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91.
库布齐沙漠治理对京津冀地区空气质量影响:2017年5月3-6日沙尘天气模拟 总被引:1,自引:1,他引:0
作为影响京津冀地区的沙尘途经地和发源地,对库布齐沙漠的治理工作一直在持续,成为使用科学技术手段将沙漠变废为宝、变害为利的成功案例,同时也是全球治沙范例。为研究库布齐沙漠治理工作对京津冀地区空气质量的改善效果,利用手工采样数据和城市空气质量监测数据,结合气团轨迹,筛选库布齐沙漠起沙并对京津冀地区产生影响的沙尘天气。选取2017年5月3-6日作为典型个例代表,使用嵌套网格空气质量预报模式系统(NAQPMS),设计不同的起沙权重系数敏感试验,模拟研究该地区起沙和治理对京津冀地区的空气质量影响。结果表明:(1)气象模式较好地把握天气系统的演变以及地面风场的特征,保证NAQPMS模式可合理模拟沙尘的起沙区域、影响范围以及时空演变特征;(2)受沙尘影响城市的PM10浓度模拟量值及变化与观测较为一致,表明模式合理再现了沙尘的输送过程;(3)库布齐沙漠起沙对京津冀地区的PM10浓度贡献为35~150 μg·m-3,贡献比例为10%~40%;(4)库布齐沙漠治理可使京津冀地区PM10浓度降低35~75 μg·m-3,下降比例为5%~20%,受影响城市PM10浓度下降比例为7%~37%,沙漠治理工作可有效降低受影响地区的PM10浓度。 相似文献
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Mission design,operation and exploitation of the gravity field and steady-state ocean circulation explorer mission 总被引:6,自引:3,他引:3
Rune?FloberghagenEmail author Michael?Fehringer Daniel?Lamarre Danilo?Muzi Bj?rn?Frommknecht Christoph?Steiger Juan?Pi?eiro Andrea?da?Costa 《Journal of Geodesy》2011,85(11):749-758
The European Space Agency’s Gravity field and steady-state ocean circulation explorer mission (GOCE) was launched on 17 March
2009. As the first of the Earth Explorer family of satellites within the Agency’s Living Planet Programme, it is aiming at
a better understanding of the Earth system. The mission objective of GOCE is the determination of the Earth’s gravity field
and geoid with high accuracy and maximum spatial resolution. The geoid, combined with the de facto mean ocean surface derived
from twenty-odd years of satellite radar altimetry, yields the global dynamic ocean topography. It serves ocean circulation
and ocean transport studies and sea level research. GOCE geoid heights allow the conversion of global positioning system (GPS)
heights to high precision heights above sea level. Gravity anomalies and also gravity gradients from GOCE are used for gravity-to-density
inversion and in particular for studies of the Earth’s lithosphere and upper mantle. GOCE is the first-ever satellite to carry
a gravitational gradiometer, and in order to achieve its challenging mission objectives the satellite embarks a number of
world-first technologies. In essence the spacecraft together with its sensors can be regarded as a spaceborne gravimeter.
In this work, we describe the mission and the way it is operated and exploited in order to make available the best-possible
measurements of the Earth gravity field. The main lessons learned from the first 19 months in orbit are also provided, in
as far as they affect the quality of the science data products and therefore are of specific interest for GOCE data users. 相似文献
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This study focused on a spatial and temporal analysis of the active channel and associated floodplain lakes using aerial photographs spanning five decades (1942, 1962, 1985, 1999) over a 140 km long reach of the Sacramento. Planimetric changes were analysed longitudinally and temporally to highlight the spatial structures and their evolution through time. The results underline complex changes and space–time pattern in bank erosion, channel length and active channel width. The bank erosion and also channel lengthening were higher between 1962 and 1985 than in the two periods studied before and after. Active channel width significantly decreased from 1942 to 1999; partly progressively from upstream to downstream with local widening whatever the studied periods. Similarly the floodplain lakes observed before 1942–1962 were significantly different in size and geometry from those which appeared during the most recent period. The creation of lakes is less frequent after the 1940s, with a secondary peak of occurrence during the 1962–1985 period. The interpretation of these changes is complex because of various human pressures acting over different time scales (bank protection, flow diversion, sediment starvation, land‐use changes) and various natural influences (flood sequences through out the period, geological setting). The findings are discussed by comparison with previous work, and highlight the important effect of dam impact on peak flow and sediment starvation modifying longitudinally hydraulic conditions within the channel, but also the increase in riprap protection which induced change in bank erosion, channel planimetry and floodplain lake characters (geometry, frequency of renewal). Variation in flood intensities is also observed as having positive effects on the bank erosion pattern. Secondarily, land‐use changes also controlled bank erosion intensity. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
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Embaie Ferrow Vivi Vajda Christian Bender Koch Pi Suhr Willumsen 《Geochimica et cosmochimica acta》2011,75(2):657-672
An integrated study of palynology, Mössbauer spectroscopy, mineralogy and osmium isotopes has led to the detection of the first K-Pg boundary clay layer in a Southern Hemisphere terrestrial setting. The K-Pg boundary layer was independently identified at centimetre resolution by all the above mentioned methods at the marine K-Pg boundary site of mid-Waipara and the terrestrial site of Compressor Creek (Greymouth coal field), New Zealand. Mössbauer spectroscopy shows an anomaly of Fe-containing particles in both K-Pg boundary sections: jarosite at mid-Waipara and goethite at Compressor Creek. This anomaly coincides with a turnover in vegetation indicated by an interval dominated by fern spores and extinction of key pollen species in both sections. In addition to the terrestrial floristic changes, the mid-Waipara section reveals a turnover in the dinoflagellate assemblages and the appearance of global earliest Danian index species. Geochemical data reveal relatively small iridium enrichments in the boundary layers of 321 pg/g at mid-Waipara and 176 pg/g at Compressor Creek. Unradiogenic 187Os/188Os values of the boundary clay reveal the presence of a significant extraterrestrial component. We interpret the accumulation of Fe nano-phases at the boundary as originating from both the impactor and the crystalline basement target rock. The goethite and jarosite are interpreted as secondary phases formed by weathering and diagenesis. The primary phases were probably controlled by the initial composition of the vapor plume and condensation kinetics rather than condensation thermodynamics. This investigation indicates that identification of Fe in nano-phases by Mössbauer spectroscopy is an accurate and cost-effective method for identifying impact event horizons and it efficiently complements widely used biostratigraphic and geochemical methods. 相似文献
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F. T. Wakida S. Martinez-Huato E. Garcia-Flores T. D. J. Piñon-Colin H. Espinoza-Gomez A. Ames-López 《International Journal of Environmental Science and Technology》2014,11(2):319-326
Stormwater runoff from urban areas is a major source of many pollutants to water bodies. Suspended solids are one of the main pollutants because of their association with other pollutants. The objective of this study was to evaluate the relationship between suspended solids and other pollutants in stormwater runoff in the city of Tijuana. Seven sites were sampled during seven rain events during the 2009–2010 season and the different particle size fractions were separated by sieving and filtration. The results have shown that the samples have high concentration of total suspended solids, the values of which ranged from 725 to 4,411.6 mg/L. The samples were analyzed for chemical oxygen demand, total phosphorus, total nitrogen, and turbidity. The results show that most of the particles in suspended solids are in the particle fraction between 10 and 62 μm. A high association between the concentrations of suspended solids was found for chemical oxygen demand, phosphorus, and turbidity but not for total nitrogen. 相似文献