210Po法在铀矿勘探中的应用效果     

曹晓满 《铀矿地质》2006,22(3):177-181

通过对210Po法的工作原理、野外工作方法、室内化学处理过程、资料整理与成果解释的详细描述和对应用实例的比较与分析研究,认为210Po法不仅在南方铀矿勘探中具有可靠的适用性,在北方砂岩型铀矿勘探中也能有效地发挥作用。  相似文献   

Nitrate in the atmospheric boundary layer of the tropical South Pacific: Implications regarding sources and transport     

Dennis L. Savoie  Joseph M. Prospero  John T. Merrill  Mitsuo Uematsu 《Journal of Atmospheric Chemistry》1989,8(4):391-415

Weekly bulk aerosol samples collected at Funafuti, Tuvalu (8°30S, 179°12E), American Samoa (14°15S, 170°35W), and Rarotonga (21°15S, 159°45W), from 1983 through most of 1987 have been analyzed for nitrate and other constituents. The mean nitrate concentration is about 0.11 g m^–3 at each of these stations: 0.107±0.011 g m^–3 at Funafuti; 0.116±0.008 at American Samoa; and 0.117±0.010 at Rarotonga. Previous measurements of mineral aerosol and trace metal concentrations at American Samoa are among the lowest ever recorded for the near-surface troposphere and indicate that this region is minimally affected by transport of soil material and pollutants from the continents. Consequently, the nitrate concentration of 0.11 g m^–3 can be regarded as the natural level for the remote marine boundary layer of the tropical South Pacific Ocean. In contrast, over the tropical North Pacific which is significantly impacted by the transport of material from Asia and North America, the mean nitrate concentrations are about three times higher, 0.29 and 0.36 g m^–3 at Midway and Oahu, respectively. The major sources of the nitrate over the tropical South Pacific are still very uncertain. A very significant correlation between the nitrate concentrations at American Samoa and the concentrations of ²¹⁰Pb suggests that transport from continental sources might be important. This continental source could be lightning, which occurs most frequently over the tropical continents. A near-zero correlation with ⁷Be indicates that the stratosphere and upper troposphere are probably not the major sources. A significant biogenic source would be consistent with the higher mean nitrate concentrations, 0.16 to 0.17 g m^–3, found over the equatorial Pacific at Fanning Island (3°55N, 159°20W) and Nauru (0°32S, 166°57E). The lack of correlation between nitrate and nss sulfate at American Samoa does not necessarily preclude an important role for marine biogenic sources.  相似文献   

The transport and mass balance of fallout radionuclides in Blelham Tarn, Cumbria (UK)     

P.G. Appleby  E.Y. Haworth  H. Michel  D.B. Short  G. Laptev  G.T. Piliposian 《Journal of Paleolimnology》2003,29(4):459-473

Although lake sediment archives are widely used for reconstructing historical records of atmospherically delivered pollutants, the quantitative relationship between fallout levels and their record in the sediments is complex and not well known. The original input signal from the atmosphere can be significantly distorted by mediating transport processes in the catchment, through the water column and within the sediments themselves. Since these processes also affect the fallout radionuclide ²¹⁰Pb commonly used to date sediments, a better understanding of their impact is also important to improving the accuracy and reliability of sediment dating. Blelham Tarn has been the subject of a number of palaeolimnological investigations using radiometric dating techniques since the early 1970s. More recently it was the site of a major study carried out within the EU Transuranics project concerning the long-term fate of fallout radionuclides in catchment/lake systems. This paper reviews the radiometric data from this study and uses the results to determine mass balances for fallout ²¹⁰Pb, ¹³⁷Cs and ^239+240Pu in Blelham Tarn, and their spatial distribution over the bed of the lake. Atmospheric fluxes were determined by measuring concentrations in rainwater and cumulative inventories in soil cores from non-eroding sites. Sediment records in a grid of 16 cores were used to determine the spatial distribution over the bed of the lake, and net inputs from the catchment. Mass balance calculations indicate that c. 47% of ²¹⁰Pb in the sediments derives from erosive inputs from the catchment. For ^239+240Pu the figure rises to 61%. Reduced amounts of ¹³⁷Cs in the sediments are attributed to greater losses of this radionuclide from the water column via the outflow due to its greater solubility. Inputs of radionuclides from the catchment are concentrated near one of the major input streams. Away from this part of the lake the sediment record is dominated by direct atmospheric fallout, though the detailed pattern is influenced by sediment focussing. A one parameter catchment/lake transport model is developed that incorporates the assumption that transport rates will decline with time as fallout on the catchment diffuses into the soil and becomes less available for removal. Values of the transport parameter were calculated for ²¹⁰Pb and ^239+240Pu and found to be comparable. The results suggest that it will take c. 11000 years to remove 50% of ^239+240Pu from the catchment to the lake.  相似文献   

Sedimentary response of Pagham Harbour, southern England to barrier breaching in AD 1910     

A. B. Cundy  A. J. Long  C. T. Hill  C. Spencer  I. W. Croudace 《Geomorphology》2002,46(3-4)

This paper examines the evolution of Pagham Harbour, southern England following storm-induced breaching of a protective barrier in AD 1910. Stratigraphic studies of sediments collected from intertidal areas show the presence of a distinct stratigraphic horizon in the northeast of Pagham Harbour at ca. 0 to +1.0 m ordnance datum (OD). Radiometric data indicate that this horizon is a ‘reclamation surface’ formed after land claim in AD 1846. Following marine flooding in AD 1910, sediment has accreted relatively rapidly (at a broadly constant rate of between 4 and 8 mm a⁻¹), wave and/or tidal energy have decreased and extensive marshes have developed. An asymptotic reduction in sediment accretion rate through time, as predicted in various theoretical models of salt marsh accretion, is not observed. Over the entire Pagham Harbour area, the period between AD 1948 and AD 1986 has seen an average marsh loss of 0.0087 km² a⁻¹, which is relatively small in comparison with other more exposed sites in the local area. Historically breached sites such as Pagham Harbour are common around European coasts, and these provide important natural laboratories within which the medium-term (decadal to centennial) coastal response to barrier breaching, and to managed-realignment coastal protection schemes, can be assessed.  相似文献   

Problems of core correlation,sediment source ascription and yield estimation in Ponsonby Tarn,West Cumbria,UK     

F. Oldfield  P. G. Appleby  K. D. Van der Post 《地球表面变化过程与地形》1999,24(11):975-992

A suite of 27 short cores, 10 of which have been used for magnetic measurements and four for radiometric dating, provides a framework for reconstructing the processes, patterns and rates of sedimentation in Ponsonby Tarn, a small artificial impoundment created towards the end of the 19th century, close to the Sellafield nuclear reprocessing plant in NW England. Spatial and temporal changes in sedimentation are reconstructed and evidence presented for non-synchroneity in magnetic property changes from core to core in the upper part of the sequence, as a result of sorting and selective deposition at different distances from the inflow to the Tarn. Magnetic measurements alone are therefore not a secure basis upon which to quantify sediment yield for defined time intervals at this site. The chronology, established mainly from ²¹⁰Pb and ¹³⁴Cs analyses, allows estimates of mean sediment yield per annum for four periods: prior to AD 1940, 1940–1964, 1964–1986 and 1986–1991. The rates of sediment accumulation have increased in recent times, especially since 1964, with evidence for input from both magnetically enhanced soils and gleyed alluvial and/or podsolized subsoil sources. Pre-1940 mean annual deposition within the present area of the lake is calculated as 19·5 t a⁻¹ and for the period since 1986 (the period of maximum sedimentation rates), as 111·3 t a⁻¹. These represent yields of 7·0 t km⁻² a⁻¹ and 39·8 t km⁻² a⁻¹, respectively, for the catchment as a whole. Rock magnetic evidence, based on measurements of both bulk samples and the finest particle size separates, suggests that bacterial magnetite, formed within the lake, contributes to the magnetic properties of the sediments, thus modifying the signatures relating to allochthonous sediment input. Copyright © 1999 John Wiley & Sons, Ltd.  相似文献   

Excess polonium-210 in the coastal atmosphere originating from marine biogenic material   总被引：2，自引：0，他引：2  

YANG Weifeng  CHEN Min  HUANG Yipu  LIU Guangshan  JIA Chengxia 《海洋学报(英文版)》2006,25(6):78-87

1Introduction In the atmosphere, gaseous radon-222 (t1/2=3.8 d) produces a series of decay products,lead-210(t1/2=22.3 a), bismuth-210 (t1/2=5.01 d), andpolonium-210 (t1/2=138.4 d), etc. These radondaughters are readilyadsorbed onto aerosols and thengrowd…  相似文献   

Age determination of paleotsunami sediments around Lombok Island,Indonesia, and identification of their possible tsunamigenic earthquakes          下载免费PDF全文

Aswan  Yahdi Zaim  Yan Rizal  I. Nyoman Sukanta  Suci Dewi Anugrah  Agus Tri Hascaryo  Indra Gunawan  Tatok Yatimantoro  Weniza  Hidayanti  Purnomo Hawati  Wahyu Dwijo Santoso  Nurochim 《地震科学（英文版）》2017,30(2):107-113

Age determination of paleotsunami sediment from Lombok Island, Indonesia, and surrounding area has been carried out using the 210 Pb method in BATAN Jakarta. The basic theory of this method assumes that weathering of sediments, including paleotsunami sediments, will result in 210 Pb enrichment. The principle of this method is to calculate 210 Pb contents accumulation in a particular sedimentation interval from the surface to the deeper buried sediments. The results are then converted into age or depositional time in years ago unit. The dating results from the paleotsunami sediments of the Gawah Pudak(S8°46’2.91’’, E115°56’34.23’’) and Gili Trawangan areas(S8°21’1.38’’, E116°2’36.6’’) indicate the Gawah Pudak sediments were deposited 37 years ago(c. in 1977)and 22 years ago(c. in 1992). Three paleotsunami sediments from Gili Trawangan were deposited 149 years ago(c. in 1865), 117 years ago(c. in 1897) and 42 years ago(c. in 1972). These results are then compared to the available Indonesian earthquake catalogue data. This study reveals that paleotsunami sediments around Lombok Islands, from older to younger, were caused by the 1857 earthquake(epicentre in Bali Sea; M7; S8°00’09.45’’,E115°29’56.41’’), 1897 earthquake(epicentre in Flores Sea;M5.5; S6°47’59.62’’, E120°48’03.5’’ or Sulu Sea earthquake; M8.5; 70 km NW of Basilan Island), the 1975 earthquake(Nusa Tenggara; S10°6’16.61’’, E123°48’09.39’’), 1977 earthquake(in Waingapu, Sumba; M8.0;S11°5’39.34’’, E118°27’50.86’’) and the 1992 earthquake(Flores; M7.8; S8°28’52.11’’, E121°53’44.3’’).  相似文献   

Natural background and anthropogenic inputs of polycyclic aromatic hydrocarbons (PAH) in sediments of South-Western Barents Sea     

Stepan Boitsov  H.K.B. Jensen  Jarle Klungsyr 《Marine environmental research》2009,68(5):236-245

Polycyclic aromatic hydrocarbons (PAH) were measured in sediment cores from 13 locations in South-Western Barents Sea as part of a detailed study of the Norwegian seabed under the MAREANO program. The generally low PAH levels found, an average around 200 ng g⁻¹ dry weight for sum PAH, indicate low inputs of petroleum hydrocarbons to the marine environment in the area. Differences in PAH composition and various PAH ratios indicate a natural, mostly petrogenic origin of PAH in sediments from the open sea locations, while the fjord locations show higher pyrogenic PAH contents with an increase towards upper sediment layers, indicating low inputs from human activities. Petrogenic PAH levels increase in deeper sediments at open sea locations, also when normalised to total organic carbon (TOC) contents, suggesting natural leakages of oil-related hydrocarbons in the area.  相似文献   

EPR 9°～10°N L喷口黑烟囱体形成环境重建:来自矿物学及铅-210年龄的限制     

姚会强  周怀阳  彭晓彤  周新茂  董从芳  吴白军  李江涛 《海洋学报》2009,31(5)

为了重建EPR 9°～10°N L喷口的形成环境,采用矿物学、地球化学及年代学的方法,对黑烟囱体的矿物组成、矿物结构、元素剖面分布以及黑烟囱体内外层铅-210测年进行了研究.矿物学观察表明,该喷口烟囱体内壁主要由方黄铜矿组成,而外壁则主要由硬石膏组成.铅-210测年结果表明,烟囱体形成于EPR 9°～10°N区域内1991年的火山喷发事件之后,并有较低的生长速率,约为0.3 cm/a.结合该喷口及其附近A喷口已发表资料认为,该烟囱体开始生长是由于蒸气相流体引起的,其后期受到卤水相流体的影响,而且流体温度应不小于330℃.  相似文献   

Changes in the Composition of the Diatom Flora During the Last Century Indicate Increased Eutrophication of the Oder Estuary, South-western Baltic Sea   总被引：1，自引：0，他引：1  

E. Andrn 《Estuarine, Coastal and Shelf Science》1999,48(6):665

Four short sediment cores from the Oder estuary, south-western Baltic Sea, were studied with respect to their siliceous microfossil and organic carbon content. The sediments were dated by²¹⁰Pb. The objective was to detect and date changes in the composition of the diatom flora and link these changes to increased human impact in the drainage area during recent centuries. Two of the cores showed an unperturbed sedimentary sequence representing a complete historical record. A change in the composition of the diatom assemblages attributable to anthropogenic factors was recorded. This was dated to about 1900 in the Oderhaff. The change consisted of an increase in species that thrive in eutrophic waters and those indicating increased salinity or the availability of inorganic nutrients.  相似文献