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Metal nanoparticles are increasingly used in industry and agriculture to enhance crop yields and combat plant diseases. Their widespread application has led to exposure across all ecosystem components, including humans. However, there is a lack of a comprehensive assessment of the effect of copper nanoparticles on spearmint plants, applied in different ways (root and foliar) in a wide range of concentrations. The effect of copper nanoparticles at the concentration range of 1–100 mg/L on Mentha spicata L. plants under root exposure and foliar spraying conditions was studied during a 28-day experiment. Copper content in soil and spearmint segments was determined using inductively coupled plasma atomic emission spectroscopy, while the morphology of nanoparticles was characterized using transmission electron microscopy. Foliar spraying showed an inverse relationship between the concentration of copper in solution and root uptake. The highest copper uptake in roots of 27.51 mg/kg was attained at a nanoparticle concentration of 1 mg/L. Root exposure inhibited soil microbial activity, with copper mainly accumulating in soil (up to 950.2 mg/kg) and roots (up to 150.5 mg/kg). Both application methods stimulated pigment production and antioxidant activity, with root irrigation showing a more pronounced effect. Copper extraction efficiency varied (3–64%) depending on exposure method and concentration, raising concerns about transfer along the food chain. Health risk assessment associated with consumption of herbal infusions, prepared from copper-contaminated spearmint leaves, did not show adverse effects when copper levels in the infusion remained below 1.53 mg/L.
Peshkova et al. (Thu,) studied this question.