In order to improve the bioremediation efficiency of petroleum-contaminated soil, five test groups were selected in this study, including native bacteria, Acinetobacter venetianus, Vetiveria zizanioides L., and Vetiveria zizanioides L. combined with Acinetobacter venetianus and biochar to compare the degradation efficiency of petroleum-contaminated soil. The results of the study showed that after a six-month bioremediation, there was no significant difference between the native bacteria and the A.V. bacteria group in the removal efficiency of TPH, and the proportion of degradable TPH accounts for about 50~70%. The removal efficiency of TPH could be increased by 18.1–29% by increasing the phytoremediation of Vetiveria zizanioides L. The cultivation of Vetiveria zizanioides L. could not only stabilize the soil’s pH and conductivity but could also increase the soil’s bacterial abundance. It was suggested that bioremediation could be carried out through the combination of native bacteria and the planting of Vetiveria zizanioides L. Although the addition of biochar to the soil was able to improve the remediation effect of Vetiveria zizanioides L., it would increase the soil conductivity and reduce the abundance of soil bacteria. Therefore, it was recommended to reduce the conductivity of biochar before adding it, which may improve processing efficiency.

Metal contamination in groundwater often occurs in various industrial processes. Studies have confirmed that polysulfide could reduce hexavalent chromium to trivalent chromium, achieving the effect of in situ stabilization. For other metal contamination in groundwater, whether polysulfide also had a stabilizing ability to achieve in situ remediation. This research focused on metals in addition to chromium that often contaminated groundwater, including lead, nickel, zinc, copper, and cadmium, to explore the feasibility of using calcium polysulfide (CaS_x) as an in situ stabilization technology for these metals’ contamination of groundwater. Results showed that CaS_x had a great removal efficiency for metals lead, nickel, zinc, copper, and cadmium. However, for nickel, zinc, copper, and cadmium, when CaS_x was added excessively, complexes would be formed, causing the result of re-dissolution, in turn reducing the removal efficiency. As it is difficult to accurately control the dosage of agents for in situ groundwater remediation, the concentration of re-dissolved nickel, zinc, copper, and cadmium may not be able to meet the groundwater control standards. CaS_x had high lead removal efficiency and for a concentration of 100 mg/L, the dose of calcium polysulfide was more than the amount of 1/1200 (volume ratio of CaSx to groundwater). In addition, the removal rate was almost 100% and it would not cause re-dissolution due to excessive CaS_x dosing. CaS_x can be used as an in situ stabilization technique for lead-contaminated groundwater.

Weathered petroleum-contaminated soil was treated with Vetiveria zizanioides (Vetiver) and Cymbopogon nardus (Lemongrasss) to investigate the efficiency of phytoremediation. The initial total petroleum hydrocarbon (TPH) concentration of soil was 3000−8000 mg/kg, and after 6 months, the TPH concentrations were degraded by 50−75% under the action of soil native microbial. Planting vetiver and lemongrass stabilized soil pH and electrical conductivity, and it accelerated the decomposition of TPH in soil. Planting vetiver showed a better effect. After 6 months of planting, the TPH decomposition efficiency reached about 90%, and most of the easily decomposed TPH has been decomposed. The results of rhizosphere soil microbiota analysis also showed that planting vetiver increased the abundance of soil microbiota.

Arsenic-rich groundwater causes arsenic accumulation in arable soils for irrigation. For such arsenic-contaminated farmland, phytoremediation is a feasible method in terms of cost and maintenance of soil. We studied arsenic-rich farmland planted with maize, Rotala rotundifolia, and the arsenic super-accumulating plant Pteris vittata and explored the arsenic absorption capacity of these plants to assess the effect of phytoremediation on arsenic-contaminated farmland. The arsenic removal by Pteris vittata was about 200 mg/m² y. It would take about 90 years to reduce the soil arsenic below the regulatory standard of 60 mg/kg using Pteris vittata. Planting maize removed about 25.5 mg/m² y of arsenic, and the arsenic concentration of the maize kernels was less than 0.2 mg/kg on a dry basis. It was below the standards of the animal food and human consumption limit. Pteris vittata needs to be planted first to rapidly reduce the bioavailable arsenic concentration in the soil. Subsequent planting of maize for remediating the soil while producing corn enables the sustainable production and utilization of farmland.

Copper and zinc are metals commonly used in industry. However, improperly disposed copper and zinc pollute soil seriously. In farmland where the concentrations of copper and zinc exceeded regulatory standards and farming has been banned for many years, we measured the copper and zinc concentrations in soil. The copper concentration ranged from 30.2 to 1082.3 mg/kg, while the zinc concentration was between 200.2 and 3335.3 mg/kg. To explore the correlation between the concentration of copper and zinc in soil and plants and plant growth, Pennisetum was chosen as the test crop. The economic and carbon reduction benefits of planting Pennisetum in copper- and zinc-polluted farmland were also investigated. The results indicated that the concentration levels of copper and zinc were not significantly impacted, and neither was the growth of Pennisetum. Farming Pennisetum produces a total of about 1100 tons of biomass per hectare per year. The income per hectare was about USD 48,000 per year. Pennisetum captures 578.8 tons of carbon every year, equivalent to 2124.2 ton-CO₂e. When used as fuel, it provides 23,649 GJ of bioenergy. Therefore, Pennisetum is an appropriate plant for the green and sustainable remediation of polluted soil.