Dragonflies (Odonata) as bioindicators of radioactivity.

Bioindicators are living organisms that are successfully used for monitoring changes in the environmental health due to natural and/or anthropogenic influences. Dragonflies (Odonata) are considered to be good indicators of water quality; however, research on dragonflies as potential indicators of radioactivity is scarce. The aim of this study was to evaluate dragonflies as potential biological indicators of ionising radiation in nature by measuring ¹³⁷Cs activity concentrations in the dragonfly and river water samples. Altogether, 11 collective samples of dragonflies were collected from the bank of the Mura-Drava-Danube Biosphere Reserve, in the area of Virovitica-Podravina County. Following the initial sample preparation, the gamma spectrometry technique, employing an ORTEC HPGe detector system, was utilised to determine the activity concentrations of ¹³⁷Cs. The results show that the activity concentrations of ¹³⁷Cs in the river water were in the range from 4 to 13 Bq/m³. The results of dragonfly samples showed that ¹³⁷Cs was in the range from 1.7 to 3 Bq/kg. This was more than a hundred times higher than in the river Drava water. According to the obtained results, we conclude that dragonflies could be used as potential bioindicators of radioactivity.