016-2019年对乌梁素海气象与冰雪条件、冰下水体环境开展原位观测,分析水温和溶解氧变化特征、冰下混合层的出现与发展动态及其对代谢速率的影响.结果显示:观测期内乌梁素海整体水温较高(可接近10℃),冻结期水温结构主要由稳定的上部逆温层和下部弱逆温层构成,...     

Diatom-inferred lake level from near-shore cores in a drainage lake from the Experimental Lakes Area,northwestern Ontario,Canada

We inferred late Holocene lake-level changes from a suite of near-shore gravity cores collected in Lake 239 (Rawson Lake), a headwater lake in the Experimental Lakes Area, northwestern Ontario. Results were reproduced across all cores. A gravity core from the deep central basin was very similar to the near-shore cores with respect to trends in the percent abundance of the dominant diatom taxon, Cylcotella stelligera. The central basin, however, does not provide a sensitive site for reconstruction of lake-level changes because of the insensitivity of the diatom model at very high percentages of C. stelligera and other planktonic taxa. Quantitative estimates of lake level are based on a diatom-inferred depth model that was developed from surficial sediments collected along several depth transects in Lake 239. The lake-level reconstructions during the past ~3,000 years indicate that lake depth varied on average by ±2 m from present-day conditions, with maximum rises of ~3–4 m and maximum declines of ~3.5–5 m. The diatom-inferred depth record indicates several periods of persistent low levels during the nineteenth century, from ~900 to 1100 AD, and for extended periods prior to ~1,500 years ago. Periods of inferred high lake levels occurred from ~500 to 900 AD and ~1100 to 1650 AD. Our findings suggest that near-shore sediments from small drainage lakes in humid climates can be used to assess long-term fluctuations in lake level and water availability.     

The sedimentation history of Lake Huron and Georgian Bay: results from analysis of seismic reflection profiles

An extensive seismic reflection profile survey conducted concurrently with a sediment coring program in northern Lake Huron, Georgian Bay, and the North Channel revealed a detailed Holocene lake level history. Seven acoustic sequences were identified in the seismic stratigraphy, and these sequences show great variation in both the character and the spatial distribution of sediment deposition through time. The depths to the acoustically-defined sequence boundaries were digitized from the analog seismic records and merged with Loran-C navigation records from the cruise, yielding a three-dimensional record of the location of each sequence boundary. Thicknesses of the sequences were calculated from these depths, and a minimum-curvature spline surface was fit to the thickness data. These surfaces were used to construct isopach maps which show the trends in thickness of sediment accumulation throughout the lake basins for each of the sequences. ¹⁴C-AMS dates of materials from the cores fixed the dates of the sediment sequence boundaries, allowing sediment accumulation rates to be calculated. The distribution of sedimentation in the basins as shown on the isopach maps allowed assessment of sediment transport and water flow through the basins over time, which when combined with the work of Lewis & Anderson (1989), provides a detailed record of the transport and drainage of water through these basins as the Wisconsinan ice sheet retreated and isostatic rebound opened and closed outlets. Reversals of flow direction through the Straits of Mackinac and through the channels connecting Lake Huron and Georgian Bay and the North Channel are indicated by changes in sediment thickness distributions.