The multiway support of phytoremediation efficiency of soil historically co-contaminated with petroleum hydrocarbons and heavy metals using Zea mays

Abstract The phytoremediation of soil co-contaminated with petroleum hydrocarbons and heavy metals was studied using Zea mays that was supported with the addition of plant growth-promoting Pseudomonas qingdaonensis ZCR6 and meat and bone meal. The introduced ZCR6 strain was able to survive in the soil and colonize the tissues of maize; however, it did not support plant growth and biomass production or have an impact on hydrocarbon removal. The amendment of the soil with meat and bone meal had a negative impact on the growth of maize however it enhanced soil microbial activity and thus the degradation of hydrocarbons. The efficacy of hydrocarbon removal estimated in fertilized soils reached a value of 32% regardless of the treatment. Z. mays was able to accumulate Zn, Cd and Cu in the presence of hydrocarbons, with the highest phytoextraction ability of Zn. The activity of the mechanisms enhancing the phytoremediation was tested through the quantification of the expression of the selected genes. Among them only acdS, encoding ACC deaminase, and CYP153, encoding cytochrome P450-type alkane hydroxylase, were expressed. As far as we are aware, these are the first results tackling the global problem of co-contaminated soils using a slow-release meat and bone meal fertilizer and a plant-growth-promoting microbe.