Intrinsic vs. spurious long-range memory in high-frequency records of environmental radioactivity Critical re-assessment and application to indoor Rn-222 concentrations from Coimbra, Portugal

• Type: Article in International Scientific Journal
• Date: 2015

Authors

Donner, RV (Author) Other; Potirakis, SM (Author) Other; Barbosa, SM (Author) Other; José Abilio de Oliveira Matos (Author) FEP; Pereira, AJSC (Author) Other; Neves, LJPF (Author) Other

Journal

Title: European Physical Journal: Special Topics

Vol. 224

Pages: 741-762

ISSN: 1951-6355

Publisher: Springer Nature

Indexing

ISI Web of Knowledge - 12 Citations

Scopus - 12 Citations

Other information

Authenticus ID: P-00G-5WE

DOI: 10.1140/epjst/e2015-02404-1

Abstract (EN): The presence or absence of long-range correlations in the environmental radioactivity fluctuations has recently attracted considerable interest. Among a multiplicity of practically relevant applications, identifying and disentangling the environmental factors controlling the variable concentrations of the radioactive noble gas radon is important for estimating its effect on human health and the efficiency of possible measures for reducing the corresponding exposition. In this work, we present a critical re-assessment of a multiplicity of complementary methods that have been previously applied for evaluating the presence of long-range correlations and fractal scaling in environmental radon variations with a particular focus on the specific properties of the underlying time series. As an illustrative case study, we subsequently re-analyze two high-frequency records of indoor radon concentrations from Coimbra, Portugal, each of which spans several weeks of continuous measurements at a high temporal resolution of five minutes.Our results reveal that at the study site, radon concentrations exhibit complex multi-scale dynamics with qualitatively different properties at different time-scales: (i) essentially white noise in the high-frequency part (up to time-scales of about one hour), (ii) spurious indications of a non-stationary, apparently long-range correlated process (at time scales between some hours and one day) arising from marked periodic components, and (iii) low-frequency variability indicating a true long-range dependent process. In the presence of such multi-scale variability, common estimators of long-range memory in time series are prone to fail if applied to the raw data without previous separation of time-scales with qualitatively different dynamics.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 22