Bioaccumulation in earthworm exposed to uranium particles and anions

Abstract

This study contains information about the bioaccumulation of uranium (U) in earthworms following exposure of the worms exposed to different uranium species in food (horse manure). Three different uranium species were used: synthesized uranium nano-micrometer particles (UO2 and U3O8) and uranyl ions at two different concentrations (50 and 500 μg/g dw manure). The study started with the culturing of worms, growing them in OECD soil and ended by performing uranium measurements by ICP-MS of four types of samples: worms, food (horse manure), soil and faeces. The analysis showed that uranyl uptake in terms of biological concentration factors (BCF, concentration in worm/concentration in food) was 10 times higher than that of particle uptake. All worms survived the treatment with no mortality during the week of uranium exposure and hence 100 % worms (50 worms) survived the experiment, although 2 worms died during the depuration period (gut emptying). However these were randomly distributed over the test groups. So, no correlation with U exposure could be observed. There were no significant effects of uranium on growth of worms, but 4 of the worms showed a reduction in weight, again randomly distributed between the groups. The test comparison of soil and manure concentration showed that the soil/manure concentration ratio for the control was much greater than for the treated soils, due to the higher concentration of natural uranium in soils with no significant difference between the different U treatments. This is the first time that UO2 and U3O8 particle uptake has been studied in the earthworm, and results should provide useful information for ecological risk assessment.