Qingwei Guo

Simazine degradation in bioaugmented soil: urea impact and response of ammonia-oxidizing bacteria and other soil bacterial communities

The objective of this study was to investigate the impact of exogenous urea nitrogen on ammonia-oxidizing bacteria (AOB) and other soil bacterial communities in soil bioaugmented for simazine remediation. The previously isolated simazine-degrading Arthrobacter sp. strain SD1 was used to degrade the herbicide. The effect of urea on the simazine degradation capacity of the soil bioaugmented with Arthrobacter strain SD1 was assessed using quantitative PCR targeting the s-triazine-degrading trzN and atzC genes. Structures of bacterial and AOB communities were characterized using terminal restriction fragment length polymorphism. Urea fertilizer could affect simazine biodegradation and decreased the proportion of its trzN and atzC genes in soil augmented with Arthrobacter strain SD1. Bioaugmentation process could significantly alter the structures of both bacterial and AOB communities, which were strongly affected by urea amendment, depending on the dosage. This study could provide some new insights towards s-triazine bioremediation and microbial ecology in a bioaugmented system. However, further studies are necessary in order to elucidate the impact of different types and levels of nitrogen sources on s-triazine-degraders and bacterial and AOB communities in bioaugmented soil.

Degradation of bisphenol A in water by the heterogeneous photo-Fenton

Bisphenol A (BPA) is a kind of a controversial endocrine disruptor, and is ubiquitous in environment. The degradation of BPA with the heterogeneous photo-Fenton system was demonstrated in this study. The Fe-Y molecular sieve catalyst was prepared with the ion exchange method, and it was characterized by X-ray radiation diffraction (XRD). The effects of pH, initial concentration of H2O2, initial BPA concentration, and irradiation intensity on the degradation of BPA were investigated. The service life and iron solubility of catalyst were also tested. XRD test shows that the major phase of the Fe-Y catalyst was Fe2O3. The method of heterogeneous photo-Fenton with Fe-Y catalyst was superior to photolysis, photo-oxidation with only hydrogen, heterogeneous Fenton, and homogeneous photo-Fenton approaches. pH value had no obvious effects on BPA degradation over the range of 2.2–7.2. The initial concentration of H2O2 had an optimal value of 20×10−4 mol/L. The decrease in initial concentration of BPA was favourable for degradation. The intensity of ultraviolet irradiation has no obvious effect on the BPA removal. The stability tests indicated that the Fe-Y catalyst can be reused and iron solubility concentration ranged from NA to 0.0062 mg/L. Based on the results, the heterogeneous photo-Fenton treatment is the available method for the degradation of BPA.

An optical-fiber sensor based on time-gated fluorescence for detecting water content in organic solvents

In this paper, the authors proposed an optical-fiber sensor based on time-gated fluorescence with high sensitivity for water content determination in organic solvents, and a type of europium ion fluorescent chelate (EIFC) with a long fluorescence lifetime was synthesized and used as the fluorescent indicator. Covalent immobilization was used to solve the problem caused by the leakage of fluorescent dye during the fabrication process of the proposed sensor. The EIFC was photo-copolymerized with 2-hydroxy-2-methyl-1-phenyl-1-propanone, triethylene glycol dimethacrylate, acrylamide, and (2-hydroxyethyl)methacrylate on a silanized glass slide, yielding the optode membrane. With increasing water content in the organic solvents, the time-gated fluorescence intensity of the optode membrane decreased obviously. The time-gated fluorescence intensity of the optode membrane changed as a linear function of the water content. For ethanol and acetonitrile this change was in the range of 0.20–10.0% (v/v), and for 1,4-dioxane it was in the range of 0.20–4.0% (v/v). The limits of detection were 0.031%, 0.016%, and 0.012% for ethanol, acetonitrile, and 1,4-dioxane, respectively. The optical-fiber sensor exhibited satisfactory reproducibility, reversibility, response times, and practicability. The lifetime of the prepared optode membrane was at least one month.

A facile fluorescent probe based on anthraldehyde for trace Fe(III) ion determination in neutral aqueous solution

A flexible fluorescent probe for the determination of Fe(III) in aqueous solution was designed and synthesized by conjugating 4-aminoacetophenone into 9-anthraldehyde as a fluorophore. Its sensing behavior toward metal ions was investigated by fluorescence spectroscopy. The fluorescence intensity of the fluorescent probe decreased with the increasing concentration of Fe(III) when it was excited at λex/λem = 402/560 nm in water–ethanol (21.5/3.5, v/v) solutions at pH = 7.20. In addition, the calibration curve was linear in the concentration range of ca. 5 × 10−9 to 1 × 10−7 mol L−1. The prepared dye presented satisfactory sensitivity, and the detection limit could be as low as 3.04 × 10−10 mol L−1. The Fe(III)-selective quenching was insensitive to the presence of Cr(III), Cd(II), Cu(II), Co(II), Ni(II), Mn(II), Ba(II), Pb(II), Ca(II), Fe(II), Zn(II), Mg(II), and Al(III). The proposed method was successfully employed for preliminary application in natural water, domestic sewage, and human serum samples.

Vegetation type and layer depth influence nitrite-dependent methane-oxidizing bacteria in constructed wetland

Nitrite-dependent anaerobic methane oxidation (n-damo) process might be an important methane sink in wetland system. However, information on n-damo microorganisms in constructed wetland (CW) system for water treatment is still lacking. The present study investigated the n-damo communities in five full-scale vertical-flow CW systems with different plants. N-damo bacterial abundance did not show a considerable shift in CW planted with Cyperus papyrus, but varied greatly in other CW systems. However, the evident vertical change of n-damo community diversity occurred in each CW system. These CW systems displayed the different vertical change trends for either n-damo community abundance or diversity. In addition, CW n-damo community structure could change with wetland layer depth. At a given wetland layer depth, the evident difference of n-damo community abundance, diversity and structure could be observed in the five different CW systems. Both wetland layer depth and vegetation type could contribute to the shift of n-damo bacterial abundance and community structure in CWs.

Response of ammonia-oxidizing archaea to heavy metal contamination in freshwater sediment

It has been well-documented that the distribution of ammonia-oxidizing bacteria (AOB) and archaea (AOA) in soils can be affected by heavy metal contamination, whereas information about the impact of heavy metal on these ammonia-oxidizing microorganisms in freshwater sediment is still lacking. The present study explored the change of sediment ammonia-oxidizing microorganisms in a freshwater reservoir after being accidentally contaminated by industrial discharge containing high levels of metals. Bacterial amoA gene was found to be below the quantitative PCR detection and was not successfully amplified by conventional PCR. The number of archaeal amoA gene in reservoir sediments were 9.62 × 102-1.35 × 107 copies per gram dry sediment. AOA abundance continuously decreased, and AOA richness, diversity and community structure also considerably varied with time. Therefore, heavy metal pollution could have a profound impact on freshwater sediment AOA community. This work could expand our knowledge of the effect of heavy metal contamination on nitrification in natural ecosystems.

Denitrifier communities impacted by heavy metal contamination in freshwater sediment

Heavy metals are widely detected in natural environments, however their impacts on denitrifier community in freshwater ecosystem remain unclear. The present study investigated the changes of denitrifier communities (based on nosZ (nitrous oxide reductase) gene) in a freshwater reservoir contaminated by a severe accidental spill of heavy metals. The abundance of nosZ-denitrifiers drastically decreased, and their community richness, diversity and structure also showed considerable variations. The mainly detected denitrifying bacteria included Pseudogulbenkiania, Pseudomonas and two unknown groups. These major nosZ-denitrifier groups responded in different ways to heavy metal pollution. Metal contamination could exert a profound influence on denitrifier community in freshwater sediment. This work could provide some new insights to the impact of metal pollution on nitrogen cycling.

Influences of Different Conditioners on Dehydration Ratio of Activated Sludge

Excess sludge contains a large quantity of water with water content reaching about 97%-99%. Besides microorganisms and germs, the sludge is of complicated composition, including heavy metals, persistent organic pollutants, PPCPs, endocrine disrupters, etc. It covers a large area with harmfulness, so it needs further treatment. However, due to existence of extracellular polymeric substances in the sludge, the sludge has poor dehydration property, so how to improve dehydration of sludge is a difficult point in water treatment industry. Chemical conditioning—mechanical dehydration method is sludge dehydration technology which has been widely applied in China. Most sludge treatment plants use organic and inorganic conditioners like polyacrylamide (PAM), polyaluminum chloride (PAC) and polymerized ferrous sulfate (PFS), etc. With characteristics of low toxicity and degradation resistance, these conditioners pose potential risks to the environment and they are adverse to follow-up resource utilization. Therefore, influences of 17 conditioners on sludge dehydration ratio were discussed in this paper, expecting to seek for green, environmentally friendly and highly efficient conditioner so as to improve resource utilization ratio of sludge.