While radioisotopes of noble gases are known to be indicators of underground nuclear explosions (UNE), McIntyre et al. (2017) was the first to report the presence of ³⁹Ar in shallow soil gas in association with a decades old UNE. While this finding hinted at the potential application of ³⁹Ar to be used as an indicator of a UNE, doing so would also require an understanding of the natural concentrations of ³⁹Ar present in soil gas. Without knowing the expected range and variability of naturally occurring concentrations of ³⁹Ar, it is difficult to determine what measured concentrations would be indicative of an elevated concentration. This paper presents results from 16 soil gas samples and three atmospheric air samples collected from various locations across the western United States. Shallow soil gas samples were collected into self-contained underwater breathing apparatus (SCUBA) tanks using a custom-built soil gas sampling system and then processed and analyzed for ³⁹Ar. The measured concentrations of ³⁹Ar varied from atmospheric air concentrations to about 3.5 times atmospheric air concentrations (58 mBq/m³). The results presented here represent the first measurements of natural background ³⁹Ar concentrations in shallow soil gas. This data will be necessary if ³⁹Ar is to be used as an indicator of UNE.

众所周知，稀有气体的放射性同位素是地下核爆炸（UNE）的指标，McIntyre等人。（2017）是第一个报告与数十年历史的UNE有关的浅层土壤气体中存在³⁹ Ar的人。尽管这一发现暗示了³⁹ Ar可能被用作UNE的指标，但这样做还需要了解土壤气体中自然存在的³⁹ Ar浓度。不知道³⁹的自然浓度的预期范围和变异性Ar，难以确定什么测量浓度将指示升高的浓度。本文介绍了从美国西部不同地点采集的16种土壤气体样品和3种大气样品的结果。使用定制的土壤气体采样系统，将浅层土壤气体样本收集到自给式水下呼吸器（SCUBA）储罐中，然后进行处理并分析³⁹ Ar。³⁹ Ar的测量浓度从大气浓度到大气浓度的约3.5倍（58 mBq / m ³）不等。此处显示的结果代表自然背景的首次测量³⁹浅层土壤气体中的Ar浓度。如果将³⁹ Ar用作UNE的指标，则该数据将是必需的。