The impact of stable 27Al in 26Al/10Be meteoric ratio in PM2.5 from an urban area

Abstract

Meteoric ¹⁰Be and ²⁶Al radionuclides are produced in the atmosphere, and the relationship between them has potential applications in atmospheric and climate research. In particular, the meteoric ²⁶Al/¹⁰Be ratio has potential applications such as a chronometer for old ice, a tracer for the air exchange between the lower stratosphere and upper troposphere, production and distribution in the atmosphere of both radionuclides, and the study on solar activity. In this work, their concentrations in the fine fraction of airborne particulate matter from an urban area have been precisely determined using Accelerator Mass Spectrometry (AMS). To obtain new data about the ²⁶Al/¹⁰Be ratio and its subsequent applications, PM_2.5 in aerosol samples has been analyzed. The average ratio in samples from Mexico City was significantly higher than those previously reported by other authors. The high enrichment factors for stable Aluminum indicate that both resuspended and anthropogenic ²⁷Al content in PM_2.5 contributes significantly to the high values of ²⁶Al in the ²⁶Al/¹⁰Be ratio. An adjustment of ²⁷Al concentrations from external contributions was carried out, and the corrected ²⁶Al/¹⁰Be ratios were similar to those previously reported. In this study, a precise assessment of the possible contribution of other Aluminum sources to the aerosol samples has been carried out. Finally, the obtained ratios indicate the possibility of its future use in applications such as the dating of glaciers.

Keywords: (10)Be; (26)Al; (26)Al/(10)Be ratio; Mexico City; PM(2.5).