Studies on plutonium in terrigenous air-dust

为了研究用环境钚作为示踪剂估算陆源气尘向海洋的通量，测定了1993 - 1998年在日本金泽金泽采集的气尘样品中的Pu-239、240和Fe。空气粉尘样品的收集使用五阶段（粒径：<1.1 μm、1.1 μm、2.0 μm、3.3 μm、7.0 μm<）安德森型大容量空气采样器、捕集板和备用过滤器每月更换一次;每隔1-8个月采集一次大气粉尘，作为一批进行分析，在上述采样年份和粒径范围内，Pu-239，大气尘中240和Fe的含量范围分别为0.1 ~ 10 μBq-Pu/mg尘和2 ~ 30 μg-Fe/mg尘。Pu/Fe的浓度比在较细的大气尘埃中趋于高，表明Pu被吸附在陆源大气尘埃的表面上。通过对Andersen型小容量空气采样器采集的空气尘样品中Po-210/Pb-210活度比值的分析，估算出空气尘的表观漂浮时间为9 ~ 140天（粒径：0.06 μm ~ 0.13 μm、0.13 μ m ~ 0.22 μm、0.22 μ m ~ 0.33 μm、0.33 μ m ~ 0.52 μm、0.52 μ m ~ 0.76 μm、0.76 μm ~ 1.3 μm、1.3 μ m ~ 2.5 μm、2.5 μm ~ 3.9 μm、3.9 μ m ~ 5.7 μm、5.7 μ m ~ 8.5 μm、8.5 μ m ~ 12.1 μm）。

For a study to estimate terrigenous air-dust fluxes to oceanic region by using environmental plutonium as a tracer, Pu-239, 240 and Fe were determined in air-dust samples collected in Kanazawa, Japan through the years from 1993 to 1998. The air-dust samples were collected using a five-stages (particle size : <1.1 μm, 1.1〜2.0 μm, 2.0〜3.3 μm, 3.3〜7.0 μm, 7.0 μm<) Andersen-type high-volume air sampler, and catcher plates and backup filter were replaced monthly ; air-dust collected every 1-8 months was analyzed as one batch.Throughout the above mentioned sampling years and particle sizes, the concentrations of Pu-239, 240 and Fe I n the air-dust samples were in a range from 0.1 to 10 μBq-Pu/mg-dust and from 2 to 30 μg-Fe/mg-dust. The Pu/Fe concentration ratios tend to be high in finer air-dust, suggesting that Pu is adsorbed on the surface of terrigenous air-dust. Through the analyses of Po-210/Pb-210 activity ratios in air-dust samples collected occasionally for a few days using Andersen-type low-volume air sampler, from 9 to 140 days were estimated as the apparent floating time of air-dust (particle size : O.06〜0.13 μm, O.13〜0.22 μm, O.22〜0.33 μm, 0.33〜0.52 μm, 0.52〜0.76 μm, 0.76〜1.3 μm, 1.3〜2.5 μm, 2.5〜3.9 μm, 3.9〜5.7 μm, 5.7〜8.5 μm, 8.5〜12.1 μm).