Figueira Rubens C L, Tessler Moyses G, de Mahiques Michel M, Cunha Ieda I L
Centro de Tecnologia e Ciências Exatas, Universidade Cruzeiro do Sul, São Paulo, Brazil.
Sci Total Environ. 2006 Mar 15;357(1-3):146-59. doi: 10.1016/j.scitotenv.2005.03.032. Epub 2005 Jul 28.
In this work levels of 137Cs, 238Pu and 239+240 Pu as well as activity ratios of anthrophogenic radionuclides in sediment samples from the southeastern Brazilian shelf are presented. Instrumental gamma spectrometry was used to determine 137Cs and alpha spectrometry to determine 238Pu and 239+240 Pu after a radiochemical procedure. The levels ranged from 0.30 to 1.79 Bq kg(-1) for 137Cs, from 15 to 150 mBq kg(-1) for 238Pu and, from 18 to 117 mBq kg(-1) for 239+240 Pu. There was a bathymetric differentiation in the radionuclides distribution. 137Cs values were generally higher in the samples collected at water depths of less than 100 m. On the other hand, plutonium isotopes exhibit higher values at greater depths. The mean ratio of 239+240 Pu/137Cs obtained was 0.112+/-0.072 which is in agreement with the value reported for the Atlantic from atmospheric fallout of nuclear explosions in the past. The 238Pu/230+240 Pu ratios varied widely (from 0.339 to 2.088) and showed the influence of the SNAP-9A accident in the 238Pu levels for this area. The main goal of this work was to present unpublished anthropogenic radionuclide levels and activity ratios related to the contamination of the southeastern Brazilian shelf.
本文给出了巴西东南部陆架沉积物样本中137Cs、238Pu和239+240Pu的含量以及人为放射性核素的活度比。采用仪器γ能谱法测定137Cs，经过放射化学程序后，用α能谱法测定238Pu和239+240Pu。137Cs的含量范围为0.30至1.79 Bq kg(-1)，238Pu为15至150 mBq kg(-1)，239+240Pu为18至117 mBq kg(-1)。放射性核素分布存在深度分异。在水深小于100米处采集的样本中，137Cs值通常较高。另一方面，钚同位素在较深水域呈现较高值。得到的239+240Pu/137Cs平均比值为0.112±0.072，这与过去报道的大西洋因核爆炸大气沉降的值一致。238Pu/230+240Pu比值变化很大（从0.339至2.088），表明该地区238Pu含量受“SNAP - 9A”事故的影响。这项工作的主要目的是展示与巴西东南部陆架污染相关的未发表的人为放射性核素含量和活度比。
