Elevated Exposure Rates Under Inclined Birch Trees Indicate the Occurrence of Rainfall During Radioactive Fallout From Chernobyl

Abstract

Knowledge of the mode of deposition (wet or dry) during the main fallout period following the Chernobyl accident in late April 1986 is one of the most important parameters in environmental reconstruction of the radiation dose to the thyroid from 113I following the accident. Meteorological data are available only for a small number of locations, but routine field measurements in 1997 of exposure rates in areas still contaminated by 137Cs revealed that there is a natural indicator of wet deposition. Follow-up measurements confirmed that there is a significant difference in exposure rates measured on different sides at the bases of inclined birch trees in areas of wet deposition. In such areas, the exposure rates measured on the "sheltered" sides of the trees were on average 2.3+/-0.2 times those measured on the unsheltered side. In areas of dry deposition the comparable ratio was 1.01+/-0.02 for similarly inclined trees. Because birch trees are a common feature in the contaminated territories, this effect has a wide potential for use in determining whether the fallout in many areas was due to wet or dry deposition.

Estimation of doses received in a dry-contaminated residential area in the Bryansk region, Russia, since the Chernobyl accident

“…It has been reported that dry deposition from the Chernobyl accident has led to local 137 Cs ground contamination levels of as much as 1 MBq m ÿ2 in the settlement of Vishkov in the Bryansk region, about 160 km away from the Chernobyl NPP (Stepanenko et al, 2002). Significantly smaller dry contamination levels have been reported for other areas in the Bryansk region, but the choice of this round figure for the contamination level on the reference surface facilitates the scaling of the results of the case study.…”

Chernobyl: Relationship between the Number of Missing Newborn Boys and the Level of Radiation in the Czech Regions

“…Rainfall can strongly increase radiation on the ground ( Pietrzak-Flis et al 2003 ; Rosner et al 1990 ; Stepanenko et al 2002 ). The most radioactive cloud, accompanied by strong rain, passed above the eastern part of the Czech Republic on 30 April and 1 May 1986 ( Kunz 1986 ).…”