This paper presents the effect of NaCl on aerobic denitrification by a novel aerobic denitrifier strain Achromobacter sp. GAD-3. Results indicated that the aerobic denitrification process was inhibited by NaCl concentrations ae<yen>20 g L-1, leading to lower nitrate removal rates (1.67 +/- 4.0 mg L-1 h(-1)), higher nitrite accumulation (50.2 +/- 87.4 mg L-1), and increasing N2O emission ratios (13 +/- 72 mg L-1/mg L-1). Poor performance of aerobic denitrification at high salinity was attributed to the suppression of active microbial biomass and electron donating capacity of strain GAD-3. Further studies on the corresponding inhibition of the denitrifying gene expression by higher salinities revealed the significant sensitivity order of nosZ (for N2O reductase) > cnorB (for NO reductase) ae nirS (for cytochrome cd(1) nitrite reductase) > napA (for periplasmic nitrate reductase), accompanied with a time-lapse expression between nosZ and cnorB based on reverse transcription and real-time quantitative polymerase chain reaction (RT-qPCR) analysis. The insights into the effect of NaCl on aerobic denitrification are of great significance to upgrade wastewater treatment plants (WWTPs) containing varying levels of salinity.
Sulfamethoxazole (SMX), as a common sulfonamide antibiotic, was reported to affect conventional anaerobic denitrification. This study presented effects of SMX on aerobic denitrification by an aerobic denitrifier strain Pseudomonas stutzeri PCN-1. Results demonstrated serious inhibition of N2O reduction as SMX reached 4 mu g/L, leading to higher N2O emission ratio (251-fold). Increase of SMX (similar to 8 mu g/L) would induce highest nitrite accumulation (95.3 mg/L) without reduction, and severe inhibition of nitrate reduction resulted in lower nitrate removal rate (0.15 mg/L/h) as SMX reached 20 mu g/L. Furthermore, corresponding inhibition of SMX on denitrifying genes expression (nosZ > nirS > cnorB > napA) was found with a time-lapse expression between nosZ and cnorB. Meanwhile, the decline in electron transport activity and active microbial biomass of strain PCN-1 was revealed. The insight into mechanism of SMX influence on aerobic denitrifier is of particular significance to upgrade nitrogen removal process in antibiotics-containing wastewater treatment plant. (C) 2017 Elsevier Ltd. All rights reserved.
Background & aims: As important virological markers, serum hepatitis B surface antigen (HBsAg) and hepatitis B virus (HBV) DNA levels show large fluctuations among chronic hepatitis B patients. The aim of this study was to reveal the potential impact and mechanisms of amino acid substitutions in small hepatitis B surface proteins (SHBs) on serum HBsAg and HBV DNA levels.
Methods: Serum samples from 230 untreated chronic hepatitis B patients with genotype C HBV were analyzed in terms of HBV DNA levels, serological markers of HBV infection and SHBs sequences. In vitro functional analysis of the identified SHBs mutants was performed.
Results: Among 230 SHBs sequences, there were 39 (16.96%) sequences with no mutation detected (wild-type) and 191 (83.04%) with single or multiple mutations. SHBs consist of 226 amino acids, of which 104 (46.02%) had mutations in our study. Some mutations (e.g., sE2G, sL21S, sR24K, sT47A/K, sC69stop (sC69∗), sL95W, sL98V, and sG145R) negatively correlated with serum HBsAg levels. HBsAg and HBV DNA levels from this group of patients had a positive correlation (r=0.61, p<0.001). In vitro analysis showed that these mutations reduced extracellular HBsAg and HBV DNA levels by restricting virion secretion and antibody binding capacity. Virion secretion could be rescued for sE2G, sC69∗, and sG145R by co-expression of wild-type HBsAg.
Conclusion: The serum HBsAg levels were lower in untreated CHB patients with novel SHBs mutations outside the major antigenic region than those without mutations. Underlying mechanisms include impairment of virion secretion and lower binding affinity to antibodies used for HBsAg measurements.
Semivolatile organic compounds (SVOCs) represent a dominant category of secondary organic aerosol precursors that are increasingly included in air quality models. In the present study, an experimental system was developed and applied to a light-duty diesel engine to determine the emission factors of particulate SVOCs (pSVOCs) and nonvolatile particulate matter (PM) components at dilution ratios representative of ambient conditions. The engine was tested under three steady-state operation modes, using ultra-low-sulfur diesel (ULSD), three types of pure biodiesels and their blends with ULSD. For ULSD, the contribution of pSVOCs to total particulate organic matter (POM) mass in the engine exhaust ranged between 21 and 85%. Evaporation of pSVOCs from the diesel particles during dilution led to decreases in the hydrogen to carbon ratio of POM and the PM number emission factor of the particles. Substituting biodiesels for ULSD could increase pSVOCs emissions but brought on large reductions in black carbon (BC) emissions. Among the biodiesels tested, tallow/used cooking oil (UCO) biodiesel showed advantages over soybean and canola biodiesels in terms of both pSVOCs and nonvolatile PM emissions. It is noteworthy that PM properties, such as particle size and BC mass fraction, differed substantially between emissions from conventional diesel and biodiesels. (C) 2017 Elsevier Ltd. All rights reserved.
Although organic compounds in marine atmospheric aerosols have significant effects on climate and marine ecosystems, they have rarely been studied, especially in the coastal regions of East China. To assess the origins of the organic aerosols in the East China coastal atmosphere, PM2.5 samples were collected from the atmospheres of the Yellow Sea, the East China Sea, and Changdao Island during the CAPTAIN (Campaign of Air PolluTion At INshore Areas of Eastern China) field campaign in the spring of 2011. The marine atmospheric aerosol samples that were collected were grouped based on the backward trajectories of their air masses. The organic carbon concentrations in the PM2,5 samples from the marine and Changdao Island atmospheres were 5.5 +/- 3.1 mu gC/m(3) and 6.9 +/- 2.4 mu gC/m(3), respectively, which is higher than in other coastal water atmospheres. The concentration of polycyclic aromatic hydrocarbons (PAHs) in the marine atmospheric PM2.5 samples was 17.0 +/- 20.2 ng/m(3), indicating significant continental anthropogenic influences. The influences of fossil fuels and biomass burning on the composition of organic aerosols in the coastal atmosphere of East China were found to be highly dependent on the origins of the air masses. Diesel combustion had a strong impact on air masses from the Yangtze River Delta (YRD), and gasoline emissions had a more significant impact on the "North China" marine atmospheric samples. The "Northeast China" marine atmospheric samples were most impacted by biomass burning. Coal combustion contributed significantly to the compositions of all of the atmospheric samples. The proportions of secondary compounds increased as samples aged in the marine atmosphere indicating that photochemical oxidation occured during transport. Our results quantified ecosystem effects on marine atmospheric aerosols and highlighted the uncertainties that arise when modeling marine atmospheric PM2.5 without considering high spatial resolution source data and meteorological parameters. (C) 2017 Published by Elsevier Ltd.
Although organic compounds in marine atmospheric aerosols have significant effects on climate and marine ecosystems, they have rarely been studied, especially in the coastal regions of East China. To assess the origins of the organic aerosols in the East China coastal atmosphere, PM2.5 samples were collected from the atmospheres of the Yellow Sea, the East China Sea, and Changdao Island during the CAPTAIN (Campaign of Air PolluTion At INshore Areas of Eastern China) field campaign in the spring of 2011. The marine atmospheric aerosol samples that were collected were grouped based on the backward trajectories of their air masses. The organic carbon concentrations in the PM2,5 samples from the marine and Changdao Island atmospheres were 5.5 +/- 3.1 mu gC/m(3) and 6.9 +/- 2.4 mu gC/m(3), respectively, which is higher than in other coastal water atmospheres. The concentration of polycyclic aromatic hydrocarbons (PAHs) in the marine atmospheric PM2.5 samples was 17.0 +/- 20.2 ng/m(3), indicating significant continental anthropogenic influences. The influences of fossil fuels and biomass burning on the composition of organic aerosols in the coastal atmosphere of East China were found to be highly dependent on the origins of the air masses. Diesel combustion had a strong impact on air masses from the Yangtze River Delta (YRD), and gasoline emissions had a more significant impact on the "North China" marine atmospheric samples. The "Northeast China" marine atmospheric samples were most impacted by biomass burning. Coal combustion contributed significantly to the compositions of all of the atmospheric samples. The proportions of secondary compounds increased as samples aged in the marine atmosphere indicating that photochemical oxidation occured during transport. Our results quantified ecosystem effects on marine atmospheric aerosols and highlighted the uncertainties that arise when modeling marine atmospheric PM2.5 without considering high spatial resolution source data and meteorological parameters. (C) 2017 Published by Elsevier Ltd.
Effects of heavy metals on aerobic denitrification have been poorly understood compared with their impacts on anaerobic denitrification. This paper presented effects of four heavy metals (Cd(II), Cu(II), Ni(II), and Zn(II)) on aerobic denitrification by a novel aerobic denitrifying strain Pseudomonas stutzeri PCN-1. Results indicated that aerobic denitrifying activity decreased with increasing heavy metal concentrations due to their corresponding inhibition on the denitrifying gene expression characterized by a time lapse between the expression of the nosZ gene and that of the cnorB gene by PCN-1, which led to lower nitrate removal rate (1.67 similar to 6.67 mg L-1 h(-1)), higher nitrite accumulation (47.3 similar to 99.8 mg L-1), and higher N2O emission ratios (5 similar to 283 mg L-1/mg L-1). Specially, promotion of the nosZ gene expression by increasing Cu(II) concentrations (0 similar to 0.05 mg L-1) was found, and the absence of Cu resulted in massive N2O emission due to poor synthesis of N2O reductase. The inhibition effect for both aerobic denitrifying activity and denitrifying gene expression was as follows from strongest to least: Cd(II) (0.5 similar to 2.5 mg L-1) > Cu(II) (0.5 similar to 5 mg L-1) > Ni(II) (2 similar to 10 mg L-1) > Zn(II) (25 similar to 50 mg L-1). Furthermore, sensitivity of denitrifying gene to heavy metals was similar in order of nosZ > nirS ae cnorB > napA. This study is of significance in understanding the potential application of aerobic denitrifying bacteria in practical wastewater treatment.
For safer geologic CO2 sequestration (GCS), it is important to understand CO2-brine-cement interactions, which affect wellbore integrity. However, potential effects of sulfate and magnesium ions on cement degradation under GCS conditions are not well understood. Here Class H Portland cement were reacted in brines containing 0.05M sulfate and/or magnesium ions under both GCS (50°C and 100atm CO2) and control (50°C and atmospheric pressure) conditions. Using optical microscopy and scanning electron microscope coupled with energy dispersive spectrometry and electron back scattered electron (SEM-EDS/BSE), slower cement carbonation rates were observed in the presence of sulfate under GCS conditions, because of gypsum precipitation on cement surfaces. Calcite rather than gypsum formed in both the inner layers of cement samples reacted under GCS conditions, and on cement surfaces reacted under atmospheric pressure conditions. Under GCS conditions, the dissolved CO2 lowered the pH of the solution surrounding cement surfaces, thus favoring the formation of gypsum over calcite on cement surfaces; while the high pH condition in pore solution inside cement favors the formation of calcite over gypsum. The presence of magnesium had no significant effect on cement degradation under GCS conditions, as brucite, magnesium carbonates and magnesium calcite did not form, due to the low pH at cement surface and the limited diffusion of Mg into cement inner layers.
AimsTopography has long been recognized as an important factor in shaping species distributions. Many studies revealed that species may show species–habitat associations. However, few studies investigate how species assemblages are associated with local habitats, and it still remains unclear how the community–habitat associations vary with species abundance class and life stage. In this study, we analyzed the community–habitat associations in a subtropical montane forest.MethodsThe fully mapped 25-ha (500×500 m) forest plot is located in Badagongshan Nature Reserve in Hunan Province, Central China. It was divided into 625 (20×20 m) quadrats. Habitat types were classified by multivariate regression tree analyses that cluster areas with similar species composition according to the topographic characteristics. Indicator species analysis was used to identify the most important species for structuring species assemblages. We also compared the community–habitat associations for two levels of species abundances (i.e. abundant and rare) and three different life stages (i.e. saplings, juveniles and adults), while accounting for sample size effects.Important FindingsThe Badagongshan plot was divided into five distinct habitat types, which explained 34.7% of the variance in tree species composition. Even with sample size taken into account, community–habitat associations for rare species were much weaker than those for abundant species. Also when accounting for sample size, very small differences were found in the variance explained by topography for the three life stages. Indicator species of habitat types were mainly abundant species, and nearly all adult stage indicator species were also indicators in juvenile and sapling stages. Our study manifested that topographical habitat filtering was important in shaping overall local species compositions. However, habitat filtering was not important in shaping rare species’ distributions in this forest. The community–habitat association patterns in this forest were mainly shaped by abundant species. In addition, during the transitions from saplings to juveniles, and from juveniles to adults, the relative importance of habitat filtering was very weak.
Anaerobic denitrification has been proved to be negatively affected by ZnO nanomaterials (NPs), but little is known about how ZnO NPs affects aerobic denitrification. In this study, inhibition of ZnO NPs to an aerobic denitrifier, Pseudomonas stutzeri PCN-1, was firstly reported. The results showed total nitrogen removal efficiency was decreased from 100% to 1.70% with the increase of ZnO NPs from 1 to 128 mg/L. The presence of ZnO NPs caused significant inhibition of gene expressions and catalytic activities of nitrate reductase and nitrite reductase, which finally led to delayed nitrate reduction and high nitrite accumulation. Further studies revealed that the deposition of nanoparticles on the bacterial surface caused by electrostatic forces and the generation of reactive oxygen species (ROS) were responsible for the cytotoxicity of ZnO NPs, where ROS played a more important role. These results were of significance to evaluating the potential ecological toxicity and risks of nanomaterials. (C) 2017 Elsevier Ltd. All rights reserved.
