Enhancing agents for phytoremediation of soil contaminated by cyanophos

Decontamination of Chlorpyrifos Residue in Soil by Using Mentha piperita (Lamiales: Lamiaceae) for Phytoremediation and Two Bacterial Strains

This study utilizes Mentha piperita (MI) for the first time to investigate the uptake and translocation of chlorpyrifos (CPF; 10 µg g-1) from soil, introducing a new approach to improve the efficacy of this technique, which includes using biosurfactants (Bacillus subtilis and Pseudomonas aeruginosa) at 107 CFU/mL to degrade CPF under greenhouse conditions. Moreover, antioxidant enzymes, including superoxide dismutase (SOD) and peroxidase (Prx), and oxidative stress due to hydrogen peroxide (H2O2) and malondialdehyde (MDA) in MI roots and leaves were evaluated under CPF stress. Our results demonstrated that amending soil with MI and B. subtilis followed by P. aeruginosa significantly reduced CPF levels in the soil (p > 0.05) and enhanced CPF concentrations in MI roots and leaves after 1, 3, 7, 10, and 14 days of the experiment. Furthermore, CPF showed its longest half-life (t1/2) in soil contaminated solely with CPF, lasting 15.36 days. Conversely, its shortest half-life occurred in soil contaminated with CPF and treated with MI along with B. subtilis, lasting 4.65 days. Soil contaminated with CPF and treated with MI and P. aeruginosa showed a half-life of 7.98 days. The half-life (t1/2) of CPF-contaminated soil with MI alone was 11.41 days. A batch equilibrium technique showed that B. subtilis is better than P. aeruginosa for eliminating CPF from soil in In vitro experiments. Notably, CPF-polluted soil treated with coadministration of MI and the tested bacteria improved the activities of SOD and Prx and reduced H2O2 and MDA compared with CPF-polluted soil treated with MI alone. Our findings demonstrated that using B. subtilis and P. aeruginosa as biosurfactants to augment phytoremediation represents a commendable strategy for enhancing the remediation of CPF contamination in affected sites while reducing the existence of harmful pesticide remnants in crop plants.

Cyclodextrin-enabled green environmental biotechnologies

Most of the organic compounds contaminating the environment can form inclusion complexes with cyclodextrins resulting in enhanced solubility (a benefit in soil remediation) or just the opposite: reduced mobility by sorption (a benefit in wastewater treatment). Combining biotechnologies with cyclodextrin, a renewable and biodegradable material, green environmental technologies of high efficiency were developed. For instance, the cyclodextrin-enabled soil washing/flushing technologies combined with bioremediation have been demonstrated in full-scale field experiments. The efficiency of tertiary wastewater treatment by sorption of non-biodegradable xenobiotics, such as residual pharmaceutics, was proved. The biofilm formation in fouling processes can be prevented or reduced either by applying cyclodextrin-based coatings or by manipulation of quorum sensing (bacterial communication) via capturing signal molecules.

Pesticide remediation with cyclodextrins: a review

The aim of this review is to highlight and provide an update on the current development of pesticide remediation methods, focusing on the utilization of different cyclodextrin (CD) molecules. Because of less environmental impact and non-toxic nature, CDs are beneficial for pesticide remediation, reducing environmental risk and health hazards. They are advantageous for the removal of pesticides from contaminated areas, as well as for better pesticide formulation and, posing significant effects on the hydrolysis or degradation of pesticides. The review focuses on the current trend and innovations regarding the methods and strategies employed for using CDs in designing pesticide remediation. Nowadays, in addition to the conventional experimental techniques, molecular simulation approaches are significantly contributing to the study of such phenomena and hence are recognized as a widely used tool.

Synergistic use of Plantago major and effective microorganisms, EM1 to clean up the soil polluted with imidacloprid under laboratory and field condition

Imidacloprid is known to induce soil pollution. Herein, we improved phytoremediation of soil contaminated with imidacoprid using Plantago major plus effective microorganisms (EM1) and peat-moss under laboratory conditions for 14-days and using P. major inoculated with EM1 in tomato field for 10-days. Concentration of imidacloprid in soil, roots and leaves was determined. Concentrations of Chlorophyll in leaves were also determined. Our results showed that lower imidacloprid degradation rate was observed in amended soil with peat-moss, while higher imidacloprid degradation rate was observed in soils vegetated with P. major, P. major inoculated by EM1, and P. major amended with peat-moss, respectively. However, degradation rate was high in the case of interaction between soil planted with P. major plus both of EM1 and peat-moss. Concentration of imidacloprid in P. major roots amended with EM1, peat-moss and both was significantly lower than that of P. major roots alone within 1-14 days of treatment. EM1 plus P. major and peat- moss plus P. major had increase of Chlorophyl content in leaves. Cultivation of P. major next to tomatoes crop and inoculated with EM-1 was found to be the most effective process for removing imidacloprid from the soil.

Nano-SiO2 combined with a surfactant enhanced phenanthrene phytoremediation by Erigeron annuus (L.) Pers

The objective of this experiment was to evaluate the effects of Triton X-100 (1000 mg kg^-1) and nano-SiO₂ (500 mg kg^-1) on Erigeron annuus (L.) Pers. grown in phenanthrene spiked soil (150 mg kg^-1) for 60 days. Results show that untreated groups, groups treated with both Triton X-100 and nano-SiO₂, exhibited better phenanthrene degradation rates and improved root biomasses, chlorophyll contents, and soil enzyme activities. This study demonstrates that Triton X-100 combined with nano-SiO₂ protects plants, alleviating the stress of polycyclic aromatic hydrocarbons (PAHs), and can provide a means for improving phytoremediation of PAH contaminated soils.

Green nano-phytoremediation and solubility improving agents for the remediation of chlorfenapyr contaminated soil and water

Chlorfenapyr is a novel class of insecticide-miticide used for crop protection. It poses substantial risks to the reproductive ability of birds as well as environmental stability. This study was focused on the remediation of chlorfenapyr-polluted soil and water through the combined application of green nanotechnology, solubility improving agents and phytoremediation. An analysis using electron microscopy showed that the green synthesis resulted in circular ficus iron nanoparticles (F-Fe⁰) with diameters of 2.46 nm-11.49 nm, while the ipomoea-silver (Ip-Ag⁰) and brassica-silver nanoparticles (Br-Ag⁰) were circular, cubical, hexagonal, triangular and rod -like in shape with sizes ranging from 6.27 to 21.23 nm in IP-Ag⁰ and from 6.05 to 15.02 nm in Br-Ag⁰. After 24 h of treatment with F-Fe⁰, Ip-Ag⁰ and Br-Ag⁰ supported on activated charcoal (Ach), the chlorfenapyr in the aqueous solution was reduced to 86%, 79.70%, and 79.70%, respectively, compared to the 6.16% in aqueous solution. Moreover, after 24 h of treatment with Plantago major plus F-Fe⁰Ach, P. major plus Ip-Ag⁰Ach, and P. major plus Br-Ag⁰Ach, the chlorfenapyr in the aqueous solution was reduced to 93.7%, 91.30%, and 92.92%, respectively, as compared to the 69.27% in P. major. After four days of exposure, the percentage of chlorfenapyr degradation in the soil (i.e. control) only reached 12.40%,while the degradation rates were enhanced by 71.22%, 57.32% and 73.10%, respectively, in the presence of P. major plus nanoparticles (F-Fe0, Ip-Ag0 and Br-Ag0). The integration of green nanotechnology, solubility-improving agents, and phytoremediation by Plantago major has played a major role in the remediation of soil and water contaminated with chlorfenapyr.

Influence of alkyl polyglucoside, citric acid, and nitrilotriacetic acid on phytoremediation in pyrene-Pb co-contaminated soils

At present, the remediation for organic pollutants and heavy metals co-contaminated soils is a challenge which needs to be broken through. In this study, alkyl polyglucoside (APG), citric acid (CA), and nitrilotriacetic acid (NTA) were chosen to enhance the phytoremediation of pyrene and Pb co-contaminated soils by perennial ryegrass. Through the comparison of the results with different applications, it could be found that the application of NTA was beneficial to the growth of perennial ryegrass, the underground and aboveground biomass were increased by 172.9-236.1% and 61.9-142.8%, respectively, meanwhile, photosynthetic activity of perennial ryegrass was affected positively. More importantly, the combined application of APG and NTA maximally promoted the accumulation and translocation of Pb (BF/TF, 0.44/0.61) and dissipation of pyrene (71.6%). These results indicated that the combined application of APG and NTA could be promising for future practical application of phytoremediation. However, the optimal dosage ratio of APG and NTA for phytoremediation needs to be further researched.

The fate of DDT in soils treated with hydroxypropyl-β-cyclodextrin (HPβCD)

Point Pelee National Park (PPNP) is highly contaminated with dichlorodiphenyltrichloroethane (DDT) due to the historical use of this persistent organochlorine pesticide. Hydroxypropyl-β-cyclodextrin (HPβCD) has previously been investigated for its role in the remediation of polyaromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs). In the present study, HPβCD's ability to promote DDT microbial degradation, enhance DDT phytoextraction by two native grasses (Schizachyrium scoparium and Panicum virgatum), and increase DDT bioavailability to redworms (Eisenia fetida) was investigated. Using a range of HPβCD concentrations (2.5% to 10%), it was determined that it did not promote DDT microbial degradation in PPNP soils, however, it was able enhance the DDT phytoextraction ability of S. scoparium plants due to the increased water solubility of DDT. Although HPβCD application to PPNP soil did not increase DDT bioavailability to redworms, its enhanced solubility allowed it to move through the soil column, and hence groundwater contamination is a possibility. Due to this important issue, in situ use of HPβCD to remediate DDT contamination is not recommended unless measures are in place to mitigate movement into groundwater.

Influence of direct and alternating current electric fields on efficiency promotion and leaching risk alleviation of chelator assisted phytoremediation

Direct and alternating current electric fields with various voltages were used to improve the decontamination efficiency of chelator assisted phytoremediation for multi-metal polluted soil. The alleviation effect of electric field on leaching risk caused by chelator application during phytoremediation process was also evaluated. Biomass yield, pollutant uptake and metal leaching retardation under alternating current (AC) and direct current (DC) electric fields were compared. The biomass yield of Eucalyptus globulus under AC fields with various voltages (2, 4 and 10 V) were 3.91, 4.16 and 3.67kg, respectively, significantly higher than the chelator treatment without electric field (2.71kg). Besides growth stimulation, AC fields increased the metal concentrations of plant tissues especially in aerial parts manifested by the raised translocation factor of different metals. Direct current electric fields with low and moderate voltages increased the biomass production of the species to 3.45 and 3.12kg, respectively, while high voltage on the contrary suppressed the growth of the plants (2.66kg). Under DC fields, metal concentrations elevated obviously with increasing voltages and the metal translocation factors were similar under all voltages. Metal extraction per plant achieved the maximum value under moderate voltage due to the greatest biomass production. DC field with high voltage (10V) decreased the volume of leachate from the chelator treatment without electric field from 1224 to 56mL, while the leachate gathered from AC field treatments raised from 512 to 670mL. DC field can retard the downward movement of metals caused by chelator application more effectively relative to AC field due to the constant water flow and electroosmosis direction. Alternating current field had more promotive effect on chelator assisted phytoremediation efficiency than DC field illustrated by more metal accumulation in the species. However, with the consideration of leaching risk, DC field with moderate voltage was the optimal supplementary technique for phytoremediation.

Phytoremediation of soil co-contaminated with Cd and BDE-209 using hyperaccumulator enhanced by AM fungi and surfactant

Pot experiments were conducted to investigate the uptake and translocation of both Cd and decabromodiphenyl ether (BDE-209) in Solanum nigrum, under the treatments of two arbuscular mycorrhizal fungi [AMF, Funneliformis mosseae (FM) and Rhizophagus intraradices (RI)] and surfactant β-cyclodextrin (β-CD). Results showed that S. nigrum treated with either FM or β-CD significantly elevated shoot biomass and Cd concentrations and contents in shoots. The concentrations of BDE-209 in shoots and the dissipation and debromination efficiencies of BDE-209 in soil were significantly enhanced in S. nigrum treated with β-CD, inoculated with or without AMF. Moreover, significant positive correlations were found between the BDE-209 dissipation efficiency, the BDE-209 concentrations and contents in roots, and the soil enzymatic activities (polyphenol oxidase or dehydrogenase activities) and between the Cd and BDE-209 contents in shoots or roots. Higher concentrations of lower-brominated products and total PBDEs were detected in shoots than in roots suggesting that BDE-209 might be initially absorbed by roots, then translocated to shoots, and then degraded into lower brominated products in shoots. Considering the plant uptake of Cd and BDE-209 and the efficient removal of those chemicals in soils, the combination of S. nigrum and β-CD inoculated with or without AMF may be viable alternatives for phytoremediation of the co-contaminated soil.

Biochemical interactions between Glycine max L. silicon dioxide (SiO2) and plant growth-promoting bacteria (PGPR) for improving phytoremediation of soil contaminated with fenamiphos and its degradation products

Fenamiphos is a systematic nematicide-insecticide used extensively for the control of soil nematodes. Fenamiphos and oxidation products have been known to induce water pollution, soil pollution and ecotoxicological effects on aquatic organisms, as well as heath issues. This contaminant can be removed by phytoremediation. Herein, we tested several strategies to improve the effectiveness of this technology. A combination of G. max plus Pseudomonas fluorescens was more efficient than G. max plus Serratia marcescens or G. max alone in degrading fenamiphos to other metabolites. Three major metabolites, namely fenamiphos sulfoxide (FSO), fenamiphos sulfone (FSO2) and fenamiphos phenol (F-phenol), were detected in roots and leaves in which G. max amended with P. fluorescens or amended with S. marcescens produced a significant accumulation of FSO and FSO2 with higher amounts than for G. max alone. Leaf concentrations of FSO were always higher than in the roots, while FSO2 accumulated significantly more in G. max roots than in G. max leaves. In soil treated with fenamiphos, G. max roots and leaves alone, and in combined effects of plant and microorganisms, resulted in the disappearance of fenamiphos and the appearance of F-SO, F-SO2 and F-phenol, which in turn caused toxic stress in G. max and the resulting production of reactive oxygen species such as H2O2 with higher content and an increase in antioxidant GPX activity. Although a batch equilibrium technique showed that use of SiO2 resulted in the efficient removal of fenamiphos when compared with other treatments for removing adsorbed fenamiphos from soil, a fewer amount of fenamiphos was removed by G. max L. with SiO2. H2O2 content and GPX activity increased in G. max under fenamiphos treatment and its degradation products, while amended G. max with SiO2 or Argal led to a decrease in GPX activity and H2O2 content.

Tween 80 surfactant-enhanced bioremediation: toward a solution to the soil contamination by hydrophobic organic compounds

The occurrence of hydrophobic organic compounds (HOCs) in the soil has become a highly significant environmental issue. This problem has been exacerbated by the strong sorption of HOCs to the soils, which makes them unavailable for most remediation processes. More and more works show that surfactant-enhanced biological technologies offer a great potential to clear up HOCs-contaminated soils. This article is a critical review of HOCs removal from soils using Tween 80 (one of the mostly used nonionic surfactants) aided biological remediation technologies. The review begins with a discussion of the fundamentals of Tween 80-enhanced desorption of HOCs from contaminated soils, with special emphasis on the biotoxicity of Tween 80. Successful results obtained by Tween 80-enhanced microbial degradation and phytoremediation are documented and discussed in section 3 and section 4, respectively. Results show Tween 80-enhanced biotechnologies are promising for treating HOCs-contaminated soils. However, considering the fact that most of these scientific studies have only been conducted at the laboratory-scale, many improvements are required before these technologies can be scaled up to the full-scale level. Moreover, further research on mechanisms related to the interaction of Tween 80 with degrading microorganisms and the plants is in high demand.