Assessment of single and joint toxic effects of Ca2+,Mg2+and K+based on luminescent bacteria method
Freshwater salinization is aggravated by human activities such as mining,agriculture and industrial discharges.However,toxicity assessments related to salinization are still at the research stage.In order to further elucidate the biotoxicity effects of salinization-associated ions,the toxicity effect intervals and toxic excitatory stimulation effect intervals of single and binary mixtures of salinization-associated cations,Ca2+,Mg2+and K+were examined,by using Photobacterium phosphoreum T3 as test strain.The toxicity mechanisms of three cations and their binary mixtures were explored from oxidative stress and luminescence damage.The results show that the single toxicity of Ca2+and Mg2+is similar,and the EC50 is 335.5 mmol/L and 333.3 mmol/L,respectively.The toxicity response of K+is different from that of Mg2+and Ca2+,and the T3 strain shows high tolerance to K+.All three cations exhibit Hormesis but shows different Hormetic responses and corresponding concentration ranges.All experimental groups of the mixture manifests a Hormetic effect in Photobacterium phosphoreum T3,and the joint toxicity represents component and concentration ratio dependence,the order of binary mixture toxicity from highest to lowest is Ca2+-Mg2+,Ca2+-K+,Mg2+-K+,and the presence of Ca2+may increase the toxicity of the mixture.The Ca2+-Mg2+binary mixture may induce oxidative stress and cause a synergistic effect.The presence of K+in a binary mixture may weaken oxidative stress and joint toxicity,showing an antagonistic effect.
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