格尔木河水质现状及生态风险评估

为了解经济迅速发展背景下格尔木河流域水体中痕量元素分布、水环境质量现状和生态风险,对格尔木河9个采样点水样21种痕量元素的分布及相关性进行了分析,以Cu、Zn、Hg、Cd、Cr和Pb为目标重金属,评估了格尔木河水质现状及生态风险。结果表明:重金属Pb浓度在所有水样中均低于检出限,其它痕量元素浓度在0.001(Cd)～6297.013(Sr)μg·L~(-1)范围变化。根据相关性分析,推测格尔木河水体中Li、Sc、Ti、V、Cu、Ge、Rb、Sr、Mo、Cd来源可能相同。采样点水样6种重金属浓度均达到地表水环境质量I类的标准。采用5种方法评价了格尔木河水质现状,研究区水质处于无污染的理想状态。格尔木河重金属引发的潜在生态风险处于低风险水平(生态风险指数变化范围为0.35～0.68)。     

基于电化学法的铬盐清洁生产工艺研究

现有铬盐生产技术阻碍了铬盐行业的清洁化发展,研发新型铬盐生产技术实属必要。中国科学院青海盐湖研究所自行研发出一套以电化学法为基础的铬盐清洁生产工艺,涵盖三条大工艺和四种母系铬盐产品。包括氢氧化钠溶液中电化学氧化铬铁制备铬酸钠联产三氧化二铬和三氧化二铁工艺,离子膜电解法从铬酸钠合成重铬酸钠工艺,以及离子膜电解法从重铬酸钠合成铬酸酐工艺。相比现有铬盐生产技术,该技术的优势主要体现在以下五点:温和化、去渣化、高值化、自动化和高效化。目前相关研发工作业已走出实验室,走过产业化中间试验,正向产业化示范线迈进。     

Reverse-Time Migration of Converted S-Waves of Varying Densities

Ocean-Bottom Node(OBN) acquisitions provide both non-converted and converted reflection energy. There is a clear advantage to independently imaging both P-and S-waves, as they provide more information collectively than either does alone. In many conventional converted-wave pre-stack migration algorithms, density is treated as a constant, which is not the real-life case on earth. S-wave velocity and density information is crucial for hydrocarbon detection because it helps in the identification of porefilling fluids. In this paper, we focused on the effect of density on imaging, and developed a method of reverse-time migration(RTM) on converted s-waves of varying densities(VD-RTMCS). Phase correction was required prior to pre-stack migration to avoid constructive interference between data from adjacent sources. Synthetic data examples showed that when density variations were included, image profiles showed advantages in signal-to-noise ratio, vertical resolution and imaging of complex structures.     

Spatial variation of the relationship between transport accessibility and the level of economic development in Qinghai-Tibet Plateau,China

As an important component of China' transportation systems, for a long time, the insufficient performance of transport in QinghaiTibet Plateau(QTP) was a bottleneck restricting the economic growth and social development in this area. Nevertheless, the implementation of the western development strategy has accelerated the preliminary construction of comprehensive transport network since 2000. Due to the large area and significant geographical heterogeneity, there is a growing need to understand the relationship between transportation and economic development based on the perspective of spatial difference. By using GIS-based raster analysis and Geographically Weighted Regression(GWR) model, we investigated the spatial-temporal distribution of highway, railway and airport accessibility, respectively, and estimated the correlation and heterogeneity between transport accessibility and the level of economic development. Results revealed that:(1) Transport accessibility in the QTP improved by 53.38% in the past 15 years, which is specifically embodied in the improvement of both highway and railway.(2) Accessibility presented prominent differentiation in the space, increasing from west to east and reducing with the rise of elevation, specifically, the best accessibility area of the highway is below 4000 m above sea level, while the area with an altitude of over 4000 m has the lowest aviation time cost.(3) In general, the long weighted average time cost to critical transport facilities posed significantly negative effect on county economic growth in QTP, more positively, the adverse effect gradually weakened over time.(4) Obvious heterogeneity exists at the influence of different transport accessibility factors on the level of economic development, reflecting both in the horizontal space and altitudinal belt. Therefore, region-specific policies should be addressed for the sustainable development of transport facilities as well as economy in the west mountain areas.     

Degradation induces changes in the soil C:N:P stoichiometry of alpine steppe on the Tibetan Plateau

Due to the Tibetan Plateau's unique high altitude and low temperature climate conditions,the region's alpine steppe ecosystem is highly fragile and is suffering from severe degradation under the stress of increasing population,overgrazing,and climate change.The soil stoichiometry,a crucial part of ecological stoichiometry,provides a fundamental approach for understanding ecosystem processes by examining the relative proportions and balance of the three elements.Understanding the impact of degradation on the soil stoichiometry is vital for conservation and management in the alpine steppe on the Tibetan Plateau.This study aims to examine the response of soil stoichiometry to degradation and explore the underlying biotic and abiotic mechanisms in the alpine steppe.We conducted a field survey in a sequent degraded alpine steppe with seven levels inNorthern Tibet.The plant species,aboveground biomass,and physical and chemical soil properties such as the moisture content,temperature,pH,compactness,total carbon(C),total nitrogen(N),and total phosphorus(P)were measured and recorded.The results showed that the contents of soil C/N,C/P,and N/P consistently decreased along intensifying degradation gradients.Using regression analysis and a structural equation model(SEM),we found that the C/N,C/P,and N/P ratios were positively affected by the soil compactness,soil moisture content and species richness of graminoids but negatively affected by soil pH and the proportion of aboveground biomass of forbs.The soil temperature had a negative effect on the C/N ratio but showed positive effect on the C/P and N/P ratios.The current study shows that degradation-induced changes in abiotic and biotic conditions such as soil warming and drying,which accelerated the soil organic carbon mineralization,as well as the increase in the proportion of forbs,whichwere difficult to decompose and input less organic carbon into soil,resulted in the decreases in soil C/N,C/P,and N/P contents to a great extent.Our results provide a sound basis for sustainable conservation and management of the alpine steppe.     

Mechanism of toppling and deformation in hard rock slope: a case of bank slope of Hydropower Station,Qinghai Province,China

Recently, various toppling slopes have emerged with the development of hydropower projects in the western mountainous regions of China. The slope on the right bank of the Laxiwa Hydropower Station, located on the mainstream of the Yellow River in the Qinghai Province of Northwest China, is a typical hard rock slope. Further, its deformation characteristics are different from those of common natural hard rock toppling. Because this slope is located close to the dam of the hydropower station, its deformation mechanism has a practical significance. Based on detailed geological engineering surveys, four stages of deformation have been identified using discrete element numerical software and geological engineering analysis methods, including toppling creep, initial toppling deformation, intensified toppling deformation, and current slope formation. The spatial and time-related deformation of this site also exhibited four stages, including initial toppling, toppling development, intensification of toppling, and disintegration and collapse. Subsequently, the mechanism of toppling and deformation of the bank slope were studied. The results of this study exhibit important reference value for developing the prevention–control design of toppling and for ensuring operational safety in the hydropower reservoir area.     

基于空间面板计量模型的雾霾对中国城市旅游流影响的空间效应

以中国342个市域单元为研究对象,借助双变量LISA模型、空间面板杜宾模型等方法,探究了1998-2016年雾霾与中国城市旅游流的空间关联特征,分析了雾霾对旅游流的影响及其空间溢出效应。结果表明,在中国雾霾PM_2.5与城市旅游流有东高西低的分布特点,在胡焕庸线两侧的空间分布呈现出与地形和城市发展等因素的空间耦合性;雾霾与城市旅游流（含国内和入境旅游流）均表现出显著的空间集聚和空间依赖特征,雾霾污染对旅游流产生明显的影响并形成相应的空间效应;雾霾对旅游流的抑制区域在不断扩大,H-L型城市数量的增加、L-H型集聚区的片状扩张和华北、华中地区的L-H型集聚的“空心化”现象均表明旅游流具有低雾霾指向性;雾霾污染与旅游流的倒“U”型曲线关系表明经典的EKC假说对中国城市旅游流同样适用,且雾霾污染的显著负向影响主要存在于入境旅游方面;雾霾和旅游流均具有明显的正向空间溢出效应,将雾霾治理同经济发展、对外联系、旅游开发、生态保护和交通建设等因素结合起来进行综合治理,才能为旅游发展创造美好的环境,实现国际、国内旅游健康、协调、可持续的高质量发展。     

2003-2017年北京市地表热力景观时空分异特征及演变规律

利用2003-2017年MODIS地表温度数据,分别从数量、形状和结构角度揭示北京市不同季相和昼夜间地表热力景观时空分异特征,并进一步通过热力等级变化图谱及质心迁移轨迹揭示城市热力景观空间演变规律,探究热力景观等级转换生态过程。结论如下：① 城市地表热力景观季节和昼夜空间特征差异显著;② 中温区在城市热环境中占主导地位。白天中温区是最不稳定的热力景观等级;夜间次低温区和次高温区不稳定性增加;③ 地表热力景观等级变化以稳定型占主,反复变化型和前期变化型次之。地表热力景观等级通常呈现逐级递增或递减规律,山区呈现逐级降温趋势,北部城郊—山地交错地带表现出次低温和中温的反复转向,南部地区有一定的升温趋势;④ 2003-2017年高温区面积增大且质心向城市中心集中,低温区质心向城市外围扩散。生态涵养发展区对北京市地表热力景观质心迁移贡献率最高。热力景观时空分异特征及演变规律可为有效缓解城市热岛效应提供管理决策支持。     

1960-2015年青海三江源地区降水时空特征

青海三江源地区是中国生态系统最为敏感和脆弱的地区,其降水特别是生长季降水的波动,是影响本区及江河中下游水资源安全、生态系统可持续发展的关键因素。综合线性趋势、Mann-Kendall检验、BG分割算法、R/S、EEMD等多方法细致辨识了1960-2015年研究区降水量序列的时空特征。结果显示：① 三江源降水量总体呈现弱增趋势,21世纪以来降水量显著增加,各子源区气候倾向率不尽相同;② 年、季降水量自东南向西北递减,澜沧江源区夏季降水和黄河源区秋季降水呈弱减趋势,雨量弱减区在空间上呈斑块状分布;③ 年、季降水量年代际变化和增湿率的空间差异较明显,春夏季降水气候倾向率与经纬度、海拔的复相关性显著高于冬季;④ 20世纪90年代中后期,各子源区降水总体显现增强信号,并于2002年前后发生突变;⑤ 年际和低值年代际显著周期是造成降水量变动的主要因素;⑥ 除澜沧江源区夏季降水趋于减少外,其他年、季降水量变化呈现增幅不一的转湿趋势;⑦ 横向比较各子源区可见,长江源区降水变化更能表征高原气候变化。研究结果显示,研究区降水时空序列变化具有明显的区域和季节差异性特征,与以往类似研究存在些许差异,可见为有效提高气候序列演变过程及突变诊断的准确性,仍需进一步融合多方法实施集成分析。