THE EFFECT OF ELECTRON BEAM TREATMENT ON DELAYED MORTALITY AND EPHIPPIA HATCH RATES

Abstract

This technical report presents findings from bench-scale tests evaluating the ability of electron beam treatment to kill aquatic algae and zooplankton, specifically examining delayed mortality within 48 hours following treatment. This evaluation was the first attempt to assess the effect of electron beam treatment on hatch rates of Daphnia magna ephippia. Researchers from the Lake Superior Research Institute (LSRI) of the University of Wisconsin-Superior (UWS) in Superior, Wisconsin, USA traveled to the Fermi National Accelerator Laboratory, hereafter Fermilab, to conduct the bench-scale evaluation in May 2022. The test apparatus is a stationary copper electron beam accelerator that supplies a radiation dose expected to cause mortality in standard test organisms. Testing conducted in this evaluation was developed based on findings from earlier tests at Fermilab that demonstrated electron beam treatment was effective at causing complete mortality in E. coli at the lowest dose employed (1 kGy) and was effective at causing immediate mortality in D. magna and Eucyclops spp. at doses between 5 and 10 kGy (Polkinghorne et al., 2022). S. capricornutum was more resistant to immediate effects of electron beam treatment in initial tests (Polkinghorne et al., 2022). All experimental exposures were conducted at Fermilab. The irradiation process was conducted by Fermilab staff in the Illinois Accelerator Research Center’s (IARC’s) Accelerator Applications Development and Demonstration (A2D2) machine. Doses ranged from 1 to 50 kGy. Dose effectiveness testing was completed in lab water only, based on initial tests demonstrating minimal differences in treatment effect between high and low challenge water (i.e., low vs. high organic carbon content, suspended solids, and UV-transmittance). In samples examined 48 hours post-treatment, S. capricornutum had >99% mortality and Eucyclops spp. had 90% mortality at the 2 kGy dose. D. magna had 100% mortality at the lowest dose. No D. magna emerged from ephippia treated at any dose with the electron beam.