Effect and Mechanism of Calcium-Magnesium-Potassium Ion Mixtures on Toxicity of Heavy Metal Ions in Water

In order to determine the effect of common calcium-magnesium-potassium ion mixtures in water on the toxicity of heavy me-tal ions, such as Cu2+, Zn2+, Cr6+, Cd2+ and Fe3+, acute toxicity tests are carried out using Photobacterium phosphorium T3 as the tested organism. Mechanistic analysis is performed through biochemical indicators and changes in the ex-pression levels of core luminescent genes. The results indicate that the toxicity of individual heavy me-tal ions to the bioluminescent bacterium T3 follows the order: Zn2+gt;Cd2+gt;Cu2+gt;Fe3+gt;Cr6+. The toxicity of heavy me-tal ions decreases after the addition of different concentrations of Ca2+-Mg2-K+ mixed solution, with the weakest combined toxicity observed when the mass concentrations of Ca2+, Mg2+, and K+ are 13.40, 8.00, and 26.20 mg/L, respectively. Moreover, when the concentration of heavy me-tal ions is low(lt;2.0 mg/L), an antagonistic effect is observed between the heavy me-tal ions and the Ca2+-Mg2+-K+ mixture, accompanied by a significant stimulating effect. As the concentration of heavy me-tal ions increases, the combined action gradually shifts towards an additive effect. The addition of Ca2+-Mg2+-K+ mixed solution leads to a decrease in intracellular reactive oxygen species levels, an increase in superoxide dismutase activity and the content of reduced nicotinamide adenine dinucleotide, enhancing the bacterium's antioxidant capacity and stimulating redox reactions to improve energy supply levels, thereby reducing the toxicity of me-tal ions. The study can provide data reference for the toxicity evaluation and regulation of mixed heavy me-tal ions in actual water bodies. © 2024 Xi'an Jiaotong University. All rights reserved.