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Photocatalytic synthesis of BSA-Au nanoclusters with tunable fluorescence for highly selective detection of silver ion
No full textA new photocatalytic synthesis strategy for rapid preparation of BSA-Au nanoclusters (NCs) with tunable fluorescence was developed and used for the highly selective detection of silver ion. In this strategy, the silver ion was firstly photo-reduced to Ag NCs under UV light illumination. Then, the produced Ag NCs would further reduce HAuCl4 to Au NCs stabilized in BSA molecules. In this process, silver ion not only acted as a photocatalyst to accelerate the formation of fluorescent Au nanocluster but also as a regulator to tune the fluorescence emission color of the BSA-Au NCs from orange to red. The maximum emission peak of BSA-Au NCs fluorescence could be tuned from 570 to 620 nm in different experimental conditions. Furthermore, a fluorescence emission peak redshifts of the as-prepared BSA-Au NCs could also be observed by subsequent adding of silver ion. Thus, a quantitative analytical method for silver ion detection could be established in the range from 5.0 to 60.0 mu M with a detection limit (LOD) of 0.226 mu M (3 sigma). The method had high selectivity that other common metal ions and small biological molecules did not have similar phenomena. It had great potential for applying for environmental water sample analysis
Maximizing the Formation of Reactive Oxygen Species for Deep Oxidation of NO via Manipulating the Oxygen-Vacancy Defect Position on (BiO)(2)CO3
No full textConstructing oxygen vacancies (OVs) in metaloxide semiconductors is an effective and simple way to enhance the photocatalytic performance via promoting the utilization of solar light and boosting the formation of surface reactive oxygen species (ROS). The presence of different oxygen atoms in the same crystal structure can possibly lead to the formation of different types of OVs with distinct physicochemical and optoelectronic properties. Particularly, the two different crystallographic positions of oxygen atoms in the [BiO](2)(2+) layer of (BiO)(2)CO3 (BOC) allow the construction of two types of OVs (OVs1 and OVs2). In this work, OVs1-BOC and OVs2-BOC are synthesized via introducing the OVs1 and OVs2 on the surface of the BOC. The influence of OVs1 and OVs2 on the generation of ROS in the BOC is demonstrated based on theoretical and experimental studies by analyzing the separation and redox potentials of photogenerated charge carriers, absorption surface adsorbates (H2O and O-2), and reaction active energy. The photocatalytic performance is evaluated by photo-oxidative nitric oxide (NO) removal efficiency under visible light irradiation. The OVsl-BOC and OVs2-BOC exhibit 50.0 and 41.6% photo-oxidative NO removal efficiencies, while generating 15.6 and 16.54 ppb NO2, respectively. The in situ Fourier transform infrared spectroscopy and estimated NO conversion pathway reveal the photo-oxidative NO removal mechanism and suppression of NO2 formation on the surfaces of OVs1-BOC and OVs2-BOC. This work demonstrates a straightforward approach for enhancing the photo-oxidative NO removal via manipulating the OV defect position in semiconductors
Brownness of Organic Aerosol over the United States: Evidence for Seasonal Biomass Burning and Photobleaching Effects
No full textLight-absorptivity of organic aerosol may play an important role in visibility and climate forcing, but it has not been assessed as extensively as black carbon (BC) aerosol. Based on multiwavelength thermal/optical analysis and spectral mass balance, this study quantifies BC for the U.S. Interagency Monitoring of Protected Visual Environments (IMPROVE) network while developing a brownness index (gamma(Br)) for non-BC organic carbon (OC*) to illustrate the spatiotemporal trends of light-absorbing brown carbon (BrC) content. OC* light absorption efficiencies range from 0 to 3.1 m(2) gC(-1) at 405 nm, corresponding to the lowest and highest BrC content of 0 and 100%, respectively. BC, OC*, and gamma(Br) explain >97% of the variability of measured spectral light absorption (405-980 nm) across 158 IMPROVE sites. Network-average OC* light absorptions at 405 nm are 50 and 28% those for BC over rural and urban areas, respectively. Larger organic fractions of light absorption occur in winter, partially due to higher organic brownness. Winter gamma(Br) exhibits a dramatic regional/urban-rural contrast consistent with anthropogenic BrC emissions from residential wood combustion. The spatial differences diminish to uniformly low gamma(Br) in summer, suggesting effective BrC photobleaching over the midlatitudes. An empirical relationship between BC, ambient temperature, and gamma(Br) is established, which can facilitate the incorporation of organic aerosol absorptivity into climate and visibility models that currently assume either zero or static organic light absorption efficiencies
Increasing atmospheric oxidizing capacity weakens emission mitigation effort in Beijing during autumn haze events
No full textAlthough strict mitigation measures have been implemented since 2013 in Beijing-Tianjin-Hebei (BTH), China, air pollution still frequently occurs. Observations reveal that during pollution episodes in autumn, fine particulate matter (PM2.5) concentrations have not decreased, and particularly, ozone (O-3) concentrations have increased remarkably from 2013 to 2015 in Beijing. Additionally, a concurrence of O-3 and particulate pollution with high secondary aerosol contributions has been observed frequently, indicating high atmospheric oxidizing capacity (AOC) during particulate pollution. The WRF-Chem model simulations show elevated O-3 concentrations and high fractions of oxygenated secondary aerosols (OSA) in PM2.5 (0.53-0.73) during the severe pollution period. During daytime there exhibits an AOC-sufficient regime with the persistently high OSA fraction and an AOC-deficient regime with varied OSA fractions, separated by the O-3 level of 80 mu g m(-3). Our results suggest that increasing AOC can considerably weaken the emission mitigation effort by enhancing the secondary aerosol formatio
A 120-year seasonally resolved speleothem record of precipitation seasonality from southeastern China
No full textSpeleothem oxygen isotope (delta O-18(s)) record as a climatic proxy in southeastern China is still in debate due to multifaceted influencing factors, a modern delta O-18(s) record, which can be calibrated or compared with observational data, is critical to explore the interpretation of delta O-18(s) proxy. Here we present a seasonally resolved delta O-18(s) record spanning the interval of 1898-2018 CE from Niubi Cave, Guangdong Province, southeastern China. A comparison between the Niubi delta O-18(s) and instrumental data reveals that the Niubi delta O-18(s) variability is primarily controlled by changes in precipitation seasonality modulated by El Nino-Southern Oscillation on interannual to interdecadal timescales. Higher (lower) delta O-18(s) values correspond to lower (higher) ratios of the East Asian summer monsoon/non-summer monsoon precipitation during the El Nino (La Nina) events associated with concomitant changes in the outgoing longwave radiation, wind field and Western Pacific Subtropical High. While similar to 73% historical drought events correlate to positive anomalies in Niubi delta O-18(s) values over the last 120 years, the rest of drought events associate with the negative delta O-18(s) anomalies. This observation suggests two different mechanisms for the drought events with more and less diminution of rainfall amount in the East Asian summer monsoon relative to the non-summer monsoon precipitation, respectively. Additionally, our Niubi delta O-18(s) record from southeastern China, together with other high-resolution speleothem and tree ring records, demonstrate a "tripole pattern" of summer precipitation during the last similar to 100 years in eastern China. (C) 2021 Elsevier Ltd. All rights reserved
Biodegradation performance and diversity of enriched bacterial consortia capable of degrading high-molecular-weight polycyclic aromatic hydrocarbons
No full textPolycyclic aromatic hydrocarbons (PAHs) are key organic pollutants in the environment that pose threats to the ecosystem and human health. The degradation of high molecular weight (HMW) PAHs by enriched bacterial consortia has been previously studied, while the involved metabolisms and microbial communities are still unclear and warrant further investigations. In this study, five bacterial consortia capable of utilizing different PAHs (naphthalene, anthracene, and pyrene) as the sole carbon and energy sources were enriched from PAH-contaminated soil samples. Among the five consortia, consortium TC exhibited the highest pyrene degradation efficiency (91%) after 19 d of incubation. The degradation efficiency was further enhanced up to 99% by supplementing yeast extract. Besides, consortium TC showed tolerances to high concentrations of pyrene (up to 1000 mg/L) and different heavy metal stresses (including Zn2+, Cd2+, and Pb2+). The dominant genus in consortium TC, GS, and PL showing relatively higher degradation efficiency for anthracene and pyrene was Pseudomonas, whereas consortium PG and GD were predominated by genus Achromobacter and class Enterobacteriaceae, respectively. Consortium TC, as a highly efficient HMW PAH-degrading consortium, could be applied for synergistic biodegradation of HMW PAHs and in situ bioremediation of the sites contaminated with both PAHs and heavy metals
Immediate temperature response in northern Iberia to last deglacial changes in the North Atlantic
No full textMajor disruptions in the North Atlantic circulation during the last deglaciation triggered a series of climate feedbacks that influenced the course of Termination I, suggesting an almost synchronous response in the ocean-atmosphere system. We present a replicated 818O stalagmite record from Ostolo cave in the northern Iberian Peninsula with a robust chronological framework that continuously covers the last deglaciation (18.5-10.5 kyr B.P.). The Ostolo 818O record, unlike other speleothem records in the region that were related to humidity changes, closely tracks the well-known high-latitude temperature evolution, offering important insights into the structure of the last deglaciation in the Northern Hemisphere. In addition, this new record is accompanied by a clear signal of the expected cooling events associated with the deglacial disruptions in North Atlantic deep convection during Heinrich event 1
Black carbon and dust in the Third Pole glaciers: Revaluated concentrations, mass absorption cross-sections and contributions to glacier ablation
No full textIn snow and ice, light-absorbing particles (LAN), such as black carbon (BC) and dust, accelerate the melting of Third Pole glaciers (TPGs). In this study, we revaluated LAP concentrations in the snow pits of TPGs (SP-TPGs), measured LAP mass absorption cross-sections (MACs), and simulated their effects on glacier darkening and melting based on the Spectral Albedo Model for Dirty Snow and a surface energy and mass balance model. The results indicated that because of their short distances to emission sources, the average BC concentrations measured in snow pits in the periphery of Third Pole were much higher than those measured in the inland Tibetan Plateau, and the average dust concentrations generally decreased from north to south. The average MACs of BC in the SP-TPCs varied from 3.1 to 7.7 m(2) g(-1) at 550 nm, most of the average spectral values were comparable in the visible and near-infrared bands to those calculated by Mie theory, except those in Urumqi Glacier No. 1 (UR), Syek Zapadniy Glacier (SZ), and Laohugou Glacier No.12 (LH), while the average spectral MACs of dust in the SP-TPGs were considerably smaller in magnitude than most of the variations measured in other regions. Compared with the pure snow surfaces. BC and dust played comparable roles in reducing albedo in UR, SZ, LH, and Renlongba Glacier, whereas BC was the most prominent absorber in the other glaciers. The combined effect of BC and dust accelerated melting by 30.4-345.9 mm w.e. (19.7-453% of the total mass balance) through surface albedo darkening (0.06-0.17) and increased radiation absorption (25.8-65.7 W m(-2)) within one month of the ablation season. This study provides a new data set of LAP concentrations and MACs and helps to clarify the roles of these factors in the cryospheric environment of the Third Pole. (C) 2021 Elsevier B.V. All tights reserved
Early Pleistocene integration of the Yellow River II: Evidence from the Plio-Pleistocene sedimentary record of the Fenwei Basin
No full textThe Yellow River is the 2nd longest river in China and the 6th longest river in the world. However, the timing and mechanism of its integration remains debated. During the establishment of its present geometry, the Yellow River captured and deeply incised into a series of local drainage basins along its Upper and Middle Reaches. The termination of basin filling, therefore, can be linked to the development of the Yellow River. The Sanmen paleolake, a Plio-Pleistocene endorheic mega-lake situated in the Fenwei Basin, was the last catchment basin captured by the Yellow River before it emptied into the sea. The final termination of the lacustrine deposition in the Fenwei Basin can therefore indicate the integration of the Yellow River. Here, we present the results of a detailed magnetostratigraphic and magnetic susceptibility study of a lacustrine-loess section from the southeastern part of the Fenwei Basin (Sanmenxia Subbasin), and aim to (1) explore the sedimentary evolution of the Sanmen paleolake and refine the age of the Sanmen Formation in this area, and (2) investigate the precise timing of the integration of the Yellow River. Our results show that the Sanmenxia Subbasin was occupied by a salty lake between 2.7 and 2.2 Ma, then it gradually changed to an alternation of shallow lake and floodplain environments between 2.2 and 1.6 Ma, and it finally irreversible dried up at similar to 1.6 Ma and was subsequently covered by loesspaleosol sequences. The drying up of the Sanmen paleolake at similar to 1.6 Ma indicated the establishment of the connection between the Middle and Lower Reaches of the Yellow River
Late Quaternary glacial history of the Altyn Tagh Range, northern Tibetan Plateau
No full textQuantifying the timing and extent of late Quaternary glaciations across the Tibetan Plateau (TP) is critical to understanding regional and global climate changes. Despite significant advancements in our knowledge of glacial histories of the TP over the past several decades, chronological constraints are still lacking for the high glaciated mountain ranges on the northern TP, including the Altyn Tagh Range. In this study, we provide thirty-two new Be-10 exposure-ages to construct a late Quaternary glacial history of the Altyn Tagh Range at the Altyn "Pass" and Akato Tagh. The dating results from Altyn "Pass" indicate that glacier might have fully melted out of this area after Marine Isotope Stage 3 (MIS 3). The tentatively-defined minimum moraine ages north of Akato Tagh show that four glacial culminations possibly occurred during MIS 5, MIS 4, MIS 3 or 2, and the late Holocene. These dating results, together with the compiled exposure-ages from Sulamu Tagh, imply that the last glacial glacier fluctuations along the Altyn Tagh Range were likely driven by several factors: North Atlantic climate oscillations, northern hemispheric high-latitude summer solar insolation, atmospheric CO2 concentrations, and geometry of glacier catchment. The progressive reduction in glacier extent during the last glacial is likely associated with available precipitation, controlled by the mid-latitude westerlies