The exploitation of petroleum, the production and use of petroleum products causes pollution that is harmful to the ecology and environment. At present, petroleum hydrocarbon pollution has become a universal concern in the world. As one of the bioremediation methods, plant root exudate repair has the effect of eliminating toxic substances in the environment. To explore the role of root exudates glycine in phytoremediation of petroleum-contaminated soil, seed germination and pot experiments were carried out to study the effects of glycine on the degradation of petroleum hydrocarbons in different plants and soil types. The results showed that when the concentration of petroleum pollutants was constant, the order of seed germination rate of the eight plants was ryegrass > sudan grass > white clover > tall fescue > alfalfa > pennisetum > canine root > maize grass.1000 mg L−1 of glycine could effectively promote plant biomass and the petroleum hydrocarbons degradation rate. The degradation effect was ryegrass + glycine > ryegrass > sudan grass + glycine > sudan grass > white clover + glycine > white clover. The degradation rate of ryegrass + glycine in 18,000 mg kg−1 petroleum-contaminated soil reached 55.7%. All plants had the highest biomass and plant height in loamy soil, while the highest degradation rate of petroleum hydrocarbons was observed in sandy soil, ranging from 50.36% to 59.36%. Among them, ryegrass combined with 1000 mg L−1 of glycine reached the highest petroleum hydrocarbons degradation rate of 59.36% in sandy soil. Ryegrass, sudan grass and white clover had the potential to remediate petroleum-contaminated soils. In the three types of soil, ryegrass had a strong remediation efficiency, and the degradation effect to petroleum hydrocarbons was more significant after the addition of glycine. Therefore, ryegrass can be planted with glycine as a priority for remediation in oil field areas contaminated by petroleum hydrocarbons.

With the development of industrialization, soils around the world have been polluted by heavy metals and oil to different degrees in recent years, and soil remediation has become a global problem. Phytoremediation has a wide application prospect because of its environmental friendliness and easy availability of materials.ObjectiveTo explore the effects of soil types and root exudates on the removal of cadmium and petroleum hydrocarbon in soils.MethodA pot experiments with three soil types (sandy, loamy and clayey) of the Changning-Weiyuan area of Sichuan province and three root exudates (citric acid, glycine, and maltose) were carried out using Sorghum sudanense (Piper) Stapf., Lolium perenne L., and Festuca arundinacea L. as test materials. Plants were grown in soils contaminated by cadmium and petroleum at different concentrations.ResultThe biomass of S. sudanense, the translocation ratio and removal rate of cadmium in S. sudanense decreased gradually with increasing soil cadmium concentration. The promotion effects of the three root exudates on S. sudanense were in the following order: citric acid > glycine > maltose. At the same cadmium pollution conditions, the biomass levels of S. sudanense in sandy, loamy, and clayey soils were in the following order: clayey soil > loamy soil > sandy soil. On the contrary, the concentration, translocation ratio, and removal rate of cadmium in S. sudanense grown in the different soils treated with root exudates were in the following order: sandy soil > loamy soil > clayey soil. Under the three soil conditions, the fresh weight of F. arundinacea (0.36 ~ 0.68 g) and S. sudanense (0.51 ~ 0.99 g) increased significantly (p < 0.05). The total petroleum hydrocarbons degradation efficiencies of F. arundinacea, L. perenne, and S. sudanense were high in sandy soil (34.27% ~ 60.52%). Changing the type of root exudate had a significant impact on the degradation of total petroleum hydrocarbons in sandy soil (p < 0.05).ConclusionThis study showed that soil types impacted the accumulation of cadmium and petroleum in plants. Phytoremediation of cadmium and petroleum contaminated soil could be enhanced by the application of root exudates. This study recommend that the method is suitable for field remediation of soils contaminated with mild cadmium and petroleum hydrocarbons.

In the published article, there was an error in the Funding statement. The correct Funding statement appears below."This work was funded by the "13th five-year" National Major Science and Technology Project of China (grant no. 2016ZX05040-002)."The authors apologize for this error and state that this does not change the scientific conclusions of the article in any way. The original article has been updated.