Abstract
This study focuses on interactions between nanoparticles and a pesticide. The aim was to investigate how nano-sized aluminum oxide (410 nm) can alter the toxic effects of thiacloprid, even if no sorption between particles and the insecticide takes place. Thus, our study investigated a rather unexplored interaction. We conducted our research with larvae of Chironomus riparius and used thiacloprid as test substance as its toxicity to C. riparius is well described. The used nano-Al2O3 particles where chosen due to their suitable properties. For testing the acute effects of the interaction, we exposed larvae to thiacloprid (0.5, 1.0, 2.0, and 5.0 μg/L) and nano-Al2O3 (300 and 1000 mg/L), either solely or in binary mixtures. While thiacloprid resulted in elevated mortality, nano-Al2O3 solely did not exert any effects. Moreover, we observed an aggregation of nano-Al2O3 within the lumen of the intestinal tract of the larvae. Further results showed a significantly reduced mortality of fourth instar larvae when they were exposed to mixtures of nanoparticles and the pesticide, compared to thiacloprid alone. With increasing nano-Al2O3 concentration, this effect became gradually stronger. Additionally, chemical analyses of internal thiacloprid concentrations implicate reduced uptake of thiacloprid in animals exposed to mixtures. However, as larvae exposed to thiacloprid concentrations > 0.5 μg/L showed severe convulsions, independent of the presence or concentration of nano-Al2O3, we assume that nano-Al2O3 leads to a delay of mortality and does not entirely prevent it. As sorption measurements on pristine or defecated nano-Al2O3 did not reveal any sorptive interaction with thiacloprid, we can exclude sorption-based reduction of thiacloprid bioavailability as a mechanism behind our results. Even though we used test substances which might not co-occur in the environment in the tested concentrations, our study gives evidence for an interaction besides adsorption, which is important to generally understand how nanoparticles might affect biota.
Highlights
From an environmental point of view nanoparticles are no particular novelty raised in the centuries of industrialization, as they are formed naturally, e.g. by volcanic activities or forest fires [1,2,3,4]
The aim of the study was to investigate possible interactions of nano-Al2O3 and thiacloprid that may potentially affect the toxicity of this neonicotinoid insecticide on the non-biting midge Chironomus riparius
The lack of toxic effects of nano-Al2O3, diverges from a former study of Oberholster et al [24], who tested the effect of nano-sized α-alumina and γ-alumina on the survival rate of 2nd– 3rd instar larvae of Chironomus tentans and observed a significant decrease in survival of the larvae compared to the control
Summary
From an environmental point of view nanoparticles (i.e. particles with a size of 1–100 nm) are no particular novelty raised in the centuries of industrialization, as they are formed naturally, e.g. by volcanic activities or forest fires [1,2,3,4]. Engineered nanoparticles (ENPs) are frequently used, and their release, e.g. via wastewater, is very likely, little is known about their fate and effects in the environment [1, 6,7,8] Due to these reasons, ENPs have the potential to pose a novel threat to the environment and, come to focus in ecotoxicology [2, 7, 9]. The adsorption of pollutants by nanoparticles can lead, amongst others, to reduced bioavailability of the contaminant and, reduced toxicity [2, 11] This kind of interaction, adsorption, is in the focus of most studies, but very little attention has been paid to effects based on the presence of chemicals and non-adsorbing nanoparticles. As nano-Al2O3 particles will settle to the substratum, the sediment-dwelling and detritus feeding larvae of C. riparius [14] will be directly exposed to these particles, as has been predicted for benthic organisms in general [7]
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