Sediment yields and sources in a welsh upland lake-catchment during the past 800 years     

J. A. Dearing 《地球表面变化过程与地形》1992,17(1):1-22

Estimates of suspended sediment yield over the past 800 years have been derived from a whole-basin study of lake sediments in Llyn Geirionydd, North Wales. Magnetic and physical sediment properties were used to correlate a suite of cores to a master chronology based on ²¹⁰Pb and ¹⁴C dates. The sources of sediment within the catchment were identified by comparing the magnetic and heavy metal properties of sediments, soils, and stream sediments. Mean suspended sediment yields range from 6 to 18 t km^?2 yr^?1 with high yields in the periods 1765-1830 and 1903-1985 corresponding to mining activities in the catchment. The impact of earlier deforestation, agricultural expansion, or climatic change on sediment yields is low, although there is evidence that agricultural activities increased levels of peak stream discharge. Afforestation in the 20th century does not appear to have significantly increased sediment yield. Sediment sources have remained fairly constant through time; they appear to be widespread and dominated by stream channel sides rather than point sources, except during the mining phases when spoil material has dominated the sediment load. Sediment loads to the lake today are still dominated by sediment derived from unvegetated spoil heaps.  相似文献   

钋──210法探测煤矿地质构造的实例与效果     

刘正林 《物探与化探》1994,18(3):166-173

本文为您介绍一种探测煤矿地质构造的新技术即钋─210探测技术,它是一种新颖的核技术在地学中的应用,利用该技术可以探测煤矿隐伏断裂构造、隐伏陷落柱、老窑采空区、煤层底板含水裂隙发育地段等。为解决矿井地质问题和煤矿防治水提供了一种快速而经济的手段。本文论述了钋─210法的基本原理、工作方法、资料处理方法、探测实例及应用前景。  相似文献   

松花湖沉积物~(137)Cs和~(210)Pb分布及沉积速率   总被引：2，自引：1，他引：1  

郝立波  刘海洋  陆继龙  孙淑梅  潘志恒  赵玉岩 《吉林大学学报(地球科学版)》2009,39(3)

松花湖沉积物柱心中存在3个明显的137Cs蓄积峰,分别是37 cm处的1964年蓄积峰、27 cm处的1971年蓄积峰和23 cm处的1975年蓄积峰.利用137Cs核素1964年和1975年对应蓄积峰计算的沉积速率分别为0.86 cm/a和0.71 cm/a.采用210Pb计年的常量初始浓度模式(CIC)计算的平均沉积速率为0.71 cm/a,两者估算的沉积速率吻合.松花湖1964-1975年间的沉积速率明显高于1975-2006年间的沉积速率.137Cs和210Pb计年方法的结合有助于提高沉积速率估算的准确性.  相似文献   

东平湖沉积物 ²¹⁰Pb、¹³⁷Cs 垂直分布及年代学意义   总被引：4，自引：1，他引：3       下载免费PDF全文

陈诗越  王苏民  陈影影  张恩楼  陈永金  朱瑜馨 《第四纪研究》2009,29(5):981-987

对东平湖沉积物柱状岩芯放射性年代学研究表明： 12cm处的 ¹³⁷Cs比活度峰值对应于1963年人工核试验高峰,9cm和6cm处的 ¹³⁷Cs比活度蓄积峰可能分别与1974年的全球核素散落和1986年前苏联切尔诺贝利核电站核泄漏有关; ²¹⁰Pb比活度随深度呈指数衰减,利用 ¹³⁷Cs核素1963年对应的蓄积峰进行校正,采用 ²¹⁰Pb计年的CRS模式建立了1889年以来东平湖现代沉积年代序列。根据 ²¹⁰Pb年代序列,计算了东平湖现代沉积速率,发现近百年来东平湖地区沉积速率有明显变化： 1889～1945年,沉积速率较高,平均达0.297g/cm2•a; 1945～1963年,沉积速率整体处于下降趋势; 1963～2000年,沉积速率比较稳定,平均约0.141g/cm2•a; 约2000年以来,沉积速率有增高趋势。通过分析认为,1945年以前东平湖较高的沉积速率可能与东平湖作为黄河水的自然滞洪区有关; 1950年代国家对东平湖的治理改造,控制了黄河水的自然倒灌,导致了东平湖沉积速率的迅速下降; 1963年以后,由于黄河上中游大型水利工程设施的修建,抑制了东平湖调洪功能的发挥,导致东平湖沉积速率低而稳定; 近年来,东平湖沉积速率有增大趋势,这可能与湖区人民发展围网养殖带入较多的沉积物有关。  相似文献   

福建兴化湾外近海210Pb法沉积速率及校正方法          下载免费PDF全文

王晓慧  吴伊婧  范代读 《古地理学报》2019,21(3):527-536

运用γ谱仪,对采自福建省兴化湾外近海海域的D37和FJ3-12孔进行了 ²¹⁰Pb 、²²⁶Ra和 ¹³⁷Cs 活度的测试,得到这3种核素活度随深度变化特征。分别运用 ²¹⁰Pb 法的CFCS模式(恒定通量恒定沉积模式,Constant Flux and Constant Sedimentation)和CRS模式(恒定供给速率模式,Constant Rate of Supply)以及 ¹³⁷Cs 时标法计算平均沉积速率,发现3种方式的计算结果存在一定差异。在排除粒度变化对核素剖面的影响后,对比不同取样深度的结果发现,指数衰减剖面不完整度(取样深度未达 ²¹⁰Pb 的本底值区)对运用CFCS和CRS模式计算平均沉积速率均有不利影响,其中对CRS模式的影响随剖面不完整性愈强而愈显著。为此提出了相关校正方法作为参考,即先根据CFCS模式估算平均沉积速率和相应的²¹⁰Pb_ex累积量,再通过CRS法建立钻孔年龄框架,由此可计算得出D37和FJ3-12孔的平均沉积速率分别为2.76cm/yr和4.53cm/yr。  相似文献   

Sources and chronology of fifteen elements in the sediments of lakes affected by metal deposition in a mining area     

Yves?CouillardEmail author  Antonella?Cattaneo  Céline?Gallon  Michel?Courcelles 《Journal of Paleolimnology》2008,40(1):97-114

Sources and chronologies of metal contamination were studied in sediment cores of three lakes of the Rouyn-Noranda mining area (Québec, Canada) affected by atmospheric deposition of anthropogenic contaminants. One of the three lakes also received acid mine drainage. The sediments were dated using ²¹⁰Pb and ¹³⁷Cs and analysed for stable Pb isotope ratios and for total concentrations of 15 elements (Ag, Al, Au, Ca, Cu, Cd, Fe, Hg, Mn, Ni, P, Pb, S, Ti, Zn). Stable lead isotopic signatures helped to determine the quantitative contributions of different industrial Pb sources to our sampling sites. This source apportionment showed the dominant influence of the Rouyn-Noranda copper smelter in airborne Pb emissions for the decades following 1926, when industrialization began in the region. The smelter source had a low ratio of ²⁰⁶Pb/²⁰⁷Pb ranging between 0.90 and 1.05, as typical of the Abitibi Archean sulphides. The relationships between element (metal) sedimentary fluxes and anthropogenic Pb fluxes allowed us to infer the origin of the anthropogenic source. These relationships strongly suggest that the copper smelter was (and may still be) an atmospheric source of Cd, Cu, Pb, Zn, Ag and Hg to the surrounding lakes. Our study indicates that the efforts made by the Rouyn-Noranda copper smelter to reduce airborne emissions of metals have been translated in reduced atmospheric metal loadings to the surrounding lakes.  相似文献   

纹层计年与137Cs、210Pb法对比研究东北二龙湾玛珥湖现代沉积速率   总被引：1，自引：0，他引：1  

游海涛  刘强  刘嘉麒  储国强  汉景泰 《吉林大学学报(地球科学版)》2007,37(1):59-64

通过对东北二龙湾玛珥湖顶部无扰动岩心显微研究,证明此岩心发育有良好的年纹层。据精确统计,0~5.5 cm间为36个年纹层,纹层计年的误差为4％~7％,年纹层厚度为1.1~2 mm不等,平均沉积速率为1.53 mm/a,5.5 cm处对应于1965年。而二龙湾沉积物（从6.5 cm到5.5 cm)岩心的¹³⁷Cs比活度值急剧增加,从（4.67±0.29） dpm/g增加到（12.06±0.47） dpm/g,在5.5 cm处有一个较为明显的蓄积峰值,这一峰值被确认对应为1963年全球¹³⁷Cs散落的高峰期。另外据²¹⁰Pb_ex比活度CIC模式,5.5 cm处约为1962年,这和¹³⁷Cs比活度曲线的1963年时标相一致。印证了纹层计年的精确性,完全可以建立高分辨率时间序列。  相似文献   

洋山港内及航道水域沉积环境分析   总被引：7，自引：0，他引：7  

赵庆英陈荣华  王小波应元康张忠华  赵忠宝 《海洋工程》2005,23(2):77-81

在洋山港内和航道水域进行沉积柱状取样,对这些沉积柱状样品分别进行沉积物粒度、^210Pb和^137Cs分析。结果表明,港内水域沉积物粒度总体较粗,砂和粉砂的含量平均近80％,粘土含量平均20％,平均粒径为5.62—6．22φ。航道和附近水域沉积物粒度比港内水域略细,砂和粉砂含量平均为75％,粘土含量平均为25％。^210Pb和^137Cs年代测年表明,港内水域的沉积速率为每年0．93—1．56cm,航道水域的平均沉积速率为每年0．66cm,航道南部水域沉积速率为每年2．71cm,北部水域平均沉积速率为每年1．77cm,局部地区处于冲刷侵蚀状态。总体来说,该海区沉积环境较为稳定,水动力作用较强,沉积速度缓慢,处于基本冲淤平衡的状态。  相似文献   

Metal concentrations, fluxes, inventories and chronologies in sediments from Sepetiba and Ribeira Bays: A comparative study     

Franciane de Carvalho Gomes  Jos Marcus Godoy  Maria Luiza D.P. Godoy  Zenildo Lara de Carvalho  Ricardo Tadeu Lopes  Joan Albert Sanchez-Cabeza  Luiz Drude de Lacerda  Julio Cesar Wasserman 《Marine pollution bulletin》2009,59(4-7):123

Three sediment cores were sampled at Sepetiba Bay and four cores at Ribeira Bay, Rio de Janeiro State, Brazil. Sediment accumulation rates and chronologies were obtained from ²¹⁰Pb activity-depth profiles. Sediment accumulation rates in Ribera Bay ranged from 1.2 mm y⁻¹ in the inner bay to 2.6 mm y⁻¹ close to its entrance. In Sepetiba Bay two sediment accumulation rates were observed: a lower rate of 0.35 cm y⁻¹ before the 1960s and 0.76 cm y⁻¹ since then. The cause of this change is due to the construction of the Santa Cecília impoundment (1955) that brings water from the Paraíba do Sul Basin into the Guandu River, which increased its flow from the original 20 m³ s⁻¹ to 160 m³ s⁻¹. Concentration of 44 elements was obtained by ICP-MS after total dissolution of samples from two selected cores. The relative differences between the concentrations of crustal elements, such as Al, Fe and Ti are only about 20% (p < 0.05). Cd and Zn are 15 and four times larger in Sepetiba Bay than in Ribeira Bay, respectively. Other major and minor elements show lower statistically significant differences. The enrichment factors and metal inventories show that Sepetiba Bay can be considered polluted with Bi, Cd, Cr, Cu, Sb and Zn. Particularly, Cd and Zn present concentrations three and four times higher than the Brazilian existing limits.  相似文献   

Pb-derived ages for the reconstruction of terrestrial contaminant history into the Mexican Pacific coast: Potential and limitations     

A.C. Ruiz-Fernndez  C. Hillaire-Marcel 《Marine pollution bulletin》2009,59(4-7):134

²¹⁰Pb is widely used for dating recent sediments in the aquatic environment; however, our experiences working in shallow coastal environments in the Pacific coast of Mexico have demonstrated that the potential of ²¹⁰Pb for reliable historical reconstructions might be limited by the low ²¹⁰Pb atmospheric fallout, sediment mixing, abundance of coarse sediments and the lack of ¹³⁷Cs signal for ²¹⁰Pb corroboration. This work discusses the difficulties in obtaining adequate sedimentary records for geochronological reconstruction in such active and complex settings, including examples of ²¹⁰Pb geochronologies based on sediment profiles collected in two contrasting areas coastal areas (mudflats associated to coastal lagoons of Sinaloa State and the continental shelf of the Gulf of Tehuantepec), in which geochemical data was used to support the temporal frame established and the changes in sediment supply recorded in the sediment cores which were related to the development of land-based activities during the last century.  相似文献