Investigation of effects of ZnO nanoparticles on survival, reproduction, absorption, weight gain and accumulation in Eisenia foetida earthworm tissues in two different substrates

In order to investigate the effect of zinc oxide nanoparticles on survival, reproduction, absorption, weight gain and accumulation in Eisenia foetida earthworm tissues, the 4 ×2 factorial experiment in the Randomized Complete Block Design in 3 iterations was done. The factors were consisted of zinc oxide NPs at four levels (0, 0.4, 0.8 and 1.2 g/kg weight of substrate) and the kind of substrate at two levels (Cow manure, spent compost of mushroom). After preparation of substrates, 30 adult worms were added to each pot which containing of 6 kg of each type of substrates and were kept for one week to get used to the new conditions. The solution of nanoparticles was added to substrate according to their weight. Then, nanoparticles accumulation amount in the earthworm tissues and its effect on weight gain, death and reproduction was measured at the end of two periods of seven and fourteen days after exposure to nanoparticles. The number of worms at the end of both periods showed that there was no death. The results of mean values comparison showed that by increasing the concentration of nanoparticles the absorption of particles were increased and the absorption in cow manure was more than that in spent compost mushroom substrate. Also by increasing nanoparticles, reproduction and weight gain of earthworms were decreased and weight gain of earthworms in cow manure substrate was more than other substrate.