Influence of goethite (alpha-FeOOH) nanoparticles on the uptake and toxic effects of clorpiryphos in Eisenia andrei

CÁCERES WENZEL MARCELA I; VERRENGIA GUERRERO, NOEMÍ; FUCHS JULIO S.; COCHÓN, ADRIANA C

Santos- San Pablo

Congreso; XII SETAC Latin American Biennial Meeting; 2017

SETAC LA

Eisenia andrei earthworms are one of the most important bioindicator organisms to evaluate the impact of environmental contaminants in soils. The aim of this work was to investigate the interactions of a binary mixture of the organophosphate pesticide clorpyriphos (0,75 µg cm-2) and a suspension of goethite nanoparticles (NPs) (50 µg cm-2) . Organisms were exposed to embedded filter papers for 72 h to evaluate contact effects. The selected clorpyriphos concentration was close to the value that induces a 50% inhibition of the acetylcholinesterase enzyme (AChE) using acetylthiocholine as substrate. The activity of carboxyl esterases (CES) was also determined using p-nitrophenyl butirate as substrate. Animals exposed to NPs alone present similar AChE and CES activities than control ones. Those exposed to the binary mixture showed a similar inhibition of CES (53%) but the AChE activity was not inhibited (91%). Spectroscopic UV/Vis studies revealed that in aqueous phase, the pesticide is strongly removed from the solution in the presence of NPs. This result could explain the lack of inhibition of AChE. The uptake of NPs by E. andrei was verified by measuring the Fe content using atomic absorption spectroscopy. Compared to controls, the iron content progressively increased after 24 and 48 h of exposure in the presence of NPs alone. However, values were lower than controls after 72 h (26 ± 3 and 54 ± 9 µg Fe gr-1, ww, respectively) suggesting that by contact exposure, a systemic effect occurred. At this time, earthworms exposed to the binary mixture containing NPs plus clorpyriphos presented higher levels of iron than controls (45.2 ± 10.3 and 27.4 ± 7.6 µg Fe gr-1, ww, respectively) while no significant changes were observed in those exposed to clorpyriphos alone (26.9 ± 4.5 µg Fe gr-1, ww). On the other hand, a suspension of bulk goethite did not modify the Fe basal levels at any time. Therefore, by contact exposure goethite NPs exhibited a different behavior than bulk goethite in E. andrei. In addition, these NPs would be able to retain the clorpyriphos since the AChE enzyme was not inhibited when the earthworms were exposed to the binary mixture. However, the inhibition of the CES could not be prevented, although the NPs alone did not exert any effect on this enzyme activity. Altogether, these results show the complex interactions that may be seen in binary mixtures of NPs and other contaminants.