210Pb, 226Ra and 32Si in Pavin lake (Massif Central,France)

Measurements of cosmogenic ³²Si and the U-decay series' nuclides ²¹⁰Pb and ²²⁶Ra in waters and sediments of lake Pavin are reported. Both ²¹⁰Pb and ²²⁶Ra are enriched in the anoxic deep waters compared to the oxic surface waters, respectively by a factor of 4 and 10, whereas ³²Si is depleted by a factor of2. Redox conditions in the lake appear to have no marked effect on the ³²Si. Using a steady-state box model it is shown that the deep-water ³²Si concentration is controlled by the underground lacustrine springs. The residence times of ²¹⁰Pb, ³²Si and ²²⁶Ra are1,10 and80 a, respectively. In the case of ³²Si, where more data are available, the assessed inventory data from the overhead atmospheric fallout and that measured in the sediments agree very well as expected. The ²¹⁰Pb- and ³²Si-based deposition rates during the past100 a ranged from 0.8 to 1.9 mm a⁻¹, earlier these were a factor of3–5 faster. The geochemistry of ³²Si and ²¹⁰Pb in lake Pavin in many ways resembles that in the ocean, only the time scales of the processes involved are faster.     

Basal flow rate of Changme-Khangpu glacier,Sikkim Himalaya based on32Si and210Pb chronology

Using environmental radioisotopes silicon-32 and lead-210, the radiometric ages of ice at the surface and at 5 m depth at the snout of the Changme-Khangpu (ck) glacier have been calculated to be 100 and >650 years respectively. Based on i) these age estimates, ii) a net uniform accumulation rate of 0·7 m/yr of ice in the accumulation zone; and iii) applying a simple ice flow model assuming melting of ice of 1 cm/yr at the base of the glacier, it is demonstrated that the average basal flow rate of theck glacier is much smaller (at least by a factor of three) than that of 40 m/yr estimated for the surface ice. This observation is in good agreement with the earlier work on basal flow rates and indicates that the deeper ice near the bed rock travels much slower than the surface ice.     

Rate of sediment accumulation in lakes of Udaipur,Rajasthan, India,using the210Pb method

Sediment accumulation rates have been determined in Udai Sagar, Fateh Sagar and Pichola lakes, which lie in the arid climatic zone, using the²¹⁰Pb method. The rate of sedimentation estimated in these lakes is 8.9, 3.42, and 2.80 mm/yr, respectively. River inflow, mining activity, and lithology contribute to controling the sediment deposition pattern in Udai Sagar Lake, whereas in Fateh Sagar and Pichola lakes, anthropogenic activity and erosion of loosely bound terrigenous material through wave action and varying lithology are the major contributors. Furthermore, a contribution from atmospheric fallout has not been ruled out due to occurrence of frequent duststorms, owing to strong wind conditions aided by barren hills devoid of vegetation as well as dumping of mining wastes in the area. The higher TDS and lower sedimentation rate in Pichola Lake compared to Fateh Sagar are due to the limestone lithology and better maintenance in the former, such as construction of parks, graveled roads, etc., to check the flow of silt into the lake. Fluctuations in metal content, for example, V, Cr, Co, Ni, Sr, and sedimentation rates are due to the variation in the sediment input at different time intervals.     

Sediment accumulation rate in the lakes of Kumaun Himalaya,India using210Pb and226Ra

The rate of sedimentation and the source of sediments in the lake basins of Nainital region, Kumaun Himalaya, have been estimated employing²¹⁰Pb and²¹⁰Ra methods. This has yielded a rate of sedimentation of 11.5, 4.70, 3.72, and 3.00 mm/yr in Nainital, Bhimtal, Naukuchiyatal, and Sattal lakes, respectively. The higher rate of sedimentation in Nainital lake, compared to other lakes, is related to faster erosion in the catchment aided by greater anthropogenic activity, while the slowest rate in Sattal lake is due to less erosion and more input of soil-derived material involving a slow rate of accumulation.     

黔中气溶胶传输的210 Pb和7 Be示踪:I.周时间尺度的解释

认识环境核素在不同地域空气中的浓度分布和沉降到地表环境的通量对气溶胶污染物全球扩散模型的建立和验证、沉积过程示踪和沉积计年、流域侵蚀示踪参比,以及生态系统受天然辐照的评价等多个领域都是关键的依据.自2001年以来在贵阳观风山等地逐周连续采样,对近地面空气和降水中210Pb和7Be浓度的观测结果表明:①因气象条件变化,近地面空气210mPb和7Be周浓度具有2～6周变幅不等的短周期波动.210Pb空气浓度在年内的总趋势呈现出受气温变化的总体影响和降水的短暂调控;而7Be空气浓度出现连续不断的峰-谷交替.②两核素在近地面空气周浓度的低值同步,210Pb/7Be比率较高(≥0.8),显示出海洋性贫210Pb-7Be气团的入侵影响;它们高的周浓度也同步耦合,比率较低(≤0.7),显示出高层大气富7Be气团的输入.③210Pb和7Be的周降水浓度及水-气分配系数在秋末春季较高,而春末-秋季明显偏低.周降水浓度随同期空气浓度呈增高趋势,其季节分界分别为0.2 Bq/L和1 Bq/L;而Kd值随同期空气浓度增大呈降低趋势.210Pb和7Be的降水沉降主要分布在每年的春夏季;周沉降量随同期降水量呈增大趋势,7Be增大的斜率约为210Pb的3倍;当近于零降水时,它们在降水中的初始比率约为2.5.它们出现高或者较高的周降水沉降都伴随当周或邻周空气浓度的急剧下降;降水中210Pb/7Be比率主要分布在≤0.5,并与空气中210Pb/7Be比率基本同步,显示出两核素被降水清洗的效率基本相近.④2008年冰冻极端天气过程中,210Pb-7Be空气浓度同步低谷并存在气溶胶低浓度与高比活度耦合.⑤观风山7Be周空气浓度显示低纬度、较高海拔地区的预期水平;短周期波动反映强下沉气流和低海拔上升气团影响分别在观风山和瓦里关山的滞后性.     

Atmospheric pollutants transport tracks revealed from 131I, 137Cs,and 134Cs leaked from Fukushima accident and 7Be and 210Pb observed at Guiyang of China

A massive earthquake measuring 9.0 on the Richter scale that occurred on March 11, 2011, on Honshu Island, Japan, caused radioactivity leakage from the Fukushima Nuclear Power Plant, which led to the leakage of artificial nuclides （131I, 137Cs, and 134Cs） and their global transportation by atmospheric circulation. This paper re- ports a systematic comparative observation on radioactive concentrations of natural nuclides （7Be and 210Pb） and artificial nuclides （131I, 137Cs, and 134Cs） at the surface level, measured in weekly continuous aerosol sampling at Mount Guanfeng, Guiyang, China, from March 17, 2011 to April 28, 2011. During this period, the variations in the nuclide concentrations associated with their transport paths were analyzed with 315 hour back-trajectories of air mass initialized 500 m above the surface level at Guiyang. The results show that the pollutants of nuclear leakage from the Fukushima accident were transported to the Guiyang region of China via two significant pathways. In the first pathway the first wave of nuclear pollutants were transported from west to east in air masses at higher altitudes via global atmospheric circulation. The nuclear pollutants encircled the Earth almost once and after about 10 days to two weeks, between March 24 and March 31,2011, intruded Guiyang from the northwestern region of China. In the second pathway, the nuclear pollutants from the Fukushima region arrived at Guiyang between April 7 and April 14, 201 l, via air masses at lower altitudes that moved southwards because of the squeezing of the northeast Asian weather system and then by the influence, in succession, of the northeastern and southeastern air currents in the low-latitude region. The first transport pathway for atmospheric pollutants is on a global scale and based on air masses at higher altitudes, and the second transport pathway is on an eastern Asia regional scale and based on the air masses at lower altitude.     

Determination of 210Pb, 226Ra and 137Cs in sediments

A method is described for bringing a sediment sample into solution and subsequently carrying out analysis for ²¹⁰Pb, ²²⁶Ra and ¹³⁷Cs. Silica is removed from the sample by cyclic HNO₃HF treatments. ¹³⁷Cs is separated from ²¹⁰Ra in a carbonate fusion, extracted by absorption on ammonium molybdophosphate, precipitated directly with BiI₃ in presence of citric acid, and β-counted. ²¹⁰Pb and ²²⁶Ra are separated out by 70–75% HNO³ precipitation. Further purification and mutual separation of the two radionuclides is achieved by solvent extraction and anion-exchange techniques. ²¹⁰Pb and ²²⁶Ra are determined by β- and α- counting of their chromate precipitates, respectively, after allowing suitable ingrowth periods for their daughters. The procedural steps effectively eliminate possible interference from other natural or fall-out radioactivities.     

Concentrations,physico-chemical states and mean residence times of 210Pb and 210Po in marine and estuarine waters

The concentrations and physico-chemical states of ²¹⁰Pb have been measured in Bikini Atoll and Washington State coastal waters, and ²¹⁰Po in Washington coastal waters. Lead-210 concentrations of 113–133 dpm · m^?3 were found in surface water collections near Bikini Atoll and 29–153 dpm · m^?3 in Bikini Lagoon. The concentrations of ²¹⁰Pb in near Bikini and in Washington State waters increased with depth in the upper 150m at a rate of 0.35–0.45dpm·m^?3 · m^?1. In the North Equatorial Current waters near Bikini Atoll ²¹⁰Pb was found associated predominantly with the soluble (colloidal) fraction, but in Washington coastal waters ²¹⁰Pb and ²¹⁰Po were found associated with the paniculate (> 0.3 μm) fraction. The mean residence times of ²¹⁰Pb, calculated from the atmospheric input to marine waters from precipitation and the concentrations measured in surface water, were consistent with the physico-chemical states of ²¹⁰Pb found in samples collected in deep ocean and coastal waters. Approximate values of the mean residence times were calculated, for the upper 50 m, to be as follows: 58 days in the Strait of Juan de Fuca, 128 days at the 5-mile (8 km) station off Cape Flattery (Washington), 163 days at the 12-mile (19 km) station off Cape Flattery, and 2.6 yr near Bikini Atoll. It appears that ²¹⁰Pb and ²¹⁰Po can be used to trace particle removal rates in the upper layers of marine waters.     

深圳市大气210Pb的活度浓度、沉降通量和沉积速率研究

2017年1月至12月,研究分析了深圳市大气气溶胶中210Pb的活度浓度、沉降通量和沉积速率.结果表明,深圳市大气210Pb比活度范围为0.59～4.72 mBq/m3(平均值为1.58 mBq/m3);沉降通量范围为0.45～1.31 Bq/(m2·d)(平均值为0.74 Bq/(m2·d));沉积速率范围为0.09...     

A biogeochemical mass balance of 210Po and 210Pb in an oligotrophic lake with seasonally anoxic hypolimnion

The mass balances of ²¹⁰Po and ²¹⁰Pb were determined for Bickford Pond, Massachusetts. Activities of these nuclides at various depths within the water column, in sediments, in streams flowing into and out of the lake and in precipitation were measured at approximately monthly intervals for a period of one year. Streamwater contained about 10 dpm/100 kg of ²¹⁰Pb, mostly filtrable and showed little variation with changing flow. ²¹⁰Pb in the streams is believed to be derived mostly from ²²²Rn that enters groundwater via alpha-recoil from aquifer matrix materials. It is therefore not meteoric in origin and represents a local source to the lake. Surface inflow was equally important as precipitation as a source of ²¹⁰Pb to the lake. Only half of total ²¹⁰Pb input was trapped in sediments; the rest was lost from the lake as outflow. The ²¹⁰Pb removal times via scavenging and sedimentation both averaged close to 40 days and ²¹⁰Pb scavenging was almost an order of magnitude greater than that of ²¹⁰Po.     

吉林小龙湾沉积速率的210Pb和137Cs年代学方法测定

吉林省辉南县、靖宇县境内有很多小型湖泊(人称龙湾),属火山成因,也可称作玛珥湖^[1]。其中小龙湾(42°18′N,126°22′E),位于辉南县境内,湖面海拔655m,近椭圆形,湖泊长、宽分别约400m和250m,是该区最小的一个积水玛珥湖,湖泊周围无地表径流输入,湖泊面积基本等同流域面积。周围山体海拔约700m,植被茂盛,主要由多旋回、互层的玄武质火山碎屑岩组成,包括火山角砾岩和凝灰岩。2001年6月在湖泊中心部位水深14.41m处,用重力取样器钻取湖泊沉积岩心,岩心长49cm。该孔沉积岩性均一,     

黄海和渤海沉积物 210Pb活度的分布特征

利用α多道能谱仪测定了黄海和渤海海域 58个表层沉积物样品的 210Pb活度,探讨了黄海和渤海表层沉积物中 210Pb活度的空间分布特征.渤海中部、北黄海中部泥质沉积区和南黄海中部泥质沉积区是 210Pb活度的高值区.渤海湾内、莱州湾内及北黄海西南部沿岸海域则是 210Pb活度的低值区.黄海和渤海海区 210Pb的富集、分布特征受到研究海区水动力条件和沉积物粒级的制约.根据位于黄海和渤海泥质沉积区的 3个岩芯 210Pb活度的垂直分布资料,并结合 2个站位所取岩芯的 210Pb活度的垂直分布资料,探讨了 210Pb活度的垂直分布与沉积环境之间的关系.黄海和渤海 210Pb活度呈现高值的泥质沉积区,其 210Pb活度随岩芯深度衰减的垂直分布很有规律且沉积速率较低,由此可以反映泥质沉积区稳定的沉积环境.     

桂林西北郊光明山峰丛坡地土壤210Pb与226Ra分布与迁移规律研究

利用单一210Pb技术来估算岩溶区土壤侵蚀、水土流失和泥沙来源等还存在一定问题。岩溶区土层厚度不一,难以准确地确定支持性210Pb放射比活度是制约该方法应用的一大关键问题。文章选取桂林西北郊光明山岩溶峰丛坡地的4个土壤剖面,测试了土壤剖面210Pb与226Ra放射性比活度,探讨其分布规律及影响因素,初步确定土壤中支持性210Pb放射性比活度。测试结果表明4个土壤剖面中210Pb垂向分布服从指数衰变规律, 226Ra放射性比活度随土壤深度增加基本不变。光明山峰丛山坡土壤中约95%的210Pbex主要聚集在0~10 cm深度处,地表20~30 cm以下基本为支持性210Pb。土壤中支持性210Pb放射性比活度约为56.60±11.97 Bq?kg-1,与226Ra放射性比活度值64.93±8.83 Bq?kg-1在误差范围内一致。进一步研究发现,土壤剖面中210Pb受研究区大气干湿沉降、植被覆盖类型、地形条件、土壤特性（特别是有机质）的影响。此外,研究区土壤剖面226Ra的差异主要与土壤特性和植被类型有关。      

High-pressure crystal chemistry of phenakite (Be2SiO4) and bertrandite (Be4Si2O7(OH)2)

Compressibilities and high-pressure crystal structures have been determined by X-ray methods at several pressures for phenakite and bertrandite. Phenakite (hexagonal, space group R \(\bar 3\) ) has nearly isotropic compressibility with β=1.60±0.03×10^?4 kbar^?1 and β=1.45±0.07×10^?4 kbar^?1. The bulk modulus and its pressure derivative, based on a second-order Birch-Murnaghan equation of state, are 2.01±0.08 Mbar and 2±4, respectively. Bertrandite (orthorhombic, space group Cmc2₁) has anisotropic compression, with β _a =3.61±0.08, β _b =5.78±0.13 and β _c =3.19±0.01 (all ×10^?4 kbar^?1). The bulk modulus and its pressure derivative are calculated to be 0.70±0.03 Mbar and 5.3±1.5, respectively. Both minerals are composed of frameworks of beryllium and silicon tetrahedra, all of which have tetrahedral bulk moduli of approximately 2 Mbar. The significant differences in linear compressibilities of the two structures are a consequence of different degrees of T-O-T bending.     

Transport and sediment accumulation of210Pb and137Cs in two Southeast Alaskan fjords

Sediment profiles of²¹⁰Pb and¹³⁷Cs in cores collected at increasing distances from the heads of Smeaton Bay and Boca de Quadra fjords indicate that watersheds influence the inventories of radioisotopes present and that the steep topographies of the fjords enhance sediment redistribution. Episodic deposition of terrestrially derived sediment was responsible for roughly 50% of the¹³⁷Cs and 45% of the²¹⁰Pb inventories in shallower (less than 180 m) locations in Wilson and Bakewell arms of Smeaton Bay.²¹⁰Pb sedimentation rates at shallower sites when corrected for episodic deposition were less than sedimentation rates obtained in the deep basins of the fjords where sediment focusing and increased primary productivity in the overlying water column occur. Higher fluxes of dissolved Mn from surficial sediments and subsequent reoxidation in the overlying water may have enhanced scavenging of²¹⁰Pb in basin locations, resulting in higher inventories. Episodic events have occurred frequently in Smeaton Bay and Boca de Quadra suggesting that steady-state conditions with respect to sedimenting particles can be achieved only when averaged over long time periods approaching the time over which¹³⁷Cs and²¹⁰Pb are useful.     

黄龙钙华210Pb计年与现代沉积的环境变化研究

本文以黄龙钙华岩芯为主要研究对象,利用210Pb定年技术在测定年轻碳酸盐样品短时间尺度上的优势建立了研究区近100年来高精度的年代标尺及环境记录;通过碳氧稳定同位素的分析,讨论了钙华稳定同位素记录与器测气候数据的相关性特征,并与其他定年技术所获得的结果进行了相互验证.研究区钙华δ18O在1908~2004年时段内的变化范围为-12.13‰~10.42‰,平均值为-11.23‰,变化幅度达到了1.7‰.同属西南季风区、由于海拔效应和距离水汽来源远近不同等因素的影响,在同时段内黄龙钙华δ18O.的变化范围和变化幅度都比董歌洞和Kahf Defore洞的δ18O记录要大,说明处于中纬度、高海拔的黄龙钙华相对于低海拔的董歌洞和Kahf Defore洞石笋对气候环境的响应可能更加敏感.     

长江河口水下三角洲210Pb分布特征及其沉积速率

通过对长江水下三角洲采集的十个沉积物柱状样中的放射性核素210Pb分析得知,长江水下三角洲表层210Pb放射性比度在2.15~4.22 dpm·g-1之间,210Pb沉降通量在1.50~11.21 dpm·cm-2 yr-1之间,过剩210Pb总量在>48.29~>361.68 dpm·cm-2之间;210Pb沉降通量以及过剩210Pb总量均高于理论值,这表明在沉积物中存在210Pb的净输入和聚集。由210Pb放射性比度剖面所反映的沉积速率可知长江水下三角洲泥质沉积区沉积速率介于1.36~4.11 cm·yr-1之间;总体上呈现近岸沉积速率较低,沿31°N纬线向20 m等深线沉积速率升高的趋势,从122°15′E到122°30′E范围为长江水下三角洲的泥质沉积物堆积中心,其平均沉积速率为3.51 cm·yr-1。     

Vulnerability of headwater catchment resources to incidences of <Superscript>210</Superscript>Pb excess and <Superscript>137</Superscript>Cs radionuclide fallout

Recent identification of elevated excess ²¹⁰Pb (≤302.6 mBq L⁻¹) and ¹³⁷Cs (≤111.3 mBq L⁻¹) activity in drinking water wells up to 20 m depth indicates some transport of airborne radionuclide fallout beyond soils in the Shaker Village catchment, Maine. Estimated airborne mass loading ²¹⁰Pb_ex fluxes of about 0.9 mBq m⁻³, canvass this headwater catchment and may be sufficient to pose risks to unprotected shallow wells. Inventories of ²¹⁰Pb_ex and ¹³⁷Cs in pond sediments indicate maximum median activities of 943 mBq g⁻¹ and 40.0 mBq g⁻¹, respectively. Calculated ²¹⁰Pb_ex fluxes in the catchment soils range from 0.62–0.78 Bq cm⁻² year⁻¹ and yield a mean residence time of near 140 years. Measured ¹³⁷Cs activity up to 51.1 mBq g⁻¹ occurs in sediments at least to 5 m depth. Assumed particle transport in groundwater with apparent ⁸⁵Kr ages less than 5 years BP (2005) may explain the correlation between these particle-reactive radionuclides and elevated activity in some drinking water wells.