科研成果 by Year: 2021

Particulate PAHs are of significant concern due to their carcinogenic and mutagenic properties. In order to investigate the characteristics and sources of particulate PAHs during heavy pollution episodes, PM2.5 samples were collected in Beijing and Dezhou in the North China Plain from November 17th, 2018 to January 19th, 2019. 26 species of PAHs in PM2.5 during six heavy pollution episodes were measured by gas chromatography-mass spectrometer (GC-MS). The results showed that: (1) The total concentration of PAHs during six heavy pollution episodes ranged from 62 to 191 ng/m3 in Dezhou, and from 61 to 129 ng/m3 in Beijing. (2) The ratios of ∑26PAHs/PM2.5 were higher in Beijing, although PM2.5 concentrations were lower. (3) The dominant components of PAHs were benzo[b]fluoranthene, benzo[a]pyrene (Bap), benzo[a]anthracene, methyl-fluoranthene and retene, accounting for about 50% of ∑26PAHs. (4) The diagnostic ratios indicated vehicle exhaust, coal combustion and biomass burning were the main sources of PAHs at both sites. A more obvious influence of biomass burning in Dezhou was found via a tracer-based approach and using the ratio of PAHs to levoglucosan in fresh biomass burning aerosols. (5) The Bap toxic equivalent concentrations (TEQ) were 6.5-17.2 ng/m3, with higher values in Dezhou than those in Beijing. The BaP concentration ranged from 5.2 to 13.1 ng/m3 and exceeded BaP standard (24 h average: 2.5 ng/m3) in China (Ambient Air Quality Standard, GB 3095-2012), indicating a potential hazardous effect on human health. The studies have shown that both sites have similar distribution characteristics and sources, while the enrichment ratios of ∑26PAHs/PM2.5 in Beijing were higher. PAHs emission control needs to be further strengthened to reduce the risk of human exposure to heavy pollution episodes and the PM2.5 pollution levels. © 2021, Editorial Board, Research of Environmental Sciences. All right reserved.

Widespread antibiotic resistance across Earth's habitats has become a critical health concern. However, large-scale investigation on the distribution of antibiotic resistance genes (ARGs) in the microbiomes from most types of ecosystem is still lacking. In this study, we provide a comprehensive characterization of ARGs for 52,515 microbial genomes covering various Earth's ecosystems, and conduct the risk assessment for ARG-carrying species based on further identification of mobile genetic elements (MGEs) and virulence factor genes (VFGs). We identify a total of 6159 ARG-carrying metagenome-assembled genomes (ACMs), and most of them are recovered from human gut and city subway. Our results show that efflux pump is the most common mechanism for bacteria to acquire multidrug resistance genes in Earth's microbiomes. Enterobacteriaceae species are the largest hosts of ARGs, accounting for 14% of total ACMs with 64% of the total ARG hits. Most of ARG-carrying species are unique in the different ecosystem categories, while 33 potential background ARGs are commonly shared by all ecosystem categories. We then detect 36 high-risk ARGs that likely threat public health in all ACMs. Based on ranking the importance of ARG-carrying species in the different ecosystem categories, several bacterial taxa such as Escherichia coli, Enterococcus faecalis, and Pseudomonas_A stutzeri are recognized as priority species for surveillance and control. Overall, our study gives a broad view of ARG-host associations in the environments.

Understanding and manipulating wettability alterations has tremendous implications in theoretical research and industrial applications. This study proposes a novel idea of applying ultrasonic for wettability alterations and also provides its quantitative characterizations and in-depth analyses. More specifically, with pretreatment of ultrasonic, mechanisms of wettability alteration were characterized from the contact angle measurements, as well as the in-depth analyses from atomic force microscopy (AFM), X-ray diffraction (XRD), and Fourier-transform infrared spectroscopy (FTIR). After ultrasonic treatments, the wettability of mineral with low permeability is determined to altered from strong hydrophilic to intermediate wettability. The mechanism interpretations are conducted by means of the AFM, XRD, and FTIR. Basically, as the time of ultrasonic treatment increases, the AFM results indicate that the roughness of rock surface and oil/rock interface (contact area) with surroundings of brine is enhanced. Meanwhile, the XRD results show the diffusions of clays from the rock surface to the aqueous phase, and FTIR indicates that the number of functional groups of Si–O–Si, C–O–C, C–O, C═O, and OH decreases while the number of COOH and C═C═O groups increases. This study clearly reveals the surface chemistry of oil-rock wettability alteration in the subsurface conditions, which would provide technical support for subsurface usage of geo-energy productions and carbon sequestrations.

To explore the concentrations, characteristics, and sources of organic aerosols in winter in Beijing, atmospheric fine particulate matter (PM2.5) samples were collected from November 10, 2016 to December 10, 2016. One hundred and twenty-nine particulate organic matters (POM) were quantified by gas chromatography-mass spectrometry, accounting for approximately 9.3%±1.2% of the total concentration of organic matter. The most abundant class was sugar, among which levoglucosan alone accounted for 18% of the quantified organic matter mass. The next most abundant classes were alkanoic acids, normal alkanes, dicarboxylic acids, and polycyclic aromatic hydrocarbons. The influence of winter heating and biomass burning emissions on organic aerosols in winter in Beijing was analyzed by the characteristics of the molecular markers in the POM. Compared with those during the non-heating period, the concentrations and proportions of hopane species, which are tracers for fossil fuels, increased in the organic matters during the heating period. Moreover, the influence of coal burning emissions on the distribution of hopane species was enhanced. The species with the maximum concentration and carbon predominance index in n-alkanes also reflected the influence of enhanced fossil fuel emissions. The results of the concentration-weighted trajectory model for levoglucosan, a tracer for biomass combustion, suggested that straw burning pollution in the surrounding areas of Beijing would affect the composition of organic aerosols in Beijing via airmass transport. A molecular marker-based chemical mass balance model was used to apportion the sources of organic carbon in the winter of 2016 in Beijing, and the results were compared with those of research in 2006 to quantify the changes in the source contributions over 10 years. The contribution of motor vehicles increased significantly in 2016 compared with that in 2006, whereas the contribution of coal burning and wood burning decreased to a large extent. The contribution of cooking emissions could not be ignored. Therefore, the control of motor vehicle and cooking emissions is of great importance to reduce the problem of PM2.5 pollution in winter in Beijing. © 2021, Science Press. All right reserved.