A methodology to determine 212Pb, 212Bi, 214Pb and 214Bi in atmospheric aerosols; Application to precisely obtain aerosol residence times and Rn-daughters' equilibrium factors

Behavior of 222Rn, 220Rn and their progenies along a daily cycle for different meteorological situations: Implications on atmospheric aerosol residence times and Rn daughters' equilibrium factors

The correct assessment of the radiological hazard from radon and daughters, external and internal doses, residence times and equilibrium factors, implies the need to properly determine 222Rn (radon), 220Rn (thoron) and their respective short-lived progenies (214Pb and 214Bi, and 212Pb and 212Bi, respectively), where the precise measurements of both progenies are quite complex due to their very short half-lives. In addition, it is important to study the temporal behavior of all these radionuclides along daily cycles. Therefore, the aim of this study was to analyze the temporal evolution of radon, thoron and their progenies, and of their activity ratios along daily cycles for two different meteorological situations (synoptic and mesoscale processes). Radon and thoron were measured using a radon monitoring system, while their respective progenies were collected onto atmospheric filters using an ASS-500 sampler, and then measured by gamma-ray spectrometry. Furthermore, the different relationships between the concentrations of radionuclides and the different meteorological variables of interest (temperature, ABL height, and speed and direction of the wind) were found. Finally, the atmospheric aerosol residence times and Rn daughters' equilibrium factors were estimated for each sampling carried out along the two daily cycles, finding results consistent with previous studies.

Array electrochemiluminescence device with ultra-high sensitivity and selectivity for rapid visualized monitoring of trace radon in environment

The World Health Organization has reported radioactive Rn gas as the second leading cause of lung cancer and gives an extreme limit to indoor Radon (Rn) concentration as 100 Bq/m³. To realize rapid and accurate Rn monitoring, we report an efficient visualized electrochemiluminescence (ECL) device for Rn detection with the lowest limit of detection (0.9 Bq/m³/3.6 Bq h m^-3) compared to known Rn detection methods and the shortest measurement time (less than 5 h) among non-pump methods. In detail, an efficient Rn probe is prepared by Au nanoparticles, Pb²⁺ aptamer, as well as NH₂-ssDNA co-reactant and then modified on ITO electrodes to obtain Rn detection devices. With tris(2,2'-bipyridyl)ruthenium(II)chloride (Ru(bpy)₃Cl₂) as an ECL emitter, the devices can exhibit ultra-high sensitivity and selectivity to trace Rn in environment via the ECL quenching caused by ²¹⁰Pb, the relatively stable decay product of Rn. Furthermore, ECL imaging technology can be applied to realize the visualized Rn detection. An efficient up-response ECL detector was also invented to support this detection device to achieve accurate Rn detection in environment. This work reports noble gas ECL detection for the first time and provides an efficient strategy for rapid and accurate monitoring of trace Rn in environment.

A new efficiency calibration methodology for different atmospheric filter geometries by using coaxial Ge detectors

The study of the different pollutants present in atmospheric aerosols such as trace elements and radionuclides is essential to assess the air quality. To analyze the particulate matter (PM), atmospheric filters with different dimensions and geometries (rectangular, circular, slotted, and square filters) are usually employed. Regarding the pollutants existing in atmospheric aerosols, radionuclides are usually analyzed due to their multiple applications such as either in the environmental radiological control or as tracers of atmospheric processes. Therefore, this study aims to develop a new and general methodology to calibrate in efficiency coaxial Ge detectors to properly determine radionuclides present in the PM by gamma-ray spectrometry for several filter types. For this, granular certified reference materials (CRM) containing only natural radionuclides (238U-series, 232Th-series, and 40 K) were selected. Several granular solid CRMs were chosen allowing us to reproduce the same PM deposition geometry and to assure the homogeneity of the added CRMs. These are the main advantages in relation to the typical methods that use liquid CRMs. Furthermore, for filters whose surfaces are relatively large, they were cut in several pieces and placed one on top of the other, achieving the same geometry than the PM deposited onto the filter. Then, the experimental full-energy peak efficiencies (FEPEs) were obtained for each energy of interest (Eγ) and they were fitted versus Eγ, finding a general FEPE function for each filter type. Finally, this methodology was validated for both natural and artificial radionuclides (from 46 to 1332 keV) by using different filter types employed in proficiency test exercises, obtaining |zscore|< 2 for all cases.

Supplementary Information

The online version contains supplementary material available at 10.1007/s11869-023-01336-x.