Abundance and sources of particulate polycyclic aromatic hydrocarbons and aromatic acids at an urban site in central China

We conducted a simultaneous field study of PM_(2.5)-bound particulate polycyclic aromatic hydrocarbons(PAHs)and aromatic acids(AAs)in a polluted city Zhengzhou to explore the concentration,sources and potential conversion pathways between PAHs and AAs in different seasons.The average concentrations of PM_(2.5),28PAHs and 8AAs during the sampling period were 77μg/m^(3),75 ng/m^(3),and 283 ng/m^(3),respectively.The concentration of both28PAHs and 8AAs were highest in winter and lowest in summer with ratios of 6.3 and 2.3,respectively.PAHs with 5-7 rings were the main components of PAHs(52%),followed by 4rings PAHs(30%)and 2-3 rings PAHs(18%).According to the source appointment results obtained by positive matrix factorization,the main sources of PAHs were combustion and vehicle emissions,which account for 37%and 34%,respectively.8AAs were divided into three groups,including four benzene dicarboxylic acids(B2CAs),three benzene tricarboxylic acids(B3CAs)and one benzene tetracarboxylic acid(B4CA).And interspecies correlation analysis with PM_(2.5)source markers were used to investigate potential sources.Phthalic acid(o-Ph)was the most abundant specie of 8AAs(157 ng/m^(3),55%of 8AAs),which was well correlated with sulfate.Meanwhile,B3CAs and B4CA were highly correlated with sulfate and weakly correlated with levoglucosan,suggesting that secondary formation was their main source.As logical oxidation products of PAHs,o-Ph and B3CAs showed good correlations with a number of PAHs,indicating possible photochemical oxidation pathway by PAHs.In addition,O_(3),NO_(2),temperature and relative humidity have positive effects on the secondary formation of B3CAs.

Recent development of a refined multiple air pollutant emission inventory of vehicles in the Central Plains of China

Central Plains region of China,represented by Henan Province,is facing serious air pollution problems.Vehicular exhaust emissions had adverse impacts on the atmospheric environment.The first comprehensive and novel vehicle emission inventory for Henan Province using vehicle kilometers traveled,localized emission factors,and activity data at city-level was developed.Furthermore,3 km×3 km gridded emission and temporal variations were determined by using localized information.Results show that the total emissions of sulfur dioxide(SO2),nitrogen oxides(NOx),carbon monoxide(CO),particular matter with aerodynamic diameter<10μm(PM10),aerodynamic diameter<2.5μm(PM2.5),volatile organic compounds(VOCs),VOCs-evaporation and ammonia in 2015 were 9.1,533.4,1190.7,23.7,21.6,150.8,31.5 and 10.4 Gg,respectively,and the emission intensities of the above pollutants were 0.05,2.7,6.0,0.1,0.1,0.8,0.2 and 0.05 g/km,respectively.Vehicles meeting the Primary China 1,China 3 and China 4 contributed 89.1%,82.7%,75.3%,75.5%,75.5%,68.2%,68.4%and 82.3%for SO2,NOx,CO,PM10,PM2.5,VOCs,VOCs-evaporation and ammonia emissions,respectively.Zhengzhou,Zhoukou,Nanyang,Luoyang,Shangqiu and Xinyang showed relatively higher emissions and contributed more than 50%of each pollutant.The spatial distribution indicated obvious characteristics of the road network,and high-level emission was concentrated in the downtown areas.Additionally,the ozone formation potential(OFP)based on the estimated speciated VOC emissions was 569.6 Gg in Henan Province.Aliphatic and aromatic hydrocarbons were the main species of VOCs,whereas olefins contributed the largest proportion of OFP,with 42.2%.

Characteristics,sources and health risks assessment of VOCs in Zhengzhou,China during haze pollution season

Zhengzhou is one of the most haze-polluted cities in Central China with high organic carbon emission,which accounts for 15%-20%of particulate matter(PM_(2.5))in winter and causes significantly adverse health effects.Volatile organic compounds(VOCs)are the precursors of secondary PM_(2.5)and O_(3)formation.An investigation of characteristics,sources and health risks assessment of VOCs was carried out at the urban area of Zhengzhou from 1^(st) to 31^(st) December,2019.The mean concentrations of total detected VOCs were 48.8±23.0 ppbv.Alkanes(22.0±10.4 ppbv),halocarbons(8.1±3.9 ppbv)and aromatics(6.5±3.9 ppbv)were the predominant VOC species,followed by alkenes(5.1±3.3 ppbv),oxygenated VOCs(3.6±1.8 ppbv),alkyne(3.5±1.9,ppbv)and sulfide(0.5±0.9 ppbv).The Positive Matrix Factorization model was used to identify and apportion VOCs sources.Five major sources of VOCs were identified as vehicular exhaust,industrial processes,combustion,fuel evaporation,and solvent use.The carcinogenic and non-carcinogenic risk values of species were calculated.The carcinogenic and non-carcinogenic risks of almost all air toxics increased during haze days.The total non-carcinogenic risks exceeded the acceptable ranges.Most VOC species posed no non-carcinogenic risk during three haze events.The carcinogenic risks of chloroform,1,2-dichloroethane,1,2-dibromoethane,benzyl chloride,hexachloro-1,3-butadiene,benzene and naphthalene were above the acceptable level(1.0×10^(-6))but below the tolerable risk level(1.0×10^(-4)).Industrial emission was the major contributor to non-carcinogenic,and solvent use was the major contributor to carcinogenic risks.

Spatiotemporal characterization and regional contributions of O3 and NO2:An investigation of two years of monitoring data in Henan,China

To investigate the characteristics of ground level ozone(O3)for Henan Province,the ambient air quality monitoring data of 2015 and 2016 were analyzed.The result showed that the 8 h-max-O3 concentrations displayed a distinct seasonality,where the maximum and minimum values,averaging 140.41,54.19μg/m3,occurred in summer and winter,respectively.There is a significant correlation between meteorological factors and O3 concentration.The Voronoi neighborhood averaging analysis indic ated that O3,temperature,and ultraviolet radiation in Henan province were decreased from northwest to southeast,while relative humidity and precipitation displayed the opposite trend.Besides meteorological factors,the chemical processes play an essential role in ozone formation.Reactions of NO,NO2 and O3 form a closed system,and the partitioning point of the OX-component(O3+NO2)was at 40 and 80μg/m3 for nitrogen oxide(NOx)in winter and summer,respectively,with NO2 dominating at higher NOx pollution and O3 being the m ajor component at lower levels.The relationship between oxidant(OX=O3+NO2)and NOx concentrations were evaluated to understand the regional and local contribution of OX.It showed that high regional contribution occurred in the spring,whereas the highest local contribution lead to the summer peak of O3 observed in Zhengzhou.This present study reveals important environment impacts from the photochemical process and the meteorological conditions in the region with better understanding on the O3 characterization.

PM_(2.5) in an industrial district of Zhengzhou,China:Chemical composition and source apportionment

Zhengzhou is a developing city in China, that is heavily polluted by high levels of particulate matter. In this study, fine particulate matter （PM2.5） was collected and analyzed for their chemical composition （soluble ions, elements, elemental carbon （EC） and organic carbon （OC）） in an industrial district of Zhengzhou in 2010. The average concentrations of PM2.5 were 181, 122, 186 and 211 μg/m3 for spring, summer, autumn and winter, respectively, with an annual average of 175 μg/m3, far exceeding the PM2.5 regulation of USA National Air Quality Standards （15 μg/m3）. The dominant components of PM2.5 in Zhengzhou were secondary ions （sulphate and nitrate） and carbon fractions. Soluble ions, total carbon and elements contributed 41%, 13% and 3% of PM2.5 mass, respectively. Soil dust, secondary aerosol and coal combustion, each contributing about 26%, 24% and 23% of total PM2.5 mass, were the major sources of PM2.5, according to the result of positive matrix factorization analysis. A mixed source of biomass burning, oil combustion and incineration contributed 13% of PM2.5. Fine particulate matter arising from vehicles and industry contributed about 10% and 4% of PM2.5, respectively.

Chemical characteristics and source apportionment of PM_(2.5) between heavily polluted days and other days in Zhengzhou, China

PM（2.5） samples were collected in Zhengzhou during 3 years of observation, and chemical characteristics and source contribution were analyzed. Approximately 96% of the daily PM（2.5） concentrations and annual average values exceeded the Chinese National Ambient Air Quality Daily and Annual Standards, indicating serious PM（2.5） pollution. The average concentration of water-soluble inorganic ions was 2.4 times higher in heavily polluted days（daily PM32.5 concentrations ＆gt; 250 μg/mand visibility ＆lt; 3 km） than that in other days, with sulfate, nitrate, and ammonium as major ions. According to the ratio of NO-3/SO2-4,stationary sources are still the dominant source of PM（2.5） and vehicle emission could not be ignored. The ratio of secondary organic carbon to organic carbon indicated that photochemical reactivity in heavily polluted days was more intense than in other days.Crustal elements were the most abundant elements, accounting for more than 60% of 23 elements. Chemical Mass Balance results indicated that the contributions of major sources（i.e., nitrate, sulfate, biomass, carbon and refractory material, coal combustion, soil dust,vehicle, and industry） of PM（2.5） were 13%, 16%, 12%, 2%, 14%, 8%, 7%, and 8% in heavily polluted days and 20%, 18%, 9%, 2%, 27%, 14%, 15%, and 9% in other days, respectively.Extensive combustion activities were the main sources of polycyclic aromatic hydrocarbons during the episode（Jan 1-9, 2015） and the total benzo[a]pyrene equivalency concentrations in heavily polluted days present significant health threat. Because of the effect of regional transport, the pollution level of PM（2.5） in the study area was aggravated.

Development of a PDRA Method for Detection of the D614G Mutation in COVID-19 Virus—Worldwide,2021

ABSTRACT Background:COVID-19 infection is a major public health problem worldwide,and the D614G mutation enhances the infectivity of COVID-19.Methods:A probe-directed recombinase amplification(PDRA)assay was discussed to detect the D614G mutation at 39℃for 30 min.The sensitivity,specificity,and reproducibility of the PDRA were evaluated by D614 and G614 recombinant plasmids.The clinical performance of PDRA assay was validated by testing of 53 previously confirmed COVID-19 positive RNAs and 10 negative samples.Direct sequencing was carried out in parallel for comparison.Result:With good reproducibility and specificity,the PDRA assay worked well with the concentration in the range of 103–107 copies/reaction.Compared with direct sequencing as a reference,the recombinase-aided amplification(RAA)assay obtained 100%sensitivity and 100%specificity using clinical samples.

Dual response of graphene-based ultra-small molecular junctions to defect engineering

It has been reported that N and B doping induce a quasi-bound state that suppresses the conduction in graphene nanoribbon （GNR）-based junctions, while an H defect or a pyridine-like N-atom （PN） substitution at the edge of the GNR does not affect the transmission close to the Fermi energy. However, these results may vary when the size of the functional unit of the GNR junction decreases to a molecular level. In this study, a defect is introduced to a test-bed architecture consisting of a polyacene bridging two zigzag GNR electrodes, which changes the molecular state alignment and coupling to the electrode states, and varies the equivalence between two eigen-channels at the Fermi level. It is revealed that B and N atom substitution, and H defects play a dual role in the molecular conductance, whereas the PN substitution acts as an ineffective dopant. The results obtained from density functional theory combined with the non-equilibrium Green＇s function method aid in determining the optimal design for the GNR-based ultra-small molecular devices via defect engineering.

Selective electrophilic di- and monofluorinations for the synthesis of 4-difluoromethyl and 4-fluoromethyl quinazolin(thi)ones by a Selectfluor-triggered multi-component reaction

A simple and efficient domino protocol for the selective synthesis of 4-difluoromethyl and 4-fluoromethylquinazolin(thi)ones was established from readily available 2-aminoacetophenones and iso(thio)cyanatesmediated by Selectfluor. The reaction outcomes are restricted by the reaction environment. Without theuse of a base, gem-difluoro-oxylated quinazolin(thi)ones were afforded effectively as a sole product. Incontrast, only monofluoro-oxylated analogues were obtained under basic conditions.

Remarkable Thermal Contraction in Small Size Single-Walled Boron Nanotubes

Density functional theory combined with the Gr¨uneisen approximation is used to calculate the thermal properties of single-walled boron nanotubes(BNTs).The specific heat and thermal expansion are investigated.The thermal expansion coeffi-cient of the BNT is found to be significantly correlated with tube size and chirality.A remarkable thermal contraction is found at small tube diameters.These results indicate that BNTs would have potential applications in sensors,actuators,and memory materials.