The aim of this task is to analyse and evaluate geogenic Rn surveys in order
- to identify the rationale and methodologies used,
- to identify the extent and possible sources of inconsistencies in the results of outdoor geogenic radon surveys and
- to propose approaches to reduce inconsistencies and improve harmonisation of geogenic radon data, in analogy to indoor Rn in Task 3.1.
Quantities physically related to geogenic radon (such as uranium concentration in rocks and soils, radon gas exhaled from soil and soil permeability, radon exhalation rate, terrestrial gamma dose rate, geological information and standardised indoor data) are used to estimate the geogenic radon potential and in consequence develop maps of geogenic radon. Its concept is to show “what the earth delivers” in terms of Rn, which is the geogenic baseline, which – given anthropogenic factors of building type and the behaviour of inhabitants– leads to a certain level of indoor Rn concentration. Hereafter the term “radon exhalation” will be used in the broad sense of “what the earth delivers”, hence also taking into account the radon concentration in soil gas.
Geogenic Rn maps may serve as a base for defining Rn priority areas (see WP4), for example by applying thresholds or certain qualitative criteria. The methodology for surveying geogenic radon quantities is different from indoor Rn and is therefore treated in a separate task.