Measurements of 131I, 134Cs and 137Cs in environmental samples in Bulgaria after the Fukushima accident

摘要

This work reports results from measurements of 131I, 134Cs and 137Cs in environmental samples in Bulgaria after the Fukushima accident. Measurements performed in the period from 25 March to 2 May by high volume air sampling on glass fiber aerosol filters showed 131I concentrations in the range 31–2240 µBq/m3. Caesium-134 and 137Cs were also detected in the air samples with concentrations in the ranges 33–456 µBq/m3 and 38–637 µBq/m3, respectively. Measurements of rainwater showed concentrations of 131I in the range 0.09–1.15 Bq/l. 131I was also found in raw milk (0.14–0.38 Bq/l) and in grass (0.33 Bq/kg). The measured concentrations are consistent with those in other European countries and do not require special actions for public protection. The measured peak concentrations in the air in Bulgaria were higher than those reported for Northern Greece and were reached on the same day (4–5 April) [3]. Long-term (15 days) air sampling have shown detectable concentrations of airborne activity concentrations of 134Cs and 137Cs with stable 137Cs to 134Cs ratio in the range 1.1 – 1.3. The results of the rainwater measurements indicate that washout was the dominant atmosphere scavenging mechanism during the rainfalls. Under these conditions roof sampling of rainwater in the early stages of the rain was found to be very appropriate for detection of trace quantities of 131I in the atmosphere. Dedicated comparison between roof sampling through a drain pipe and direct sampling shows that the roof sampling is more efficient as it appears to be more sensitive to 131I in the air.