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1.
Sensors (Basel) ; 20(2)2020 Jan 10.
Artigo em Inglês | MEDLINE | ID: mdl-32284500

RESUMO

In order to obtain a better perspective of the impacts of brownfields on the land-atmosphere exchange of mercury in urban areas, total gaseous mercury (TGM) was measured at two heights (1.8 m and 42.7 m) prior to 2011-2012 and after 2015-2016 for the remediation of a brownfield and installation of a parking lot adjacent to the Syracuse Center of Excellence in Syracuse, NY, USA. Prior to brownfield remediation, the annual average TGM concentrations were 1.6 ± 0.6 and 1.4 ± 0.4 ng · m - 3 at the ground and upper heights, respectively. After brownfield remediation, the annual average TGM concentrations decreased by 32% and 22% at the ground and the upper height, respectively. Mercury soil flux measurements during summer after remediation showed net TGM deposition of 1.7 ng · m - 2 · day - 1 suggesting that the site transitioned from a mercury source to a net mercury sink. Measurements from the Atmospheric Mercury Network (AMNet) indicate that there was no regional decrease in TGM concentrations during the study period. This study demonstrates that evasion from mercury-contaminated soil significantly increased local TGM concentrations, which was subsequently mitigated after soil restoration. Considering the large number of brownfields, they may be an important source of mercury emissions source to local urban ecosystems and warrant future study at additional locations.

2.
Ecotoxicol Environ Saf ; 196: 110541, 2020 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-32247960

RESUMO

Urban emissions are a major contributor to atmospheric Hg budgets. Continuous measurements of total gaseous mercury (TGM) and particulate-bound mercury (PHg) in PM2.5 were conducted from October 2015 to July 2016 in a metropolis, Jinan, in eastern China. Average TGM and PHg concentrations were 4.91 ± 3.66 ng m-3 and 451.9 ± 433.4 pg m-3, respectively, in the entire study period. During the winter heating period (HP), mean concentrations of TGM and PHg were 5.79 ng m-3 and 598.7 pg m-3, respectively, twice higher than those during the non-heating periods (NHPs). During the HP, TGM exhibited a distinct diurnal pattern with a peak in the morning and a minimum in the afternoon on less polluted days but a singular peak at midday on heavily polluted days. The diurnal variation of TGM during the NHPs was predominantly influenced by the variation in boundary layer height while during the HP by anthropogenic emissions. The ratio of PHg/PM2.5 in Jinan was one to two orders of magnitude larger than those elsewhere worldwide and those in soil and coal, which suggested the high enrichment of PHg in PM2.5 in Jinan. Correlation and principle component analysis results suggested that PHg and TGM had common combustion sources during the HP, whereas PHg resulted mainly from biomass burning and meteorological variations during the NHPs. High Hg concentrations in Jinan were mostly caused by emissions from coal-fired power plants, especially for those situated east of the sampling site. In addition, TGM and PHg concentrations significantly increased during haze and fog episodes, but decreased during a dust episode due possibly to strong ventilation conditions combined with partitioning of Hg between adsorption to PM2.5 and coarse dust particles.


Assuntos
Poluentes Atmosféricos/análise , Mercúrio/análise , China , Cidades , Carvão Mineral , Poeira , Monitoramento Ambiental , Material Particulado/análise , Centrais Elétricas , Estações do Ano
3.
Chem Commun (Camb) ; 56(10): 1609-1610, 2020 Feb 04.
Artigo em Inglês | MEDLINE | ID: mdl-31960002

RESUMO

Retraction of 'Sublimable cationic Ir(iii) phosphor using chlorine as a counterion for high-performance monochromatic and white OLEDs' by Lei Ding et al., Chem. Commun., 2018, 54, 11761-11764.

4.
Inorg Chem ; 58(20): 13807-13814, 2019 Oct 21.
Artigo em Inglês | MEDLINE | ID: mdl-31580057

RESUMO

Recently, solution-processable PhOLEDs have been attracting great interest for their low cost and high productivity relative to the vacuum-deposited devices. Similar to vacuum-deposited OLEDs, however, they usually suffer from serious efficiency roll-offs, especially in high brightness. Finding a feasible way and/or designing novel materials to increase efficiencies and reduce roll-offs simultaneously are highly desired. Herein, a new family of solution-processable cyclometalated iridium(III) phosphors with carbazole (Cz) and/or diphenylphosphoryl (Ph2PO) units functionalized main ligands has been designed. Owing to Cz and Ph2PO moieties possessing bulky steric effects, they can suppress the intermolecular strong packing and then decrease TTA effects and emission quenching. Meanwhile, the resulting OLEDs based on the designed phosphors exhibit considerable efficiencies and relatively small efficiency roll-offs. The device based on 4 containing both Cz and Ph2PO units realized a maximum current efficiency of 21.3 cd A-1, accompanied by a small roll-off. By optimization of the configuration of OLEDs, the device performance can be further enhanced, demonstrating their potential for high-performance solution-processable PhOLEDs.

5.
Ecotoxicology ; 2019 Oct 04.
Artigo em Inglês | MEDLINE | ID: mdl-31586287

RESUMO

Atmospheric deposition is a major input of mercury (Hg) to aquatic and terrestrial ecosystems. To evaluate Hg pollution mitigation strategies for inland lakes, the two Great Lakes (Ontario and Erie) adjacent to New York State (NYS), and rural land areas of Upstate New York, the relative contributions to atmospheric Hg deposition from anthropogenic emission reductions and meteorological variations were investigated using a regional three-dimensional chemical transport model with detailed Hg and bromine chemistry (CMAQ-newHg-Br). Our simulations suggested that NYS in-state emissions and the Northeastern US emission reductions from 2005 to 2011 did not significantly alter Hg wet and dry deposition in all study areas when averaged over time and space. However, such emission changes significantly altered intensive emission sources (>10 lb/year) with subsequent effects on deposition to nearby water bodies. For the Great Lakes, Hg dry deposition was enhanced by a factor of 2-5 in the adjacent model grids (within distances of ~12 km downwind), and the enhancements decreased to negligible values over ~50 km distances. Over land, anthropogenic emissions contributed 30% of the spatial variation in Hg dry deposition and 46% in ambient concentrations of gaseous oxidized Hg (GOM). Spatial and temporal variations in meteorology and foliar characteristics were found to affect both Hg wet and dry deposition. Convective precipitation significantly contributed to spatial and seasonal variations (~65%) in Hg wet deposition over both lake and land surfaces, whereas wind speed and surface heat flux were the main factors contributing to the spatial variation in Hg dry deposition over the lake surfaces through their impacts on dry deposition velocities of GOM and PBM. Leaf area index, which regulates deposition velocity, contributed 14% of the spatial variation in dry deposition flux over land. Variation in solar radiation, which influences photochemical formation of GOM and PBM, explained ~10% of the spatial variation over lake and land surfaces alike. Findings from our highly focused study suggested broad implications. Future climate change will likely serve to enhance Hg concentrations in biota via increases in Hg dry and wet deposition to varying degrees contingent on land surface type. Hence, liminating the health risks of Hg requires mitigation of both anthropogenic Hg emission hotspots and human-induced climate change.

6.
Artigo em Inglês | MEDLINE | ID: mdl-30626168

RESUMO

Concentrations of PM2.5-bound trace elements have increased in China, with increasing anthropogenic emissions. In this study, long-term measurements of PM2.5-bound trace elements were conducted from January 2014 to January 2015 in the urban city of Jinan, east China. A positive matrix factorization model (PMF) and health risk assessment were used to evaluate the sources and health risks of these elements, respectively. Compared with most Chinese megacities, there were higher levels of arsenic, manganese, lead, chromium, and zinc in this city. Coal combustion, the smelting industry, vehicle emission, and soil dust were identified as the primary sources of all the measured elements. Heating activities during the heating period led to a factor of 1.3⁻2.8 higher concentrations for PM2.5 and all measured elements than those during the non-heating period. Cumulative non-carcinogenic and carcinogenic risks of the toxic elements exceeded the safety levels by 8⁻15 and 10⁻18 times, respectively. Arsenic was the critical element having the greatest health risk. Coal combustion caused the highest risk among the four sources. This work provides scientific data for making targeted policies to control air pollutants and protect human health.


Assuntos
Poluentes Atmosféricos/análise , Material Particulado/toxicidade , População Urbana , China , Cidades , Carvão Mineral/análise , Poeira/análise , Monitoramento Ambiental , Calefação , Humanos , Indústrias , Material Particulado/análise , Fatores de Risco , Estações do Ano , Solo , Oligoelementos/análise , Emissões de Veículos/análise
7.
Chem Commun (Camb) ; 54(83): 11761-11764, 2018 Oct 16.
Artigo em Inglês | MEDLINE | ID: mdl-30276412

RESUMO

Different from the previous design strategy, herein, a cationic Ir(iii) complex ([(ptbi)2Ir(bisq)]Cl) with a small chlorine as the counterion was synthesized, which realized the formation of a solid film via a vacuum-deposition process. The white OLED, employing it as an orange-emitting layer, achieved excellent performances with a brightness of 50 122 cd m-2, a CE of 25.5 cd A-1, an EQE of 13.1%, accompanied by a low CE efficiency roll-off of 4.7%. These are the best results among evaporated cationic Ir(iii)-based white OLEDs reported so far.

8.
Environ Sci Technol ; 52(9): 5125-5134, 2018 05 01.
Artigo em Inglês | MEDLINE | ID: mdl-29630344

RESUMO

Cloud effects on heterogeneous reactions of atmospheric mercury (Hg) are poorly understood due to limited knowledge of cloudwater Hg chemistry. Here we quantified Hg species in cloudwater at the summit of Mt. Tai in northern China. Total mercury (THg) and methylmercury (MeHg) in cloudwater were on average 70.5 and 0.15 ng L-1, respectively, and particulate Hg (PHg) contributed two-thirds of THg. Chemical equilibrium modeling simulations suggested that Hg complexes by dissolved organic matter (DOM) dominated dissolved Hg (DHg) speciation, which was highly pH dependent. Hg concentrations and speciation were altered by cloud processing, during which significant positive correlations of PHg and MeHg with cloud droplet number concentration ( Nd) were observed. Unlike direct contribution to PHg from cloud scavenging of aerosol particles, abiotic DHg methylation was the most likely source of MeHg. Hg adsorption coefficients Kad (5.9-362.7 L g-1) exhibited an inverse-power relationship with cloud residues content. Morphology analyses indicated that compared to mineral particles, fly ash particles could enhance Hg adsorption due to more abundant carbon binding sites on the surface. Severe particulate air pollution in northern China may bring substantial Hg into cloud droplets and impact atmospheric Hg geochemical cycling by aerosol-cloud interactions.


Assuntos
Mercúrio , Compostos de Metilmercúrio , Poluentes Químicos da Água , Adsorção , China , Monitoramento Ambiental
9.
J Environ Manage ; 215: 195-205, 2018 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-29571100

RESUMO

The concentrations of particulate mercury (PHg) and other trace elements in PM2.5 and PM10 in the atmosphere were measured at the summit of Mount Tai during the time period of 15 June - 11 August 2015. The average PHg concentrations were 83.33 ±â€¯119.1 pg/m3 for PM2.5 and 174.92 ±â€¯210.5 pg/m3 for PM10. Average concentrations for other trace elements, including Al, Ca, Fe, K, Mg, Na, Pb, As, Se, Cu, Cd, Cr, V, Mo, Co, Ag, Ba, Mn, Zn and Ni ranged from 0.06 ng/m3 (Ag) to 354.33 ng/m3 (Ca) in PM2.5 and 0.11 ng/m3 (Co) to 592.66 ng/m3 (Ca) in PM10. The average concentrations of PHg were higher than those at other domestic mountain sites and cities in other counties, lower than those at domestic city sites. Other trace elements showed concentrations lower than those at the domestic mountain sites. Due possibly to increased control of emissions and the proportion of new energy, the PHg and trace element concentrations decreased, but the PHg showed concentrations higher than those at the Mountain sites, this showed that the reasons was not only severely affected by anthropogenic emissions, but also associated with other sources. The concentration changed trend of the main trace elements indicated that PHg, trace elements and particle matters present positive correlation and fine particulate matter has a greater surface area which was conductive to adsorption of Hg and trace elements to particles. On June 19, June 27 and July 6, according to the peak of mercury and trace elements, we can predict the potential sources of these three days. The results of principal component analysis (PCA) suggested that, crustal dust, coal combustion, and vehicle emissions were the main emission sources of PHg and other trace elements in Mount Tai. The 24-h backward trajectories and potential source contribution function (PSCF) analysis revealed that air masses arriving at Mount Tai were mainly affected by Shandong province. Mount Tai was subjected to five main airflow trajectories. Clusters 1, 2, 3, and 5 represented four pathways for local and regional sources and cluster 4 originated long-distance transportation. Central Shandong was the main source regions of PHg, Pb, Se, As, Cu and Cd. Southeastern and northwestern Shandong province and northern Jiangsu province were the most polluted source regions of Mn, Zn, and Ni. The crustal elements Fe and Ca had similar distributions of potential source regions, suggested by the highest PSCF values in southeastern Shandong and northern Jiangsu.


Assuntos
Poluentes Atmosféricos/análise , Mercúrio/análise , China , Cidades , Monitoramento Ambiental , Tamanho da Partícula , Material Particulado , Oligoelementos
10.
Inorg Chem ; 56(16): 9979-9987, 2017 Aug 21.
Artigo em Inglês | MEDLINE | ID: mdl-28795817

RESUMO

Nondoped electroluminescent devices offer advantages over their doped counterparts such as good reproducibility, reduced phase separation between host and guest materials, and potential of lower-cost devices. However, low luminance efficiencies and significant roll-off values are longstanding issues for nondoped devices, and a rational design strategy for the preparation of efficient phosphors is highly desired. In this work, cyclometalated Ir(III) complexes 3CzIr(mtpy), 4CzIr(mtpy), 3POIr(mtpy), and 4POIr(mtpy) bearing carbazole (Cz) or diphenylphosphoryl (Ph2PO) groups substituted at different positions of 1,2-diphenyl-H-benzimidazole (HPBI) were designed and synthesized. Owing to the steric effects induced by these groups, a significant intermolecular interaction was avoided, thereby reducing self-quenching and triplet-triplet annihilation (TTA) at high brightness. Simultaneously, attached functional moieties manipulate the charge-carrier character and enhance the EL performance of the complexes. Device N3-10, based on 3POIr(mtpy), successfully realized excellent performance and improved efficiency stability, rendering a turn-on voltage of 2.5 V, a maximum current efficiency of 29.7 cd A-1, and a maximum power efficiency of 31.1 lm W-1, which are all almost 3-fold higher than that of the control device N-10 based on parent complex. Inspiringly, all of the devices showed reduced efficiency roll-off as luminance increased. To the best of our knowledge, these are good results for green-emitting PHOLEDs using vacuum evaporation techniques, and they provide fundamental insights into the future realization of efficient phosphorescent Ir(III) complexes and corresponding nondoped devices.

11.
Sci Total Environ ; 574: 1424-1431, 2017 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-27531466

RESUMO

Measurements of atmospheric particulate mercury (PHg) were conducted at a suburban site in Jinan, China from June 2014 to December 2015. The average PHg concentration was 508.5±402.7pgm-3, and the average Hg content in PM2.5 (particles with a diameter of 2.5µm or less) was 6.60±5.82µgg-1. Both PHg and Hg content in PM2.5 aerosols were comparable to levels in some cities in China and were much higher than in cities in North America and Europe. Weak correlations were found between PHg and meteorological parameters. The correlations between PHg and other pollutants in ambient air, including SO2, CO and NOχ, together with their wind dependence were used for source analysis, which suggested coal-fired industries, cement plants and traffic emissions as potential local sources for the site. Cluster analysis of 36-h backward trajectories suggested that the regional transport from southwestern Shandong Province also contributed to PHg in Jinan.

13.
Environ Sci Technol ; 47(13): 7295-306, 2013 Jul 02.
Artigo em Inglês | MEDLINE | ID: mdl-23305532

RESUMO

From August 22 to September 16, 2012, atmospheric mercury (Hg) was measured from a common manifold in the field during the Reno Atmospheric Mercury Intercomparison eXperiment. Data were collected using Tekran systems, laser induced fluorescence, and evolving new methods. The latter included the University of Washington-Detector for Oxidized Mercury, the University of Houston Mercury instrument, and a filter-based system under development by the University of Nevada-Reno. Good transmission of total Hg was found for the manifold. However, despite application of standard protocols and rigorous quality control, systematic differences in operationally defined forms of Hg were measured by the sampling systems. Concentrations of reactive Hg (RM) measured with new methods were at times 2-to-3-fold higher than that measured by Tekran system. The low RM recovery by the latter can be attributed to lack of collection as the system is currently configured. Concentrations measured by all instruments were influenced by their sampling location in-the-manifold and the instrument analytical configuration. On the basis of collective assessment of the data, we hypothesize that reactions forming RM were occurring in the manifold. Results provide a new framework for improved understanding of the atmospheric chemistry of Hg.


Assuntos
Poluentes Atmosféricos/análise , Mercúrio/análise , Poluentes Atmosféricos/química , Brometos/análise , Monóxido de Carbono/análise , Monitoramento Ambiental/instrumentação , Monitoramento Ambiental/métodos , Mercúrio/química , Compostos de Mercúrio/análise , Nevada , Ozônio/análise
14.
Environ Sci Technol ; 44(1): 222-8, 2010 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-19954179

RESUMO

A study on emissions associated with oversnow travel in Yellowstone National Park (YNP) was conducted for the time period of February 13-16, 2002 and February 12-16, 2003. Whole air and exhaust samples were characterized for 85 volatile organic compounds using gas chromatography. The toxics including benzene, toluene, ethylbenzene, xylenes (p-, m-, and o-xylene), and n-hexane, which are major components of two-stroke engine exhaust, show large enhancements during sampling periods resulting from increased snowmobile traffic. Evaluation of the photochemical history of air masses sampled in YNP revealed that emissions of these air toxics were (i) recent, (ii) persistent throughout the region, and (iii) consistent with the two-stroke engine exhaust sample fingerprints. The annual fluxes were estimated to be 0.35, 1.12, 0.24, 1.45, and 0.36 Gg yr(-1) for benzene, toluene, ethylbenzene, xylenes, and n-hexane, respectively, from snowmobile usage in YNP. These results are comparable to the flux estimates of 0.23, 0.77, 0.17, and 0.70 Gg yr(-1) for benzene, toluene, ethylbenzene, and xylenes, respectively, that were derived on the basis of (i) actual snowmobile counts in the Park and (ii) our ambient measurements conducted in 2003. Extrapolating these results, annual emissions from snowmobiles in the U.S. appear to be significantly higher than the values from the EPA National Emissions Inventory (1999). Snowmobile emissions represent a significant fraction ( approximately 14-21%) of air toxics with respect to EPA estimates of emissions by nonroad vehicles. Further investigation is warranted to more rigorously quantify the difference between our estimates and emission inventories.


Assuntos
Veículos Automotores , Recreação , Emissões de Veículos/toxicidade , Fotoquímica , Wyoming
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