Dominant Chemical Species Research Articles

Trivalent lanthanide sorption onto illite in the presence of carbonate: A study combining thermodynamic sorption modeling, time-resolved laser fluorescence spectroscopy, and parallel factor analysis

Formation of aqueous actinide complexes with dissolved inorganic carbon (DIC) in groundwater decreases the sorption of actinides onto clay minerals in a geological disposal environment. Hence, the effect of DIC on actinide sorption must be evaluated quantitatively. In this study, batch sorption experiments using Eu(III) and Sm(III) as the chemical analogs of trivalent actinides were performed to assess their sorption behavior onto illite in the presence of DIC. In the studied pH region between 8.4 and 11, the sorption was significantly lower in the presence of DIC, with the largest effect being observed at pH 9–10. The effect increased with increasing DIC from 10 to 50 mM. A thermodynamic sorption model (TSM) was used to evaluate the results of batch sorption experiments. The experimental results can only be predicted when ternary-surface complexes with carbonate ions are considered. Moreover, information on the chemical forms of sorbed Eu on illite was obtained via time-resolved laser fluorescence spectroscopy (TRLFS) measurements. Parallel factor analysis of TRLFS data indicated the presence of two chemical species of Eu. These chemical species exhibited pH dependence, which is consistent with that of the surface species predicted using the TSM. In the presence of DIC, the dominant chemical species showed a long fluorescence lifetime and was inferred to coordinate with carbonate ions, supporting the validity of the TSM.

Anthropogenic pollutants induce enhancement of aerosol acidity at a mountainous background atmosphere in southern China

Aerosol acidity plays a crucial role in atmospheric physicochemical processes, climate change and human health, particularly in the formation of secondary organic aerosols (SOA). However, understanding the characteristics and driving factors of aerosol acidity in background mountains has been limited. In this study, we conducted intensive field measurements in the Nanling mountains during the dry and wet seasons to analyze aerosol pH characteristics and their driving factors using sensitivity tests. The mean aerosol pH in the background mountains was found to be 2.68 ± 0.55, with values ranging from 0.38 to 4.44, significantly lower than predicted values in northern China. Sensitivity tests revealed that aerosol acidity in the background atmosphere was more responsive to dominant chemical species (T-NH3 (= NH4+ + NH3) and SO42−) rather than relative humidity and temperature. Additionally, we observed that sulfate and ammonium, transported occasionally by dryer northern air masses, had a substantial impact on decreasing aerosol pH at the site. Similar to the southeastern United States, NH4+/NH3 also dominated the total buffer capacity of aerosol acidity in the Nanling mountains. The strong aerosol acidity in this area is expected to have adverse effects on regional air quality and climate by enhancing SOA formation and regulating the dry deposition of inorganic reactive nitrogen.

Competitive formation of NO, NO2, and O3 in an air-flowing plasma reactor: A central role of the flow rate

Beyond ozone (O3) generation, diverse applications of dielectric barrier discharge (DBD) have been developed. When using ambient air, one of the longstanding challenges of DBD reactors has been the selective production of nitric oxide (NO), nitrogen dioxide (NO2), and O3. In this work, we report the competitive formation of NO, NO2, and O3 in an air-flowing surface DBD reactor. The temporal evolution of each chemical species was obtained by using in situ optical absorption spectroscopy. The possibility to select the plasma-chemistry mode (i.e., NO–, NO2–, or O3-dominant conditions) by adjusting the gas flow rate of the reactor was demonstrated with constant temperature and input power. As the flow rate increased from 260 to 1380 standard cubic centimeters per minute, the dominant chemical species changed from NO to NO2 [the achieved purity of NO2/(NO + NO2 + O3) was 99%]. With even higher flow rates, O3 appeared and dominated in the reactor [O3/(NO + NO2 + O3) was nearly 100%]. The experimental results were compared with zero-dimensional modeling, and the reactions involving NO, NO2, and O3 were analyzed in depth. Our findings will provide great guidance for future studies and for plasma applications of DBD reactors.

Assessing the impacts of CPM emitted from stationary sources on PM2.5 source appointment of Wuhan, China

The condensable particulate matter (CPM) emissions from stationary sources have attracted widespread attentions due to its negative environmental impacts. In this study, we collected some CPM samples from fourteen different stationary sources in Wuhan based on the US EPA Method 202 for investigating emission factors (EFs) and source profiles of the CPM, as well as its impact on source apportionment of PM2.5 (particulate matter with aerodynamic diameters ≤ 2.5 µm). The CPM mass concentrations and chemical components including water-soluble ions, elements and organic fractions in the CPM were explicitly analyzed. Our results revealed that the emission level of CPM was 0.8 to 14 times that of filterable particulate matter (FPM). The EF of CPM from coal-fired power plant was 168.91 g/t of coal, that was about 1–28 times higher than other stationary sources tested in this study. Alkanes (4 %–35 %), esters (9 %–46 %), and water-soluble ions (24 %–64 %) were dominant chemical species in the CPM, which significantly differed from that of the FPM. As such, we built a new emission inventory that included CPM and applied it to the chemical mass balance (CMB) model for source apportionment of PM2.5. The results showed that the contribution of stationary sources to PM2.5 increased from 17 % to 23 %, while the contribution of vehicle sources to PM2.5 decreased from 16 % to 11 % when considering the impact of CPM. In addition, isotope values of δ13C and δ15N in the CPM were measured to apportion the sources of carbon and nitrogen in aerosols. We found that the contributions of vehicle sources to carbon and nitrogen components in PM2.5 decreased by 3 % to 5 %, contribution of coal combustion sources increased by 6 % to 8 %, when considering the impact of CPM. Therefore, it is necessary to update emission inventory by including the CPM in further research for a greater accuracy of the source apportionment of PM2.5. This study has important implications for achieving improved air quality management via emission mitigation of CPM from stationary sources at the local, regional, and national scales.

LES/FGM investigation of ignition and flame structure in a gasoline partially premixed combustion engine

This paper presents a joint numerical and experimental study of the ignition process and flame structures in a gasoline partially premixed combustion (PPC) engine. The numerical simulation is based on a five-dimension Flamelet-Generated Manifold (5D-FGM) tabulation approach and large eddy simulation (LES). The spray and combustion process in an optical PPC engine fueled with a primary reference fuel (70% iso-octane, 30% n-heptane by volume) are investigated using the combustion model along with laser diagnostic experiments. Different combustion modes, as well as the dominant chemical species and elementary reactions involved in the PPC engines, are identified and visualized using Chemical Explosive Mode Analysis (CEMA). The results from the LES-FGM model agree well with the experiments regarding the onset of ignition, peak heat release rate and in-cylinder pressure. The LES-FGM model performs even better than a finite-rate chemistry model that integrates the full-set of chemical kinetic mechanism in the simulation, given that the FGM model is computationally more efficient. The results show that the ignition mode plays a dominant role in the entire combustion process. The diffusion flame mode is identified in a thin layer between the ultra fuel-lean unburned mixture and the hot burned gas region that contains combustion intermediates such as CO. The diffusion flame mode contributes to a maximum of 27% of the total heat release in the later stage of combustion, and it becomes vital for the oxidation of relatively fuel-lean mixtures.

Applying synchrotron radiation-based attenuated total reflection-Fourier transform infrared to evaluate the effects of shipping emissions on fluctuations of PM10-bound organic functional groups and ionic species

The intense light of synchrotron radiation, with the assistance of infrared spectroscopy, allows for the measurement of extremely low levels of organic functional groups. In this study, PM10 samples (n = 84) were collected at three air quality observatory sites strategically situated on the periphery of the seaport, residential zone, and industrial area of Laem Chabang, Thailand from May 27 to June 23, 2020. Aliphatic carbons, carbonyl species, organo-nitrates, aromatic nitro compounds, ammonium ions, carbonate, nitrate ions, sulfate species, and calcium carbonate were successfully characterised in all PM10 samples. Sulfate and aliphatic carbons were the two dominant chemical species detected at all monitoring sites. Sulfate and bisulfate ions were two major ionic species with the percentage contribution of 64%, 74% and 46% to the port area, the urban background and the industrial area, respectively. Aliphatic carbons were the most abundant organic functional groups, contributing 27% and 15% to the industrial area and the port area, respectively. While aliphatic carbons, organo-nitrates, and aromatic nitro compounds were closely related to shipping activities, sea salt aerosols and fertiliser dust can be considered as two potential sources of sulfate and ammonium, respectively.

The toxicokinetic of arsenic in the edible and non-edible tissues of freshwater shellfish

Although the chemical speciation and distribution characteristics of arsenic in freshwater shellfish have been adequately studied, little is known about the differences in arsenic speciation and bioaccumulation in the edible and non-edible tissues. In this study, we collected Parafossarulus eximius from the Xiang River, which is heavily polluted by mining activities in China. The levels of arsenic species in the shellfish specimens were determined using HPLC-ICP-MS. The average concentration of total arsenic (tAs) in the muscle of dried shellfish was 9.934 ± 7.173 mg ⋅ kg −1 . As(V) and arsenobetaine were the dominant chemical species in the collected samples. Correlations analysis showed that As concentration in sediments directly affects the As concentration in shellfish, especially the non-edible part. A significant correlation between As(III) and As(V) in the edible and the non-edible parts was observed, suggesting a mutual transformation between the two species. Further results from the correlation analysis indicated that when the intake of inorganic arsenic (iAs) by shellfish was high, the biological transformation process from iAs to AsB reached a saturation. The chronic health risk for consumers from P. eximius was not observed. Whereas, continuous consumption would pose considerably carcinogenic risk. • Shellfish from the Xiang River was heavily polluted by mining activities. • As(V) and AsB were the dominant chemical species. • As concentration in sediments directly affects the As concentration in shellfish. • The biological transformation of iAs to AsB has a threshold value. • Continuous consumption of P. eximius would pose considerably to local consumers.

Source profiles and emission factors of organic and inorganic species in fine particles emitted from the ultra-low emission power plant and typical industries

Accurate source markers, source profiles and species-based emission factors (EFs) are currently the key limitations for source apportionment and emission inventory researches. Fine particles (PM2.5) were collected from stack gases of eight types of stationary sources with a dilution sampling system. The mass percentages and EFs of 89 kinds of chemical species in PM2.5 including water-soluble ions, elements, carbonaceous species and molecular organic species were obtained. Results showed that water-soluble ions (8%–54%) and elements (5%–45%) were the dominant chemical species. Palmitic acid (0.19%–0.62%) and stearic acid (0.21%–0.59%) were the most abundant organic species. PM2.5 source profiles of the eight sources were different from each other with the coefficient of divergence values all higher than 0.4. The addition of organic species could help to further distinguish them. The indicatory chemical components and specific species ratios were obtained by both a statistical equation and randomForest. These indicatory chemical components (e.g. F− for glass factory) and species ratios (e.g. K+/Mg2+ & OC/Mg for pharmaceutical factory) improved the current knowledges of their indicatory performance in source identification of ambient PM2.5. The EFs of PM2.5 from the eight stationary sources ranged from 0.019 to 51.6 kg t−1 of fuel used. The EFs of PM2.5 from the pharmaceutical factory were about 70–2600 times higher than other seven types of sources due to the lack of dust-removing devices. Certain EFs measured in this study were about 10–36,000 times lower than corresponding EFs estimated in previous studies which didn't perform field measurements, indicating the necessity for improving emission inventories continuously. This study contributes to identifying emission sources of PM2.5 especially for subtypes of stationary sources and to establishing species-based emission inventories.

PM1 chemical composition and light absorption properties in urban and rural areas within Sichuan Basin, southwest China.

Sichuan Basin is encircled by high mountains and plateaus with the heights ranging from 1km to 3km, and is one of the most polluted regions in China. However, the dominant chemical species and light absorption properties of aerosol particles is still not clear in rural areas. Chemical composition in PM1 (airborne particulate matter with an aerodynamic diameter less than 1μm) and light-absorbing properties were determined in Chengdu (urban) and Sanbacun (rural) in western Sichuan Basin (WSB), Southwest China. Carbonaceous aerosols and secondary inorganic ions (NH4+, NO3- and SO42-) dominate PM1 pollution, contributing more than 85% to PM1 mass at WSB. The mean concentrations of organic and elemental carbon (OC, EC), K+ and Cl- are 19.69μgm-3, 8.00μgm-3, 1.32μgm-3, 1.16μgm-3 at the rural site, which are 26.2%, 65.3%, 34.7% and 48.7% higher than those at the urban site, respectively. BrC (brown carbon) light absorption coefficient at 405nm is 63.90±27.81Mm-1 at the rural site, contributing more than half of total absorption, which is about five times higher than that at urban site (10.43±4.74Mm-1). Compared with secondary OC, rural BrC light absorption more depends on primary OC from biomass and coal burning. The rural MAEBrC (BrC mass absorption efficiency) at 405nm ranges from 0.6 to 5.1m2g-1 with mean value of 3.5±0.8m2g-1, which is about three times higher than the urban site.

Evaluation of the IMPROVE formulas based on Mie model in the calculation of particle scattering coefficient in an urban atmosphere

To assess the uncertainties in particle scattering coefficient (bsp) estimated from using the original and revised IMPROVE formulas, particle mass size distribution, bulk PM2.5 and PM10 and their major chemical compositions, and bsp under dry condition were synchronously measured in urban Guangzhou during 2015–2016. The estimated bsp, mass concentrations (Cm), and mass scattering efficiencies (MSEs) of the dominant chemical species in the fine, condensation and droplet modes were compared between those calculated using the original and revised IMPROVE formulas and the Mie model. On annual average, the reconstructed bsp using the original IMPROVE formula, the revised IMPROVE formula, and the Mie model explained 81%, 91%, and 98% of the measured bsp at 550 nm, respectively. The better performance of the Mie model than the original and revised IMPROVE formula in the reconstructed bsp was mainly due to the inclusion of the unidentified chemical species which explained 14% of the measured bsp at 550 nm. The estimated percentage contributions of the dominant chemical species to the measured bsp differed by < 3% in most cases, except for (NH4)2SO4 between the Mie model and the revised IMPROVE formula (6%). By including the unidentified chemical species in the revised IMPROVE formula can best reconstructed bsp to within 5% of the measured value.

Impact of particle number and mass size distributions of major chemical components on particle mass scattering efficiency in urban Guangzhou in southern China

Abstract. To grasp the key factors affecting particle mass scattering efficiency (MSE), particle mass and number size distribution, PM2.5 and PM10 and their major chemical compositions, and the particle scattering coefficient (bsp) under dry conditions were measured at an urban site in Guangzhou, southern China, during 2015–2016. On an annual average, 10±2 %, 48±7 % and 42±8 % of PM10 mass were in the condensation, droplet and coarse modes, respectively, with mass mean aerodynamic diameters (MMADs) of 0.78±0.07 in the droplet mode and 4.57±0.42 µm in the coarse mode. The identified chemical species mass concentrations can explain 79±3 %, 82±6 % and 57±6 % of the total particle mass in the condensation, droplet and coarse mode, respectively. Organic matter (OM) and elemental carbon (EC) in the condensation mode, OM, (NH4)2SO4, NH4NO3, and crustal element oxides in the droplet mode, and crustal element oxides, OM, and CaSO4 in the coarse mode, were the dominant chemical species in their respective modes. The measured bsp can be reconstructed to the level of 91±10 % using Mie theory with input of the estimated chemically resolved number concentrations of NaCl, NaNO3, Na2SO4, NH4NO3, (NH4)2SO4, K2SO4, CaSO4, Ca(NO3)2, OM, EC, crustal element oxides and unidentified fraction. MSEs of particle and individual chemical species were underestimated by less than 13 % in any season based on the estimated bsp and chemical species mass concentrations. Seasonal average MSEs varied in the range of 3.5±0.1 to 3.9±0.2 m2 g−1 for fine particles (aerodynamic diameter smaller than 2.1 µm), which was mainly caused by seasonal variations in the mass fractions and MSEs of the dominant chemical species (OM, NH4NO3, (NH4)2SO4) in the droplet mode. MSEs of the dominant chemical species were determined by their lognormal size-distribution parameters, including MMADs and standard deviation (σ) in the droplet mode.

Investigation on the formation process of metal atomic filament for metal sulfide atomic switches by electrical measurement

We have studied the formation process of the metal atomic filament for metal sulfide atomic switches by electrical measurement. The switching between ON and OFF states of the atomic switch is controlled by the application of the bias voltage for the atomic switches. The SET (OFF → ON) and RESET (ON → OFF) voltages were investigated for the atomic switch where the Ag2S or Cu2S layer were sandwiched between the Pt and Ag or Cu electrodes. The SET and RESET voltages of the Ag/Cu2S/Pt and Cu/Ag2S/Pt were close to those of the Ag/Ag2S/Pt atomic switch, and different from those of the Cu/Cu2S/Pt atomic switch. These results indicated that the dominant chemical species of the making and breaking part of the metal filament was Ag, and that the source of the metal filament was both the sulfide layer and the metal electrode.

Deposition Mapping of Polycyclic Aromatic Compounds in the Oil Sands Region of Alberta, Canada and Linkages to Ecosystem Impacts.

This study produced gridded deposition estimates of polycyclic aromatic compounds (PACs), including 17 polycyclic aromatic hydrocarbons (PAHs), 21 alkylated PAHs (alk-PAHs), and 5 dibenzothiophenes (DBTs), over the oil sands region of Alberta, Canada and surrounding communities. Gridded annual total deposition of PACs in 2011 ranged from 55 to 175 000 μg m-2 yr-1 and the mean and median fluxes were 1700 and 760 μg m-2 yr-1, respectively. The domain-wide mean dry and wet deposition were 600 and 1100 μg m-2 yr-1. PAHs, alk-PAHs and DBTs contributed 19%, 74%, and 7% to the total dry deposition, and 42%, 49%, and 9% to the total wet deposition. Dominant chemical species contributing to total deposition were naphthalene, retene and phenanthrene for PAHs and C2-benz[a]anthracene/triphenylene/chrysene, C2-fluoranthene/pyrene and C2-fluorene for alk-PAHs. The highest PAC deposition was found over the surface mineable area, which received 9 times the deposition flux of outlying areas. Additional deposition hotspots were also observed south of the surface mineable area notably over in situ bitumen production sites. The deposition of alk-PAHs impacted a more extensive area than that of PAHs or DBTs. This result suggests that atmospheric deposition is a key process in wildlife exposure to PACs across the region.

Comet 29P/Schwassmann-Wachmann 1 dust environment from photometric observation at the SOAR Telescope

We report photometric observations of comet 29P/Schwassmann-Wachmann 1 made on August 12, 2016 with the broad-band B, V, R and I filters and the SOAR 4.1-meter telescope (Chile). We find the comet active at that time. Enhanced images obtained in all filters reveal three radial features in the 29P/Schwassmann-Wachmann 1 coma, regardless of the image-processing algorithm. Using a high-resolution spectrum of comet 29P/Schwassmann-Wachmann 1 reported by Ivanova et al. (2018) on the same date, we estimate the relative contribution of the gaseous emission and the continuum to the total response measured with our broadband B and V filters. The gaseous-emission contribution appears to be very small, 2.5%. We compute the dust production Afρ in 29P/Schwassmann-Wachmann 1 for the four filters and find its growth with the wavelength, from 3,393 ± 93 cm in the B filter to 8,561 ± 236 cm in the I filter. We model the color slope of dust in Comet 29P/Schwassmann-Wachmann 1 using agglomerated debris particles. Simultaneous analysis of the color slope in the B–R and R–I pairs suggests a single dominant chemical species of 29P/Schwassmann-Wachmann 1 dust particles consisting of Fe–Mg silicates and obeying a power-law size distribution with index n ≈ 2.55. This conclusion is consistent with the previous thermal-emission study of 29P/Schwassmann-Wachmann 1.

Interplay among ozone and nitrogen oxides in air plasmas: Rapid change in plasma chemistry

Air is obligatorily used as a supply gas in most of the plasma-aided processing (e.g., plasma-catalysis) systems because it is the most cost-effective approach, but the simultaneous production of gaseous ozone and nitrogen oxides is an unavoidable issue. Consequently, facilitating the separate production of ozone and nitrogen oxides is the primary requirement for achieving the desired plasma performance for specific purposes, yet it is poorly studied. Here, we report the chemical interplay among ozone and nitrogen oxides (i.e., NO, NO2, NO3, N2O4, N2O5) in air-based plasmas using surface dielectric barrier discharge (DBD) actuators as a reference plasma. A gas-tight chamber containing a DBD apparatus was designed for in-situ optical absorption spectroscopy to measure the concentrations of the chemicals. The temporal evolution of each chemical was successfully observed, and a rapid change in the plasma-chemistry mode (i.e., O3- to NO2-dominant mode) was clearly demonstrated. As a control parameter, the gas temperature, which ranged from 25 °C to 250 °C, was set in separate experiments. As the gas temperature was increased, ozone decomposed faster, while NO2 became a dominant chemical species in the reactor earlier. All experimental results were compared with zero-dimensional modeling results, and the interplay among ozone and nitrogen oxides in air plasma was qualitatively analyzed. The gas temperature, which can be influenced by ohmic heating of the plasma itself, convective cooling from external or internal gas flow, or external settings, should be carefully considered for future study and commercialization.

Influence of city municipal waste disposal on groundwater quality and assessment of groundwater suitability in agriculture

This study focuses on the impact of the disposal of Tirunelveli city municipal waste in the quality of groundwater in Ramayanpatti village where the waste is disposed; the study also assesses the quality of the groundwater suitability in irrigation in the disposed region. Tirunelveli city generates municipal waste of nearly 15 MLD of domestic wastewater and 100 tons of solid waste in a day. The domestic wastewater is treated by waste stabilization pond. The solid waste is dumped in the open yard. These two disposal sites are located in the Ramayanpatti area and their boundaries are at a distance of 500m from each other. Ground water resources are extracted in use for agriculture in the area of Ramayanpatti. Around thirty, locations have been identified in the Ramayanpatti area for sampling, based on the contour and flow direction. The dominant chemical cation species in the majority of the groundwater samples are in the order of Na&gt;Ca&gt;Mg&gt;K and anion species are in the order of HCO3&gt;Cl&gt;SO4&gt;NO3. Gibbs plot shows that the region is dominated by evaporation and dilution phenomenon. Rhode’s plot shows that there is no reduction in the rate of infiltration of soil in the Ramayanpatti region. Dendrogram shows that the leachates infiltration is predominant in the winter season. The study shows that the groundwater quality, nearer and to the southeastern side of the disposal sites are most affected and contaminated by solid waste leachates. The inference with various irrigation plots show that the quality of groundwater in the southeastern region is doubtful for use in irrigation and the groundwater needs to be assessed in order to use in irrigation for agriculture.

Chemical Explosive Mode Analysis for a Jet-in-Hot-Coflow burner operating in MILD combustion

Large Eddy Simulations (LES) of Moderate and Intense Low oxygen Dilution (MILD) combustion of a Jet-in-Hot-Coflow (JHC) burner were performed using detailed chemistry. On the contrary to traditional flames, where heat release is occurring in very thin fronts, MILD combustion occurs in the distributed reaction regime where the reaction zone is broad, thus, this paper applies a direct Arrhenius closure with detailed chemistry to resolve important details of the fuel oxidation reactions. Comparisons of LES results are in good agreement with experiments, demonstrating that the simulations capture the intermediate species and finite reaction rate effects. A Chemical Explosive Mode Analysis (CEMA) was used to determine the flame structure and to detect the pre- and post-ignition regions, including the contributions to the CEMs analyzing the Explosion Index (EI) and Participation Index (PI). To the best of our knowledge, a detailed study of CEMA on MILD or flameless regime has never been reported. The flame structure was clearly visualized with CEMA, as well as the lean and the rich flame fronts. Different flame zones close to the anchoring points of these turbulent lifted flames were selected and the analysis demonstrates the contributions of dominant chemical species, such as HO2 and O. The reactions related to the dominant local CEM were obtained to highlight the nature of the stabilization in these highly diluted operating conditions.

An analysis of chemical and meteorological characteristics of haze events in the Seoul metropolitan area during January 12–18, 2013

The chemical characteristics of secondary inorganic and carbonaceous aerosols as well as their formation mechanisms during the haze event of January 12–18, 2013, in the Seoul Metropolitan Area (SMA) were investigated using measurements at the Baengnyeong and Seoul supersites with data available from LIDAR, meteorology, and modeling. An extraordinary haze event that occurred in northern China during that period extended to the Korean Peninsula and initiated the haze event in the SMA. Local emissions of primary aerosol and gaseous precursors in the SMA then made the situation worse under adverse meteorological conditions.OM (Organic Matter) and SO42− were the major long-range transport (LRT) aerosols from the Beijing, Tianjin and Hebei province (BTH) area to the SMA during the initial stage of the haze event. The LRT of SO42− from the BTH area, which was detected at Baengnyeong Island, was mostly acidic, while in Seoul, it was fully neutralized to (NH4)2SO4.The SIAs (Secondary Inorganic Aerosols) consisting of 56.5% PM2.5 during the haze period were the major chemical species causing haze problems in the SMA. NO3− was the most dominant chemical species among the SIAs and was locally formed by a heavy burden of NOx emissions from mobile sources in the SMA. Carbonaceous aerosols of OM and EC (Elemental Carbon) in the SMA during the haze period consisted of 18.9% PM2.5, but secondary organic carbon (SOC) was not the key species inducing the haze event during the January episode in the SMA.

Valid evaluation of volatile flavor composition of fresh and dehydrated Tuber indicum with different drying methods

ABSTRACTThe effects of three drying methods on volatile flavor components of Tuber indicum were studied. After hot air drying (AD), vacuum drying (VD), and vacuum-freeze drying (FD), flavor components were analyzed by headspace solid phase microextraction GC-MS and electronic nose (E-nose). The results from GC-MS showed that aldehydes (54.8%) and alcohols (31.4%) are the two dominant chemical species in fresh T. indicum and eight carbon (C8) compounds including 1-octen-3-ol, 3-octanol, n-octanol, 3-octanone. After dehydrating, C8 compounds, aldehyde, and ester components reduced, while alkanes, heterocyclic, and sulfur components were produced. Multivariate statistical analysis of the GC-MS revealed the components responsible for the chemical differences between fresh and three drying samples. In addition, E-nose could discriminate fresh and three drying samples. The result obtained by E-nose showed good identity compared with GC–MS. Therefore, FD was the optimal dehydrating method to preserve Tuberaceae with the most retained fresh flavor.

Estimates of greenhouse gas and black carbon emissions from a major Australian wildfire with high spatiotemporal resolution

AbstractEstimates of greenhouse gases and particulate emissions are made with a high spatiotemporal resolution from the Kilmore East fire in Victoria, Australia, which burnt approximately 100,000 ha over a 12 h period. Altogether, 10,175 Gigagrams (Gg) of CO2 equivalent (CO2‐e) emissions occurred, with CO2 (∼68%) being the dominant chemical species emitted followed by CH4 (∼17%) and black carbon (BC) (∼15%). About 63% of total CO2‐e emissions were estimated to be from coarse woody debris, 22% were from surface fuels, 7% from bark, 6% from elevated fuels, and less than 2% from tree crown consumption. To assess the quality of our emissions estimates, we compared our results with previous estimates which used the Global Fire Emissions Database version 3.1 (GFEDv3.1) and the Fire INventory from the National Center for Atmospheric Research version 1.0 (FINNv1), as well as Australia's National Inventory System (and its revision). The uncertainty in emission estimates was addressed using truncated Monte Carlo analysis, which derived a probability density function for total emissions from the uncertainties in each input. The distribution of emission estimates from Monte Carlo analysis was lognormal with a mean of 10,355 Gigagrams (Gg) and a ±1 standard deviation (σ) uncertainty range of 7260–13,450 Gg. Results were in good agreement with the global data sets (when using the same burnt area), although they predicted lower total emissions by 15–37% due to underestimating fuel consumed. Emissions estimates can be improved by obtaining better estimates of fuel consumed and BC emission factors. Overall, this study presents a methodological template for high‐resolution emissions accounting and its uncertainty, enabling a step toward process‐based emissions accounting to be achieved.