10Be和26Ai揭示的合黎山西南部侵蚀速率初步研究

地表侵蚀速率是衡量地貌演化的一个重要因子。本研究利用原地宇宙成因核素 10Be 和 26Al 对合黎山西南部地表岩石侵蚀速率进行了首次测定。结果显示：约 30 ka 以来，合黎山西南部的地表岩石侵速率约为 24 mm∙ka-1。这一结果与已见报道的其他基岩侵蚀速率值一致。这一结果与 Small et al 获得的非干旱地区的基岩侵蚀速率也基本一致，但是显著高于干旱的南极地区和半干旱的澳大利亚。10Be 和26Al 获得的侵蚀速率的良好一致性表明本研究中所用侵蚀模式的有效性。所得的侵蚀速率小于 Palumbo et al 测定的合黎山平均流域侵蚀速率（99 mm∙ka-1），原因解释尚待更多地点和样品的研究。<br style="line-height: normal; text-align: -webkit-auto; text-size-adjust: auto;" /

Authentication of red wine vintage using bomb-pulse 14C

As a result of atmospheric atomic explosions carried out in the 1950's to 1963 a potential method for the short term dating of wines has emerged based on the determination of 14C in wine components. The atmospheric nuclear explosions released relatively large quantities of 14C into the atmosphere which was incorporated into carbon dioxide. The immediate post test 14CO2 concentration in the atmosphere initially decreased due to its uptake in marine and terrestrial carbon reservoirs. More recently, the dilution of 14CO2 in the atmosphere has been driven by the burning of fossil fuels which are depleted in 14C (because of radioactive decay).The uptake and sequestering of atmospheric CO2 by plants means that by accurately measuring the amount of residual 14C in plant derived-products, the year when that sequestration took place can be determined. The amount of 14C in grape-derived components in the wine, such as alcohol, has been used to reliably determine red wine vintage. Measurement of the residual levels of 14C in additional components in the wine, such as the phenolic compounds, makes the method more robust and less easily circumvented by illicit additions. © 2011 American Chemical Society.Robert E. Asenstorfer, Graham P. Jones, Gerald Laurence, and Ugo Zopp

Performance of Accelerator Mass Spectrometry for I-129 using AgI-AgCl carrier-free coprecipitation

I-129 has been successfully applied as tracer in environmental, geological, and oceanographic research. For samples with low stable iodine concentration and ultra low level I-129, the sample preparation technique to separate iodine prior to AMS measurement has been a bottleneck, limiting the applicability of I-129 We have reported a carrier-free method, using coprecipitation, to avoid the potential introduction of I-129 through the use of stable iodine carrier iodine. In this work, the detection limit and the analytical uncertainty of this method are investigated and minimum sample amount required to obtain reliable analytical results are estimated. The method is validated with a series of samples in ranges of known iodine concentrations and I-129/I-127 ratios. The results confirm our previous conclusion that an AMS target containing 5.0 mu g iodine can be used for analyzing samples with I-129/I-127 &gt; 10(-12), and that for samples with I-129/I-127 &lt; 10(-13) more than 25 mu g iodine is necessary.</p

A preliminary study of small-mass radiocarbon samplemeasurement at Xi’an-AMS

To meet the measurement demands on small-mass radiocarbon (carbon content at 10&minus;6 g level) which are becoming increasingly significant, Xi&rsquo;an-AMS has made improvements to the existing method of sample loading and has upgraded the Cs sputter ion source from the original SO-110 model. In order to study the feasibility of small-mass samples in Xi&rsquo;an-AMS and evaluate the radiocarbon sample preparation ability using existing routine systems of H2/Fe and Zn/Fe, the small-mass samples prepared by four different methods are tested. They are the mass division method, mass dilution method, H2/Fe reduction method and Zn/Fe reduction method. The results show that carbon mass above 25 &micro;g can be prepared using the existing Zn/Fe system, but no less than 100 &micro;g is required using the existing H2/Fe system, which can be improved. This indicates Xi&rsquo;an-AMS are now able to analyze small-mass radiocarbon samples.</p

Be-10 signature of the Matuyama-Brunhes transition from the Heqing paleolake basin

We present a new 10Be record spanning the Matuyama-Brunhes (M-B) reversal from the Heqing paleolake basin in southern China. It provides a robust proxy for past geomagnetic variations that can be compared with paleomagnetic records. The M-B transition is identified as a pronounced maximum of authigenic 10Be/9Be ratio between 768.6 and 778.5 ka, that is consistent with all other available 10Be-proxy records from marine, ice and loess archives. However, it is offset by approximately 0–60 cm depth from the magnetic signature of the polarity transition recorded in the same sediments. We attribute this offset to the lock-in effect of the remanence acquisition process, which is similar to the phenomenon that exists in marine sediments. We suggest that after eliminating the climatic-hydrological signal, the Heqing sediments may be used as an archive for atmospheric 10Be production rate changes. The combination of magnetic remanence measurements and the cosmogenic 10Be allows for a more precise geochronology of geomagnetic polarity reversals

Observations of Atmospheric Δ14CO2 at the Global and RegionalBackground Sites in China: Implication for Fossil Fuel CO2 Inputs

Six months to more than one year of atmospheric &Delta;14CO2 were measured in 2014-2015 at one global background site in Waliguan (WLG) and four regional background sites at Shangdianzi (SDZ), Lin&#39;an (LAN), Longfengshan (LFS) and Luhuitou (LHT), China. The objectives of the study are to document the &Delta;14CO2 background levels at each site and to trace the variations in fossil fuel CO2 (CO2ff) inputs at regional background sites. &Delta;14CO2 at WLG varied from 7.1&plusmn;2.9&permil; to 32.0&plusmn;3.2&permil; (average 17.1&plusmn;6.8&permil;) in 2015, with high values generally in autumn/summer and low values in winter/spring. During the same period, &Delta;14CO2 values at the regional background sites were found to be significantly (p &lt; 0.05) lower than those at WLG, indicating different levels of CO2ff inputs at those sites. CO2ff concentrations at LAN (12.7&plusmn;9.6 ppm) and SDZ (11.5&plusmn;8.2 ppm) were significantly (p &lt; 0.05) higher than those at LHT (4.6&plusmn;4.3 ppm) in 2015. There were no significant (p &gt; 0.05) seasonal differences in CO2ff concentrations for the regional sites. Regional sources contributed in part to the CO2ff inputs at LAN and SDZ, while local sources dominated the trend observed at LHT. These data provide a preliminary understanding of atmospheric &Delta;14CO2 and CO2ff inputs for a range of Chinese background sites.</p

Level and source of 129I of environmental samples in Xi'an region, China

Iodine-129 is widely used as a tracer in various environmental practices such as monitoring of nuclear environmental safety, seawater exchange and transport, geochemical cycle of stable iodine and dating of geological events. The spatial distribution of (129)I concentration varies significantly on global scale because of anthropogenic input from nuclear activities coupled with scarcity of data on environmental (129)I variability in many parts of the world including Asia. Here we report new data on (129)I and (127)I concentrations in soil, vegetation, river water and precipitation collected from Xi&#39;an area, China. The results indicate values for environmental (129)I/(127)I ratios in the investigated area range from 1.1 x 10(-10) to 43.5 x 10(-10) with a mean of 20.6 x 10(-10), which is 1-3 orders of magnitude lower than the ratios observed in Europe, but comparable with those observed in the locations far from direct effect of point release sources and at similar latitude. The main source of (129)I in the investigated area is attributed to the global fallout of both atmospheric nuclear weapons testing and long distance dispersion of fuel reprocessing releases. (C) 2011 Elsevier B.V. All rights reserved.</p

HIGH-LEVEL (14)C CONTAMINATION AND RECOVERY AT XI'AN AMS CENTER

A sample with a radiocarbon concentration estimated to be greater than 10(5) times Modern was inadvertently graphitized and measured in the Xi&#39;an AMS system last year. Both the sample preparation lines and the ion source system were seriously contaminated and a series of cleaning procedures were carried out to remove the contamination from them. After repeated and careful cleaning as well as continuous flushing with dead CO(2) gas, both systems have recovered from the contamination event. The machine background is back to 2.0 x 10(-16) and the chemical blank is beyond 50 kyr.</p

Determination of Low Level 129I in Soil Samples Using Coprecipitation Separation of Carrier Free Iodine and Accelerator Mass Spectrometry Measurement

The accurate determination of ultra low level (129)I in sample is critical and essential for the application of natural (129)I in geological dating and environmental tracer studies. In this work, iodine was first separated from soil by combustion at high temperature; the released iodine was collected in an alkali trap solution. AgI-AgCl coprecipitaiton was used to separate carrier free iodine from the trap solution and to prepare target. (129)I in the target was then measured using a 3. 0 MV accelerator mass spectrometer. The recovery of iodine during the combustion is higher than 95%. An iodine recovery of about 75%-85% was obtained in the coprecipitation and the total recovery of iodine is above 70%. The developed method has been successfully used to determine (129)I in soil sample with low iodine content. A (129)I/(127)I atomic ratio as low as 10(-11) in the deep soil has been determined. The determination of (129)I/(127)I was ratio down to 10(-12) in solid samples.</p