Cota Glenn F, Cooper Lee W, Darby Dennis A, Larsen I L
Center for Coastal Physical Oceanography, Department of Ocean, Earth, and Atmospheric Sciences, Old Dominion University, Norfolk, VA 23508, USA.
Sci Total Environ. 2006 Jul 31;366(1):253-61. doi: 10.1016/j.scitotenv.2005.08.021. Epub 2005 Sep 28.
Unexpectedly high specific activities of (137)Cs (1800-2000 Bq kg(-1) dry weight) have been detected in fine-grained sediments entrained in multi-year sea ice floes grounded in Resolute Bay near the center of the Northwest Passage through the Canadian Arctic Archipelago. These results are remarkable because: (1) the specific activities are about two orders of magnitude higher than average specific activities detected in previous studies of sea ice rafted sediments from the Arctic Ocean, (2) two independent observations of these unexpectedly high specific activities were made several years apart, (3) the sampling site is on the opposite side of the Arctic basin from potential radioactive sources such as disposal and weapons testing sites of the former Soviet Union and nuclear fuel reprocessing sites in western Europe, and (4) the closest compositional match to known geologic source regions is Banks Island, on the western edge of the Arctic Archipelago, although a smaller number of grains from one of the two samples were mineralogically matched to sediments in the Laptev Sea. Consequently, the sediments are probably not from a single distinct source and were likely mixed during sea ice transport. Coupled with previous observations of higher radionuclide specific activities in some sea ice rafted sediments relative to bottom sediments, these new observations indicate that comparatively high as well as variable radioactive contaminant burdens in ice rafted sediments must be common and geographically independent of proximity to known contaminant sources. The mechanisms that would facilitate these unexpected high radionuclide burdens in sea ice are not known and require additional study, as well as investigations of the implications for the transport and fate of contaminants in Arctic sea ice.
在加拿大北极群岛西北航道中心附近的雷索卢特湾搁浅的多年海冰浮冰夹带的细粒沉积物中，检测到了出乎意料的高比活度的¹³⁷Cs（1800 - 2000 Bq kg⁻¹干重）。这些结果很显著，原因如下：（1）这些比活度比之前北冰洋海冰漂流沉积物研究中检测到的平均比活度高出约两个数量级；（2）对这些出乎意料的高比活度进行了两次独立观测，时间相隔数年；（3）采样地点位于北极盆地与潜在放射性源（如前苏联的废物处置和武器试验场以及西欧的核燃料后处理场）相对的一侧；（4）与已知地质源区最接近的成分匹配是北极群岛西部边缘的班克斯岛，尽管两个样本之一中少量颗粒在矿物学上与拉普捷夫海的沉积物匹配。因此，这些沉积物可能并非来自单一独特来源，很可能是在海冰运输过程中混合而成。结合之前在一些海冰漂流沉积物中相对于底部沉积物更高的放射性核素比活度的观测结果，这些新观测结果表明，冰漂流沉积物中相对较高且变化的放射性污染物负荷必定很常见，并且在地理上与已知污染物源的距离无关。目前尚不清楚促成海冰中这些出乎意料的高放射性核素负荷的机制，需要进一步研究，同时也需要调查其对北极海冰中污染物的运输和归宿的影响。
