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1.
40Ar/39Ar method is a high precision dating means, of which the age is obtained by contrasting the un- known sample with those of standards. Usually the age of standard is determined by K-Ar method in which the 38Ar spike should be added for measurement. However, the absolute concentration of 38Ar spike is measured through the calibrated standards in turn, al- though occasionally the concentration of 38Ar spike is determined by other dating methods, such as Rb-Sr, U-Pb methods, which is kn… 相似文献
2.
Wang Fei He Huaiyu Zhu Rixiang Sang Haiqing Wang Yinglan Yang Liekun 《中国科学D辑(英文版)》2006,49(5):461-470
Four international standards, Ga1550, MMhb-1, Lp-6, Bem 4M, and one domestic standard BT-1 have been intercalibrated. The
repeated measurements on MMhb-1 with different mass demonstrate that MMhb-1 is inhomogeneous in age and its average age is
519.8 Ma. The results of Bern 4M and Lp-6 reflect that they have an invariable value of 40Ar*/39Ark (F) and the ages we obtained are consensus with their K-Ar age: Lp-6=127.7Ma; Bern 4M=18.2 Ma. Analyses of BT-1 age spectra,
Ca/K and Cl/K spectra as well as inverse isochrons indicate that the sample is homogeneous and invariable and keeps close
chemically, with its trapped argon isotope composition close to the atmosphere. The dating results show that age values are
reproducible and steady, total fusion age, step-heating age, plateau age and isochron age are in accord with each other within
the error range (2σ). Therefore, we recommend 28.7 Ma as the calibrated age of BT-1.
We also discuss the variation in neutron flux gradients of Beijing 49-2 reactor. It was found that the neutron flux gradient
varies considerably, and more monitors (standard samples) are needed to fix the trend of variation. The coefficient of the
49-2 reactor that transfers the ratio of production rate of 37ArCa/39ArK into Ca/K ratio is 1.78. This is different from that reported earlier, 2.0, which may be caused by the reconstruction of
the reactor. 相似文献
3.
本文基于对传统不变目标区域校正法的改进,选择4期辐射定标参考影像对DMSP-OLS影像进行了饱和校正与时间序列连续性校正。通过阈值法去除了NPP-VIIRS影像的背景噪声及异常值,利用对数变换压缩了其灯光辐射值的动态范围,使其亮度分布更接近于DMSP-OLS数据。利用BiDoseResp函数模型对NPP-VIIRS影像进行了一致性校正,获得了1992-2019年长时间序列夜间灯光影像。从定性、定量及校正影像与社会经济参量的相关性方面对校正结果进行了精度验证。结果表明,改进后的校正方法改善了DMSP-OLS影像饱和严重的现象,使其获得了长时间序列纵向可比性。BiDoseResp函数模型可以很好地拟合DMSP-OLS和对数变换后的NPP-VIIRS之间的回归。校正后的长时间序列灯光影像数据与社会经济参量高度契合。校正结果对推广长时间序列夜间灯光影像的广泛应用、深化长时间序列科学问题的研究具有重要价值。 相似文献
4.
The crater lake water from Maly Semiachik volcano in Kamchatka was used for the international analytical laboratory comparison of major and minor elements, and hydrogen, sulfur, and oxygen isotope data. Eight institutions participated in this program, giving analytical results of 9 major and 20 minor elements mainly by using ICP-AES for cations and IC for anions. Among the major elements, Na, Mg and Si showed coefficients of variation (CV) of 10% or more, whereas B, Al, Fe, Mn had coefficients less than 7%. The CV% of the minor elements Co, Cu, P, Cr, Pb was much greater (>30%) while the V analyses agreed well (<10%). Ti, Sr, Zn, and F were intermediate (between 10 and 20 CV%). The errors observed for these constituents are inherent to the methods applied: large dilutions and spectrometric interferences. Even the major anions such as Cl (>2000 ppm) and SO4 (>5000 ppm) gave considerable ranges (5.1 and 8.8 CV%, respectively) as did the obtained pH values (22 CV%). The measured δ18O of the water samples and δ34S of sulfate are in excellent agreement but the δD values had CV% of 8. Technical recommendations are presented to improve the analytical results for these elements with significant deviations from the mean values. 相似文献
5.
Salinization is one of the major soil problems around the world. However, decadal variation in soil salinization has not yet been extensively reported. This study exploited thirty years (1985–2015) of Landsat sensor data, including Landsat-4/5 TM (Thematic Mapper), Landsat-7 ETM+ (Enhanced Thematic Mapper Plus) and Landsat-8 OLI (Operational Land Imager), for monitoring soil salinity of the Yellow River Delta, China. The data were initially corrected for atmospheric effects, and then matched the spectral bands of EO-1 (Earth Observing One) ALI (Advanced Land Imager). Subsequently, soil salinity maps were derived with a previously developed PLSR (Partial Least Square Regression) model. On intra-annual scale, the retrievals showed that soil salinity increased in February, stabilized in March, and decreased in April. On inter-annual scale, soil salinity decreased within 1985–2000 (−0.74 g kg−1/10a, p < 0.001), and increased within 2000–2015 (0.79 g kg−1/10a, p < 0.001). Our study presents a new perspective for use of multiple Landsat data in soil salinity retrieval, and further the understanding of soil salinization development over the Yellow River Delta. 相似文献
6.
为了使搭载在风云三号B星上的微波成像仪MWRI（Microwave Radiation Imager）与搭载在GCOM-W1(Global Change Observation Mission 1st-Water)卫星上的AMSR-2（Advanced Microwave Scanning Radiometer 2）的数据可以衔接使用，并为以后FY-3B/MWRI北极地区遥感参数反演研究提供基础，以GCOM-W1/AMSR-2数据为对比数据，北极海洋区域为研究区域，对两传感器对应的10个通道的升、降轨亮温数据进行交叉定标。首先，对MWRI和AMSR-2各通道逐月在研究区域进行偏差分析；其次，对MWRI和AMSR-2各通道逐月在海冰区域和开阔水域进行偏差分析；最后，对MWRI和AMSR-2各通道逐月在研究区域进行交叉定标，并对定标结果进行评价。研究结果表明：（1）MWRI各通道亮温数据小于AMSR-2，且相同频率下，垂直极化各通道逐月平均偏差的绝对值大于水平极化各通道，升、降轨数据在各通道的差异较小，逐月平均偏差的差值小于1 K；（2）在海冰区域，升、降轨各通道逐月平均偏差相差小于1 K，在开阔水域则介于0—1.5 K；（3）通过进行线性回归分析，MWRI和AMSR-2各通道相关系数大于0.99，具有强相关性，并得到升、降轨各通道各月份交叉定标的斜率和截距；（4）定标后MWRI的亮温值与AMSR-2的亮温值一致性较好，说明交叉定标的效果较好。 相似文献
7.
Raphaelle Escoube Olivier J. Rouxel Béatrice Luais Emmanuel Ponzevera Olivier F.X. Donard 《Geostandards and Geoanalytical Research》2012,36(2):149-159
Recent analytical developments in germanium stable isotope determination by multicollector ICP‐MS have provided new perspectives for the use of Ge isotopes as geochemical tracers. Here, we report the germanium isotope composition of the NIST SRM 3120a elemental reference solution that has been calibrated relative to internal isotopic standard solutions used in the previous studies. We also intercalibrate several geological reference materials as well as geological and meteoritic samples using different techniques, including online hydride generation and a spray chamber for sample introduction to MC‐ICP‐MS, and different approaches for mass bias corrections such as sample–calibrator bracketing, external mass bias correction using Ga isotopes and double‐spike normalisation. All methods yielded relatively similar precisions at around 0.1‰ (2s) for δ74/70Ge values. Using igneous and mantle‐derived rocks, the bulk silicate Earth (BSE) δ74/70Ge value was re‐evaluated to be 0.59 ± 0.18‰ (2s) relative to NIST SRM 3120a. Several sulfide samples were also analysed and yielded very negative values, down to ?4.3‰, consistent with recent theoretical study of Ge isotope fractionation. The strong heavy isotope depletion in ore deposits also contrasts with the generally positive Ge isotope values found in many modern and ancient marine sediments. 相似文献
8.
Some results from phytoplankton counting intercalibrations 总被引：34，自引：0，他引：34
Dr. Eugen Rott 《Aquatic Sciences - Research Across Boundaries》1981,43(1):34-62
Phytoplankton samples from 7 different lakes were processed in 2 intercalibration series using Utermöhl's sedimentation method. Total biomass volumes obtained by most of the investigators give reliable results in respect to the mean. Numbers of individuals and mean volumes of selected species obtained by the different participants were compared and show larger variations than the overall results. Therefore a certain delimitation of particular sources of errors was tried in the 2nd intercalibration series by giving recommendations for the different steps of the whole procedure. 相似文献
9.
Intercalibration of benthic flux chambers I. Accuracy of flux measurements and influence of chamber hydrodynamics 总被引：2，自引：0，他引：2
The hydrodynamic properties and the capability to measure sediment-water solute fluxes, at assumed steady state conditions, were compared for three radically different benthic chamber designs: the “Microcosm”, the “Mississippi” and the “Göteborg” chambers. The hydrodynamic properties were characterized by mounting a PVC bottom in each chamber and measuring mixing time, diffusive boundary layer thickness (DBL thickness) shear velocity (u∗), and total pressure created by the water mixing. The Microcosm had the most even distribution of DBL thickness and u∗, but the highest differential pressure at high water mixing rates. The Mississippi chamber had low differential pressures at high u∗. The Göteborg chamber was in between the two others regarding these properties. DBL thickness and u∗ were found to correlate according to the following empirical formula: DBL=76.18(u∗)−0.933. Multiple flux incubations with replicates of each of the chamber types were carried out on homogenized, macrofauna-free sediments in four tanks. The degree of homogeneity was determined by calculating solute fluxes (of oxygen, silicate, phosphate and ammonium) from porewater profiles and by sampling for porosity, organic carbon and meiofauna. All these results, except meiofauna, indicated that there were no significant horizontal variations within the sediment in any of the parallel incubation experiments. The statistical evaluations also suggested that the occasional variations in meiofauna abundance did not have any influence on the measured solute fluxes. Forty-three microelectrode profiles of oxygen in the DBL and porewater were evaluated with four different procedures to calculate diffusive fluxes. The procedure presented by Berg, Risgaard-Petersen and Rysgaard, 1989 [Limnol. Oceanogr. 43, 1500] was found to be superior because of its ability to fit measured profiles accurately, and because it takes into consideration vertical zonation with different oxygen consumption rates in the sediment. During the flux incubations, the mixing in the chambers was replicated ranging from slow mixing to just noticeable sediment resuspension. In the “hydrodynamic characterizations” these mixing rates corresponded to average DBL thickness from 120 to 550 μm, to u∗ from 0.12 to 0.68 cm/s, and to differential pressures from 0-3 Pa. Although not directly transferable, since the incubations were done on a “real” sediment with a rougher surface while in the characterizations a PVC plate simulated the sediments surface, these data give ideas about the prevailing hydrodynamic condition in the chambers during the incubations. The variations in water mixing did not generate statistically significant differences between the chamber types for any of the measured fluxes of oxygen or nutrients. Consequently it can be concluded that, for these non-permeable sediments and so long as appropriate water mixing (within the ranges given above) is maintained, the type of stirring mechanism and chamber design used were not critical for the magnitude of the measured fluxes. The average measured oxygen flux was 11.2 ± 2.7 (from 40 incubations), while the diffusive flux calculated (from 43 profiles using the Berg et al., 1989 [Limnol. Oceanogr. 43, 1500] procedure) was 11.1 ± 3.0 mmol m−2 day−1. This strongly suggests that accurate oxygen flux measurements were obtained with the three types of benthic chambers used and that the oxygen uptake is diffusive. 相似文献
10.
海洋生物体中痕量金属分析方法的实验室间分析互校 总被引：3，自引：0，他引：3
本文介绍了我国首次海洋生物体中痕量金属分析方法的实验室间互校结果。38个实验室分别参加了铜、铅、锌、镉、铬、硒、砷和汞8种元素,共22个分析方法的分析互校。互校结果表明,除了铅的分光光度法外,其余21个分析方法均能获得准确可比的分析结果。 相似文献