Anwei Chen

Treatment of landfill leachate using immobilized Phanerochaete chrysosporium loaded with nitrogen-doped TiO2 nanoparticles

This study investigated the performance of immobilized Phanerochaete chrysosporium loaded with nitrogen-doped TiO2 nanoparticles in the treatment of raw landfill leachate with a very low biodegradability ratio (BOD5/COD) of 0.09. The effects of various operating parameters, such as initial chemical oxygen demand (COD) concentration, pH, temperature, and biosorbent dosage, were evaluated with respect to the removal efficiency of total organic carbon (TOC) and ammonia nitrogen (NH3-N). For the immobilized biosorbents, an optimum pH of 6.0 for TOC and 7.0 for NH3-N were found suitable for TOC and NH3-N removal at temperature of 37°C, respectively. The most superior removal efficiencies of TOC and NH3-N of landfill leachate were over 75% and 74% in 72 h at an initial COD concentration of 200 mg L(-1), respectively. In addition, heavy metals were partly removed by the immobilized biosorbents during the process of landfill leachate treatment. The species and mass percentage of organic compounds in landfill leachate after the treatment were found to have considerably declined according to the gas chromatography coupled with mass spectrometry (GC-MS) system. These results indicate that the immobilized P. chrysosporium loaded with nitrogen-doped TiO2 nanoparticles could be a convenient and efficient method for the treatment of landfill leachate.

Comprehensive evaluation of the cytotoxicity of CdSe/ZnS quantum dots in Phanerochaete chrysosporium by cellular uptake and oxidative stress

The growing potential of quantum dots (QDs) in biological and biomedical applications has raised considerable concern due to their toxicological impact. Consequently, it is urgent to elucidate the underlying toxicity mechanism of QDs. In this work, we comprehensively investigated the cellular uptake of four CdSe/ZnS QDs (COOH CdSe/ZnS 525, COOH CdSe/ZnS 625, NH2 CdSe/ZnS 525, and NH2 CdSe/ZnS 625) and induced physiological responses in Phanerochaete chrysosporium (P. chrysosporium) through inductively coupled plasma optical emission spectroscopy, confocal laser scanning microscopy, and the determination of malondialdehyde content, superoxide level, superoxide dismutase activity, catalase activity and glutathione level. The results showed that the four CdSe/ZnS QDs accumulated largely in the hyphae and caused oxidative stress to P. chrysosporium in the tested concentration range (10–80 nM). Furthermore, the cellular uptake and cytotoxicity were related to the physicochemical properties of the QDs, such as particle size and surface charges. Negatively charged CdSe/ZnS QDs with small size could be more easily ingested by P. chrysosporium than large ones; thus small size CdSe/ZnS QDs were more cytotoxic to P. chrysosporium. On the other hand, small negatively charged CdSe/ZnS QDs resulted in greater cytotoxicity than large negatively charged CdSe/ZnS QDs. The obtained results offer valuable information for revealing the toxicity mechanism of QDs in living cells.

Carbon disulfide-modified magnetic ion-imprinted chitosan-Fe(III): A novel adsorbent for simultaneous removal of tetracycline and cadmium

A novel composite of carbon disulfide-modified magnetic ion-imprinted chitosan-Fe(III), i.e., MMIC-Fe(III) composite, was prepared as an efficient adsorbent for the simultaneous removal of tetracycline (TC) and Cd(II). This adsorbent showed excellent performance in removing TC and Cd(II) due to its rapid kinetics, high adsorption capacity, good reusability, and was well suited for use with real water samples. Kinetics studies demonstrated that the adsorption proceeded according to a pseudo-second order model. The adsorption isotherms were well described by the Langmuir model, with maximum adsorption capacity for TC and Cd(II) being 516.29 and 194.31mg/g, respectively. The synergistic effect of TC and Cd(II) adsorption might be due to the formation of TC-Cd(II) complex bridging the adsorbate and adsorbent. These properties demonstrate the potential application of MMIC-Fe(III) for the simultaneous removal of TC and Cd(II), and may provide some information for the synergistic removal of antibiotics and heavy metals from aquatic environments.

Silica fertilization and nano-MnO2 amendment on bacterial community composition in high arsenic paddy soils

Silica fertilization and nano-MnO2 amendment are reported as useful approaches in lowering the accumulation of arsenic in rice grains, but the effects of silica fertilization or nano-MnO2 amendment on microbial community in the paddy soils containing high concentration of arsenic are still unknown. In order to elucidate this question, the structures and composition of microbial community in the paddy soils, in response to silica fertilization and nano-MnO2 amendment, were investigated using pyrosequencing technique. The results indicated that Proteobacteria, Chloroflexi, and Acidobacteria were the main dominating phyla in these paddy soils. A decrease in the relative abundance of Chloroflexi and Cyanobacteria, but an increase in the relative abundance of Acidobacteria was observed after silica fertilization and nano-MnO2 amendment. The changes of Acidobacteria, Chloroflexi, and Cyanobacteria were strongly correlated with pH and the concentration of bioavailable arsenic in the paddy soils. The α-diversity of bacteria in the paddy soils increased in response to silica fertilization at low amendment level, but decreased under silica or nano-MnO2 amendment at high amendment level. Results of β-diversity analysis indicated that the microbial communities in the control treatment shared more similarity with that of those received low level of nano-MnO2 amendment, and the two silica fertilization treatments also shared more similarity with each other.

The application of iron-based technologies in uranium remediation: A review.

Remediating uranium contamination is of worldwide interest because of the increasing release of uranium from mining and processing, nuclear power leaks, depleted uranium components in weapons production and disposal, and phosphate fertilizer in agriculture activities. Iron-based technologies are attractive because they are highly efficient, inexpensive, and readily available. This paper provides an overview of the current literature that addresses the application of iron-based technologies in the remediation of sites with elevated uranium levels. The application of iron-based materials, the current remediation technologies and mechanisms, and the effectiveness and environmental safety considerations of these approaches were discussed. Because uranium can be reduced and reoxidized in the environment, the review also proposes strategies for long-term in situ remediation of uranium. Unfortunately, iron-based materials (nanoscale zerovalent iron and iron oxides) can be toxic to microorganisms. As such, further studies exploring the links among the fates, ecological impacts, and other environmentally relevant factors are needed to better understand the constraints on using iron-based technologies for remediation.

Ammonia-oxidizing bacterial communities and shaping factors with different Phanerochaete chrysosporium inoculation regimes during agricultural waste composting

This research was conducted to determine the effects of Phanerochaete chrysosporium inoculation on the ammonia-oxidizing bacterial (AOB) communities during agricultural waste composting. AOB communities with different inoculation regimes were investigated by quantitative PCR and denaturing gradient gel electrophoresis. Results showed that P. chrysosporium inoculation imposed certain stimulatory effects on the AOB amoA gene abundance. Samples with different inoculation regimes were dominated by different AOB species. Linear regression analysis indicated that the AOB community abundance had a significant positive correlation with pile pH (P < 0.05). The AOB amoA gene structure was best related to water soluble carbon (WSC) (P = 0.002, F = 14.17) and pile temperature (P = 0.04, F = 2.72). Variance partition analysis suggested that the sample property heterogeneity induced by inoculation imposed a greater impact (42.9%, P = 0.006) on the bacterial amoA gene structure than different inoculation regimes (23.6%, P = 0.022).

Bioaccumulation and toxicity of CdSe/ZnS quantum dots in Phanerochaete chrysosporium

The growing potential of quantum dots (QDs) in biomedical applications has raised considerable concerns regarding their toxicological impact. Consequently, there has been a need to understand the underlying toxicity mechanism of QDs. In this work, we comprehensively investigated the bioaccumulation and toxicity of three CdSe/ZnS QDs (COOH CdSe/ZnS 525, NH2 CdSe/ZnS 525, and NH2 CdSe/ZnS 625) in Phanerochaete chrysosporium (P. chrysosporium) using confocal laser scanning microscopy, reactive oxygen species (ROS) measurements, and cell viability assays. Confocal laser scanning microscopy analytical results indicated that all the CdSe/ZnS QDs, with the concentration ranging from 10 to 80nM, could accumulate largely in the hyphae and induce the generation of ROS, showing a direct toxicity to P. chrysosporium. And the bioaccumulation and toxicity of CdSe/ZnS QDs presented dose-dependent and time-dependent effects on P. chrysosporium. Furthermore, the CdSe/ZnS QDs-induced cytotoxicity was also related to their physicochemical properties, including particle size and surface charges: NH2 CdSe/ZnS 525 with small size was more cytotoxic as compared to NH2 CdSe/ZnS 625 with large size, and the smaller negative charged NH2 CdSe/ZnS 525 resulted in greater cytotoxicity than the larger negative charged COOH CdSe/ZnS 525. The obtained results provide valuable information for exploring and understanding of toxicity mechanism of QDs in living cells.

Effects of silver nanoparticles with different dosing regimens and exposure media on artificial ecosystem

Due to the wide use of silver nanoparticles (AgNPs) in various fields, it is crucial to explore the potential negative impacts on the aquatic environment of AgNPs entering into the environment in different ways. In this study, comparative experiments were conducted to investigate the toxicological impacts of polyvinylpyrrolidone-coated silver nanoparticles (PVP-AgNPs) with two kinds of dosing regimens, continuous and one-time pulsed dosing, in different exposure media (deionized water and XiangJiang River water). There were a number of quite different experimental results (including 100% mortality of zebrafish, decline in the activity of enzymes, and lowest number and length of adventitious roots) in the one-time pulsed dosing regimen at high PVP-AgNP concentration exposure (HOE) compared to the three other treatments. Meanwhile, we determined that the concentration of leached silver ions from PVP-AgNPs was too low to play a role in zebrafish death. Those results showed that HOE led to a range of dramatic ecosystem impacts which were more destructive than those of other treatments. Moreover, compared with the continuous dosing regimen, despite the fact that higher toxicity was observed for HOE, there was little difference in the removal of total silver from the aquatic environment for the different dosing regimens. No obvious differences in ecological impacts were observed between different water columns under low concentration exposure. Overall, this work highlighted the fact that the toxicity of AgNPs was impacted by different dosing regimens in different exposure media, which may be helpful for assessments of ecological impacts on aquatic environments.

The elucidation of surrounding alginate gels on the pollutants degradation by entrapped nanoscale zero-valent iron

The adsorption capacity of calcium alginate (Ca-alginate) beads was evaluated by measuring the removal of three organic compounds with different charges (malachite green, p-chlophenol and methyl orange). The diffusion was investigated in Ca-alginate hydrogel as a function of solute charge. It was found that an increased electrostatic attraction between the hydrogel and solute would improve the mobility of solute and hence enhance its adsorption efficiency. The degradation kinetics of charged pollutants by Ca-alginate with NZVI entrapped (NZVI-alginate) beads was compared to that of bare NZVI and the data followed a pseudo-first-order kinetic model. Negatively charged Ca-alginate hydrogel strongly adsorbed positively charged pollutant, which led to an enhancement in degradation rate. However, the degradation efficiency of neutral and negatively charged pollutants by NZVI-alginate was comparable with that by bare NZVI. Thus, the degradation ability of NZVI-alginate was related with the diffusion and adsorption behavior of solutes in Ca-alginate hydrogel. The experimental results showed that the free calcium ions containing in Ca-alginate had a significant impact on the adsorption and degradation behaviors of positively charged pollutant, but those of neutral and negatively charged pollutants were only moderately affected. With the dispersity of NZVI particles in beads (1:1-1:4, w/w) increasing, the degradation efficiency of malachite green was improved, whereas further increase of NZVI dispersity (1:6, w/w) brought about a depressed degradation.

Control of Microcystis (Cyanobacteria) using the fruit of Macleaya cordata: from laboratory experiment to in situ field test

Abstract: Biologically derived algicidal substances are regarded as environmentally friendly in the control of harmful cyanobacterial blooms. To evaluate the possible control of Microcystis-based water blooms using fruit from Macleaya cordata (MC-fruit), the effects of MC-fruit on the growth, polyphasic chlorophyll fluorescence transients, microcystin production and efficacy of in situ cyanobacterial bloom removal were investigated. The results showed that MC-fruit could effectively inhibit the growth of M. aeruginosa PCC7806 at a concentration of 1 mg l−1. MC-fruit stress caused severe damage to photosynthesis of M. aeruginosa and decreased the content of cellular microcystin-LR. The results of an in situ field test showed that MC-fruit effectively reduced the biomass of Microcystis and improved water quality. Accordingly, MC-fruit may be a useful biologically derived algicide for cyanobacterial bloom control.