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��׷�  �ؽ���  ������  ���κ�  ������  ����־ 《大地测量与地球动力学》2014,34(6):81-85

????BDS/GPS CORS????????????α??????????????????λ????????BDS/GPS?????????λ?????о?????????????????BDS/GPS????????????????λ????????1 m??40??????????????λ????0.5 m????????????????α??λ?????????????????????????λ????????0.1??10 m????  相似文献   

PCDD/Fs in sediments of Central Vietnam coastal lagoons: in search of TCDD     

Piazza R  Giuliani S  Bellucci LG  Mugnai C  Cu NH  Nhon DH  Vecchiato M  Romano S  Frignani M 《Marine pollution bulletin》2010,60(12):2303-2310

Samples from nine Central Vietnam coastal lagoons, together with three soils and sediments collected in two freshwater reservoirs of the Thua Thien-Hué province, were analysed for polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs). Total concentrations are low, from 192 to 2912 pg g⁻¹ and depth profiles in Tam Giang-Cau Hai (TG-CH) sediment cores show only minor changes over time in PCDD/F input and composition. Octachloro dibenzo-p-dioxin (OCDD) is the prevailing congener (approximately 90%), indicating combustion as the main PCDD/F source to these coastal systems, whereas natural formation might be partly responsible for the presence at depth. 2,3,7,8-Tetrachloro dibenzo-p-dioxin (TCDD), largely sprayed together with Agent Orange over the study areas during the war (1961–1971), is absent or very low. This result supports the hypothesis of strong degradation soon after spraying. Multivariate statistical analyses account for the presence of local, short-range sources as observed in the northern part of the TG-CH lagoon.  相似文献   

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巩岩  党亚民 《大地测量与地球动力学》2010,30(5):86-89

??????????е??????????????????????????????????????????IGS????????TEC??????????????????????ò??????λ???30??40 ???50 ?????????з??????????????????????0.8 TECU???????????仯?????????￡????????????????????????????γ???й??  相似文献   

Environmental impacts on the distribution of microbial tetraether lipids in Chinese lakes with contrasting pH: Implications for lacustrine paleoenvironmental reconstructions     

XinYue Dang  JianTao Xue  Huan Yang  ShuCheng Xie 《中国科学:地球科学(英文版)》2016,59(5):939-950

Glycerol dialkyl glycerol tetraethers(GDGTs) in lake sediments are useful biomarkers for the continental paleoclimatic reconstruction. However, the environmental controls on the distribution of these compounds, in particular the 6-methyl isomers of bacterial branched GDGTs(bGDGTs), in the lakes with contrasting pH, are still unknown, hindering their application for paleo-reconstructions. Here, we investigated the environmental impacts on the distribution of GDGTs in 17 alkaline lakes and 1 acid lake in China. It was found that the dissolved oxygen content in water column may have an impact on the distribution of archaeal isoprenoid GDGTs(iGDGTs) by causing the change in archaeal communities. The ratio of GDGT-0/crenarchaeol increases with decreasing oxygen content, indicating that the relative abundance of anaerobic methanogenic archaea or Miscellaneous Crenarchaeotic Group(MCG) vs. aerobic Thaumarchaeota is controlled by the oxygen content dissolved in water of these lakes. Thaumarchaeota are likely to contribute only a small proportion of iGDGTs in the relatively oxygen-depleted lakes, and thus TEX_(86) is not suitable for the reconstruction of the surface temperature of these lakes. The abundance ratio of iGDGTs to bGDGTs(R_(i/b)) appears to show no relationship with water pH in all the lakes, but exhibits a significant positive correlation with the water depth of the acid Lake Qinghai in Tengchong. As expected, the methylation degree of bGDGTs(MBT′) was found to correlate with both mean annual air temperature(MAT) and water pH, and the cyclization degree of bGDGTs(CBT) correlates only with water pH in these lakes. However, the MBT′_(5ME), an index to measure the methylation degree of 5-methyl bGDGTs, exhibits no relationship with MAT, whereas MBT′_(6ME), the methylation degree of 6-methyl bGDGTs, was found to correlate significantly with MAT. This is opposite to the situation observed in the global soils, pointing to a different adaptation of b GDGT-producing bacteria to environmental variables or different microbial sources of bGDGTs in these lakes. The relative abundance of 6- vs. 5-methyl bGDGTs is controlled by pH in these lakes, similar to that observed in worldwide soils. Hence, the isomer ratio(IR) of 6-methyl bGDGTs or CBT′ can be used as a proxy for water pH, although they might be influenced by other environmental factors including temperature in the lakes with a narrow range of pH.  相似文献   

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刘晓辉  党亚民  王潜心  杨磊 《大地测量与地球动力学》2013,33(1):123-127

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党学会  乔学军  赵斌  吕健  王恒信  张昀龙 《大地测量与地球动力学》2013,33(4):13-16

????“??????”2009??2011??????GPS?????????????????????296????????????????????????????????????μ?????????????η??????????????????????????????????????1?????????????????????б??????????????????????ο?????????????????????2????????????????????P????????????????????????????????????????????????????3?????????????????????????λ???????????????丽???????????????????????κ??????????????????????????????????????????  相似文献   

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宋传峰  党亚民  秘金钟  薛树强 《大地测量与地球动力学》2014,34(3):108-110

???????????????????????ж????????????????????????????????????????λ?ú?????????????Ч?????????????????8 h???????????????????в????mm????  相似文献   

Regional gravity field modeling based on rectangular harmonic analysis     

JIANG Tao  LI JianCheng  DANG YaMin  ZHANG ChuanYin  WANG ZhengTao  KE BaoGui 《中国科学:地球科学(英文版)》2014,57(7):1637-1644

Regional gravity field modeling with high-precision and high-resolution is one of the most important scientific objectives in geodesy,and can provide fundamental information for geophysics,geodynamics,seismology,and mineral exploration.Rectangular harmonic analysis(RHA)is proposed for regional gravity field modeling in this paper.By solving the Laplace’s equation of gravitational potential in local Cartesian coordinate system,the rectangular harmonic expansions of disturbing potential,gravity anomaly,gravity disturbance,geoid undulation and deflection of the vertical are derived,and so are the formula for signal degree variance and error degree variance of the rectangular harmonic coefficients(RHC).We also present the mathematical model and detailed algorithm for the solution of RHC using RHA from gravity observations.In order to reduce the edge effects caused by periodic continuation in RHA,we propose the strategy of extending the size of computation domain.The RHA-based modeling method is validated by conducting numerical experiments based on simulated ground and airborne gravity data that are generated from geopotential model EGM2008 and contaminated by Gauss white noise with standard deviation of 2 mGal.The accuracy of the 2.5′×2.5′geoid undulations computed from ground and airborne gravity data is 1 and 1.4cm,respectively.The standard error of the gravity disturbances that downward continued from the flight height of 4 km to the geoid is only 3.1 mGal.Numerical results confirm that RHA is able to provide a reliable and accurate regional gravity field model,which may be a new option for the representation of the fine structure of regional gravity field.  相似文献   

Deep soil water infiltration and its dynamic variation in the shifting sandy land of typical deserts in China   总被引：6，自引：0，他引：6  

WenBin Yang  JinNian Tang  HaiRong Liang  HongZhong Dang  Wei Li 《中国科学:地球科学(英文版)》2014,57(8):1816-1824

Soil moisture is the key resource constraint in arid ecosystems, and has been a focus of research on restoration. However, quantitative studies on the contribution of rainfall to deep soil rainfall infiltration are lacking. In this study, we used the YWB-01 Deep Soil Infiltration Water Recorder which had been invented by ourselves to measure the quantity of rain infiltration into deep soil, 150 cm below ground, in four locations in China: Mu Us Sandy Land and Ulan Buh, Tengger, and Badan Jilin deserts over a 2-year period. We found: (1) Deep soil rainfall infiltration decreased progressively from east to west and from semiarid to arid areas, with two locations completely lacking rainfall infiltration. Heavy rain was important to deep soil infiltration in shifting sandy land of arid and semiarid areas. (2) Seasonal variation of infiltration was correlated with rainfall, with a time lag that was less apparent in areas with more rainfall. (3) For single intense rainfall events, infiltration maximums occurred 40–55 h after the rainfall, during which the infiltration rates increased rapidly before reaching a peak, and then decreased slowly. Continuous infiltration could last about 150 h. Rainfall infiltration was determined by the combined action of intensity, quantity and duration. Rainfall with low intensity, long duration, and large quantity was most favorable for deep soil infiltration. Our results can be used in water resource assessments and protection during eco-restoration in the arid and semiarid areas in China.  相似文献   

毛乌素沙地流动沙丘土壤水分对降雨的响应   总被引：10，自引：3，他引：7  

冯伟  杨文斌  党宏忠  李卫  石星  王永胜  梁海荣 《中国沙漠》2015,35(2):400-406

为探讨半干旱区流动沙丘土壤水分对降雨的响应,采用AV-3665R型雨量传感器、ECH₂O-5土壤水分传感器同步监测毛乌素沙地东北缘流动沙丘2013年降雨及0～200 cm深度土壤体积含水量动态,分析土壤水分含量变化特征、降雨入渗特征及降雨对土壤水的补给作用。结果表明:5-11月累积降雨399.4 mm,显著(p<0.01)影响0～200 cm深度土壤水分含量; 且0～200 cm深度土壤体积含水量较低(6.49%±1.12%)时53.8 mm降雨、较高(10.22%±1.96%)时24.2 mm降雨湿润锋能够到达200 cm; 试验期间399.4 mm累积降雨对土壤水有一定补给作用,其中45.7±14.1 mm降雨蓄存在0～200 cm深度土壤中,占同期降雨的(11.4%±3.5%,且随着时间的延长,蓄存水大部分将渗漏到200 cm以下补给深层土壤水。  相似文献