Τετάρτη, 28 Αυγούστου 2019

Concentrations and chemical compositions of PM10 during hazy and non-hazy days in Beijing
Publication date: January 2020
Source: Journal of Environmental Sciences, Volume 87
Author(s): Xianchu Wu, Bin Chen, Tianxue Wen, Ammara Habib, Guangyu Shi
Abstract
In order to study the concentrations of major components, characteristics and comparison in hazy and non-hazy days of PM10 in Beijing, aerosol samples were collected at urban site in Beijing from December 29, 2014 to January 22, 2015. Heavy metals like Zn, Pb, Mn, Cu, As, V, Cr and Cd were deeply studied considering their toxic effects on human being; nine water-soluble inorganic ions (SO42−, NO3, NH4+, Na+, K+, Cl, Ca2+ and Mg2+) and carbon fractions (OC and EC) were also analyzed. The concentrations of heavy metals were 1.03–1.98 times higher in hazy days than those in non-hazy days, mainly due to biomass burning and coal burning. The trends in total heavy metals concentrations were basically consistent with the trends in PM concentrations except for two obvious periods (12.29–12.30; 1.14–1.15); but when air masses accumulated locally or around Beijing, trends in PM concentrations and heavy metals were opposite. The proportion for NO3/SO42− indicated that mobile sources such as automobiles were important reasons for haze in Beijing. Correlation between OC and EC during non-hazy days was strong (R2 = 0.95) but it was low (R2 = 0.67) during hazy days, and large variations for OC/EC values occurred in hazy days. The calculated mass concentration of SOC is 2.58 μg/m3, which only accounted for 10.1% of the OC concentration. When air masses from the far north-west, they decreased PM concentration in Beijing and they were relatively clean; however, those from the near east, south-east and south of the mainland increased PM concentration and they were dirty.
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Identification of potential electrotrophic microbial community in paddy soils by enrichment of microbial electrolysis cell biocathodes
Publication date: January 2020
Source: Journal of Environmental Sciences, Volume 87
Author(s): Xiaomin Li, Longjun Ding, Haiyan Yuan, Xiaoming Li, Yongguan Zhu
Abstract
Electrotrophs are microbes that can receive electrons directly from cathode in a microbial electrolysis cell (MEC). They not only participate in organic biosynthesis, but also be crucial in cathode-based bioremediation. However, little is known about the electrotrophic community in paddy soils. Here, the putative electrotrophs were enriched by cathodes of MECs constructed from five paddy soils with various properties using bicarbonate as an electron acceptor, and identified by 16S rRNA-gene based Illumina sequencing. The electrons were gradually consumed on the cathodes, and 25%–45% of which were recovered to reduce bicarbonate to acetic acid during MEC operation. Firmicutes was the dominant bacterial phylum on the cathodes, and Bacillus genus within this phylum was greatly enriched and was the most abundant population among the detected putative electrotrophs for almost all soils. Furthermore, several other members of Firmicutes and Proteobacteria may also participate in electrotrophic process in different soils. Soil pH, amorphous iron and electrical conductivity significantly influenced the putative electrotrophic bacterial community, which explained about 33.5% of the community structural variation. This study provides a basis for understanding the microbial diversity of putative electrotrophs in paddy soils, and highlights the importance of soil properties in shaping the community of putative electrotrophs.
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Carbonaceous matter in glacier at the headwaters of the Yangtze River: Concentration, sources and fractionation during the melting process
Publication date: January 2020
Source: Journal of Environmental Sciences, Volume 87
Author(s): Zhaofu Hu, Shichang Kang, Xiaobo He, Fangping Yan, Yulan Zhang, Pengfei Chen, Xiaofei Li, Shaopeng Gao, Chaoliu Li
Abstract
Carbonaceous matter has an important impact on glacial retreat in the Tibetan Plateau, further affecting the water resource supply. However, the related studies on carbonaceous matter are still scarce in Geladaindong (GLDD) region, the source of the Yangtze River. Therefore, the concentration, source and variations of carbonaceous matter at Ganglongjiama (GLJM) glacier in GLDD region were investigated during the melting period in 2017, which could deepen our understanding on carbonaceous matter contribution to glacier melting. The results showed that dissolved organic carbon (DOC) concentration of snowpit samples (283 ± 200 μg/L) was much lower than that of precipitation samples (624 ± 361 μg/L), indicating that large parts of DOC could be rapidly leached from the snowpit during the melting process. In contrast, refractory black carbon (rBC) concentration measured by Single Particle Soot Photometer of snowpit samples (4.27 ± 3.15 μg/L) was much higher than that of precipitation samples (0.97 ± 0.49 μg/L). Similarly, DOC with high mass absorption cross-section measured at 365 nm value was also likely to enrich in snowpit during the melting process. In addition, it was found that both rBC and DOC with high light-absorbing ability began to leach from the snowpit when melting process became stronger. Therefore, rBC and DOC with high light-absorbing ability exhibited similar behavior during the melting process. Based on relationship among DOC, rBC and K+ in precipitation, the main source of carbonaceous matter in GLJM glacier was biomass burning during the study period.
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100 years of high GEM concentration in the Central Italian Herbarium and Tropical Herbarium Studies Centre (Florence, Italy)
Publication date: January 2020
Source: Journal of Environmental Sciences, Volume 87
Author(s): Jacopo Cabassi, Valentina Rimondi, Zhang Yeqing, Antonella Vacca, Orlando Vaselli, Antonella Buccianti, Pilario Costagliola
Abstract
Up to 1980s, the most used preservative for herbaria specimens was HgCl2, sublimating at ambient air conditions; ionic Hg then reduces to Hg0 (gaseous elemental mercury, GEM) and diffuses throughout poor ventilated environments. High GEM levels may indeed persist for decades, representing a health hazard. In this study, we present new GEM data from the Central Italian Herbarium and Tropical Herbarium Studies Centre of the University of Florence (Italy). These herbaria host one of the largest collection of plants in the world. Here, HgCl2 was documented as plant preservative up to the 1920s. GEM surveys were conducted in July 2013 and July and December 2017, to account for temporal and seasonal variations.
Herbaria show GEM concentrations well above those of external locations, with peak levels within specimen storage cabinets, exceeding 50,000 ng/m3. GEM concentrations up to ~ 7800 ng/m3 were observed where the most ancient collections are stored and no ventilation systems were active. On the contrary, lower GEM concentrations were observed at the first floor. Here, lower and more homogeneously distributed GEM concentrations were measured in 2017 than in 2013 since the air-conditioning system was updated in early 2017.
GEM concentrations were similar to other herbaria worldwide and lower than Italian permissible exposure limit of 20,000 ng/m3 (8-hr working day). Our results indicate that after a century from the latest HgCl2 treatment GEM concentrations are still high, i.e., the treatment itself is almost irreversible. Air conditioning and renewing is probably the less expensive and more effective method for GEM lowering.
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Experimental study on the space charge properties in haze events
Publication date: January 2020
Source: Journal of Environmental Sciences, Volume 87
Author(s): Xiaobin Zhang, Sen Yang, Tianli Bo
Abstract
In recent years, haze has posed a serious threat to the global climate change, ecological balance and human health. In this study, the laboratory experiments and field observations were performed and a possible charging mechanism was proposed to investigate the space charge properties in haze events. The laboratory experiments showed that the charge polarity of primary aerosol is determined by species of combustion fuels while the magnitude is dependent on the combustion completeness. The field observations revealed that the space charge of atmosphere aerosol in haze events differs from that of fair weather and is closely related to PM2.5 concentration when Relative Humidity (RH) < 60%, with 1 to 2 orders of magnitude less than the case when RH ≥ 60%. The analysis of equivalent charge-to-mass ratio (ECTM) suggested that in haze events the space charge is governed by primary aerosol emitted by combustion of fossil fuel in a low relative humidity, whereas it is manipulated by the secondary chemical reaction of atmosphere aerosol in a high relative humidity. And we can identify the main pollutants in haze events according to the polarity of atmosphere aerosol and quickly take measures when RH < 60%. Accordingly, the dust-haze of RH < 80% can be divided into dry-dust-haze when RH < 60% and wet-dust-haze when 60% ≤ RH < 80%. Our study firstly elucidated the space charge properties of atmosphere aerosol in haze events and can provide a new perspective for the prevention and control of air pollution.
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Sorption kinetics of parent and substituted PAHs for low-density polyethylene (LDPE): Determining their partition coefficients between LDPE and water (KLDPE) for passive sampling
Publication date: January 2020
Source: Journal of Environmental Sciences, Volume 87
Author(s): Pei Lei, Jinjie Zhu, Ke Pan, Hong Zhang
Abstract
Low-density polyethylene (LDPE) has been widely used as a sorbent for passive sampling of hydrophobic organic contaminants (HOCs) in aquatic environments. However, it has seen only limited application in passive sampling for measurement of freely dissolved concentrations of parent and substituted PAHs (SPAHs), which are known to be toxic, mutagenic and carcinogenic. Here, the 16 priority PAHs and some typical PAHs were selected as target compounds and were simultaneously determined by gas chromatography–mass spectrometer (GC–MS). Some batch experiments were conducted in the laboratory to explore the adsorption kinetics of the target compounds in LDPE membranes. The results showed that both PAHs and SPAHs could reach equilibrium status within 19–38 days in sorption kinetic experiments. The coefficients of partitioning between LDPE film (50 μm thickness) and water (KLDPE) for the 16 priority PAHs were in good agreement with previously reported values, and the values of KLDPE for the 9 SPAHs are reported in this study for the first time. Significant linear relationships were observed, i.e., log KLDPE = 0.705 × log KOW + 1.534 for PAHs (R2 = 0.8361, p < 0.001) and log KLDPE = 0.458 × log KOW + 3.092 for SPAHs (R2 = 0.5609, p = 0.0077). The selected LDPE film was also proven to meet the condition of “zero sink” for the selected target compounds. These results could provide basic support for the configuration and in situ application of passive samplers.
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N-Nitrosamine formation from chloramination of two common ionic liquids
Publication date: January 2020
Source: Journal of Environmental Sciences, Volume 87
Author(s): Ian J. Vander Meulen, Ping Jiang, Di Wu, Steve E. Hrudey, Xing-Fang Li
Abstract
Ionic liquids (ILs) are a class of solvents increasingly used as “green chemicals.” Widespread applications of ILs have led to concerns about their accidental entry to the environment. ILs have been assessed for some environmental impacts; however, little has been done to characterize their potential impacts on drinking water if ILs accidentally enter surface water. IL cations are often aromatic or alkyl quaternary amines that resemble structures of previously confirmed N-nitrosamine (NA) precursors. Therefore, this study has evaluated two common ILs, 1-ethyl-3-methylimidazolium bromide (EMImBr) and 1-ethyl-1-methylpyrrolidinium bromide (EMPyrBr), for their NA formation potential. Each IL species was reacted with pre-formed monochloramine under various laboratory conditions. The reaction mixtures were extracted using liquid–liquid extraction and analyzed for NAs using high performance liquid chromatography tandem mass spectrometry. At low concentration of IL (250 μmol/L), the yields of NAs (NMEA or NPyr) increased with increasing doses of monochloramine from both IL species. The total NA yield was as high as 2.5 ± 0.3 ng/mg from EMImBr, and as high as 8.6 ± 0.8 ng/mg from EMPyrBr. At high concentration of IL (5 mmol/L), the NA yield reached a maximum at 2.5 mmol/L NH2Cl, and then decreased with subsequent increases in the reactant concentrations, demonstrating ILs' solvent effects. This study re-emphasizes the importance of preventing discharge of ILs to water bodies to prevent secondary impacts on drinking water.
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Revealing the changes of bacterial community from water source to consumers tap: A full-scale investigation in eastern city of China
Publication date: January 2020
Source: Journal of Environmental Sciences, Volume 87
Author(s): Xu Ma, Guiwei Li, Ruya Chen, Ying Yu, Hui Tao, Guangming Zhang, Baoyou Shi
Abstract
This study profiled the bacterial community variations of water from four water treatment systems, including coagulation, sedimentation, sand filtration, ozonation-biological activated carbon filtration (O3-BAC), disinfection, and the tap water after the distribution process in eastern China. The results showed that different water treatment processes affected the bacterial community structure in different ways. The traditional treatment processes, including coagulation, sedimentation and sand filtration, reduced the total bacterial count, while they had little effect on the bacterial community structure in the treated water (before disinfection). Compared to the traditional treatment process, O3-BAC reduced the relative abundance of Sphingomonas in the finished water. In addition, ozonation may play a role in reducing the relative abundance of Mycobacterium. NaClO and ClO2 had different effects on the bacterial community in the finished water. The relative abundance of some bacteria (e.g. FlavobacteriumPhreatobacter and Porphyrobacter) increased in the finished water after ClO2 disinfection. The relative abundance of Mycobacterium and Legionella, which have been widely reported as waterborne opportunistic pathogens, increased after NaClO disinfection. In addition, some microorganisms proliferated and grew in the distribution system, which could lead to turbidity increases in the tap water. Compared to those in the finished water, the relative abundance of SphingomonasHyphomicrobiumPhreatobacterRheinheimeraPseudomonas and Acinetobacter increased in the tap water disinfected with NaClO, while the relative abundance of Mycobacterium increased in the tap water disinfected with ClO2. Overall, this study provided the detailed variation in the bacterial community in the drinking water system.
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Long-term effects of silver nanoparticles on performance of phosphorus removal in a laboratory-scale vertical flow constructed wetland
Publication date: January 2020
Source: Journal of Environmental Sciences, Volume 87
Author(s): Juan Huang, Jun Xiao, Yang Guo, Wenzu Guan, Chong Cao, Chunni Yan, Mingyu Wang
Abstract
Silver nanoparticles (AgNPs) have been widely used in many fields, which raised concerns about potential threats to biological sewage treatment systems. In this study, the phosphorus removal performance, enzymatic activity and microbial population dynamics in constructed wetlands (CWs) were evaluated under a long-term exposure to AgNPs (0, 50, and 200 μg/L) for 450 days. Results have shown that AgNPs inhibited the phosphorus removal efficiency in a short-term exposure, whereas caused no obviously negative effects from a long-term perspective. Moreover, in the coexisting CW system of AgNPs and phosphorus, competition exhibited in the initial exposure phase, however, cooperation between them was observed in later phase. Enzymatic activity of acid-phosphatase at the moderate temperature (10–20°C) was visibly higher than that at the high temperature (20–30°C) and CWs with AgNPs addition had no appreciable differences compared with the control. High-throughput sequencing results indicated that the microbial richness, diversity and composition of CWs were distinctly affected with the extension of exposure time at different AgNPs levels. However, the phosphorus removal performance of CWs did not decline with the decrease of polyphosphate accumulating organisms (PAOs), which also confirmed that adsorption precipitation was the main way of phosphorus removal in CWs. The study suggested that AgNPs and phosphorus could be removed synergistically in the coexistence system. This work has some reference for evaluating the influences of AgNPs on the phosphorus removal and the interrelation between them in CWs.
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An investigation of changes in water quality throughout the drinking water production/distribution chain using toxicological and fluorescence analyses
Publication date: January 2020
Source: Journal of Environmental Sciences, Volume 87
Author(s): Xue Han, Xin Ji, Xuan Ma, Jun-Ling Liu, Zhen-Yu He, Wei Chang, Fei Tang, Ai-Lin Liu
Abstract
Changes in water quality from source water to finished water and tap water at two conventional drinking water treatment plants (DWTPs) were monitored. Beside the routine water quality testing, Caenorhabditis elegans-based toxicity assays and the fluorescence excitation–emission matrices technique were also applied. Both DWTPs supplied drinking water that met government standards. Under current test conditions, both the investigated finished water and tap water samples exhibited stronger lethal, genotoxic and reprotoxic potential than the relative source water sample, and the tap water sample was more lethal but tended to be less genotoxic than the corresponding finished water sample. Meanwhile, the nearly complete removal of tryptophan-like substances and newly generated tyrosine-like substances were observed after the treatment of drinking water, and humic-like substances were identified in the tap water. Based on these findings, toxic pollutants, including genotoxic/reproductive toxicants, are produced in the drinking water treatment and/or distribution processes. Moreover, further studies are needed to clarify the potentially important roles of tyrosine-like and humic-like substances in mediating drinking water toxicity and to identify the potential sources of these contaminants. Additionally, tryptophan-like fluorescence may be adopted as a useful parameter to monitor the treatment performance of DWTPs. Our observations provided insights into the importance of utilizing biotoxicity assays and fluorescence spectroscopy as tools to complement the routine evaluation of drinking water.
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