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We studied the profitable phytoremediation method with commercial chrysanthemum (Chrysanthemum indicum L.) in order to remediate the soils contaminated with heavy metals and generate economy income from the contaminated sites. A field experiment was carried out to remediate the contaminated soil through growing the commercial chrysanthemum plants in a farmland polluted with heavy metals of Cd and Zn due to application of creek sediments in the western suburb of Shanghai, Southeast China, since June 2013. After the consecutive 3 years of phytoremediation, Cd and Zn contents in the soil were reduced by 78.1% and 28.4%, respectively. We also found that the rice grain growing on the 3-year phytoremediated soil met the requirements of dietary safety, so did the vegetable growing on the 5-year phytoremediated soil. Growing chrysanthemum plants as a method of phytoremediation can not only remove a large amount of toxic heavy metals from the contaminated soil but also be highly profitable from the sales of chrysanthemum flowers.

This study aims to establish a simple and efficient method for the mass culture of bdelloid rotifers, which is the basis for the application of bdelloid rotifers as biological manipulators to improve wastewater biological treatment performance. A common bdelloid rotifer, Habrotrocha sp., in a wastewater biological treatment system was selected as the culture target. Rotifers fed on flour could reproduce faster than those fed traditional food such as Chlorella vulgaris or mixed bacteria. As a rotifer food, flour has the advantages of simple preparation, effortless preservation, and low cost compared to live Chlorella vulgaris or mixed bacteria, so it is more suitable for the mass culture of rotifers. The optimal rotifer culture conditions using flour as food were also studied. According to the experimental results, the recommended rotifer culture conditions are a flour particle size of 1 µm, a flour concentration of 6 × 106 cell/mL, a temperature of 28°C, a pH level of 6.5 and salinity of 100–500 mg/L. In addition, the sludge volume index in the sequencing batch reactor (SBR) with the addition of cultured rotifers was 59.9 mL/g at the end of operation and decreased by 18.2% compared to SBR without rotifer, which indicates that the cultured rotifers still retained the function of helping to improve sludge settling. This function may be related to the rotifer’s role in inhibiting bacteria from producing loosely bound extracellular polymeric substances in the SBR.

Phytoremediation is a kind of efficient strategy for remediating soils polluted with heavy metals. The aim of this study was to investigate the influence of spent mushroom substrate (SMS) on the phytoremediation potential of Ricinus communis in Cd- and Zn-polluted soil. We treated the soil with SMS before growing plants and analyzed the contents, distribution of heavy metals, and response of plants after growth. SMS increased the contents of Cd (5%-13%) and Zn (16%-20%) in the cell wall. This finding suggested that high amounts of Cd and Zn were absorbed and bonded to the cell wall through metabolism adaption and formed stable compounds, which reduced the damage of the heavy metal to cells. SMS also decreased the levels of superoxide dismutase, peroxidase, and catalase by 9.5%-27.7%, 8.8%-30.0% and 8.5%-28.1%, respectively. Treatment of SMS alleviated the toxicity of heavy metal in plants and increased the extracted amounts of Zn and Cd by 101%-227% and 51%-189%, respectively. Hence, SMS treatment could reduce the toxicity of heavy metals to plants and strengthen the phytoremediation potential.

Crop co-planting is widely used in agriculture because it can increase total crop yields through increased resource use efficiency, and phytoremediation is based on the contaminant remediation system in plants. This study focused on the phytoextractive effects of co-planting Ricinus communis and/or legumes in Cd- and Zn-contaminated soil. A Cd- and Zn-contaminated factory relocation site in Shanghai was selected for the experiment, and according to the results of a potential ecological risk assessment of heavy metals, the study area was divided into 3 levels of pollution: slight, moderate, and high. The results showed that the presence of Medicago sativa can significantly increase the height and biomass of R. communis, and there was a greater impact on the chlorophyll content of R. communis at higher pollution levels. Differences in pollution levels could significantly change the oil content of R. communis plants, but M. sativa can alleviate the impact of heavy metals. The presence of M. sativa increased the cumulative amount of cadmium and zinc in R. communis by 1.14 and 2.19 times, respectively. In short, co-planting R. communis and legumes remediated contaminated soil and may be one practical phytoremediation pathway for heavy metal-contaminated soil in the future.

Cd and Zn pollution was observed to often occur simultaneously in soils. However, previous studies focused on single heavy metal instead of Cd and Zn combined pollution. Castor (Ricinus communis) is considered to have great potential for contaminated soil remediation. The resistance of castor seedlings to heavy metals and the mechanism behind it remain unknown. In this study, the tolerance and accumulation ability of castor seedlings to Cd and Zn were investigated, and the accumulation mechanism involving the subcellular distribution in different tissues was further explored. The results on biomass and chlorophyll revealed that castor seedlings have good tolerance to the pollution with 0–5 mg/kg Cd and 380 mg/kg Zn, while not to the heavy pollution with 25 mg/kg Cd and 380 mg/kg Zn. The maximum accumulation concentrations of Cd and Zn, 175.3 mg Cd/kg and 386.8 mg/kg Zn, appeared in castor seedling root instead of stem and leaf, indicating that root played a significant part in accumulating Zn and Cd. The relative low dosage of Cd (0–5 mg/kg) promoted the accumulation of Zn in the subcellular component, while high dosage (25 mg/kg) inhibited the accumulation of Zn. In subcellular accumulation and distribution of castor seedlings, Cd (27.1%–69.4%) and Zn (39.6%–66.6%) in the cell wall was the highest. With the increase of Cd addition, the accumulation of Cd increased in cell wall while decreased in organelle and soluble fraction. Hydroxyl, amino, amides and carboxyl functional groups on cell wall might provided the main binding sites for Cd and Zn.

Phytoremediation is an eco-friendly and low-cost biotechnology using plants to extract, contain, degrade, or immobilize pollutants from the contaminated environment. Selection of the ideal plant species and suitable enhancing measures to obtain high remediation efficiency and large valuable biomass are essential requirement for a successful phytoremdaition. Sorghum (Sorghum bicolor L.) is one of the most attractive bioenergy crops for producing biofuels with high biomass production. In this study, the phytoremediation potential of sorghum to heavy metals and the promotion effects by a lead-tolerant fungus (LTF) were investigated using a multiple heavy metal contaminated soil with Pb, Ni, and Cu. The results showed that the sorghum survived the heavy contamination, and LTF inoculation promoted the plant growth and increased the phytoextraction yields of Pb, Ni, and Cu. The phytoextraction potential (μg/plant) of the whole sorghum for Sorghum were 410 (Pb), 74 (Ni), and 73 (Cu), and for Sorghum with LTF inoculation were 590 (Pb), 120 (Ni), and 93 (Cu), respectively. The results suggested that sorghum would be one of the ideal candidates for phytoremediation of contaminated soil because of its high phytoremediation potential, large biomass production, and utilization in biofuel production.

Phytoremediation is a low cost and eco-friendly emerging technology for treatment of contaminated soils with the use of green plants. In this study, the accumulation potential to heavy metals by two biofuel crops (maize and sunflower) and two metal accumulator plants (Elsholtzia splendens (ES), Tagetes patula L. (TP)) was studied with pot culture filled with a heavy metal contaminated soil, in order to compare their suitability for phytoremediation of contaminated soils. Sunflower showed the highest accumulation level for Cu (150 ug/pot) and Zn (10893 ug/pot) in the shoot part compared to other three plants. Maize showed a similar accumulation level for Cu (104 ug/pot) and Zn (7454 ug/pot) to TP, but a much higher level than ES. TP showed noticeable accumulation levels for Pb (196 ug/pot) and Cd (637 ug/pot). ES generally had the lowest accumulation capacity for Cu (38.5 ug/pot), Zn (2784 ug/pot), Pb (35.4 ug/pot) and Cd (18.2 ug/pot). Therefore, the two biofuel plants had higher or similar phytoremediation potential of heavy metals compared to the two accumulator plants. This study provided useful data for considering biofuel plants as potential economic crops for phytoremediation.

Ricinus communis L. is a bioenergetic crop with high-biomass production and tolerance to cadmium (Cd) and lead (Pb), thus, the plant is a candidate crop for phytoremediation. Pot experiments were performed to study the effects of citric acid in enhancing phytoextraction of Cd/Pb by Ricinus communis L. Citric acid increased Cd and Pb contents in plant shoots in all treatments by about 78% and 18-45%, respectively, at the dosage of 10 mM kg(-1) soil without affecting aboveground biomass production. Addition of citric acid reduced CEC, weakened soil adsorption of heavy metals and activated Cd and Pb in soil solutions. The acid-exchangeable fraction (BCR-1) of Pb remained lower than 7% and significantly increased with citric acid amendment. Respective increases in soil evaluation index induces by 14% and 19% under the Cd1Pb50 and Cd1Pb250 treatments upon addition of citric acid resulted in soil quality improvement. Ricinus communis L. has great potential in citric acid-assisted phytoextraction for Cd and Pb remediation.