Assessing the impacts of fine sediment removal on endogenous pollution release and microbial community structure in the shallow lakes.

Resuspension is a crucial process for releasing endogenous pollution from shallow lakes into the overlying water. Fine particle sediment, which has a higher contamination risk and longer residence time, is the primary target for controlling endogenous pollution. To this end, a study coupling aqueous biogeochemistry, electrochemistry, and DNA sequencing was conducted to investigate the remediation effect and microbial mechanism of sediment elution in shallow eutrophic water. The results indicated that sediment elution can effectively remove some fine particles in situ. Furthermore, sediment elution can inhibit the release of ammonium nitrogen and total dissolved phosphorous into the overlying water from sediment resuspension in the early stage, resulting in reductions of 41.44 %-50.45 % and 67.81 %-72.41 %, respectively. Additionally, sediment elution greatly decreased the concentration of nitrogen and phosphorus pollutants in pore water. The microbial community structure was also substantially altered, with an increase in the relative abundance of aerobic and facultative aerobic microorganisms. Redundancy analysis, PICRUSt function prediction, and the correlation analysis revealed that loss on ignition was the primary factor responsible for driving changes in microbial community structure and function in sediment. Overall, the findings provide novel insights into treating endogenous pollution in shallow eutrophication water.

Enhancement of nitrogen and phosphorus removal from eutrophic water by economic plant annual ryegrass (Lolium multiflorum) with ion implantation.

Severe eutrophication of surface water has been a major problem of increasing environmental concern worldwide. In the present study, economic plant annual ryegrass (Lolium multiflorum) was grown in floating mats as an economic plant-based treatment system to evaluate its potential after ion implantation for removing nutrients in simulated eutrophic water. The specific weight growth rate of L. multiflorum with ion implantation was significantly greater than that of the control, and the peroxidase, nitrate reductase, and acid phosphatase activities of the irradiated L. multiflorum were found to be greater than those plants without ion implantation. Higher total nitrogen (TN) and total phosphorus (TP) removal efficiencies were obtained for the L. multiflorum irradiated with 25 keV 5.2 × 10(16) N(+) ions/cm(2) and 30 keV 4.16 × 10(16) N(+) ions/cm(2), respectively (p < 0.05). Furthermore, the nitrogen and phosphorus contents in the plant biomass with ion implantation were also greater than those in the control and were positively correlated with TN and TP supplied. L. multiflorum itself was directly responsible for 39-49 and 47-58 % of the overall N and P removal in the experiment, respectively. The research results suggested that ion implantation could become a promising approach for increasing phytoremediation efficiency of nutrients from eutrophic water by L. multiflorum.

Inactivation of Microcystis aeruginosa by DC glow discharge plasma: Impacts on cell integrity, pigment contents and microcystins degradation.

We proposed a method to inactivate M. aeruginosa by using discharge plasma taking at the gas-solution interface supplied by DC power. Multiple analysis techniques including fluorescence excitation-emission matrix (EEM) and flow cytometry (FCM) were used to reveal the inactivation mechanism of M. aeruginosa. The photosynthetic pigment contents including phycocyanin, chlorophyll and metabolites were examined quantitatively. The DC glow discharge plasma caused an increased level of reactive oxygen species (ROS), and the damage of M. aeruginosa cells are mainly attributed to the oxidative stress including OH attack and H2O2 oxidation. Our findings demonstrate that plasma oxidation is a promising technology for inactivation of M. aeruginosa cells with simultaneous removal of microcystins and so it may lead us to a new route to efficient treatment of cyanobacterial blooms.

Controlling nitrogen migration through micro-nano networks.

Nitrogen fertilizer unabsorbed by crops eventually discharges into the environment through runoff, leaching and volatilization, resulting in three-dimensional (3D) pollution spanning from underground into space. Here we describe an approach for controlling nitrogen loss, developed using loss control fertilizer (LCF) prepared by adding modified natural nanoclay (attapulgite) to traditional fertilizer. In the aqueous phase, LCF self-assembles to form 3D micro/nano networks via hydrogen bonds and other weak interactions, obtaining a higher nitrogen spatial scale so that it is retained by a soil filtering layer. Thus nitrogen loss is reduced and sufficient nutrition for crops is supplied, while the pollution risk of the fertilizer is substantially lowered. As such, self-fabrication of nano-material was used to manipulate the nitrogen spatial scale, which provides a novel and promising approach for the research and control of the migration of other micro-scaled pollutants in environmental medium.

[Effect of ZnSO4 on L-lactic acid production by Rhizopus oryzae].

OBJECTIVE: To improve the yield and quality of L-lactic acid by Rhizopus oryzae, we aim to understand the relationship between inorganic salts utilization and the L-lactic acid metabolism of the strain RLC41-6, through systematic analysis of the effects of zinc ion concentration on the production of L-lactic acid and the Lactic Dehydrogenase (LDH) activity. METHODS: Rhizopus oryzae was cultured at 36 degrees C for 36h with different quantity of ZnSO4 in fermentation medium. The fermentation products were monitored by reversed-phase high performance liquid chromatography (RP-HPLC), LDH isoenzyme composition in the cell was analysed by non-denatured polyacrylamide gel electrophoresis (PAGE). RESULTS: Our results showed that the concentration of ZnSO4 in medium could modulate the expression of LDH isoenzyme except LDH1, especially stimulated the expression of LDH4 and LDH5. When initial concentration of ZnSO4 is above 0.02%, the LDH4 and LDH5 reached the highest level. However, the activity of LDH was inhibited by higher concentration zinc ion in extracellular environment. When ZnSO4 concentration is 0.02%, LDH activity reaches its maximum 200U/mL, the HPLC assay showed only L-lactic in the fermentation products (137 g/L), while the conversion rate of glucose to lactic acid is 91%. CONCLUSION: Zinc ion can regulate the metabolic processes of Rhizopus oryzae and modulate the types of the final fermentation products. An optimal concentration of ZnSO4 can not only facilitate the LDH expression but also prevent pyruvate from transformation into the malic acid and fumaric acid during the metabolism process, thereby enhance the metabolism of glucose to lactic acid of Rhizopus oryzae.

Degradation of microcystin-LR in water by glow discharge plasma oxidation at the gas-solution interface and its safety evaluation.

Microcystin-LR (MC-LR) is one of the most commonly found microcystins (MCs) in fresh water and it poses danger to human health due to its potential hepatotoxicity. In the present study, we employed a novel method by using discharge plasma taking place at the gas-solution interface in gas atmosphere to degrade MC-LR in aqueous solution. The initial degradation rate of MC-LR was fastest under acidic conditions (5.41 ± 0.17 × 10(-3) mM min(-1) at pH 3.04) and decreased to 2.22 ± 0.11 × 10(-3) mM min(-1) and 0.912 ± 0.02 × 10(-3) mM min(-1) at pH 4.99 and 7.02, respectively. The effects of total soluble nitrogen (TN), total soluble phosphorus (TP) and natural organic matter (NOM) on the degradation efficiency were studied. The degradation rate was remarkably affected by TP and TN. Mass spectrometry was applied to identify the products of the reactions. Major degradation pathways are proposed according to the results of liquid chromatography/mass spectrometry (LC/MS) results. It suggests that the degradation of MC-LR is initiated via the attack of hydroxyl radicals on the conjugated carbon double bonds of Adda and on the benzene ring of Adda. Finally, the toxicity of intermediates or end-products from MC-LR degraded by this method was assessed using Caenorhabditis elegans. Our findings demonstrates that discharge plasma oxidation is a promising technology for degradation and removal of MC-LR and it may lead us to a new route to efficient treatment of other cyanotoxins from aqueous solutions.

Reduction and removal of aqueous Cr(VI) by glow discharge plasma at the gas-solution interface.

Aqueous chromium(VI) reduction and removal induced by glow discharge taking place at the gas-solution interface in an argon atmosphere was studied. The effect of initial pH and hydroxyl radical scavenger (ethanol) on the reduction efficiency was examined. High reduction efficiency was obtained when initial pH ≤ 2.0 or ≥ 8.0. In particular, addition of ethanol into the solution substantially increased the reduction efficiency and facilitated chromium removal from the solution in the form of sediment after discharge. The optimum pH values for Cr(VI) removal were within 6.0-7.0. Fourier transform-infrared (FTIR) spectroscopy and X-ray diffraction (XRD) analysis confirmed that the main constituent of the sediment is chromium hydroxide.

Abscopal mutagenic effect of low-energy-ions in Arabidopsis thaliana seeds.

PURPOSE: To demonstrate the abscopal mutagenic effect of low-energy-ion irradiation in dormant plant seeds, and its dependence on the targeted portion of seeds. MATERIALS AND METHODS: Arabidopsis thaliana-lines transgenic for b-glucuronidase (GUS) recombination substrates and A. thaliana RADiation54 (AtRAD54) promoter::GUS were adopted. The seeds were irradiated from four specialised orientations with 30 KeV (40)Ar(+) ions. The homologous recombination frequency (HRF) and the expression levels of the AtRAD54 genein non-irradiated aerial plants were measured. Moreover, several post-embryonic developments, such as growth of primary roots, differentiation of root hairs, and germination of seeds and growth of true leaves, were also analysed. RESULTS: It was shown that low-energy-ion irradiation of seeds led to significant increases in HRF in the non-irradiated aerial parts of irradiated plants and the aerial parts of naïve plants from irradiated progenitors. The low-energy-ion irradiation was also shown to induce an elevated expression of AtRAD54 gene in aerial plants, and to inhibit the post-embryonic developments of seeds. Moreover, the changes in HRF, expression level of the AtRAD54 gene and post-embryonic developments depended largely on the orientation of seeds with regard to low-energy-ion irradiation; and the root apical meristem (RAM)-orientated irradiation exhibited the largest effects on all biological endpoints assayed here. CONCLUSIONS: Low-energy-ion irradiation can induce an abscopal mutagenic effect in dormant plant seeds, the extent of which depends greatly on the targeted portion of seeds.

The time course of long-distance signaling in radiation-induced bystander effect in vivo in Arabidopsis thaliana demonstrated using root micro-grafting.

The radiation-induced bystander effect has been demonstrated in whole organisms as well as in multicellular tissues in vitro and single-cell culture systems in vitro. However, the time course of bystander signaling, especially in whole organisms, is not clear. Long-distance bystander/abscopal effects in vivo in plants have been demonstrated by our group. Plant grafting is a useful experimental tool for studying the root-shoot signaling of plants. In the present study, we developed a root micro-grafting technique with young seedlings of Arabidopsis thaliana in which the bystander signaling communication of root-to-shoot could easily be stopped or started at specific times after root irradiation. Using this methodology, we demonstrated the time course of long-distance signaling in radiation-induced bystander effects at the level of the organism using the expression level of the AtRAD54 gene as a biological end point. Briefly, an 8-h accumulation of damage signals in bystander parts after irradiation was essential for eliciting a bystander response. The protraction of signal accumulation was not related to the transmission speed of signaling molecules in plants and did not result from the delayed initiation of bystander signals in targeted root cells. It was suggested that the bystander effect might be induced jointly by multiple bystander signals initiated at different stages after irradiation. Moreover, reactive oxygen species (ROS) were shown to be implicated in the response process of bystander cells to radiation damage signals rather than in the generation of bystander signals in targeted cells.

Flocculation of harmful algal blooms by modified attapulgite and its safety evaluation.

Natural attapulgite (N-AT) and modified attapulgite (M-AT) were used in this study to evaluate their flocculation efficiencies and mechanisms in freshwater containing harmful algal blooms through conventional jar test procedure. The experimental results showed that the efficiency of flocculation can be significantly improved by M-AT under appropriate conditions. It was found that the attapulgite modified by hydrochloric acid was similar to polyaluminum ferric silicate chloride (PAFSiC). The high efficiency for M-AT to flocculate Microcystis aeruginosa in freshwater was due to the mechanism of bridging and netting effect. Caenorhabditis elegans was used to detect the toxicity of N-AT and M-AT. The results showed that there was no significant toxicity on this organism. Attapulgite is a natural material, which can be readily available, abundant, and relatively inexpensive. Using modified attapulgite to remove the harmful algal blooms could have the advantages of high effectiveness, low cost, and low impact on the environment.

Toxicity of carbon nanotubes to p21 and hus1 gene deficient mammalian cells.

Carbon nanotubes including single wall and multi wall carbon nanotubes (SWNT and MWNT) are attractive nanomaterials with great promise in industrial and medical applications. However, little is known about the role of p21 and hus1 gene in the toxic response of SWNT and MWNT to mammalian cells. The aim of this study is to investigate the role of the p21 and hus1 genes in the toxicity of carbon nanotubes. Comparison of micronucleus fraction between the wild type and p21 -/- , hus1 +/+ mouse embryo fibroblast (MEF) cells was performed experimentally. Our results show that the yield of the micronucleus ratio in p21 gene knock-out MEF cells is lower than that in the wild type counterpart, indicating that p21 may play as anti-apoptosis factor during the signal transduction of DNA damage caused by carbon nanotubes in mammalian cells.

The induction of bystander mutagenic effects in vivo by alpha-particle irradiation in whole Arabidopsis thaliana plants.

Our previous studies demonstrated distant/abscopal bystander effects in A. thaliana seeds and embryos; the postembryonic development of bystander tissues, such as root hair differentiation, primary root elongation, lateral root initiation and survival, were inhibited significantly by localized irradiation with microbeam protons and low-energy ions. In the present study, we further investigated radiation-induced bystander mutagenic effects in vivo in A. thaliana plants using homologous recombination (HR) and the expression level of the HR-related AtRAD54 gene as mutagenic end points. We found that alpha-particle irradiation of distal primary roots of young seedlings resulted in a significant increase in the frequency of HR in the aerial plants; the increased induction of HR occurred in every true leaf over the course of rosette development. Moreover, we also found that localized alpha-particle irradiation of roots induced a short-term up-regulated expression of the HR-related AtRAD54 gene in the nonirradiated aerial plants. These results suggested the existence of bystander mutagenic effects in vivo in plants. Treatment with the ROS scavenger DMSO dramatically reduced the effects of localized root irradiation on the induction of HR and expression of the AtRAD54 gene in bystander tissues, suggesting that ROS play a critical role in mediating the bystander mutagenic effects in plants.

Hexavalent chromium removal from aqueous solution by algal bloom residue derived activated carbon: equilibrium and kinetic studies.

A novel approach to prepare activated carbon from blue-green algal bloom residue has been tried for first time and its adsorption capability to remove hexavalent chromium Cr(VI) from aqueous solution has been examined. For this algal bloom residue derived activated carbon, the physical characters regarding adsorption capability were analyzed by scanning electron microscope (SEM), energy dispersive X-ray spectroscope (EDS) and Fourier transform infrared (FTIR) spectroscopy. Batch studies showed that initial pH, absorbent dosage, and initial concentration of Cr(VI) were important parameters for Cr(VI) absorption. It was found that initial pH of 1.0 was most favorable for Cr(VI) removal. The adsorption process followed the pseudo-second-order equation and Freundlich isotherm. The maximum adsorption capacity for Cr(VI) was 155.52 mg g(-1) in an acidic medium, which is comparable to best result from activated carbons derived from biomass. Therefore, this work put forward a nearly perfect solution which on one hand gets rid of environment-unfriendly algae residue while on the other hand produces high-quality activated carbon that is in return advantageous to environment protection.

Genotoxicity/mutagenicity of formaldehyde revealed by the Arabidopsis thaliana plants transgenic for homologous recombination substrates.

Formaldehyde (FA) is a major industrial chemical and has been extensively used in the manufacture of synthetic resins and chemicals. The use of FA-containing industrial materials in daily life exposes human to FA extensively. Numerous studies indicate that FA is genotoxic, and can induce various genotoxic effects in vitro and in vivo. The primary DNA lesions induced by FA are DNA-protein crosslinks (DPCs). Recently, it has been reported that the homologous recombination (HR) mechanism is involved in the repair of DPCs, suggesting the homologous recombination could be a potential indicator for the genotoxicity/mutagenicity of FA. However, it has not yet been reported that organisms harboring recombination substrates are used for the detection of genotoxic/mutagenic effects of FA. In this present study, an Arabidopsis thaliana-line transgenic for GUS recombination substrates was used to study the genotoxicity/mutagenicity of FA, and the results showed that FA-exposure significantly increased the induction of HR in growing plants, but not in dormant seeds. We also observed an early up-regulation of expression of HR-related gene, AtRAD54, after FA-exposure. Moreover, the pretreatment with glutathione (GSH) suppressed drastically the induction of HR by FA-exposure.

Nickel-induced apoptosis and relevant signal transduction pathways in Caenorhabditis elegans.

Many investigations have shown that nickel exposure can induce micronuclei generation, inhibit DNA repair and induce cell apoptosis, both in cells and tissues. However, there is a lack of appropriate in vivo animal models to study the underlying mechanisms of nickel-induced apoptosis. The model organism, Caenorhabditis elegans, has been shown to be a good model for investigating many biological processes. In the present study, we detected 0.01 mM nickel induced significantly germline cell apoptosis after treatment for 12 hours, which demonstrated that C. elegans could be a mammalian in vivo substitute model to study the mechanisms of apoptosis. Then gene knockout C. elegans strains were utilized to investigate the relationship between nickel-induced apoptosis and relevant signal pathways, which were involved in DNA damage and repair, apoptosis regulation and damage signal transduction. The results presented here demonstrated that nickel-induced apoptosis was independent of the DNA damage response gene, such as hus-1, p53/cep-1 and egl-1. The loss-of-function of the genes that related to Jun N-terminal kinase (JNK) and p38 mitogen-activated protein kinases (MAPK) signaling cascades suppressed nickel-induced germline apoptosis, while ERK signaling cascades have no effects on the nickel-induced germline apoptosis.

L(+)-lactic acid production by co-fermentation of glucose and xylose with Rhizopus oryzae obtained by low-energy ion beam irradiation.

Low-energy ion beam irradiation (10-200 keV) has been proved to have a wide range of biological effects in recent years. When Rhizopus oryzae PW352 was irradiated with a 15-keV low-energy ion beam an L(+)-lactic acid high-yield mutant, RQ4015, was obtained. When 150 g/l glucose was used as the sole carbon source, L(+)-lactic acid of RQ4015 reached 121 g/l after 36 h shake-flask cultivation. However, the highest lactic acid concentration 74 g/l was obtained when 100 g/l xylose was present in the medium as the sole carbon source. When mixed xylose (25 g/l) and glucose (75 g/l) were present in a bubble column, L(+)-lactic acid production of RQ4015 reached 83 g. A high mutation rate and a wide mutation spectrum of low-energy ion implantation were observed in the experiment, suggesting that ion implantation can be a highly efficient mutagenic means for microorganism breeding in many commercial applications.

A unique technology to transform inorganic nanorods into nano-networks.

An inorganic nano-network of attapulgite is formed from rigid nanorods using ion beam bombardment. The structure of the nano-networks depends on the ion beam fluence for the same ion energy. Scanning electron microscopy reveals that ion beam bombardment improves the dispersion of the attapulgite particles and the change in the shape of the rod-shaped attapulgite particles stems from the thermal stress induced by ion beam bombardment. This phenomenon is more obvious for higher ion fluences. The bent or twisted rod-shaped attapulgite particles cross-link to form a network structure, which is stable in water, and when the ion fluence is increased further, the cross-linked points are permanently sealed. The improved materials are more useful than clava attapulgite particles.

Intracellular chromosome breaks on silicon surface.

The genotoxicity of silicon (Si) is investigated by soaking crystalline Si in a complete culture medium for 60 days and conducting micronuclei tests (MNTs) utilizing hamster ovary (CHO) cells and its Ku80 deficient CHO mutant (xrs5) cells (DNA double-strand breaks repair deficiency). The intracellular concentrations of reactive oxygen/nitrogen species (ROS/RNS) on Si are determined to elucidate the relationship between ROS/RNS and Si-induced genotoxicity by using CHO cells. The cells are treated with ROS scavenger (dimethyl sulfoxide) and MNT are performed. The results indicate that the intracellular concentration of ROS and nitrogen oxide (NO) on Si is higher than those on the control group by about 38% and 12%. ROS/RNS include superoxide (O(2)*(-)) anion, NO, and peroxynitrite (ONOO(-)) which can injure chromosomes and induce high cellular DNA double-strand breaks (DSBs).

Enhanced nitrogen and phosphorus removal from eutrophic lake water by Ipomoea aquatica with low-energy ion implantation.

Ipomoea aquatica with low-energy N+ ion implantation was used for the removal of both nitrogen and phosphorus from the eutrophic Chaohu Lake, China. The biomass growth, nitrate reductase and peroxidase activities of the implanted I. aquatica were found to be higher than those of I. aquatica without ion implantation. Higher NO3-N and PO4-P removal efficiencies were obtained for the I. aquatica irradiation at 25 keV, 3.9 x 10(16) N+ ions/cm(2) and 20 keV 5.2 x 10(16) N+ ions/cm(2), respectively (p < 0.05). Moreover, the nitrogen and phosphorus contents in the plant biomass with ion implantation were also greater than those of the controls. I. aquatica with ion implantation was directly responsible for 51-68% N removal and 54-71% P removal in the three experiments. The results further confirm that the ion implantation could enhance the growth potential of I. aquatica in real eutrophic water and increase its nutrient removal efficiency. Thus, the low-energy ion implantation for aquatic plants could be considered as an approach for in situ phytoremediation and bioremediation of eutrophic waters.