AVALIAÇÃO DA INFLUÊNCIA DE NANOPARTÍCULAS DE ÓXIDO DE ZINCO NO POTENCIAL DE FITORREMEDIAÇÃO DE ÁGUA CONTAMINADA POR ATRAZINA

Abstract

Atrazine (Atz) is a widely used herbicide for weed control, acting on the photosystem II D1 protein and inhibiting photosynthesis. The high atrazine concentration in aquatic ecosystems, combined with its high toxicity, makes it urgent to develop effective methods for removing this contaminant from the environment. Although phytoremediation is interesting to achieve this goal, plants are sensitive to damage triggered by triazine-based herbicides, requiring alternative methodologies to minimize this effect. An important technology to limit the damage caused by pollutants in plants is the use of zinc oxide nanoparticles (ZnO-NP). The objective of this study was to evaluate the atrazine phytoremediation capacity - associated with zinc oxide nanoparticles - by the aquatic species Pistia stratiotes. For this, specimens of P. stratiotes were exposed to the following treatments: control, atrazine (0.025 mg/L), zinc oxide (10 mg/L) and atrazine + zinc oxide with six repetitions. The plants remained under these conditions for 15 days, then it was evaluated the physiology, growth and cellular damage. The water phytoremediated by the plants was collected at the end of 15 days and used to evaluate the locomotor speed (pLMV) of the tropical freshwater invertebrate Girardia tigrina, which has been pointed out as a potential bioindicator in freshwater systems. The herbicide application considerably decreased the photosynthetic rate, Rubisco carboxylation efficiency, effective quantum yield of photosystem II and photochemical quenching. The nanoparticles application, however, was able to restore these parameters to levels similar to control. For stomatal conductance no statistical difference was observed and for transpiration rate ZnO-NP application was higher than Atz. It is likely that ZnO-NP have a protective effect against the damage caused by the herbicide. Zinc (Zn) is associated with several important biological functions, such as carbohydrate metabolism, membrane integrity, proteins involved in DNA replication and gene expression, in addition to playing a structural and catalytic role in enzymes such as superoxide dismutase, alcohol dehydrogenase and carbonic anhydrase, which prevent photo-oxidative damage. Thus, the results indicate that the ZnO-NP addition improves the toxic effects of Atz on Pistia stratiotes, but more future studies are needed to understand the action mode of these nanoparticles on plants to this pollutant. The results of the planarian locomotion tests showed that the organisms were more sensitive in the treatment with atrazine without phytoremediation inhibiting their locomotion. These results will contribute to the improvement of the phytoremediation process and to the contaminated water reuse in agriculture, and the potential impacts for adjacent ecosystems, such as freshwater systems, contributing to sustainable rural development and environmental conservation.