Effects of Zinc Oxide Nanoparticles on Panagrellus redivivus (Nematoda) and Folsomia candida (Collembola) in Various Test Media

Abstract

The toxic effects of zinc oxide (ZnO) nano- and non-nanoparticles on two species of soil organisms, the free-living nematode Panagrellus redivivus and the springtail Folsomia candida, were investigated. The toxicity of ZnO particles (with 15 and 140 nm average particle size) and ZnCl2 (used as a positive control for zinc ion dissolution) was tested in two different kinds of test media. Milli-Q water vs. soil solution was used for the tests involving P. redivivus, and plaster of paris vs. artificial soil for F. candida. For P. redivivus, application of the soil solution decreased the toxic effect. It is considered that this may be due to the less dissolved zinc ions, the organic matter content and ZnO aggregation. Furthermore, all of the compounds caused concentration-dependent mortality to the tested nematode species. In the tests with F. candida, the toxic effects of both ZnO and ZnCl2 were significantly lower in the tests involving plaster of paris. This could have resulted from the avoidance of the contaminated foods by the springtails. A decreasing effect on reproduction was observed only in the tests using artificial soil. Additionally, the ZnO particles of 140 nm significantly increased mortality in the soil solution test with P. redivivus and in the artificial soil in the tests with F. candida. Possibly, this is a consequence of a greater aggregation of the nanoparticle-sized ZnO at the end of the experiment, which resulted in a lower level of toxicity.