Toxic effects of binary toxicants of cresol frother and Cu (II) on soil microorganisms

As the scale and intensity of mining increase, the application of mineral agents raises concerns about its environmental impact, but little information is available on the combined toxic effect of cresol frothing agent and Cu2+ on the soil microbial activity. In this work, microcalorimetric method, enzyme activity and Illumina HiSeq 2500 high throughput sequencing technology were combined to determine the effect of binary toxicants on soil microorganisms. The dose-toxicity relationship obtained from microcalorimetry experiments indicated that an increase in dosage was associated with a decrease in metabolic rate constant k (or an increase in the inhibitory ratio). The ratio of 400/0.08 (mg·L−1/mg·g−1) of Cu2+/cresols stimulated the growth of microorganisms in soil. Urease and fluorescein diacetate esterase activities upon the exposure of binary toxic mixture showed a negative impact and the toxicity order followed: Cu2+/p-cresol > Cu2+/o-cresol > Cu2+/m-cresol. By Illumina HiSeq 2500 high throughput sequencing technology, the results of microbial communities in 3 soil samples showed no significant differences, and Proteobacteria, Acidobacteria, Gemmatimonadetes and Bacteroidetes phyla were the dominant species as Gram-negative bacteria.