Microorganisms are involved in a variety of biogeochemical processes in natural environments. The differences between bacterial communities in freshwaters and upslope soils remain unclear. The present study investigated the bacterial distribution in a plateau freshwater lake, Erhai Lake (southwestern China), and its upslope soils. Illumina MiSeq sequencing illustrated high bacterial diversity in lake sediments and soils. Sediment and soil bacterial communities were mainly composed of Proteobacteria, Acidobacteria, Actinobacteria, Bacteroidetes, Chloroflexi and Planctomycetes. However, a distinctive difference in bacterial community structure was found between soil and sediment ecosystems. Water content, nitrogen and pH affected the distribution of the bacterial community across Erhai Lake and its upslope soils. Moreover, the soil bacterial community might also be shaped by plant types. This work could provide some new insights into plateau aquatic and terrestrial microbial ecology. (C) 2015 The Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V.
Telomere length (TL) is associated with an increased risk of aging-related diseases. As a preventable environmental hazard of morbidity and mortality, smoking has been reported to promote TL attrition by producing a variety of oxidants and free radicals. Since DNA methylation has been demonstrated to play an important role in the pathways of smoking and smoking-induced diseases, this study aimed to address whether the smoking-associated DNA methylation changes could be associated with accelerated TL shortening. We obtained DNA methylation profiles in whole blood samples by Illumina Infinium Human Methylation 450 Beadchip array in two independent subsamples of the ESTHER study and measured their relative TL by quantitative PCR. Terminal Restriction Fragment analysis was additionally performed in a subsample to obtain absolute TL in base pairs. TL measurements across panels were standardized by z-transformation. After correction for multiple testing, we successfully confirmed that seven out of 151 smoking-related CpG sites were associated with TL (FDR <0.05). A smoking index based on the seven loci showed monotonic associations with TL, cumulative smoking exposure and time after smoking cessation. In conclusion, our study supports suggestions that epigenetic alterations could play a role in smoking-associated disproportionate aging as reflected by TL. Further research is required to examine whether the identified epigenetic signatures of smoking can be of value in clinical practice to assess individual aging across the lifespan.
Using a newly constructed panel dataset that covers the 14-year period from 1997 to 2011 for more than 100 villages in China, this study analyzes the dynamic effect of rural-to-urban migration on inequality in source villages. Given that income inequality is time persisting, we use a system GMM framework. We found that the dynamic relationship between migration and income inequality is inversely U-shaped. Specifically, contemporary migration increases income inequality, whereas lagged migration has a strong income inequality-reducing effect on the sending villages. A 50 percent increase in the lagged migration rate translates into a one-ninth to one-tenth standard deviation reduction in income inequality.
Secondary organic aerosol (SOA) formation from photooxidation of alpha-pinene has been investigated in a photochemical reaction chamber under varied inorganic seed particle acidity levels at moderate relative humidity. The effect of particle acidity on SOA yield and chemical composition was examined under high-and low-NOx conditions. The SOA yield (4.2-7.6 %) increased nearly linearly with the increase in particle acidity under high-NOx conditions. In contrast, the SOA yield (28.6-36.3 %) was substantially higher under low-NOx conditions, but its dependency on particle acidity was insignificant. A relatively strong increase in SOA yield (up to 220 %) was observed in the first hour of alpha-pinene photooxidation under high-NOx conditions, suggesting that SOA formation was more effective for early alpha-pinene oxidation products in the presence of fresh acidic particles. The SOA yield decreased gradually with the increase in organic mass in the initial stage (approximately 0-1 h) under high-NOx conditions, which is likely due to the inaccessibility to the acidity over time with the coating of alpha-pinene SOA, assuming a slow particle-phase diffusion of organic molecules into the inorganic seeds. The formation of later-generation SOA was enhanced by particle acidity even under low-NOx conditions when introducing acidic seed particles after alpha-pinene photooxidation, suggesting a different acidity effect exists for alpha-pinene SOA derived from later oxidation stages. This effect could be important in the atmosphere under conditions where alpha-pinene oxidation products in the gas-phase originating in forested areas (with low NOx and SOx) are transported to regions abundant in acidic aerosols such as power plant plumes or urban regions. The fraction of oxygen-containing organic fragments (CxHyO1+ 33-35% and CxHyO2+ 16-17 %) in the total organics and the O / C ratio (0.52-0.56) of alpha-pinene SOA were lower under high-NOx conditions than those under low-NOx conditions (39-40, 17-19, and 0.61-0.64 %), suggesting that alpha-pinene SOA was less oxygenated in the studied high-NOx conditions. The fraction of nitrogen-containing organic fragments (CxHyNz+ and CxHyOzNp+) the total organics was enhanced with the increases in particle acidity under high-NOx conditions, indicating that organic nitrates may be formed heterogeneously through a mechanism catalyzed by particle acidity or that acidic conditions facilitate the partitioning of gas-phase organic nitrates into particle phase. The results of this study suggest that inorganic acidity has a significant role to play in determining various organic aerosol chemical properties such as mass yields, oxidation state, and organic nitrate content. The acidity effect being further dependent on the timescale of SOA formation is also an important parameter in the modeling of SOA.
Combination of emergent and submerged plants has been proved to be able to enhance pollutant removal efficiency of surface flow-constructed wetland (SFCW) during winter. However, intensive photosynthesis of submerged plants during summer would cause pH increase, which may have adverse effects on emergent plants. In this study, nitrogen transformation of lab-scale SFCW under pH gradient of 7.5, 8.5, 9.5 and 10.5 was systematically investigated. The results showed that total nitrogen (TN) removal efficiency decreased from 76.3 +/- 0.04 to 51.8 +/- 0.04 % when pH increased from 7.5 to 10.5, which was mainly attributed to plant assimilation decay and inhibition of microbe activities (i.e., nitrite-oxidizing bacteria and denitrifiers). Besides, the highest sediment adsorption in SFCW was observed at pH of 8.5. In general, the combination of submerged and emergent plants is feasible for most of the year, but precaution should be taken to mitigate the negative effect of high alkaline conditions when pH rises to above 8.5 in midsummer.
Surface/interface effect plays a significant role in the study of the mechanical properties of nano composites. Most previous papers in the literature only considered the surface/interface elasticity, whereas some papers only considered the residual surface/interface stress (surface/interface tension). In this paper, an energy-based surface/interface theory is applied to systematically study the effective thermo-elastic properties of unidirectional fiber-reinforced nanocomposites, in which both the surface/interface elasticity and the residual surface/interface stress are included. The emphasis is particularly placed on the influence of the residual interface stress on the effective thermo-elastic properties of such nanocomposites, since this influence was ignored by many previous authors. Analytical expressions of five effective transversely isotropic elastic constants are derived, in which a modified generalized self consistent method is suggested to obtain an explicit expression of the size-dependent effective transverse shear modulus. Furthermore, with an introduced concept of 'equivalent fiber' (i.e., a fiber together with its interface), the effective thermal expansion coefficients and the effective specific heat at constant strain of the fiber-reinforced nanocomposite are obtained. Finally, numerical examples are illustrated, and the effect of residual interface stress on the effective thermo-elastic properties of the fibrous nanocomposite is discussed. It is shown that the residual interface stress has a significant effect on the overall thermo-elastic properties of the nanocomposites. (C) 2016 Elsevier Ltd. All rights reserved.
Surface/interface effect plays a significant role in the study of the mechanical properties of nano composites. Most previous papers in the literature only considered the surface/interface elasticity, whereas some papers only considered the residual surface/interface stress (surface/interface tension). In this paper, an energy-based surface/interface theory is applied to systematically study the effective thermo-elastic properties of unidirectional fiber-reinforced nanocomposites, in which both the surface/interface elasticity and the residual surface/interface stress are included. The emphasis is particularly placed on the influence of the residual interface stress on the effective thermo-elastic properties of such nanocomposites, since this influence was ignored by many previous authors. Analytical expressions of five effective transversely isotropic elastic constants are derived, in which a modified generalized self consistent method is suggested to obtain an explicit expression of the size-dependent effective transverse shear modulus. Furthermore, with an introduced concept of 'equivalent fiber' (i.e., a fiber together with its interface), the effective thermal expansion coefficients and the effective specific heat at constant strain of the fiber-reinforced nanocomposite are obtained. Finally, numerical examples are illustrated, and the effect of residual interface stress on the effective thermo-elastic properties of the fibrous nanocomposite is discussed. It is shown that the residual interface stress has a significant effect on the overall thermo-elastic properties of the nanocomposites. (C) 2016 Elsevier Ltd. All rights reserved.
Nanoceria (i.e., CeO2 nanoparticles) fuel additives have been used in Europe and elsewhere to improve fuel efficiency. Previously we have shown that the use of a commercial fuel additive Envirox in a diesel-powered electricity generator reduced emissions of diesel exhaust particle (DEP) mass and other pollutants. However, such additives are currently not permitted for use in on-road vehicles in North America, largely due to limited data on the potential health impact. In this study, we characterized a variety of physicochemical properties of DEPs emitted from the same engine. Our methods include novel techniques such as Raman spectrometry for analyzing particle surface structure and an assay for DEP oxidative potential. Results show that with increasing Envirox concentrations in the fuel (0x, 0.1x, 1x, and 10x of manufacturer recommended 0.5 mL Envirox per liter fuel), DEP sizes decreased from 194.6 +/- 20.1 to 116.3 +/- 14.8 nm; the zeta potential changed from -28.4 mV to -22.65 mV; DEP carbon content decreased from 91.8% to 79.4%; cerium and nitrogen contents increased from 0.3% to 6.5% and 0.2% to 0.6%, respectively; the ratio of organic carbon (OC) to elemental carbon (EC) increased from 22.9% to 38.7%; and the ratio of the disordered carbon structure to the ordered carbon structure (graphitized carbon) in DEPs decreased. Compared to DEPs emitted from 0x, 0.1x, and 1x fuels, DEPs from the 10x fuel had a lower oxidative potential likely due to the increased ceria content because pure ceria nanoparticles exhibited the lowest oxidative potential compared to all the DEPs. Since the physicochemical parameters tested here are among the determinants of particle toxicity, our findings imply that adding ceria nanoparticles into diesel may alter the toxicity of DEPs. The findings from the present study, hence, can help future studies that will examine the impact of nanoceria additives on DEP toxicities.
The adsorption of Cr(III) or Cr(VI) in the absence and presence of Cu(II) onto kaolin was investigated under pH 2.0–7.0. Results indicated that the adsorption rate was not necessarily proportional to the adsorption capacity. The solutions’ pH values played a key role in kaolin zeta potential , especially the hydrolysis behavior and saturation index of heavy metal ions. In the presence of Cu(II), reached the maximum adsorption capacity of 0.73 mg·g−1 at pH 6.0, while the maximum adsorption capacity for the mixed Cr(VI) and Cu(II) system () was observed at pH 2.0 (0.38 mg·g−1). Comparing the adsorption behaviors and mechanisms, we found that kaolin prefers to adsorb hydrolyzed products of Cr(III) instead of Cr3+ ion, while adsorption sites of kaolin surface were occupied primarily by Cu(II) through surface complexation, leading to Cu(II) inhibited Cr(VI) adsorption. Moreover, Cr(III) and Cr(VI) removal efficiency had a positive correlation with distribution coefficient . Cr(III) and Cr(VI) removal efficiency had a positive correlation with distribution coefficient and that of adsorption affinities of Cr(III) or Cr(VI) on kaolin was found to be Cr(III) < Cr(III)-Cu(II) and Cr(VI) > Cr(VI)-Cu(II).
The present study investigated the effects of lead on the morphological structure, physical and chemical properties, wastewater treatment performance and microbial community structure of aerobic granular sludge (AGS) in sequencing batch reactors (SBRs). The results showed that at Pb2+ concentration of 1mg/L, the mixed liquid suspended solids decreased, the settling velocity increased and the sludge volume index increased sharply. Meanwhile, AGS began to disintegrate and show an irregular shape. In terms of wastewater treatment in an SBR, the phosphorus removal rate was affected only until the Pb2+ concentration was up to 1mg/L. The NH4+- N removal efficiency began to decline when the Pb2+ concentration increased to 6mg/L, while the removal of chemical oxygen demand increased slightly within the Pb2+ concentration range of 1-6mg/L. Significant changes were observed in the microbial community structure, especially the dominant bacteria. Compared to the Pb2+ accumulation on the sludge, the Pb2+ concentration in the aqueous phase played a more important role in the performance and microbial community of AGS in SBRs.