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991.
流域生态补偿研究现状及关键问题剖析 总被引:3,自引:0,他引:3
在流域,因竞争性用水导致上下游之间、人类发展与生态环境之间的矛盾日益尖锐,急需建立健全流域生态补偿机制.通过对国内外流域生态补偿研究进展进行梳理,发现流域生态补偿研究主要集中在流域尺度的补偿计划实施评价、补偿尺度的选择、补偿标准的测算、生态补偿与减少贫困关系、流域生态补偿的空间差异性等方面,其关键问题在于生态补偿主体和对象的确定以及补偿标准的制定;研究认为通过流域断面水量水质及相关利益分析方法来确定补偿主体和对象;而补偿标准则以流域上下游生态损益、机会成本、居民支付意愿分别作为补偿上限、参考值和下限来综合确定.以此为基础,构建流域多种生态要素、多元主体间的流域生态补偿机制研究框架.最后,就流域生态补偿机制构建过程中有待解决的科学问题进行了讨论. 相似文献
992.
对拉萨地块东段日多地区新厘定的雄来组火山岩进行了岩石地球化学、锆石U-Pb定年及Lu-Hf同位素研究。研究区雄来组火山岩以中基性熔岩及火山碎屑岩占优势为特征。LA-ICP-MS锆石U-Pb测年获得安山岩和玄武安山岩的206Pb/238U年龄加权平均值为201.3±6.0 Ma和184.5±4.4 Ma,表明雄来组火山岩形成于晚三叠世—早侏罗世。其中,基性火山岩SiO2含量为48.53%~49.92%,MgO含量较高,为10.68%~11.43%,Mg#值平均为72.67,高Cr(224.7×10-6~347.8×10-6)和Ni(90.1×10-6~109.7×10-6)含量,富集大离子亲石元素Rb、Th、U、Sr和轻稀土元素,亏损高场强元素Nb、Ta、P、Ti;中性火山岩的SiO2含量为53.93%~60.54%,Al2O3含量为14.74%~16.12%,MgO含量为2.45%~8.12%,富集大离子亲石元素Rb、Th、U、K、Ba和轻稀土元素,亏损高场强元素Nb、Ta、P、Ti,锆石εHf(t)值介于-12.25~-3.64之间,二阶段模式年龄(tDMC)为1621~2004 Ma。岩石地球化学特征和构造环境判别图解均指示,雄来组火山岩形成于后碰撞的构造背景,基性火山岩起源于亏损岩石圈地幔的部分熔融,中性火山岩起源于古老下地壳物质的部分熔融,上升过程中受古老地壳混染,代表了直孔-松多古特提斯造山带后碰撞伸展背景作用下的岩浆响应。 相似文献
993.
蒙陕接壤区煤炭高强度开采诱发的煤层顶板水害问题日益凸显,高效智能地判别煤层顶板涌水水源是顶板水害防治的关键。以蒙陕接壤区3个典型矿井为研究对象,将无机指标K++Na+、Ca2+、Mg2+、Cl−、SO4 2−、HCO3 −、TDS和有机指标UV254、TOC、溶解性有机质(DOM)的荧光光谱作为判别指标,利用主成分分析法(PCA)对80组地下水水样数据进行主成分提取,提出一种人工鱼群算法(AFSA)改进随机森林(RF)的PCA-AFSA-RF顶板涌水水源智能判别方法。首先,建立PCA-RF判别模型,其准确率(
994.
995.
LI Jianchao LI Guangxue XU Jishang QIAO Lulu MA Yanyan DING Dong LIU Shidong 《中国海洋大学学报(英文版)》2019,(1):31-42
A two-month seabed-mounted observation(YSG1 area) was carried out in the western Yellow Sea Cold Water Mass(YSCWM) using an RDI-300 K acoustic Doppler current profiler(ADCP) placed at a water depth of 38 m in late summer, 2012. On August 2012, Typhoon Bolaven passed east of YSG1 with a maximum wind speed of 20 m s-1. The water depth, bottom temperature, and profile current velocities(including u, v and w components) were measured, and the results showed that the typhoon could induce horizontal current with speed greater than 70 cm s-1 in the water column, which is especially rare at below 20 meters above bottom(mab). The deepening velocity shear layer had an intense shear velocity of around 10 cm s-1 m-1, which indicated the deepening of the upper mixed layer. In the upper water column(above 20 mab), westward de-tide current with velocity greater than 30 cm s-1 was generated with the typhoon's onshore surge, and the direction of current movement shifted to become southward. In the lower water column, a possible pattern of eastward compensation current and delayed typhoon-driven current was demonstrated. During the typhoon, bottom temperature variation was changed into diurnal pattern because of the combined influence of typhoon and tidal current. The passage of Bolaven greatly intensified local sediment resuspension in the bottom layer. In addition, low-density particles constituted the suspended particulate matter(SPM) around 10 mab, which may be transported from the central South Yellow Sea by the typhoon. Overall, the intensive external force of the Typhoon Bolaven did not completely destroy the local thermocline, and most re-suspended sediments during the typhoon were restricted within the YSCWM. 相似文献
996.
The concentration of suspended load can be determined by its linear relationship to turbidity. Our results present the basic
distribution of suspended load in North Yellow Sea. In summer, the suspended load concentration is high along the coast and
low in the center of the sea. There are four regions of high concentration in the surface layer: Penglai and Chengshantou
along the north of the Shandong Peninsula, and the coastal areas of Lüshun and Changshan Islands. There is a 2 mg/L contour
at 124°E that separates the North Yellow Sea from regions of lower concentrations in the open sea to the west. And there is
a 2 mg/L contour at 124°E that separates the North Yellow Sea from regions of lower concentrations in the open sea to the
west. The distribution features in the 10 m and bottom layer are similar to the surface layer, however, the suspended load
concentration declines in the 10 m layer while it increases in the bottom layer. And in the bottom layer there is a low suspended
load concentration water mass at the region south of 38°N and east of 123°E extending to the southeast. In general, the lowest
suspended load concentration in a vertical profile is at a depth of 10 to 20 m, the highest suspended load concentration is
in the bottom near Chengshantou area.
In winter, the distribution of suspended load is similar to summer, but the average concentrations are three times higher.
There are two tongue-shaped high suspended load concentration belt, one occurring from surface to seafloor, extends to the
north near Chengshantou and the other invades north to south along the east margin of Dalian Bay. They separate the low suspended
load concentration water masses in the center of North Yellow Sea into east and west parts. Vertical distribution is quite
uniform in the whole North Yellow Sea because of the cooling effect and strong northeast winds. The distribution of suspended
load has a very close relationship to the current circulation and wind-induced waves in the North Yellow Sea. Because of this,
we have been able to show for the first time that the distribution of suspended load can be used to identify water masses. 相似文献
997.
998.
QI Lin QIAO Yan-song LIU Zong-xiu PENG Sha-sha CHENG Yu WANG Yan ZHANG Xu-jiao TIAN Ming-zhong YANG Shuai-bin BAI Wen-bin 《山地科学学报》2021,(4):878-890
The marginal areas of the Tibetan Plateau have great vertical altitude gradient and abundant vegetation, they are therefore the ideal places for investigating the relationships among carbon isotope composition(δ~(13)C) of modern soils, vegetation and environmental factors, which would be very useful for the reconstructions of both paleovegetation and paleoclimate. In this paper, modern soil samples collected in different vegetation vertical zones along 4km elevation gradient in the eastern margin of the Tibetan Plateau were analyzed for their carbon isotope composition. The results show that the modern soils in different vegetation vertical zones show apparent difference of δ~(13)C values, which get heavier in the sequence of mixed evergreen and deciduous broad-leaved forest(-27.28‰ on average), evergreen broad-leaved forest(-27.25‰), subalpine shrub-meadow(-25.81‰), subalpine coniferous forest(-25.81‰), alpine bush-meadow(-25.16‰), and drought-enduring shrub(-24.07‰). 1800 m and 3500 m are two critical points for the δ~(13)C values with respect to altitude. Specifically, the δ~(13)C values decrease with increasing altitude below both points while increasing with increasing altitude above both points. Further analyses indicate that the declining δ~(13)C values are mainly controlled by the decreasing proportion of C4 plants with elevation and the increasing δ~(13)C values are attributed to the plant physic-morphological adaptation to the alpine environment. In the absence of drought stress, temperature is the main controlling factor for the carbon isotopic variations with altitude gradient. 相似文献
999.
利用平均法、生物光学模型法和最优插值法3种数据融合方法对卫星传感器MODIS-Aqua、MOIDS-Terra及MERIS获取的南海叶绿素a浓度的数据进行了融合,通过比较融合产品的质量,对3融合方法进行了评价。(1)利用现场测量的南海遥感反射率和叶绿素a浓度数据建立了南海叶绿素a浓度的反演模型,并应用于MODIS-Aqua、MOIDS-Terra及MERIS Level 2反射率数据,获取南海叶绿素a浓度。(2)将平均法、生物光学模型法、最优插值法分别应用于上述3颗卫星的叶绿素a数据进行数据融合,并用现场测量的同步叶绿素数据对融合后的产品进行了印证。(3)利用3种融合方法分别对南海2011年MODIS-Aqua、MODIS-Terra和MERIS等3个传感器的叶绿素a数据进行了月融合,分析了融合的南海叶绿素a浓度的时空分布特征。结果表明,融合数据大幅度提高了空间覆盖率,且具有较高可信度。平均法、生物光学法和优化插等3种融合方法性能有较大的不同,生物光学法具有高的运行速度,但有时空间覆盖率仍不能满足要求;优化插值法具有高的空间覆盖率,但其运行速度较慢。因此,在具体应用中,应根据需求选择合适的融合方法。 相似文献
1000.