Secondary aerosol formation from atmospheric reactions of aliphatic amines

Although aliphatic amines have been detected in both urban and rural atmospheric aerosols, little is known about the chemistry leading to particle formation or the potential aerosol yields from reactions of gas-phase amines. We present here the first systematic study of aerosol formation from the atmospheric reactions of amines. Based on laboratory chamber experiments and theoretical calculations, we evaluate aerosol formation from reaction of OH, ozone, and nitric acid with trimethylamine, methylamine, triethylamine, diethylamine, ethylamine, and ethanolamine. Entropies of formation for alkylammonium nitrate salts are estimated by molecular dynamics calculations enabling us to estimate equilibrium constants for the reactions of amines with nitric acid. Though subject to significant uncertainty, the calculated dissociation equilibrium constant for diethylammonium nitrate is found to be sufficiently small to allow for its atmospheric formation, even in the presence of ammonia which competes for available nitric acid. Experimental chamber studies indicate that the dissociation equilibrium constant for triethylammonium nitrate is of the same order of magnitude as that for ammonium nitrate. All amines studied form aerosol when photooxidized in the presence of NOx with the majority of the aerosol mass present at the peak of aerosol growth consisting of aminium (R3NH+) nitrate salts, which repartition back to the gas phase as the parent amine is consumed. Only the two tertiary amines studied, trimethylamine and triethylamine, are found to form significant non-salt organic aerosol when oxidized by OH or ozone; calculated organic mass yields for the experiments conducted are similar for ozonolysis (15% and 5% respectively) and photooxidation (23% and 8% respectively). The non-salt organic aerosol formed appears to be more stable than the nitrate salts and does not quickly repartition back to the gas phase

Intestinal parasites from public and private latrines and the harbour canal in Roman Period Ephesus, Turkey (1st c. BCE to 6th c. CE)

To improve our knowledge of the parasite species affecting the inhabitants of Roman period Asia Minor, we analysed faecal material from Ephesus, Turkey. Mineralised material from the drain from a private house latrine (3rd c. CE), sediment samples from the sewer drain of a public communal latrine (6th c. CE), and sediment from the harbour canal (ca. 1st c. BCE to ca. 6th c. CE) were studied for the presence of intestinal parasites. Samples were viewed by light microscopy for helminth eggs, and commercial enzyme-linked immunosorbent assay (ELISA) kits were used to test for protozoal parasites that cause dysentery. Eggs of roundworm were found in the public latrine, whipworm in the house latrine, and both whipworm and roundworm in the harbour canal. Sequential sampling of the harbour core suggests that whipworm was by far the most common parasite throughout the Roman period, and there was no clear evidence for change in parasite species over the centuries. Whipworm and roundworm are both spread by the contamination of food and drink by human faeces. Despite the large number of travellers to Ephesus, as the capital of its province and a major port city in the Roman Empire, there was a surprising lack of diversity in parasite species found. This is especially apparent when we consider that ten species of intestinal parasite have been found across the Roman Empire. This is the first Roman site to be directly assessed for differences between infection in individuals using private latrines, public latrines, and mixed town effluent (in the harbour) at the same site.This research was supported by a doctoral award from the Social Sciences and Humanities Research Council of Canada [752-2016-2085] and a Tidmarsh Cambridge Scholarship from the Cambridge Commonwealth, European and International Trust and Trinity Hall Colleg

Influence of aerosol acidity on the chemical composition of secondary organic aerosol from β-caryophyllene

The secondary organic aerosol (SOA) yield of β-caryophyllene photooxidation is enhanced by aerosol acidity. In the present study, the influence of aerosol acidity on the chemical composition of β-caryophyllene SOA is investigated using ultra performance liquid chromatography/electrospray ionization-time-of-flight mass spectrometry (UPLC/ESI-TOFMS). A number of first-, second- and higher-generation gas-phase products having carbonyl and carboxylic acid functional groups are detected in the particle phase. Particle-phase reaction products formed via hydration and organosulfate formation processes are also detected. Increased acidity leads to different effects on the abundance of individual products; significantly, abundances of organosulfates are correlated with aerosol acidity. To our knowledge, this is the first detection of organosulfates and nitrated organosulfates derived from a sesquiterpene. The increase of certain particle-phase reaction products with increased acidity provides chemical evidence to support the acid-enhanced SOA yields. Based on the agreement between the chromatographic retention times and accurate mass measurements of chamber and field samples, three β-caryophyllene products (i.e., β-nocaryophyllon aldehyde, β-hydroxynocaryophyllon aldehyde, and β-dihydroxynocaryophyllon aldehyde) are suggested as chemical tracers for β-caryophyllene SOA. These compounds are detected in both day and night ambient samples collected in downtown Atlanta, GA and rural Yorkville, GA during the 2008 August Mini-Intensive Gas and Aerosol Study (AMIGAS)

Characterization and Quantification of Isoprene-Derived Epoxydiols in Ambient Aerosol in the Southeastern United States

Isoprene-derived epoxydiols (IEPOX) are identified in ambient aerosol samples for the first time, together with other previously identified isoprene tracers (i.e., 2-methyltetrols, 2-methylglyceric acid, C5-alkenetriols, and organosulfate derivatives of 2-methyltetrols). Fine ambient aerosol collected in downtown Atlanta, GA and rural Yorkville, GA during the 2008 August Mini-Intensive Gas and Aerosol Study (AMIGAS) was analyzed using both gas chromatography/quadrupole mass spectrometry (GC/MS) and gas chromatography/time-of-flight mass spectrometry (GC/TOFMS) with prior trimethylsilylation. Mass concentrations of IEPOX ranged from ~1 to 24 ng m^(−3) in the aerosol collected from the two sites. Detection of particle-phase IEPOX in the AMIGAS samples supports recent laboratory results that gas-phase IEPOX produced from the photooxidation of isoprene under low-NO_x conditions is a key precursor of ambient isoprene secondary organic aerosol (SOA) formation. On average, the sum of the mass concentrations of IEPOX and the measured isoprene SOA tracers accounted for about 3% of the organic carbon, demonstrating the significance of isoprene oxidation to the formation of ambient aerosol in this region

Intrinsic solidification behaviour of basaltic to rhyolitic melts: a cooling rate experimental study

Dynamic cooling-induced solidification experiments were run using six silicate glasses along the basalt - rhyolite join (B100= 100 wt % of basalt, R100= 100 wt % of rhyolite), i.e. B100, B80R20, B60R40, B40R60, B20R80 and R100; the glasses directly quenched from 1300 °C after a dwell of 120 minutes (experiment E0) contain 50-400 ppm H2O, << 1 area% μm-sized bubble, and Fe2+/Fetot between 0.34 and 0.46. Experiments were performed in Pt capsules at room pressure and fO2 of air, between 1300 and 800 °C using three different cooling rates of 0.0167, 3 and 30 °C/min; these cooling rates were run two times: E1-E2 experiments at 0.0167°C/min, S1-E3 at 3 °C/min, and E4-E5 at 30 °C/min. In experiments E1 to E5, samples were annealed for 120 minutes at 1300 °C, whereas in the experiment S1 the samples were firstly heated for 30 minutes at 1400 °C followed by a dwell time of 2400 minutes at 1300°C before cooling. In the experiments a preferential crystallization was not observed at the melt/gas interface. B100, B80R20 and B60R40 run-products have a low tendency to preferentially crystallize on Pt walls, while B40R60, B20R80 and R100 are not affected by the presence of Pt substrata. All run-products show very homogeneous textures, except for B60R40 and B40R60 at 0.0167°C/min in the E1 experiment. The duplicates of B40R60 and B60R40 at 0.0167°C/min and B100 at 30 °C/min show relatively large differences in crystal content (> 4 and < 14 area%). B40R60 and B60R40 duplicated run-products have the same amount of earlycrystallized clinopyroxene and spinel, but different contents in lately-formed plagioclase. The run-products with the same starting composition from E3-S1 (3 °C/min) show a high reproducibility in terms of crystal shape, size, and amount (< 4 area%). This demonstrates that the crystallization path is not affected by the different heat treatment above the liquidus temperature, i.e. the time scale of structural re-equilibration (relaxation) and chemical rehomogenization are shorter than our experimental time scale. Possible chemicalheterogeneities on a length scale of several micrometers for R100 and several hundreds of micrometers for B100 can be removed at 1300 °C within 120 minutes. A heat treatment at 1300 °C for 120 minutes significantly reduces the amount of μm-sized bubbles, potentially responsible for the onset of nucleation and unreveals the intrinsic solidification of silicate melts. The experimental reproducibility is low when the cooling path intersects the tip of the time-temperature-transformation (TTT) curves, i.e. when the nucleation rate is near its maximum (Imax). In that case, even small thermal variations in cooling rate and local composition can have large effects on phase abundance and crystal size. Dynamic crystallization experiments can be properly interpreted and compared only if they are texturally homogeneous and the physico-chemical state of the superheated silicate liquid is known. The solidification conditions used in this study mirror those of aphyric lavas and dikes emplaced at shallower crustal levels

Investigating the influences of SO2 and NH3 levels on isoprene-derived secondary organic aerosol formation using conditional sampling approaches

Filter-based PM2.5 samples were chemically analyzed to investigate secondary organic aerosol (SOA) formation from isoprene in a rural atmosphere of the southeastern US influenced by both anthropogenic sulfur dioxide (SO2) and ammonia (NH3) emissions. Daytime PM2.5 samples were collected during summer 2010 using conditional sampling approaches based on pre-defined high and low SO2 or NH3 thresholds. Known molecular-level tracers for isoprene SOA formation, including 2-methylglyceric acid, 3-methyltetrahydrofuran-3,4-diols, 2-methyltetrols, C5-alkene triols, dimers, and organosulfate derivatives, were identified and quantified by gas chromatography coupled to electron ionization mass spectrometry (GC/EI-MS) and ultra performance liquid chromatography coupled to electrospray ionization high-resolution quadrupole time-of-flight mass spectrometry (UPLC/ESI-HR-Q-TOFMS). Mass concentrations of six isoprene low-NOx SOA tracers contributed to 12–19% of total organic matter (OM) in PM2.5 samples collected during the sampling period, indicating the importance of the hydroxyl radical (OH)-initiated oxidation (so-called photooxidation) of isoprene under low-NOx conditions that lead to SOA formation through reactive uptake of gaseous isoprene epoxydiols (IEPOX) in this region. The contribution of the IEPOX-derived SOA tracers to total organic matter was enhanced by 1.4% (p = 0.012) under high-SO2 sampling scenarios, although only weak associations between aerosol acidity and mass of IEPOX SOA tracers were observed. This suggests that IEPOX-derived SOA formation might be modulated by other factors simultaneously, rather than only aerosol acidity. No clear associations between isoprene SOA formation and high or low NH3 conditional samples were found. Positive correlations between sulfate aerosol loadings and IEPOX-derived SOA tracers for samples collected under all conditions indicates that sulfate aerosol could be a surrogate for surface accommodation in the uptake of IEPOX onto preexisting aerosols

Intercomparison of an Aerosol Chemical Speciation Monitor (ACSM) with ambient fine aerosol measurements in downtown Atlanta, Georgia

Currently, there are a limited number of field studies that evaluate the long-term performance of the Aerodyne Aerosol Chemical Speciation Monitor (ACSM) against established monitoring networks. In this study, we present seasonal intercomparisons of the ACSM with collocated fine aerosol (PM_2.5) measurements at the Southeastern Aerosol Research and Characterization (SEARCH) Jefferson Street (JST) site near downtown Atlanta, GA, during 2011–2012. Intercomparison of two collocated ACSMs resulted in strong correlations (<i>r</i>² > 0.8) for all chemical species, except chloride (<i>r</i>² = 0.21) indicating that ACSM instruments are capable of stable and reproducible operation. In general, speciated ACSM mass concentrations correlate well (<i>r</i>² > 0.7) with the filter-adjusted continuous measurements from JST, although the correlation for nitrate is weaker (<i>r</i>² = 0.55) in summer. Correlations of the ACSM NR-PM₁ (non-refractory particulate matter with aerodynamic diameter less than or equal to 1 μm) plus elemental carbon (EC) with tapered element oscillating microbalance (TEOM) PM_2.5 and Federal Reference Method (FRM) PM₁ mass are strong with <i>r</i>² > 0.7 and <i>r</i>² > 0.8, respectively. Discrepancies might be attributed to evaporative losses of semi-volatile species from the filter measurements used to adjust the collocated continuous measurements. This suggests that adjusting the ambient aerosol continuous measurements with results from filter analysis introduced additional bias to the measurements. We also recommend to calibrate the ambient aerosol monitoring instruments using aerosol standards rather than gas-phase standards. The fitting approach for ACSM relative ionization for sulfate was shown to improve the comparisons between ACSM and collocated measurements in the absence of calibrated values, suggesting the importance of adding sulfate calibration into the ACSM calibration routine

Contributions of domestic sources to PM2.5 in South Korea

We use the CAMx (Comprehensive Air Quality Model with Extensions) chemical transport model (CTM) with 4-km horizontal resolution over the Korean Peninsula to investigate source contributions to PM2.5 in Korea from domestic and upwind sources. We modeled 2015 and 2016 to account for meteorological variation with Korean emissions from the Clean Air Policy Supporting System (CAPSS), meteorology from WRF (Weather, Research, and Forecasting) model, and regional boundary concentrations from the GEOS-Chem global CTM. The CAMx particulate source apportionment technology (PSAT) provided PM2.5 source contributions from 5 source sectors and 6 geographic regions within Korea, international sources, and boundary concentrations. PM2.5 contributions from outside Korea are important with boundary concentrations plus the “other” emissions sector (includes marine shipping, agricultural ammonia, and international emissions from North Korea and Japan within the CAMx domain) contributing 67% of annual average PM2.5 in Seoul in 2016 and 71% in 2015. The boundary concentrations contributed between 30% and 50% of PM2.5 at different Korean cities with contributions generally lower in 2016 than in 2015. For Korean sources, PM2.5 contributions from Electric Generating Unit (EGU) emissions were smaller than contributions from mobile and industrial emissions sources although there is considerable day-to-day variation in contributions. On an annual basis in 2016, the “other” category contributed 25% followed by mobile sources at 23%, industrial sources at 6%, and EGU sources at 3%. For 2015, the contributions were similar. Focusing on March when PM2.5 concentrations were higher than other months, the contributions from other, mobile, industrial, and EGUs were 21%, 18%, 4%, and 4%, respectively in 2016. For 2015, contributions from these four categories were 18%, 15%, 3%, and 3%, respectively

Contributions of international sources to PM2.5 in South Korea

The air quality in Republic of Korea, especially in cities such as Seoul, has been a serious public health concern over the years. The key pollutant in the atmosphere leading to poor air quality in Korea is fine particulate matter (PM2.5). Here, we use a 3-D global chemistry model (GEOS-Chem) to conduct source attribution to PM2.5 in Korea from international and domestic emissions. The modeling was done for 2015 and 2016 to account for different meteorological conditions. We ran the GEOS-Chem model for both years, conducted model evaluation using ground and aloft observations, and then conducted sensitivity simulations without domestic anthropogenic emissions and Chinese anthropogenic emissions, respectively. Results show that the Chinese influence on PM2.5 in Korea varies from month to month with the highest contribution during spring when observed concentrations are also the highest. Chinese contributions to PM2.5 concentrations in South Korea reach a maximum of up to ~60% in January and February and gradually decrease until August when they reach a minimum at about 20%. On an annual basis, our analysis estimated that in 2016, Chinese anthropogenic emissions contributed 45% to PM2.5 in South Korea. The 2016 contribution from China was generally 3–5% lower than in 2015 because of emissions reductions in China. Compared to the Chinese contribution, the rest of the world contributions (which also include contributions from natural emissions worldwide) were minor except for summer in the South Sea

Characterization of Polar Organic Components in Fine Aerosols in the Southeastern United States: Identity, Origin, and Evolution

Filter samples of fine aerosols collected in the Southeastern United States in June 2004 were analyzed for the characterization of polar organic components. Four analytical techniques, liquid chromatography –mass spectrometry, ion trap mass spectrometry, laser desorption ionization mass spectrometry, and high-resolution mass spectrometry, were used for identification and quantification. Forty distinct species were detected, comprising on average 7.2% and 1.1% of the total particulate organic mass at three inland sites and a coastal site, respectively. The relative abundance of these species displays a rather consistent distribution pattern in the inland region, whereas a different pattern is found at the coastal site. Chemical and correlation analyses suggest that the detected species are secondary in nature and originate from terpene oxidation, with possible participation of NOx and SO2. It is estimated that polar, acidic components in fine aerosols in the Southeastern United States cover a molecular weight range of 150–400 Da and do not appear to be oligomeric. Other components with MW up to 800 Da may also be present. The detected polar organic species are similar to humic-like substances (HULIS) commonly found in fine aerosols in other rural areas. We present the first, direct evidence that atmospheric processing of biogenic emissions can lead to the formation of certain HULIS species in fine aerosols, and that this may be a typical pathway in the background atmosphere in continental regions; nevertheless, a natural source for HULIS, such as from aquatic and/or terrestrial humic/fulvic acids and their degradation products, cannot be precluded