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163.
电感耦合等离子体发射光谱法测定镍矿石中镍铝磷镁钙 总被引:5,自引:4,他引:1
样品用硝酸溶解,氢氟酸助溶,高氯酸冒烟除去氢氟酸,盐酸溶解盐类后,在选定的测量条件下用电感耦合等离子体发射光谱法( ICP - AES)测定镍矿中镍、铝、磷、镁、钙.选择Ni 221.6 nm、Al 396.1nm、P 178.2 nm、Mg 285.2 nm、Ca 393.3 nm分别作为镍、铝、磷、镁、钙的分析线;... 相似文献
164.
The effect of seasonally reversing monsoons in the northern Indian Ocean is to impart significant changes in surface salinity (SS). Here, we report SS changes during the last 32 kyr in the Lakshadweep Sea (southeastern Arabian Sea) estimated from paired measurements of d18O and sea surface temperature (SST) using Globigerinoides sacculifer, an upper mixed layer dwelling foraminifera. The heaviest d18OG.sacculifer (–0.07±0.08‰) is recorded between 23 and 15 ka, which could be defined as the last glacial maximum (LGM). The d18OG.sacculifer shift between the LGM and Holocene is 2.07‰. The SST shows an overall warming of 2°C from the LGM to Holocene (28°C to 30°C). However, coldest SSTs are observed prior to LGM, i.e., ~27 ka. The SS was higher (~38 psu) throughout most of the recorded last glacial period (32.5–15 ka). This high salinity together with generally lower SSTs suggests a period of sustained weaker summer or stronger winter monsoons. The deglacial warming is associated with rapid reorganization of monsoons and is reflected in decreased salinity to a modern level of ~ 36.5 psu, within a period of ~5 kyr. This indicates intensification of summer monsoons during cold to warm climate transition. 相似文献
165.
Kunchithapadam Gopalan 《Geostandards and Geoanalytical Research》2011,35(2):175-181
Two independent articles published more than a decade ago pointed to the potential of the somewhat neglected K‐Ca system for very precise K‐Ca dating and thermochronology, but have not been followed up since. In the first of these articles, highly precise determination of K and hence the K/Ca ratio in lunar granites showed the feasibility of K‐Ca dates of micas with an analytical precision known so far in only U‐Pb and Ar/Ar dating. In the second article, it was shown that responses of the K‐Ca and Rb‐Sr isotopic systems in micas subjected to a slow post‐metamorphic cooling could provide new insights into thermochronology. Crucial to the follow‐up of these two promising leads is the development of a simple and user‐friendly method for routine high precision K determination in real samples, such as the one described in this report. 相似文献
166.
Jens Jakobsen 《Geografisk tidskrift / udgivet af Bestyrelsen for Det Kongelige danske geografiske selskab》2013,113(2):103-114
Geografisk Tidsskrift, Danish Journal of Geography 106(2): 103–114, 2006 Periods characterized by agricultural change and transitions are often associated with insecurity and vulnerability regarding food production and food supplies. Forests and forest products tend to play an important buffer role during the process of change and uncertainty, where forest and fallows provide food products or income that people can temporarily fall back on. In the upland village of Que in North Central Vietnam, several different drivers are currently changing land use and land cover. The Forest Land Allocation policy, implemented in 1998, is one of the major driving forces, allocating farmers a reduced area of land for shifting cultivation in order to prevent any further deforestation and land degradation. However, the reduction in agricultural land set aside for shifting cultivation has lead to a severe decrease in hill rice production. The land use system is in a transition phase—from a conventional shifting cultivation system to a composite swiddening system. The area under shifting cultivation has been reduced, and the system has been intensified via the introduction of paddy rice cultivation, increased livestock rearing and commercial exploitation of non-timber forest products (NTFPs). Yet, the current transformation of the system has resulted in a drastic reduction in overall rice production. Thus, the collection and selling of NTFPs such as bamboo shoots, broom grass and pherynium leaves seem to prevent severe shortage of food since farmers are able to purchase food products with the money generated from the selling of NTFPs. 相似文献
167.
We conducted paired measurements of the Mg/Ca ratio and δ18O of planktonic foraminifera, Globigerina bulloides, from a sediment core (MD01‐2420) off central Japan in the northwest Pacific, to reconstruct current movements since the Last Glacial Maximum (LGM). These methods make it possible to determine the magnitude and timing of the sea surface temperature (SST) changes and to reconstruct the variations of the past seawater δ18O (δ18Ow) off central Japan. The amplitude of Mg/Ca‐based SST changes between the Holocene and the LGM was about 10°C. The strong resemblance of the SSTs estimated from both methods, Mg/Ca‐based and δ18O‐based, suggests that the SST changes were caused primarily by latitudinal displacement of the Kuroshio–Oyashio currents and no distinct change in the carbonate dissolution of the core. The southward migration of the water mass was 5–6° in latitude at the LGM. The values for regional δ18Ow changes, which were obtained by subtracting the ice volume contribution from the calculated δ18Ow, describe the millennial‐scale water mass migration over the last 30 kyr. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
168.
Genesis of underground brine along south coast of Laizhou Bay: hydrochemical characteristics 总被引:1,自引:0,他引:1
1 INTRODUCTION Two large-scale concentration mechanisms, evaporation and freezing, have been proposed for marine origin brine production (Bein and Arad, 1992; Bottomley et al., 1999). There are three basic requirements for brine formation by seawater evap… 相似文献
169.
Synchrotron radiation X-ray fluorescence (SR-XRF) approach was applied to analyzing of Chinstrap penguin ( Pygoscelis Antarctica) cortical bone. The method enabled the in situ determination of Ca and P concentrations and the Ca/P ratio in cortical bone. The preliminary results show that : ( 1 ) there is the bone site-related difference for Ca and P concentrations. The mean values for the investigated parameters ( on a dry-weight basis) are: 30.7% (Ca) and 14.9% (P) for the femoral cortical bone, 21.4% (Ca) and 11.5% (P) for wing cortical bone. (2) The variation for the Ca/P ratio in cortical bone is lower than those for Ca and P separately. This is in agreement with the previous report that the specificity of the Ca/P ratio is better than that of Ca and P concentrations and is more reliable for the diagnosis of bone disorders. The authors suggest that further studies be conducted to establish norreal values of Ca, P and Ca/P ratio for polar animals and provide a basis for the diagnosis of bone disorders. 相似文献
170.
Heather M. Stoll Christine M. Klaas Ian Probert Jorge Ruiz Encinar J. Ignacio Garcia Alonso 《Global and Planetary Change》2002,34(3-4)
Five common placolith-bearing coccolithophorid algae—Gephyrocapsa oceanica, Coccolithus pelagicus, Calcidiscus leptoporus, Umbilicosphaera sibogae (var. sibogae and var. foliosa), and Emiliania huxleyi—were cultured to investigate controls on Sr partitioning in coccolith calcite. For identical temperature and media composition, Sr partitioning varies by more than 30% in exponential phase cultures of the five species and is linearly related to rates of calcite production/cell (ρ=0.91). Exponential phase culture experiments with three strains of C. leptoporus and six strains of G. oceanica at varying temperatures show variations in Sr partitioning of 20% and 30%, respectively. With C. leptoporus, Sr partitioning is equally correlated with temperature and calcification rate (ρ=0.8), which themselves are highly correlated; the slope of the relationship between DSr and calcification rate is comparable to that observed in all species at constant temperature. However, in G. oceanica, increased temperature appears to enhance Sr incorporation by up to 2% to 1.6% °C−1 in the range of 15 to 30 °C. The strong influence of calcification rate on Sr partitioning may be useful for inferring past variations in coccolithophorid productivity from Sr partitioning in coccolith sediments if the influence of temperature on Sr partitioning can be resolved. Because the relationship between calcite production and Sr partitioning is linear, a proportional change in calcification should be expressed much more strongly in the Sr/Ca ratio of large species with rapid calcite production than in smaller species, which produce calcite more slowly. Consequently, it may be possible to separate temperature and calcification influences on coccolith Sr/Ca by separately analyzing Sr/Ca in species that produce calcite rapidly and those that produce calcite slowly, if both undergo comparable relative changes in calcification rates. 相似文献