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1.
黄河流域是中国重要的生态屏障和经济地带,上中下游面临着不同生态环境问题,水在生态环境问题的形成演化过程中起着重要作用。本文从黄河流域地下水动态特征、地下水资源的数量、质量及开发利用等方面,分析了黄河流域地下水资源及饮水安全状况。黄河流域年度地下水资源量393.55亿m~3,银川平原、河套平原等7处主要平原(盆地)地下水资源量为81.91亿m~3,占比超过20%;黄河流域地下水质量以Ⅰ~Ⅳ类为主,劣质地下水主要受总硬度、硫酸盐、铁、溶解性总固体等天然原生组分影响,砷、氟、硒、碘等原生组分超标是流域部分地区地下水饮水安全的主要威胁;2020年与2019年同期相比,黄河流域地下水位呈上游稳定、中游局部上升、下游下降的态势,主要地下水降落漏斗形态基本稳定。针对黄河源区、宁蒙河套平原等重点区段,分析了存在的主要生态环境问题,提出了全面开展流域水文地质与水资源调查评价,深入开展黄河流域及重点地区水平衡分析等工作建议。 相似文献
2.
Sherri L. Johnson Don Henshaw Greg Downing Steve Wondzell Mark Schulze Adam Kennedy Greg Cohn Stephanie A. Schmidt Julia A. Jones 《水文研究》2021,35(5):e14187
The H. J. Andrews Experimental Forest (HJA) encompasses the 6400 ha Lookout Creek watershed in western Oregon, USA. Hydrologic, chemistry and precipitation data have been collected, curated, and archived for up to 70 years. The HJA was established in 1948 to study the effects of harvest of old-growth conifer forest and logging-road construction on water quality, quantity and vegetation succession. Over time, research questions have expanded to include terrestrial and aquatic species, communities and ecosystem dynamics. There are nine small experimental watersheds and 10 gaging stations in the HJA, including both reference and experimentally treated watersheds. Gaged watershed areas range from 8.5 to 6242 ha. All gaging stations record stage height, water conductivity, water temperature and above-stream air temperature. At nine of the gage sites, flow-proportional water samples are collected and composited over 3-week intervals for chemical analysis. Analysis of stream and precipitation chemistry began in 1968. Analytes include dissolved and particulate species of nitrogen and phosphorus, dissolved organic carbon, pH, specific conductance, suspended sediment, alkalinity, and major cations and anions. Supporting climate measurements began in the 1950s in association with the first small watershed experiments. Over time, and following the initiation of the Long Term Ecological Research (LTER) grant in 1980, infrastructure expanded to include a set of benchmark and secondary meteorological stations located in clearings spanning the elevation range within the Lookout Creek watershed, as well as a large number of forest understory temperature stations. Extensive metadata on sensor configurations, changes in methods over time, sensor accuracy and precision, and data quality control flags are associated with the HJA data. 相似文献
3.
回顾了湿空气热动力学的研究进展,对未饱和湿大气、饱和湿大气及非均匀饱和湿大气的动热力方程、能量方程、连续方程等进行了梳理,指出饱和湿空气动量方程与非均匀饱和湿空气动量方程的最大区别在于对凝结过程的处理不同。饱和湿大气中,由于大气均是饱和的,由饱和造成的水凝物可处处出现,不能区分真正发生水汽凝结的区域。而非均匀饱和湿空气中,凝结发生与相对湿度的幂次方有关(即与凝结概率函数的分布有关),在相对湿度较小的区域不会出现水汽凝结,凝结区与非凝结区可自动区别,其描述的凝结过程与实际大气更接近。同时,总结了湿大气水汽凝结饱和非均匀分布的动热力物理量在高影响天气分析中的应用,最后讨论了未来推进湿空气动力学研究需重点考虑的一个内容。 相似文献
4.
Farmland abandonment is a global problem and considered one of the most important areas in land use change research. Farmland abandonment research currently focuses on understanding the factors that affect farmland abandonment and developing scientific models to simulate farmland abandonment. The study reviewed the natural and political factors driving farmland abandonment and summarized the main models for farmland abandonment simulation together with their advantages and disadvantages. We discuss the main ecological effects of farmland abandonment and propose farmland abandonment research directions. The study found that: (1) the influence of labor cost change and ageing labor force on farmland abandonment needs further investigation, (2) simulation models for farmland abandonment must include the decision-making mechanism of individual farmers and focus on macro large-scale abandonment prediction models, and (3) the influence of farmland abandonment on landscape culture must be investigated in detail. 相似文献
5.
作为矿物学的重要基础研究方向之一,新矿物的发现及其晶体结构、晶体化学的研究始终备受各发达国家的一贯重视。新矿物的研究和发现及其成果具有国际性,在一定程度上反映了国家在该领域以及整体科技水平和对科学发现的贡献。笔者近年来参与了对若干存疑矿物进行的精细晶体结构与晶体化学研究和矿物学研究,从2005年至今参与发现的23种新矿物均获得国际矿物学协会新矿物及分类命名委员会(IMA-CNMNC)所批准。这些新矿物的获批得益于成功地获取了成分数据、衍射数据和晶体结构的阐明。本文就新矿物的认定规则、申报内容和数据、分类命名、研究内容及工作方法等进行综述,在此抛砖引玉,希望通过交流促进我国新矿物研究领域的发展。 相似文献
6.
中华人民共和国成立以来,中国的资源科学研究在自然资源考察的基础上形成了一门综合性的学科体系。本文系统总结中国资源科学从自然资源综合考察到资源科学综合研究的发展历程,大致可划分为自然资源综合考察初期(20世纪50—60年代)、区域资源综合科学考察与资源科学研究时期(20世纪70—80年代)、资源科学学科体系的形成与发展时期(20世纪90年代—2000年)及现代资源科学迈向新发展时期(21世纪以来)等4个阶段,促进了中国自然资源的考察和开发利用事业不断向前发展,对中国资源科学形成与发展影响深远。当下面向生态文明建设和美丽中国建设两个国家先进发展需求,资源科学研究要以史为鉴,推陈出新,不断丰富学科的新概念、新知识与新方法,促进资源科学的蓬勃发展。 相似文献
7.
The Jalovecký Creek catchment, Slovakia (area 22.2 km2, mean elevation 1500 m a.s.l.), is likely the last big valley complex in the Carpathian Mountains, in which the hydrological cycle is still governed by natural processes. Hydrological research is conducted there since the end of the 1980s. The overall mission of the research is to increase the knowledge about the hydrological cycle in the highest part of the Carpathians. The research agenda, briefly introduced in the first part of this article, is focused on water balance, snow accumulation and melt and runoff formation. Recent analysis of precipitation, discharge, snow cover and isotopic data from period 1989–2018 indicates that hydrological cycle has become more dynamic since 2014. Although several indicators suggest that it could be related to the cold part of the year, direct links with snow storage and the contribution of snowmelt water to catchment runoff were not confirmed. The second part of the article is therefore focused on an analysis of daily cycles in streamflow in March to June 1988–2018 to obtain a deeper insight into the snowmelt process. We describe characteristics of the cycles and examine their variability over the study period. The results indicate that less snow at the lowest elevations (800–1150 m a.s.l.) since 2009 could have influenced the cessation of the cycles in June since 2010. The possible role of the decreased amount of snow at the lowest elevations in changes in runoff characteristics is also suggested by an increase in time lags between maximum discharges during the events and maximum air temperatures preceding discharge maxima measured near the catchment outlet (at 750 m a.s.l.) in spring 2018 compared to springs with a similar number of streamflow cycles in the years 1988, 2000 and 2009. Wavelet analysis did not indicate changes in global power spectra in hourly discharge and air temperature data. 相似文献
8.
Jeff Rose 《The Professional geographer》2018,70(2):305-310
Community engagement curricula and course design can provide substantial experiences for both community members and participating students. Using a case study approach, this research focuses on four steps in this process: initial community relationship forming, engaging in community service, transitioning to civic engagement, and developing a community-based research program. Narrative examples from student course evaluations position these community-based experiences as transformative for multiple parties. Institutional structures are presented as helpful entrees to engagement for students, while noting that community relationships provide contextualized, powerful, and meaningful relationships, supporting recommendations for emerging and existing community engagement programs. 相似文献
9.
Anne Vogelpohl 《Urban geography》2018,39(9):1345-1365
These days, it is often claimed that democratic procedures are under threat. The detachment of policy decisions from political debates is partly a result of the increasing influence of non-elected organizations and experts. Following a conceptual discussion of the spatiality of democracy, this paper focuses on management consultants as constraint on collective political participation in urban development; namely on McKinsey and Roland Berger. (De-)democratization is assessed alongside processes of inclusion and exclusion of both topics and people from political decisions. Based on a comparison of strategy-making projects in six German cities, the findings reveal three different types of urban policymaking ranging between expert-led and participatory versions. Despite the differences, each of the projects relied on a notion of passive citizens, who primarily need to be “gotten on board” and who lack the power to make decisions. This paper exposes the political tactics involved in an expert-influenced curtailment of democratic procedures. 相似文献
10.
Mark Purdon 《社会与自然资源》2018,31(9):1082-1093
Carbon markets as a policy tool to mitigate emissions of greenhouse gases continue to be controversial, especially in developing countries. It is thus refreshing that Carton and Andersson (2017) undertook a field investigation of a transnational forest carbon offset project in Uganda. However, I am concerned that assumptions of structural Marxism that underwrite subsumption theory may have led the authors to see the project as inherently conflict ridden and exploitative and to neglect actual benefits. Their presentation of the project’s local impact jarred with my own empirical research into this project, undertaken in 2009, as well as more recent news accounts. While my field effort preceded the authors’ by 6 years, I attribute our different interpretations largely to theoretical and methodological differences. Evidence I present below suggests considerable alignment between the interests of transnational carbon markets and Ugandan smallholder farmers. Additional fieldwork might be able to resolve these differences in interpretation. 相似文献