Status of the European Indoor Radon Map

Transcription

1 Status of the European Indoor Radon Map Tore Tollefsen 1, Marc De Cort 1, Peter Bossew 2 1 Joint Research Centre Institute for Environment and Sustainability Radioactivity Environmental Monitoring (REM) group 2 Privatier, Vienna Slide 1 of 13 1

2 State of knowledge 26 EUR indoor radon survey 25: - Collage of European radon maps published by National Authorities - Measurement techniques and mapping strategies differ between countries - Most countries have indoor measurements made on ground floor - Access to data and privacy-related issues of indoor measurements Status of EUR radon survey 25 Prague Radon conference 26: - JRC to collect statistics of these data from National Authorities on a 1 km x 1 km grid White areas: no maps published Slide 2 of 13 2

3 Choosing a suitable European grid Design criteria: - metric grid - projection realistic image of Europe - compatible with other European databases EC NUTS 1 km x 1km raster, country masks Spatial reference frame: - GISCO Lambert Azimuthal Equalarea projection - EC NUTS 1:1M country layer JRC CIS processing: - Converted to 1 km x 1 km raster - Land masks for all countries (except new states in Balkan area) GISCO LAEA projection JRC CIS processing Slide 3 of 13 3

4 From measurement to map (1) Grid geometry file xmin, xmax, ymin, ymax original measurement data, unprojected lat-long Projection file φ: (lat, long) (x, y) (Excel sheet) national competence! Data aggregation into common grid, cell statistics (Basic program) Output = Cell statistics file (txt file) -cell centre x(m), y(m) -no. samples -AM(z), AM(ln(z)) -SD(z), SD(ln(z)) -min, median, max Thus, original source data do not appear in cell statistics next slide Slide 4 of 13 4

5 From measurement to map (2) previous slide cell statistics files country 1, country 2, mosaic file: - mosaic option of Surfer or - identification of cells filled by two participants on either side of border and recalculation of cell contents (Basic program) country-wise: - exploratory analysis - diagnostics - outliers, errors: identification of questionable cells, which one may choose to remove diagnostic file for each country plotting: Surfer THE MAP from mosaic file: - exploratory analysis, statistical graphs - diagnostics: 2 18 across-border homogeneity 16 MED ± MAD, AM (Bq/m 3 ) AM MED ± MAD CZ EE CH ES AT FI IT FR BE PL PT DE LT UK NL all Slide 5 of 13 5

6 Where we are today (end-april 29) Indoor Rn, ground floor, 1 km x 1 km grid, AM per cell Current status: - 15 countries have delivered cell statistics - 2 countries have data in national grid (IE, SI) - Some countries have not yet replied - Others (mainly non- EU) have not yet been contacted Slide 6 of 13 6

7 Number of measurements per cell Different survey designs and resulting sampling strategies: - homogeneous coverage of territory; - sampling density proportional to population density; - preferential sampling in high-rn areas; - according to regional political conditions, public interest etc. No. measurements per 1 km x 1 km cell Median No. measurements per cell CZ CH UK AT EE BE ES IT DE FI PL LT NL PT FR all Variability bars: Median absolute deviation MAD = median i { x i median j (x j ) } Slide 7 of 13 7

8 Coverage and sampling density Coverage of territory Density of measurements >1%: border effect 2 1 coverage of territory (%) no. measurements / km UK CH CZ BE AT FR NL FI LT DE PT IT EE PL ES partic.eur UK CZ CH BE AT FI NL LT DE IT EE PT FR PL ES partic.eur Partic participants so far Eur European territory (1,18, km 2 ) Coverage < 1%: - survey not finished; - uninhabited regions not sampled; - preferentially high-rn regions (known or assumed) sampled. (# meas. per cell) x coverage = sampling density Slide 8 of 13 8

9 Rn means and dispersions per country MED ± MAD, AM (Bq/m 3 ) Insert text here 4 2 AM MED ± MAD CZ EE CH ES AT FI IT FR BE PL PT DE LT UK NL all Dispersion within cells remarkably uniform! MED ± MAD dispersion Cell means are very nicely log-normal over Europe (as available so far), with a few outliers CV (%) GSD 1. CH BE AT UK ES PT IT CZ LT EE FI NL FR DE PL all Slide 9 of 13 9

10 High-Rn regions Prob (Rn>4 Bq/m 3 ) Direction:. Tolerance: percent cells above 4 Bq/m CZ CH EE AT ES FR FI PL IT PT DE BE UK LT NL all Variogram Lag Distance (m) prob(rn>4) Prob (Rn>4 Bq/m 3 ) Map: assumption: log-normality within cell, GSD=1.91 data transform: y:=1-cumulln(4,z,s), z=am{ln(x)} within cell, s=ln(gsd)=sd{ln(x)} OK of y, point, grid=1 km, based on variogram; blank: s K < Slide1of 13 1

11 Remaining issues & annoyances Harmonization issues: - different survey designs and sampling strategies e.g. cell statistics based on very different numbers of individual measurements; - different measurement techniques - model-based data standardization, e.g. for temporal standardization (estimated annual mean) Possible result of disharmony: heterogeneity across borders examples: next slide Georeferencing issues: - in some countries only national projections; - referencing of original measurements: per building or assigned to post codes, municipalities etc. Administrative issues: - no access to data? Rn data are sensitive! - labyrinthic administrative structures - some countries (mainly non-eu) have yet to be contacted Slide11of 13 11

12 Examples: Radon data in national grids Ireland Slovenia to 5 5 to 1 1 to 2 2 to 5 5 to 1 1 to Transverse Mercator projection? Data in Irish national grid - Source data not available - Resample Irish grid into European grid via transformation? Ongoing study Data in Slovenian national grid - Retrieve old source data - Use street address national coordinates - Unproject φ -1 : (x, y) (lat, long) Follow above procedure Slide12of 13 12

13 European Indoor Radon Map: - Further collection of national 1 km x 1 km indoor radon grids, will probably still take a while; - Research information per country about survey design, measurement techniques, data evaluation etc. report Other maps to follow What comes next? In conclusion, the European Indoor Radon Map was started first: - because of the feasibility of mapping indoor Radon; - because indoor radon is the most important contributor to the natural radiation dose for the population THANK YOU! Slide13of 13 13