Iodine-129 enrichment in sediment of the Baltic Sea

Sediments are an excellent archive for evaluation of time-series environmental contamination of water systems. Measurements of ultra-trace radioactive species, such as ¹²⁹I, provide information for both chronologic calibration and anthropogenic emissions during the nuclear era. Here data are presented on ¹²⁹I and other chemical parameters from two sediment cores collected in the Baltic Sea during 1997. The sediment sections have a relatively uniform grain size (clay–mud) and cover a period of about 50 a. Distribution of ¹²⁹I in the sediment strongly relates to the liquid release records from the nuclear reprocessing facilities at Sellafield and La Hague. However, syn- and post-depositional alteration of organic matter at the sediment–water interface and within the sediment column may have contributed to slightly obliterating the anthropogenic ¹²⁹I signals. Indication of Chernobyl-derived ¹²⁹I occurs in the sediment profile, but is apparently overridden by the overwhelming flux from the nuclear reprocessing facilities. Although the record did not cover the pre-nuclear era (before 1945) sections, the ultra sensitive ¹²⁹I profile provides a potential tool for relative dating and monitoring sources of water and sediment to the region.     

Cosmogenic 7Be in air: A complex mixture of production and transport

The long-time series of ⁷Be activity in surface air have been studied with the wavelet analysis technique in order to find coherence between ⁷Be activity, theoretical production in the troposphere and climatic indices. The ⁷Be activity were obtained from five different locations, Angra in the tropics in Brazil, Skåne in mid-latitudes in Southern Sweden, Kiruna in Polar region in Northern Sweden, Loviisa in Southern Finland and Rovaniemi in polar region in Northern Finland. The ⁷Be data from the Northern hemisphere sites where tested for coherence with theoretical production of the isotope in troposphere and with the North Atlantic Oscillation index. In the Southern hemisphere separate theoretical production was calculated in order to describe local production and Southern Annular Mode was used as the climatic index. Consistent and significant coherence were found with theoretical production at Skåne, Kiruna and Loviisa at time-scales of four years or longer. At Angra and Rovaniemi sites, no coherence was detected between ⁷Be theoretical tropospheric production and measured activity at ground level. The coherence between ⁷Be data from Skåne and Angra and climatic indices is insignificant while data from Northern and Eastern Scandinavia show clear coherence with climatic indices at time-scales of four years or longer. Additionally, significant coherence was found between the cosmic ray induced production and NAO at the time band of 8–12 years whereas the coherence between cosmic ray induced production and SAM was insignificant. This feature implies that the ground level ⁷Be activity contain mixed information on both production and transport. This conclusion means that further evaluation through models which enable accurate realistic models that will be investigated in future studies.     

Anthropogenic 129I in seawaters along the north-central part of the English Channel: Levels and tracer applications

The English Channel (the Channel) represents a major sink and transport pathway of anthropogenic radioactive 129I. Despite this important role, data concerning the distribution of 129I in seawater of the Channel are scarce, and most of existing data are restricted to the eastern part of the Channel. The advection and dispersion of 129I from the French coast toward the central and further the English coast, especially in the Channel west of Cap de La Hague, are not fully investigated. We present results of iodine isotopes (127I and 129I) analyses of surface water samples collected along the central English Channel in October, 2010. The data show high 129I concentrations between Dover Strait and La Hague, followed by a dramatic drop towards the Celtic Sea and reveal the dispersal of 129I towards central and northern part of the Channel. Our observation also implies that the entire British coast is contaminated by 129I. 129I levels in the westernmost English Channel, close to the English coast, may reflect combined influences from La Hague and Sellafield. Evolution of 129I between 2005 and 2010 suggests a strong link to temporal marine discharges from La Hague plant. The discharges from the nuclear reprocessing facility have continued since 2010 and thus an ecological evaluation of 129I radioactive hazards in the environment of the Channel may be needed.     

A late Cenozoic Earth's crust and climate dynamics record from Lake Baikal

The sedimentary record from Lake Baikal (Siberia, Russia) has been an important source of information about paleoclimatic variability in the northern hemisphere and dynamics of continental rift development. A lack of reliable chronology has, however, been a major obstacle to fully utilizing the Baikal archive for time scales beyond about 4-5 Myr. In this paper we use the distribution of ¹⁰Be to establish a new chronology for the longest core drilled in Lake Baikal so far. The ¹⁰Be-based chronology spans the last 8 Myr and provides better constraints on sedimentation rates and consequently on an east-west tectonic extension in the lake, which has been apparently coeval with other rifts in Asia that are related to the Tibetan plateau uplift. Our data also show higher ¹⁰Be flux in the sediment section older then 5 Myr compared with the younger period. This can be explained partly by warm and humid climatic conditions of the Miocene and partly by a high cosmic ray flux to the Earth resulting from possible low geomagnetic field intensity during that time.     

怒江峡谷构造地貌的演化:阶地宇宙成因核素定年的初步结果

地貌产生于构造活动和各种地表营力驱动的侵蚀夷平和堆积过程,如在构造抬升活跃的地区,河流强烈的侵蚀作用往往造就深切的峡谷地貌。对于这样的地区河流下切速率往往被用来衡量构造抬升速率[1,2]。然而河流下切速率的变化不仅与构造抬升有关,而且与气候变化有关。因此,正确理解