Copper and Nickel Accumulation and Translocation in Leafy Vegetables Irrigated with Metal-Containing Effluents

The laboratory experiment was performed to assess the accumulation and translocation of Cu and Ni in aerial and underground parts of lettuce (Lactuca sativa), green onion (Allium fistulosum L.), arugula (Eruca vesicaria), and chard (Beta vulgaris var. cicla) irrigated with metal-containing effluents and to evaluate the potential health risks associated with consumption of wastewater-irrigated vegetables. The highest Cu content was found in the edible parts of lettuce (8.34 ± 1.24 mg/kg) and chard (9.79 ± 0.27 mg/kg). Arugula (16.8 ± 2.21 mg/kg) and lettuce (24.1 ± 5.34 mg/kg) exhibited the highest Ni content. The highest bioaccumulation factor for Cu (1.0) and Ni (1.5) were determined in chard and lettuce, respectively. Overall, the studied leafy vegetables showed a low capacity for Cu and Ni translocation to the above-ground parts, with the highest translocation factor determined in arugula (0.7—Ni) and in lettuce (0.8—Cu). The effect of the effluents on pigment composition and antioxidant activity varied significantly among plant species. Onion showed an ability to enhance antioxidant protection by increasing phenols synthesis. In contrast, chard manifested high sensitivity for Cu and Ni, which was expressed in a decrease in both pigments and antioxidant activity. The estimated daily intake values for Ni and Cu through vegetable consumption were found to be one to two orders of magnitude lower than the recommended dietary requirements for adults (1.0 mg/day for Ni and 2–3 mg/day for Cu).