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41.
Characterizing the properties of dissolved organic matter isolated by XAD and C-18 solid phase extraction and ultrafiltration 总被引:1,自引:0,他引:1
42.
The Neoproterozoic Katangan R.A.T. (“Roches Argilo-Talqueuses”) Subgroup is a sedimentary sequence composed of red massive to irregularly bedded terrigenous-dolomitic rocks occurring at the base of the Katangan succession in Congo. Red R.A.T. is rarely exposed in a continuous section because it was affected by a major layer-parallel décollement during the Lufilian thrusting. However, in a number of thrust sheets, Red R.A.T. is in conformable sedimentary contact with Grey R.A.T which forms the base of the Mines Subgroup. Apart from the colour difference reflecting distinct depositional redox conditions, lithological, petrographical and geochemical features of Red and Grey R.A.T. are similar. A continuous sedimentary transition between these two lithological units is shown by the occurrence of variegated to yellowish R.A.T. The D. Strat. “Dolomies Stratifiées” formation of the Mines Subgroup conformably overlies the Grey R.A.T. In addition, a transitional gradation between Grey R.A.T. and D. Strat. occurs in most Cu–Co mines in Katanga and is marked by interbedding of Grey R.A.T.-type and D. Strat.-type layers or by a progressive petrographic and lithologic transition from R.A.T. to D. Strat. Thus, there is an unquestionable sedimentary transition between Grey R.A.T. and D. Strat. and between Grey R.A.T. and Red R.A.T.The R.A.T. Subgroup stratigraphically underlies the Mines Subgroup and therefore R.A.T. cannot be comprised of syn-orogenic sediments deposited upon the Kundelungu (formerly “Upper Kundelungu”) Group as suggested by Wendorff (2000). As a consequence, the Grey R.A.T. Cu–Co mineralisation definitely is part of the Mines Subgroup Lower Orebody, and does not represent a distinct generation of stratiform Cu–Co sulphide mineralisation younger than the Roan orebodies. 相似文献
43.
Bruce J. MacFadden 《Quaternary Research》2005,64(2):113-124
The toxodont megaherbivores Toxodon and Mixotoxodon were endemic to South and Central America during the late Quaternary. Isotopic signatures of 47 toxodont teeth were analyzed to reconstruct diet and ancient habitat. Tooth enamel carbon isotope data from six regions of South and Central America indicate significant differences in toxodont diet and local vegetation during the late Quaternary. Toxodonts ranged ecologically from C3 forest browsers in the Amazon (mean δ13C = −13.4‰), to mixed C3 grazers and/or browsers living either in C3 grasslands, or mixed C3 forested and grassland habitats in Honduras (mean δ13C = −9.3‰), Buenos Aires province, Argentina (δ13C = −8.7‰), and Bahia, Brazil (mean δ13C = −8.6‰), to predominantly C4 grazers in northern Argentina (δ13C = −4.4‰), to specialized C4 grazers in the Chaco of Bolivia (δ13C = −0.1‰). Although these toxodonts had very high-crowned teeth classically interpreted for grazing, the isotopic data indicate that these megaherbivores had the evolutionary capacity to feed on a variety of dominant local vegetation. In the ancient Amazon region, carbon isotope data for the toxodonts indicate a C3-based tropical rainforest habitat with no evidence for grasslands as would be predicted from the Neotropical forest refugia hypothesis. 相似文献
44.
孙建军 《测绘与空间地理信息》2016,(3)
将ITRF2008解算结果 GPS、SLR、VLBI实测站速度信息和北美CORS网络、中国陆态网络、欧洲CORS网络站速度信息进行基准统一,联合解算IERS组织划定的全球14个主要大陆板块的欧拉矢量,对原有的板块运动参数进行精化;提出了基于最小二乘法的海量台站选择方法,实验结果表明,该台站选取方法能够有效提高海量台站的筛选效率和可靠性。稳定台站的数量越多,分布越均匀,越能够体现板块运动的现势性。 相似文献
45.
基于FY3A/MERSI资料分析广东省气溶胶光学厚度分布 总被引:3,自引:3,他引:0
利用国产极轨气象卫星FY3A的MERSI AOD产品分析2010—2013年广东省气溶胶光学厚度的分布规律。结果表明:MERSI AOD产品与地面太阳光度计实测数据的相关系数为0.72,其平均绝对值误差为0.12,均方根误差为0.15,数据精度可满足研究需要;从AOD的空间分布看,珠三角西翼东翼山区五市,其中佛山市、东莞市、中山市为广东省AOD均值最高的地区,梅州市、河源市为广东省AOD均值最低的地区;从AOD的时间分布看,2010—2013年间,AOD呈现先升高后降低的趋势,2011年为拐点,与此同时,AOD还表现出明显的季节变化特征,春季为AOD高值期,夏季、秋季次之,冬季最低。 相似文献
46.
47.
针对HY-2A卫星定轨中存在系统误差的问题,该文提出了加入经验加速度补偿系统误差。为了获得HY-2A卫星的高精度轨道,采用星载DORIS距离变率数据探索了经验加速度对定轨精度的影响。探讨了1d、3d和7d作为经验加速度周期的定轨精度差异,分析了3d作为经验加速度周期时在径向、法向和切向3个方向设置经验加速度对定轨精度的不同影响。研究结果表明:HY-2A卫星在径向和切向不存在系统误差,而在法向存在系统误差,因而在法向设置经验加速度进行力学模型补偿能够取得较好的定轨结果;3d作为经验加速度的补偿周期较为合适,不仅能够减少解算参数个数,缩短计算时间,而且径向定轨精度可达到1.00cm,满足HY-2A卫星精密定轨需求。 相似文献
48.
Variation in 13C/12C-isotope ratios of fracture filling calcite was analyzed in situ to investigate carbon sources and cycling in fractured bedrock. The study was conducted by separating sections of fracture fillings, and analyzing the 13C/12C-ratios with secondary ion mass spectrometry (SIMS). Specifically, the study was aimed at fillings where previously published sulfur isotope data indicated the occurrence of bacterial sulfate reduction. The results showed that the δ13C values of calcite were highly variable, ranging from −53.8‰ to +31.6‰ (VPDB). The analysis also showed high variations within single fillings of up to 39‰. The analyzed calcite fillings were mostly associated with two calcite groups, of which Group 3 represents possible Paleozoic fluid circulation, based on comparison with similar dated coatings within the Baltic Shield and the succeeding Group 1–2 fillings represent late-stage, low temperature mineralization and are possibly late Paleozoic to Quaternary in age. Both generations were associated with pyrite with δ34S values indicative of bacterial sulfate reduction. The δ13C values of calcite, however, were indicative of geochemical environments which were distinct for these generations. The δ13C values of Group 3 calcite varied from −22.1‰ to +11‰, with a distinct peak at −16‰ to −12‰. Furthermore, there were no observable depth dependent trends in the δ13C values of Group 3 calcite. The δ13C values of Group 3 calcite were indicative of organic matter degradation and methanogenesis. In contrast to the Group 3 fillings, the δ13C values of Group 1–2 calcite were highly variable, ranging from −53.8‰ to +31.6‰ and they showed systematic variation with depth. The near surface environment of <30 m (bsl) was characterized by δ13C values indicative of degradation of surface derived organic matter, with δ13C values ranging from −30.3‰ to −5.5‰. The intermediate depth of 34–54 m showed evidence of localized methanotrophic activity seen as anomalously 13C depleted calcite, having δ13C values as low as −53.8‰. At depths of ∼60–400 m, positive δ13C values of up to +31.6‰ in late-stage calcite of Group 1–2 indicated methanogenesis. In comparison, high CH4 concentrations in present day groundwaters are found at depths of >300 m. One sample at a depth of 111 m showed a transition from methanogenetic conditions (calcite bearing methanogenetic signature) to sulfate reducing (precipitation of pyrite on calcite surface), however, the timing of this transition is so far unclear. The results from this study gives indications of the complex nature of sulfur and carbon cycling in fractured crystalline environments and highlights the usefulness of in situ stable isotope analysis. 相似文献
49.
基于浮标数据的卫星雷达高度计海浪波高数据评价与校正 总被引:1,自引:1,他引:0
卫星雷达高度计是海浪有效波高(significant wave height,SWH)观测的重要手段之一,本文利用时空匹配方法对T/P、Jason-1、Envisat、Jason-2、Cryosat-2和HY-2A共6颗卫星雷达高度计SWH数据与NDBC(National Data Buoy Center,NDBC)浮标SWH数据进行对比验证,并对雷达高度计SWH数据进行校正。全部卫星雷达高度计SWH数据时间跨度为1992年9月25日到2015年9月1日,对比验证NDBC浮标共53个,包括7个大洋浮标。精度评价发现除T/P外,各卫星雷达高度计SWH的RMSE都在0.4~0.5 m之间,经过校正后,RMSE都有显著下降,下降程度最大为13.82%;对于大洋浮标,评价结果RMSE在0.20~0.28 m之间,结果明显优于全部NDBC浮标的精度评价结果;HY-2A卫星雷达高度计SWH在经过校正后数据质量与国外其他5颗卫星雷达高度计SWH数据质量差异较小。 相似文献
50.
自2007年以来, 黄海海域每年的5月初~8月中下旬浒苔(Ulva prolifera)会周期性地暴发与消亡,导致海洋生态环境被破坏以及经济损失。利用2014 年的HJ-1A/1B遥感影像, 利用神经网络监督分类及RULE规则影像重分类动态阈值法, 对2014年的浒苔的漂移路径、各时期影响的海域面积、分布面积以及暴发高峰期的最大面积进行了动态监测。结果表明, 2014年浒苔持续时间为101 d, 5月中旬开始在江苏省盐城市近海出现零星斑点, 分布面积为2.299 km2, 影响面积为1 744.799 km2; 6月初到6月中旬浒苔广泛分布于黄海海域, 分布面积扩大至1 367.145 km2, 达到当年的峰值; 从6月下旬开始, 浒苔进入衰退期, 浒苔分布面积、相对聚集密度均急剧缩小, 但影响面积的峰值出现在该时期; 8月初消亡于青岛附近海岸, 8月20日遥感影像已难以监测到浒苔的存在。2014年黄海海域浒苔经过了“出现—发展—暴发—衰退—消亡”5个发展阶段。 相似文献