Mercury accumulation potential of aquatic plant species in West Dongting Lake, China.

West Dongting Lake is a protected wetland with the potential for high levels of mercury release via wastewater and deposition from industry and agriculture during the last decade. To find out the ability of various plant species to accumulate mercury pollutants from soil and water, nine sites were studied in the downstream direction of the flow of the Yuan and Li Rivers, which are tributaries of the Yellow River flowing into West Dongting Lake, where mercury levels arere high in soil and plant tissues. The total mercury (THg) concentration in wetland soil was 0.078-1.659 mg/kg, which varied along the gradient of water flow along the river. According to canonical correspondence analysis and correlation analysis, there was a positive correlation between the soil THg concentration and the soil moisture in West Dongting Lake. There is high heterogeneity in the spatial distribution of soil THg concentration in West Dongting Lake, which may be related to the spatial heterogeneity of the soil moisture. Some plant species had higher THg concentrations in aboveground tissues (translocation factor >1), but none of these plant species fit the criteria as hyperaccumulators of mercury. And some species of the same ecological type (e.g., emergent, submergent, floating-leaved) exhibited very different strategies for mercury uptake. The concentrations of mercury in these species were lower than in other studies but these had relatively higher translocation factors. To phytoremediate soil mercury in West Dongting Lake, the regular harvest of plants could help remove mercury from soil and plant tissue.

Co-cultivation as a Strategy to Reduce Food Chain-Mediated Arsenic Contamination in Human Beings.

Arsenic (As) is a highly toxic metalloid present naturally in the earth's crust. In developing countries apart from drinking water, one major reason for arsenic toxicity among human beings is through contaminated crops and vegetables. The nutritional quality of the crops and vegetables grown in the arsenic-infested area gets compromised. A major challenge is to protect the vegetables and crops from arsenic contamination. Attempts have been made through different remediation technologies. The present research is designed to reduce the arsenic load in arsenic-sensitive (non-hyperaccumulator) plants by co-cultivation with hyperaccumulator plants, thus saving food chain contamination to humans. In the present study, done in potted plants, it has been found that co-cultivated B. oleracea has 1.5 times decreased arsenic translocation compared to the control plant; on the contrary, hyperaccumulator B. juncea showed higher translocation. Plant health biomarkers like total chlorophyll and protein contents were two times higher in co-cultivated B. oleracea compared to the As-treated control which actually seconds the fact of less translocation in the co-cultivated plants. The stress marker like proline content, super oxide dimutase, and malondialdehyde content showed a decrease in co-cultivated B. oleracea compared to the control plant grown in arsenic-infested soil which again reflected less stress in co-cultivated plants. From these findings of the research, we can hypothesize that hyperaccumulator B. juncea might save B. oleracea from arsenic-induced toxicity when co-cultivated and thus can save food chain-mediated contamination to human beings.

Facile Synthesis of Magnetic Iron-Based Nanoparticles from the Leach Solution of Hyperaccumulator Plant Pinus brutia for the Antibacterial Activity and Colorimetric Detection of Ascorbic Acid.

It has been well known that metallic nanoparticles with striking properties possess wide application prospects in the processes of colorimetric detection, catalysis, disease diagnosis and treatment, energy, wastewater treatment, remediation, and antibacterial activity in recent years. Herein, iron-based nanoparticles (FeNPs), metallic nanoparticles, were synthesized via a facile chemical reduction method using a hyperaccumulator plant. Also, their use in antibacterial activity applications and colorimetric ascorbic acid (AA) detection was investigated. It was observed that FeNPs presented high antibacterial potency against Gram-positive bacteria of Listeria monocytogenes and Staphylococcus aureus and also Gram-negative bacteria of Escherichia coli(O157: H7), E. coli(ATCC 25922), Salmonella enteritidis, and Salmonella typhimurium. Moreover, it was found that FeNPs exhibited superior peroxidase-like activity to catalyze the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) to produce a blue color product, oxidized TMB (oxTMB), in the presence of H2O2. The colorimetric AA detection could be carried out by making the solution color lighter owing to the antioxidant property of AA. The quantitative detection of AA could be performed simply, selectively, and sensitively with FeNPs with a detection limit (LOD) of 0.5462 µM in a linear range of 30-200 µM.

The parameters determining hyperaccumulator rhizobacteria diversity depend on the study scale.

Soils harbor some of the most diverse microbiomes on Earth and are essential for both nutrient cycling and carbon storage. Numerous parameters, intrinsic to plant physiology, life history and the soil itself, can influence the structure of rhizomicrobial communities. While our knowledge of rhizosphere microbial diversity is increasing, opinion is divided as to whether the factors that most impact this diversity are abiotic, climatic or plant selection. Here we focused on the rhizosphere bacterial diversity of nickel hyperaccumulator plants (28 species from Mediterranean or tropical climates). We showed, by leveraging 16S Illumina sequencing of 153 ultramafic rhizosphere soils, that bacterial genetic diversity was highest in Mediterranean habitats where plant diversity was the lowest. Concerning those parameters driving this diversity, we demonstrated that climate drives bacterial diversity, in particular with the annual temperature variation. Focusing on each region, we underlined the substantial role of soil physicochemical parameters. Our results highlight the importance of considering spatial scale when explaining bacterial community diversity.

Hybrid technologies for remediation of highly Pb contaminated soil: sewage sludge application and phytoremediation.

Phytoremediation techniques and stabilization of heavy metals with municipal sewage sludge (SW) in soils are usually studied separately. We aimed to verify the potential of the combined use of phytoextraction method and metal stabilization with SW in the recovery of soil with high Pb content (total = 28,650 mg kg-1 and exchangeable = 1,120 mg kg-1) and to verify the effect of the association of these two techniques on the Pb fractions in the soil (stabilization). We have tested five doses of SW (0; 13.4; 26.7; 53.4; 106.8 Mg ha-1) and three cultivation conditions (uncultivated, black oats and forage turnip). The SW application in soil with a high Pb content favored the nutrition and growth of the plants (shoots and roots) and promoted an increase in the Pb absorption, a desirable combination in phytoextraction. The SW application and the cultivation of plants had a positive effect on the stabilization of Pb in the soil. It was verified decrease of the exchangeable fraction and increase precipitated and adsorbed by inner-sphere at the edges of the kaolinite and gibbsite. The combined use of SW and phytoremediation is very promising and should be tested on soils with moderate levels of heavy metals. Novelty statement: We believe that the study presents a more comprehensive methodology to assess and to recover soils highly contaminated with heavy metals. Conditions of the high toxicity of heavy metals in the soil compromise the growth of plants and limit the effectiveness of phytoremediation. We aimed to verify the potential of the combined use of phytoextraction and stabilization with sewage sludge in the recovery of soil with a high Pb content and to verify the effect of the association of these two techniques on the Pb fractions in the soil (stabilization). Often, the simple evaluation of the reduction in total Pb contents with phytoremediation is not sufficient to describe the magnitude of soil decontamination. The ideal is also to determine the different forms of Pb (such as: soluble; exchangeable; precipitate; complexed in organic matter; inner-sphere adsorption in Fe and Mn oxides; inner-sphere adsorption in gibbsite and kaolinite; residue) in soil before and after the recovery techniques to access the possible migration to more stable environmental Pb fractions.

Effects of living hyperaccumulator plants and their straws on the growth and cadmium accumulation of Cyphomandra betacea seedlings.

To determine whether the living hyperaccumulator plants and their straws have the same effects on the growth and heavy metal accumulation of common plants, two pot experiments (intercropping experiment and straw mulch experiment) were conducted to study the effects of living hyperaccumulator plants (Solanum photeinocarpum, Tagetes erecta, Galinsoga parviflora and Bidens pilosa) and their straws on the growth and cadmium (Cd) accumulation of common plant Cyphomandra betacea seedlings. Intercropping with T. erecta or B. pilosa promoted the growth of C. betacea seedlings compared with the monoculture, while intercropping with S. photeinocarpum or G. parviflora inhibited that. Intercropping with S. photeinocarpum decreased the Cd contents in the roots and shoots of C. betacea seedlings compared with the monoculture, but intercropping with the other plants did not. In the straw mulch experiment, the straw of S. photeinocarpum or T. erecta promoted the growth of C. betacea seedlings compared with the control, while the straw of G. parviflora or B. pilosa did not. The straw of S. photeinocarpum or T. erecta decreased the Cd contents in the shoots of C. betacea seedlings, and the straw of G. parviflora or B. pilosa increased the shoot Cd contents. Thus, intercropping with S. photeinocarpum and applying S. photeinocarpum or T. erecta straw can reduce the Cd uptake of C. betacea.

Purified isolation of vacuoles from Sedum alfredii leaf-derived protoplasts.

This study aims to develop a method for isolating and purifying protoplasts/vacuoles from fresh leaves of the Cd hyperaccumulator plant species, Sedum alfredii. The results revealed that preheating cellulase and macerozyme at 50 °C for 5 min significantly accelerated the cell wall degradation. For the most optimal conditions for mesophyll protoplast isolation, the mixture of fresh leaves and cell lysates was followed by a 2-h-long vibration. The protoplast lysate for vacuole isolation was diluted, and 0.675 mmol/L was identified as the most appropriate 3-[(3-cholamidopropyl) dimethylammonio]-1-propanesulfonic acid (CHAPS) level, in which S. alfredii large vacuoles are characterized by a high metal and malic acid content. For the best vacuole purification results, we established that 0.8 mol/L was the most optimal mannitol level in the vacuole buffer in terms of vacuole protection during centrifugation, whereas a Ficoll concentration of 0.10 g/ml was adopted in the density-gradient centrifugation.