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Surfactant-enhanced phytoremediation is a green technology for the treatment of contaminated soil. In a pot experiment, two biosurfactants (rhamnolipid and soybean lecithin) and a synthetic surfactant (Tween 80) were used to facilitate phytoremediation of crude oil contaminated soil by maize (Zea mays. L). Results showed that these surfactants did not significantly affect the biomass production of maize, but they inhibited the chlorophyll fluorescence of the maize leaf. Rhamnolipid and soybean lecithin enhanced the soil microbial population, resulting in increased removal of total petroleum hydrocarbons from the soil. Saturated hydrocarbons were the main component of petroleum hydrocarbons decreased in the soil. In addition, the accumulation of polycyclic aromatic hydrocarbons was inhibited in the maize leaf by all selected surfactant treatments, but was facilitated in maize root by the treatments of rhamnolipid and Tween 80. This work indicates that biosurfactant amended phytoremediation may be a useful biotechnological approach for the remediation of petroleum hydrocarbon polluted soil.

A pot experiment was conducted to investigate the effects of pollination on cadmium (Cd) phytoextraction from soil by mature maize plants. The results showed that the unpollinated maize plants accumulated 50% more Cd than that of the pollinated plants, even though the dry weight of the former plants was 15% less than that of the latter plants. The Cd accumulation in root and leaf of the unpollinated maize plant was 0.47 and 0.89 times higher than that of the pollinated plant, respectively. The Cd concentration in the cob was significantly decreased because of pollination. Preventing pollination is a promising approach for enhancing the effectiveness of phytoextraction in Cd-contaminated soils by maize. This study suggested that in low Cd-contaminated soil pollination should be encouraged because accumulation of Cd in maize grains is very little and maize seeds can bring farmers economic benefits, while in high Cd-contaminated soil, inhibition of pollination can be applied to enhance phytoextraction of Cd from soil by maize plant.

Maize is an economic crop that is also a candidate for use in phytoremediation in low-to-moderately Cd-contaminated soils, because the plant can accumulate high concentration of Cd in parts that are nonedible to humans while accumulating only a low concentration of Cd in the fruit. Maize cultivars CT38 and HZ were planted in field soils contaminated with Cd and nitrilotriacetic acid (NTA) was used to enhance the phytoextractive effect of the maize. Different organs of the plant were analyzed to identify the Cd sinks in the maize. A distinction was made between leaf sheath tissue and leaf lamina tissue. Cd concentrations decreased in the tissues in the following order: sheath > root > lamina > stem > fruit. The addition of NTA increased the amount of Cd absorbed but left the relative distribution of the metal among the plant organs essentially unchanged. The Cd in the fruit of maize was below the Chinese government’s permitted concentration in coarse cereals. Therefore, this study shows that it is possible to conduct maize phytoremediation of Cd-contaminated soil while, at the same time, harvesting a crop, for subsequent consumption.

This study has investigated the use of screened maize for remediation of soil contaminated with crude oil. Pots experiment was carried out for 60 days by transplanting maize seedlings into spiked soils. The results showed that certain amount of crude oil in soil (≤2 147 mg·kg(-1)) could enhance the production of shoot biomass of maize. Higher concentration (6 373 mg·kg(-1)) did not significantly inhibit the growth of plant maize (including shoot and root). Analysis of plant shoot by GC-MS showed that low molecular weight polycyclic aromatic hydrocarbons (PAHs) were detected in maize tissues, but PAHs concentration in the plant did not increase with higher concentration of crude oil in soil. The reduction of total petroleum hydrocarbon in planted soil was up to 52.21-72.84%, while that of the corresponding controls was only 25.85-34.22% in two months. In addition, data from physiological and biochemical indexes demonstrated a favorable adaptability of maize to crude oil pollution stress. This study suggested that the use of maize (Zea mays L.) was a good choice for remediation of soil contaminated with petroleum within a certain range of concentrations.

Understanding the uptake of organic pollutants by plants is an important part of the assessment of risks from crops grown on contaminated soils. This study was an investigation of the effects of surfactants added to PAHs-contaminated soil on the uptake and accumulation of PAHs in maize tissues during phytoremediation. The accumulation of phenanthrene (PHE) and pyrene (PYR) by maize plant was not influenced significantly by the surfactant amendment to the soil. The distribution of PHE and PYR in maize tissues was not positively correlated with the corresponding lipid contents. Remarkably, the concentrations of PHE (20.9 ng g(-1)) and PYR (0.9 ng g(-1)) in maize grain were similar to or even much lower than those in some foods. Moreover, surfactants could enhance the removal of pollutants from contaminated soil during phytoremediation, which might be due to surfactant desorption ability and microbial activity in soil. The study suggests that use of maize plant with surfactant is an alternative technology for remediation of PAHs-contaminated soils.