Accumulation Mode Particle Number Concentration Research Articles

The influence of alcohol, carbonate and polyethers as oxygenated fuels on the soot characteristics from a CI engine

Dimethyl carbonate (DMC), ethanol (EtOH), polyoxymethylene dimethyl ether 1 (PODE1) and polyoxymethylene dimethyl ether 4 (PODE4) were blended with Jet A1 into fuel blends with 5 % oxygen content to investigate the effect of the oxygenated fuels on the soot produced by a compression ignition engine. Particle size distribution (PSD) was measured using a differential mobility spectrometer. Thermogravimetric analysis (TGA), Raman spectroscopy, ultraviolet–visible spectroscopy (UV–Vis) and Fourier transform infrared (FT-IR) spectroscopy were performed on the soot collected from the engine. The addition of EtOH, PODE1 improves brake thermal efficiency (BTE) by up to 4.5 %, while DMC reduces BTE by 0.9–1.5 % compared to Jet A1. EtOH fuel blends have the shortest combustion duration (10.0 deg), followed by PODE1, DMC and PODE4. EtOH blends also have the highest heat release rate peak (4–14 % higher than Jet A1). This, combined with improved premixing of EtOH fuel blend in the engine improves the combustion and reduces soot growth. PSD measurements showed that the addition of EtOH significantly reduces accumulation mode particle number concentrations by up to 70 % but promotes the formation of nucleation mode particles. Meanwhile, TGA revealed that the soot from oxygenated fuel blends oxidises at a lower temperature than Jet A1. Notably, PODE1 exhibited a reduction of 54 °C in the starting oxidation temperature, which is the largest reduction among the oxygenated fuel blends. Lastly, the conjugation length of the soot aromatic structure for the organic carbons (derived from the optical band gap of UV–Vis) is up to 11 % greater for the oxygenated fuel blends, indicating that oxygenated fuel blends promote organic carbon formation. The blending of oxygenated fuels in influencing the soot properties through the dilution effect, combustion condition effect and chemical effect is then critically assessed.

Brownian coagulation of particles in the gasoline engine exhaust system: Experimental measurement and Monte Carlo simulation

In this article, Brownian coagulation of particles in the exhaust system of a gasoline engine were investigated by measuring particle size distribution (PSD) at different sampling points and Monte Carlo simulation. The measurement results show that the particle size distributions of nucleation mode (NM) change remarkably after the exhaust gas passes through the exhaust plenum chamber. The constructed coagulation model based on the classic coagulation theory can well catch the measured PSDs, particle number (PN) concentrations, and count median diameters (CMDs) along the exhaust system under both the in-cylinder direct injection and port fuel injection modes, indicating that the particle process in the exhaust system is dominated by coagulation. The NM PN concentration decreases, and the NM CMD increases in the downstream exhaust gas, and the changes are more significant at higher accumulation mode (AM) PN concentration conditions. The coagulation history provided by modelling shows that coagulation mainly occurs between two NM particles (NM-NM) or one NM and one AM particles (NM-AM). At higher AM PN concentration conditions, the NM-AM coagulation dominates and quickly eliminates NM particles, resulting in more significant NM particle reduction. The PN concentration variation as a function of time indicates that PN concentration decreases quickly at first and then the decreasing rate slows down.

Long-term exposure to ambient source-specific particulate matter and its components and incidence of cardiovascular events – The Heinz Nixdorf Recall study

BackgroundFew studies have examined the risk of long-term exposure to source-specific airborne pollutants on incidence of cerebrovascular and cardiovascular events. ObjectivesWe aimed to estimate the effect of long-term exposure to source-specific air pollution and particulate matter (PM) components on incidence of stroke, coronary heart disease (CHD), and total cardiovascular events (CVE) in the population-based Heinz Nixdorf Recall study (HNR). MethodsWe used baseline (2000–2003) and 14-year follow-up data of the HNR Study, an ongoing population-based prospective cohort study in Western Germany. Participants’ residential mean exposures to NO2 and total and source-specific PM10, PM2.5, accumulation mode particle number concentration (PNAM), and PM components were modelled using a dispersion and chemical transport model. We used Cox regression to evaluate the effect of pollutants (per 1 μg/m3 increase and per interquartile range – IQR) on risk of stroke and CHD, adjusting for socio-demographic characteristics, lifestyle risk factors and nighttime traffic noise exposure. ResultsIn 4,105 included participants (aged 45–76 at baseline, 52.5% women), we observed 118 cases of first stroke and 373 cases of first CHD during 46,748 person-years under risk. The median survival time within the cohort was 13.3 years. No effect of exposure to ambient air pollution on risk of CHD was observed, but distinct effects were observed for stroke. Ambient traffic-specific PM showed a stronger effect on stroke than industry-specific PM: hazard ratios (95% confidence interval) for total, traffic-specific, and industry-specific PM2.5 were 1.16 (1.02–1.34), 2.53 (1.07–5.97), and 1.27 (1.03–1.56) per 1 μg/m3 increase, respectively. PM components showed no substantially different effects from those of total PM per IQR, but higher associations were observed for NH4 and SO4 per 1 μg/m3. However, the exposure contrast of ammonium and sulfate components was very low. ConclusionTraffic-specific PM exhibited stronger effects than total and industry-specific PM on risk of stroke. Among components, NH4 and SO4 showed higher effects. No effect was observed for PM and CHD.

Atmospheric aerosol properties at a semi-rural location in southern India: particle size distributions and implications for cloud droplet formation

Particle number size distributions in the diameter range of 5 nm–34 µm were measured in tropical southern India during the transition season from May (pre-monsoon) to June–July (monsoon). Averaged over the entire measurement period, the particle number size distributions were bimodal with a total particle number concentration of NTot = (4.5 ± 2.7) × 103 cm−3 (arithmetic mean ± standard deviation). The ratio of Aitken to accumulation mode particle number concentrations (NAit/NAcc) ranged from 1.06 to 2.07, increasing from May to June–July due to a pronounced decrease in the accumulation mode particles with the onset of the monsoon. Cloud condensation nuclei concentrations at 0.4% supersaturation (CCN0.4) were calculated under the assumption of an average continental hygroscopicity parameter of κ = 0.3. The calculated CCN0.4 concentrations are mostly sensitive to variations in NAcc and vary accordingly between the May and June–July. Using a cloud parcel model, we investigated the formation of cloud droplets using the measured average particle number size distributions, updraft velocities up to 20 m s−1, and initial aerosol particle number concentrations up to 25,000 cm−3. We found different regimes of CCN activation and cloud formation for the month of May (shifting from aerosol-limited regime to transitional regime) and for June–July (transitional regime), which was primarily due to the variability of particle number concentrations in the accumulation mode.

All-source and source-specific air pollution and 10-year diabetes Incidence: Total effect and mediation analyses in the Heinz Nixdorf recall study

BackgroundAn increasing number of studies have been published recently on the association between ambient air pollution (AP) and incident diabetes mellitus (DM), but studies investigating source-specific AP toxicity and potential mediating pathways are rare. We investigated the associations of all-source, traffic-specific, and industry-specific outdoor AP exposure with 10-year incidence of DM and potential mediation via inflammation-associated biomarkers. MethodsData from participants of the prospective Heinz Nixdorf Recall cohort study who attended the baseline (t0; 2000–2003), 5-year follow-up (t1; 2006–2008), and 10-year follow-up (t2; 2011–2015) examinations was used. For participants without DM at baseline (determined using information on physician diagnosis and glucose-lowering medication), residential long-term exposure (total, traffic-specific, and industry-specific) to particulate matter (PM2.5, PM10), nitrogen dioxide (NO2), and accumulation mode particle number concentration (PNAM) were estimated using a chemistry transport model. Covariate-adjusted modified Poisson regression models with robust standard errors were applied to estimate relative risks (RR) for the associations between baseline AP and incident DM at t2. Mediation analyses for adiponectin, high-sensitivity C-reactive protein (hsCRP), and interleukin-1 receptor antagonist (IL-1RA) were conducted to estimate natural direct and indirect effects. ResultsOf the 4,814 participants at t0, 2,451 participants (mean baseline age: 58.2 years) were included in the main analysis. Interquartile range (IQR) increases in total PM10 and PNAM were associated with increased risk of DM (e.g., RR: 1.25 [95% Confidence Interval (CI): 1.02, 1.53] per 3.8 µg/m3 PM10). Whereas traffic-specific exposures were associated with DM risk for all air pollutants (e.g., RR: 1.24 [95% CI: 1.06, 1.46] per 0.3 µg/m3 PM10), significant associations for industry exposures were limited to NO2 and PNAM (e.g., RR: 1.24 [95% CI: 1.03, 1.49] per 230 particles/mL PNAM). Potential mediation of the association between AP and DM was observed for adiponectin but not for hsCRP and IL-1RA. ConclusionOur study shows that long-term exposure to total and source-specific ambient AP may increase DM risk, with consistent results observed across traffic-specific exposures. Decreases in adiponectin may play a potential role along the causal pathway.

Statistical modelling of roadside and urban background ultrafine and accumulation mode particle number concentrations using generalized additive models

Quantification of the exposure of urban residents to ultrafine particle number concentrations (UFP) is challenging due to its high spatial and temporal variability. Hence, statistical models, e.g. generalized additive models (GAM), may be used to estimate time series or spatial characteristics of UFP. The GAM approach allows the representation of non-linear relations of a response variable with explanatory variables without the need to pre-define model functions. Up to now, GAMs were usually fitted to UFP data from a single site or from mobile measurement campaigns with limited temporal coverage. In this study, GAMs were used to determine UFP, accumulation mode particle (ACC) and total number concentration (TNC) at five urban sites in the cities of Leipzig and Dresden, Germany for the period 2011–2013. As explanatory variables, reanalysis data sets of meteorological quantities, urban geometry and traffic volume data were evaluated. Variables causing concurvity, which is the equivalent to collinearity in non-linear model approaches, were neglected to guarantee the interpretability of the final models. The models were then validated in a ten-fold cross-validation approach. The final models contained smooth functions for the building surface fraction, planetary boundary layer height, traffic volume, air temperature, wind direction, atmospheric pressure, relative humidity, global radiation and precipitation. Adjusted coefficients of determination (R2adj.) for the final models were R2adj. = 0.44 for UFP, R2adj. = 0.51 for ACC and R2adj. = 0.48 for TNC. Coefficients of determination of the cross-validation were in a similar range (0.44 for UFP, 0.51 for ACC, 0.49 for TNC). Finally, our study shows that GAMs are able to represent important processes that contribute to the particle number concentration from the smooth functions, i.e. emission, dilution, nucleation, deposition and long-range transport.

Long-term exposure to air pollution components (total and source-specific) and incidence of stroke and cardiac events in the Heinz Nixdorf Recall study

OPS 06: Health effects of source-specific outdoor air pollution, Room 117, Floor 1, August 27, 2019, 10:30 AM - 12:00 PM Background/Aim: Epidemiological studies have established that air pollution (AP) exposure adversely affects cardiovascular health. However, there has been little research on the effects of source-specific (industry and traffic) AP and individual components of particulate pollution. We therefore investigated the association between long-term exposure to components of total and source-specific AP and incidence of stroke and cardiac events (CE). Methods: We used data from the Heinz Nixdorf Recall cohort study (N = 4,814, aged 45–75). We estimated long-term residential AP exposures over the baseline period (2001-2003) using the European Air Pollution Dispersion chemical transport model (EURAD). Exposure was modelled for total NO2, total and source-specific particulate matter (PM) PM10, PM2.5, accumulation mode particle number concentration (PNAM), and PM components (anthropogenic organic compounds, black carbon, elemental carbon, NH4, NO3, SO4). Outcomes were defined as time to first stroke or CE during follow-up (until 2017). We applied Cox proportional hazards model to estimate hazard ratios (HR) per interquartile range increase in exposure to each pollutant/component, controlling for baseline sex, age, socio-economic status, body mass index, smoking, alcohol consumption, physical activity, nutrition, and traffic noise. In the analyzed population without stroke or CE prior to baseline (N = 4,224), a total of 120 strokes and 200 CE were observed during the study period (mean follow-up 12 years). Results: We observed positive associations between AP exposure and incidence of stroke, e.g. for industry-specific PM10 (HR: 1.34, 95% CI: 1.01, 1.78 per 2.22 µg/m3), industry-specific PNAM (HR: 1.28 [1.00, 1.64] per 208 particles/mL), and traffic-specific PNAM (HR: 1.30 [1.01, 1.68] per 138 particles/mL). Point estimates for CE were less consistently elevated. Adjustment for traffic noise did not change the results substantially. Conclusions: Our results support a positive association of long-term residential exposure to source-specific AP and PM components with incidence of stroke.

Air pollution and diabetes-related biomarkers in non-diabetic adults: A pathway to impaired glucose metabolism?

BackgroundWhile prior studies have linked air pollution (AP) to diabetes prevalence and incidence, few have investigated whether AP exposure is also associated with alterations in diabetes-related biomarkers in metabolically healthy adults. ObjectiveTo evaluate the associations between short-, medium-, and long-term AP and diabetes-related biomarkers (adiponectin, interleukin-1 receptor antagonist [IL-1RA], high sensitivity C-reactive protein [hsCRP], fibrinogen) in persons without diabetes. MethodsAdiponectin, IL-1RA, hsCRP, and fibrinogen were measured in blood samples collected at the baseline (t0; 2000–2003) and first follow-up (t1; 2006–2008) examinations of the prospective Heinz Nixdorf Recall (HNR) cohort study in Germany. Participants' residential mean exposures to PM10, PM2.5, NO2, and accumulation mode particle number concentration (PNAM) were estimated for several time windows (1- to 365-day) prior to examination using a dispersion and chemistry transport model. We fitted covariate-adjusted linear mixed effects models using a random participant intercept and investigated effect modification by obesity status. ResultsWe analyzed 6727 observations (nt0 = 3626, nt1 = 3101) from 4052 participants of the HNR study (52% women; ages 45–76 years at t0). For all air pollutants, medium-term exposures (60- to 120-day) were negatively associated with adiponectin (e.g., 91-day PNAM: −2.51% change [−3.40%, −1.53%] per interquartile [IQR] increase). Several short-, medium-, and long-term AP exposures were positively associated with IL-1RA (e.g., 365-day PM10: 2.64% change [1.25%, 4.22%] per IQR increase). Long-term exposures were positively associated with hsCRP level while no consistent patterns were observed for fibrinogen. Stronger associations for adiponectin were observed among non-obese participants. ConclusionIn persons without diabetes, we observed differing patterns of association between AP and diabetes-related biomarkers across a range of exposure windows, supporting the hypothesis that AP may play a role in the development of diabetes.

Accumulation and Coarse Modes Particle Concentrations during Dew Formation and Precipitation

This study investigates the number concentrations of accumulation mode (0.3–1 µm) and coarse mode (1–10 µm) particles in the eastern Mediterranean urban environment with and without precipitation and dew formation. The results show that the number concentrations of both the accumulation mode and coarse mode particles decreased (with ratios of ~0.7 and ~0.36, respectively) during precipitation. In our analysis, we assumed that dew formation occurred in Amman during nighttime when the relative humidity (RH) was higher than 80% and the difference between the temperature and dew point temperature (i.e., T–DP) was less than 2.5°C. In general, the accumulation mode particle number concentration increased with relative humidity and doubled, on average, during dew formation. On the other hand, the coarse mode particle number concentration was 30% lower during conditions with dew formation than without. The increased number concentration of the accumulation mode particles during dew formation conditions is most likely due to enhanced water vapor condensation on existing ultrafine aerosols (diameter < 0.1 µm), enabling particles to grow to detectable sizes, including the accumulation mode. The decreased number concentration of the coarse mode particles during dew formation conditions may be due to enhanced wet deposition.

Experimental investigation on performance, combustion and emission characteristics of a common-rail diesel engine fueled with polyoxymethylene dimethyl ethers-diesel blends

Polyoxymethylene dimethyl ethers (PODE) was blended with diesel fuel at volume ratio of 10%, 20% and 30% in the preparation of PODE-diesel blend fuels (marked as P10, P20 and P30). The volatility and oxidation characteristics of blend fuels, and the thermal parameters were analyzed using thermogravimetric method and Coast-Redfern integral method respectively. Also, the effects of PODE-diesel blends on the performance, combustion and emission characteristics were carried out on a 4-cylinder turbocharged intercooled common-rail diesel engine. The results show that P10, P20 and P30 have good stability at room temperature, and also the kinematic viscosity of PODE-diesel blends gradually decreases with increasing PODE blending ratio and temperature. Also with the increase of the blending ratio of PODE, the activation energy of blend fuels decreases and the comprehensive combustion index improves. When the diesel engine is fueled with PODE-diesel blends, the ignition delay period is shortened, shifting the rate of heat release and the rate of pressure rise curves forward. This increment in PODE blending ratio increases the maximum in-cylinder pressure and improves the brake thermal efficiency. The blend fuel has little impact on NOX emissions, however, it can significantly improve HC, CO and smoke emissions. Compared with pure diesel fuel, the smoke emissions of P10, P20 and P30 at full load are reduced by 27.6%, 41.5% and 47.6%, respectively. PODE-diesel blends therefore could reduce particle number concentration and particle mass concentration in diesel exhausts, shifting the distribution peak to small particle sizes. Compared with pure diesel fuel, the peak number concentration of accumulation-mode particles (50nm<Dp<1000nm) of P10, P20 and P30 decrease by 15.97%, 32.28% and 43.79%, respectively. This indicates that PODE as one of the emerging alternative fuels has the potential to achieve high efficient and clean combustion for diesel engines.

Aerosol optical properties at urban and coastal sites in Shandong Province, Northern China

In-situ observations of aerosol optical properties were conducted in Jinan, an urban site, from December 2013 to May 2014 and on Tuoji Island, a coastal site, from December 2014 to January 2015; both locations are located in Shandong Province, Northern China. Aerosol optical properties, such as the scattering coefficient (σsp), absorption coefficient (σap) and single-scattering albedo (ω), were obtained using nephelometer and aethalometer. The mean values (±standard deviation) for σsp at 550nm and σap at 532nm, were 204±188Mm−1 and 43±33Mm−1, respectively, in Jinan and 210±246Mm−1 and 8±6Mm−1 on Tuoji Island, respectively. The average ω at 532nm was 0.80±0.09 in Jinan and 0.93±0.04 on Tuoji Island. Pronounced diurnal cycles were observed at both locations for σsp, σap and ω, but the diurnal cycles at the two locations exhibited distinct properties for some of the aerosol optical parameters. The values of σsp and σap peaked between 0800 and 1100 local time (LT) due to traffic emissions and low wind speeds at both locations. And a unimodal ω diurnal cycle, which peaked between 1000 and 1400 LT, was observed in the spring in Jinan. This spring diurnal pattern was mainly related to secondary aerosol formation and aging processes. The high σsp and σap values in Jinan winter were accompanied by calm winds (<2m/s) from 0° to 90°, while the high σsp and σap values on Tuoji Island were observed during the period of stronger wind speeds (>2m/s) from 180° to 270°. This indicates that local emissions were a key source of strongly absorbing and scattering aerosols in Jinan during heating period, whereas, high σsp and σap values on Tuoji Island were mainly influenced by middle- and long-distance transport from Shandong Province and the Jing-Jin-Ji region. Additionally, middle- and long-distance regional transport from direction at 180° to 270° occasionally enhanced the σsp and σap values in the spring at Jinan after heating period. The σsp values in Jinan and Tuoji Island both exhibited relatively profound correlation with the accumulation-mode particle number concentrations.

The influence of emission control on particle number size distribution and new particle formation during China's V-Day parade in 2015

Temporary strict emission control strategies were conducted to ensure good air quality for China's V-Day parade (August 20–September 3, 2015) in Beijing and nearby cities. The influence of the emission control on particle number size distribution (PNSD) was evaluated based on the long-term measurements of PNSD at a rural site (Shangdianzi) located northeast of Beijing. This study also presented the comparison results of PNSD during the parade in 2015 and the Olympics in 2008 (August 8–23), as well as the same period without strict emission control in 2010–2013 (August 20–September 3). Compared with the same period in 2010–2013 and 2008 Olympics, the accumulation mode particle number concentration showed a significant reduction in 2015, and the PM1 mass concentration decreased by approximately 60–90%. The alleviation of the PM1 was also associated with the weather conditions. The back trajectories analysis results showed that the southerly air mass passing through the polluted areas accounted for 14% of the total back trajectories in 2015, which contributed to approximately 60% in the other years. During the control period in 2015, there were six new particle formation (NPF) events observed, with a higher frequency, but a lower formation rate and growth rate than the same period in 2010–2013. The comparison of the condensation sink (CS), sulfuric acid, solar radiation and relative humidity among the different years indicated that at Shangdianzi station, the first factor in determining the NPF occurrence was the CS, and the second factor could be the concentration level of precursor vapors participating in the NPF event (e.g., sulfuric acid).

Influence of sulfur in fuel on the properties of diffusion flame soot

Previous studies indicate that sulfur in fuel affects the hygroscopicity of soot. However, the issue of the effect of sulfur in fuel on soot properties is not fully understood. Here, the properties of soot prepared from fuel with a variable sulfur content were investigated under lean and rich flame conditions. Lean flame soot was influenced more by sulfur in fuel than rich flame soot. The majority of sulfur in fuel in lean flame was converted to gaseous SO2, while a small fraction appeared as sulfate and bisulfate (referred to as sulfate species) in soot. As the sulfur content in fuel increased, sulfate species in lean flame soot increased nonlinearly, while sulfate species on the surface of lean flame soot increased linearly. The hygroscopicity of lean flame soot from sulfur-containing fuel was enhanced mainly due to sulfate species. Meanwhile, more alkynes were formed in lean flame. The diameter of primary lean flame soot particles increased and accumulation mode particle number concentrations of lean flame soot from sulfur-containing fuel increased as a result of more alkynes. Because the potential effects of soot particles on air pollution development greatly depend on the soot properties, which are related to both chemical aging and combustion conditions, this work will aid in understanding the impacts of soot on air quality and climate.

An experimental study on the combustion and emission characteristics of a diesel engine under low temperature combustion of diesel/gasoline/n-butanol blends

Based on a small-scale high-speed diesel engine, the low temperature combustion and emission characteristics of four different fuels were experimentally investigated at different EGR ratios. The following fuels were studied: pure diesel (D100), a diesel and gasoline blend with a volume ratio of 70:30 (D70G30), a diesel and n-butanol blend with a volume ratio of 70:30 (D70B30) and a blend of diesel, gasoline and n-butanol with a volume ratio of 70:15:15 (D70G15B15). During the combustion of all four kinds of fuels, when the EGR ratio was smaller than 25%, the increase of EGR ratio sorted little effects on the maximum pressure rising ratio, as well as on the emission of soot, CO and total hydrocarbons (THC). Conversely, the emission of NOx decreased significantly as the EGR ratio increased. At the same EGR ratio, the variation of fuel characteristics by adding gasoline or n-butanol into diesel did not sort significant effects on the NOx emission, whereas it was found to greatly affect the maximum pressure rising ratio. When the EGR ratio was greater than 25%, the emissions of soot, CO and THC increased rapidly with the rising EGR ratio due to the decrease in excess air coefficient and to the excessively long ignition delay period. The D70B30 blended fuel exhibited more remarkable results in soot emission reduction than the D70G30 blended fuel. When the EGR ratio was close to 40%, NOx emissions almost approached zero. As the EGR ratio increased, the number concentration of nucleation-mode particles (Dp<50nm) during the combustion of the examined fuels first decreased and then increased; the number concentration of accumulation-mode particles (50nm<Dp<1000nm) increased continuously. When the EGR ratio was smaller than 25%, the total particulate matters (PM) number concentration during the combustion of the four fuels did not present a clear trend; when the EGR ratio was higher than 25%, the total PM number concentration during the combustion of the four tested fuels increased rapidly, with a descending order of rising amplitude, D100>D70G30>D70G15B15>D70B30. At a fixed EGR ratio, the count median diameters (CMD) corresponding to the peak values of the number concentration of both nucleation-mode and accumulation-mode particles had an ascending order of D70B30<D70G15B15<D70G30<D100. The emissions of soot, NOx, CO and THC and the number concentration of particles reached their optimum values during the combustion of D70B30 at an EGR ratio of approximately 25%.

MATCH-SALSA – Multi-scale Atmospheric Transport and CHemistry model coupled to the SALSA aerosol microphysics model – Part 1: Model description and evaluation

Abstract. We have implemented the sectional aerosol dynamics model SALSA (Sectional Aerosol module for Large Scale Applications) in the European-scale chemistry-transport model MATCH (Multi-scale Atmospheric Transport and Chemistry). The new model is called MATCH-SALSA. It includes aerosol microphysics, with several formulations for nucleation, wet scavenging and condensation. The model reproduces observed higher particle number concentration (PNC) in central Europe and lower concentrations in remote regions. The modeled PNC size distribution peak occurs at the same or smaller particle size as the observed peak at four measurement sites spread across Europe. Total PNC is underestimated at northern and central European sites and accumulation-mode PNC is underestimated at all investigated sites. The low nucleation rate coefficient used in this study is an important reason for the underestimation. On the other hand, the model performs well for particle mass (including secondary inorganic aerosol components), while elemental and organic carbon concentrations are underestimated at many of the sites. Further development is needed, primarily for treatment of secondary organic aerosol, in terms of biogenic emissions and chemical transformation. Updating the biogenic secondary organic aerosol (SOA) scheme will likely have a large impact on modeled PM2.5 and also affect the model performance for PNC through impacts on nucleation and condensation.

Acidic reaction products of monoterpenes and sesquiterpenes in atmospheric fine particles in a boreal forest

Abstract. Biogenic acids were measured in aerosols at the SMEAR II (Station for Measuring Forest Ecosystem-Atmosphere Relations II) station in Finland from June 2010 until October 2011. The analysed organic acids were pinic, pinonic, caric, limonic and caryophyllinic acids from oxidation of α-pinene, β-pinene, limonene, Δ3-carene and β-caryophyllene, respectively. Due to a lack of authentic standards, the caric, limonic and caryophyllinic acids were synthesised for this study. The mean, median, maximum and minimum concentrations (ng m−3) were as follows: limonic acid (1.26, 0.80, 16.5, below detection limit (&lt; LOD)), pinic acid (5.53, 3.25, 31.4, 0.15), pinonic acid (9.87, 5.07, 80.1, &lt; LOD), caric acid (5.52, 3.58, 49.8, &lt; LOD), and caryophyllinic acid (7.87, 6.07, 86.1, &lt; LOD). The highest terpenoic acid concentrations were measured during the summer. Of the acids, β-caryophyllinic acid showed the highest concentrations in summer, but during other times of the year pinonic acid was the most abundant. The β-caryophyllinic acid contribution was higher than expected, based on the emission calculations of the precursor compounds and yields from oxidation experiments in smog chambers, implying that the β-caryophyllene emissions or β-caryophyllinic acid yields were underestimated. The concentration ratios between terpenoic acids and their precursors were clearly lower in summer than in winter, indicating stronger partitioning to the aerosol phase during the cold winter season. The β-caryophyllinic and caric acids were weakly correlated with the accumulation-mode particle number concentrations.

Chemical composition and sources of coastal marine aerosol particles during the 2008 VOCALS-REx campaign

Abstract. The chemical composition of aerosol particles (Dp ≤ 1.5 μm) was measured over the southeast Pacific Ocean during the VAMOS (Variability of the American Monsoon Systems) Ocean-Cloud-Atmosphere-Land Study Regional Experiment (VOCALS-Rex) between 16 October and 15 November 2008 using the US Department of Energy (DOE) G-1 aircraft. The objective of these flights was to gain an understanding of the sources and evolution of these aerosols, and of how they interact with the marine stratus cloud layer that prevails in this region of the globe. Our measurements showed that the marine boundary layer (MBL) aerosol mass was dominated by non-sea-salt SO42−, followed by Na+, Cl−, Org (total organics), NH4+, and NO3−, in decreasing order of importance; CH3SO3− (MSA), Ca2+, and K+ rarely exceeded their limits of detection. Aerosols were strongly acidic with a NH4+ to SO42− equivalents ratio typically &lt; 0.3. Sea-salt aerosol (SSA) particles, represented by NaCl, exhibited Cl− deficits caused by both HNO3 and H2SO4, but for the most part were externally mixed with particles, mainly SO42−. SSA contributed only a small fraction of the total accumulation mode particle number concentration. It was inferred that all aerosol species (except SSA) were of predominantly continental origin because of their strong land-to-sea concentration gradient. Comparison of relative changes in median values suggests that (1) an oceanic source of NH3 is present between 72° W and 76° W, (2) additional organic aerosols from biomass burns or biogenic precursors were emitted from coastal regions south of 31° S, with possible cloud processing, and (3) free tropospheric (FT) contributions to MBL gas and aerosol concentrations were negligible. The very low levels of CH3SO3− observed as well as the correlation between SO42− and NO3− (which is thought primarily anthropogenic) suggest a limited contribution of DMS to SO42− aerosol production during VOCALS.

Ambient fine particulate air pollution triggers ST-elevation myocardial infarction, but not non-ST elevation myocardial infarction: a case-crossover study

BackgroundWe and others have shown that increases in particulate air pollutant (PM) concentrations in the previous hours and days have been associated with increased risks of myocardial infarction, but little is known about the relationships between air pollution and specific subsets of myocardial infarction, such as ST-elevation myocardial infarction (STEMI) and non ST-elevation myocardial infarction (NSTEMI).MethodsUsing data from acute coronary syndrome patients with STEMI (n = 338) and NSTEMI (n = 339) and case-crossover methods, we estimated the risk of STEMI and NSTEMI associated with increased ambient fine particle (<2.5 um) concentrations, ultrafine particle (10-100 nm) number concentrations, and accumulation mode particle (100-500 nm) number concentrations in the previous few hours and days.ResultsWe found a significant 18% increase in the risk of STEMI associated with each 7.1 μg/m3 increase in PM2.5 concentration in the previous hour prior to acute coronary syndrome onset, with smaller, non-significantly increased risks associated with increased fine particle concentrations in the previous 3, 12, and 24 hours. We found no pattern with NSTEMI. Estimates of the risk of STEMI associated with interquartile range increases in ultrafine particle and accumulation mode particle number concentrations in the previous 1 to 96 hours were all greater than 1.0, but not statistically significant. Patients with pre-existing hypertension had a significantly greater risk of STEMI associated with increased fine particle concentration in the previous hour than patients without hypertension.ConclusionsIncreased fine particle concentrations in the hour prior to acute coronary syndrome onset were associated with an increased risk of STEMI, but not NSTEMI. Patients with pre-existing hypertension and other cardiovascular disease appeared particularly susceptible. Further investigation into mechanisms by which PM can preferentially trigger STEMI over NSTEMI within this rapid time scale is needed.

Ground-fixed and on-board measurements of nanoparticles in the wake of a moving vehicle

An integrated experimental methodology has been applied to measure number and size distributions of particles in the 5-560nm size range in the wake of a diesel car running at different speeds. Measurements were made at both ground-fixed (0.10 and 0.25m above the ground level) and on-board (in 12 different sampling locations behind the moving car) measurement configurations using a fast response differential mobility spectrometer (Cambustion DMS50) with a sampling frequency up to 10Hz. Results from both the experimental campaigns were analysed to understand the dynamics, dispersion and transport of nanoparticle emissions in the wake of a moving vehicle. Temporal changes in results were divided into three main stages (pre-evolution, evolution and post-evolution) after the release of exhaust emissions from the tailpipe. Evolution stage is of most interest where all the changes to particle number and size distribution occurred. Up to four evolution sub-stages were observed, each showing distinct evolution patterns of particle size distributions, depending on the particular experimental run. In agreement with previous studies, dilution was found to be the dominant process throughout all the evolution stages. The first evolution sub-stage was common to all the measurements, and consisted of an initial particle number concentrations and distributions change due to rapid (less than 1s) nucleation followed by a rapid increase of accumulation mode particle number concentrations. After this first sub-stage the presence of vehicle wake with recirculating particles and the possible influence of other transformation processes lead to complex interactions. Results from the two experimental datasets clearly confirm the presence of two separate groups of particles: (i) new particles, which are freshly emitted and come directly from the tailpipe and (ii) relatively aged particles, which are entrained within the recirculation vortices of the vehicle wake and reside there for a longer time. The two groups have different characteristics and interact with each other. This interaction has often been overlooked in past studies about local scale dispersion of nanoparticle from moving vehicles.

Overview of the synoptic and pollution situation over Europe during the EUCAARI-LONGREX field campaign

Abstract. In May 2008 the EUCAARI-LONGREX aircraft field campaign was conducted within the EUCAARI intensive observational period. The campaign aimed at studying the distribution and evolution of air mass properties on a continental scale. Airborne aerosol and trace gas measurements were performed aboard the German DLR Falcon 20 and the British FAAM BAe-146 aircraft. This paper outlines the meteorological situation over Europe during May 2008 and the temporal and spatial evolution of predominantly anthropogenic particulate pollution inside the boundary layer and the free troposphere. Time series data of six selected ground stations are used to discuss continuous measurements besides the single flights. The observations encompass total and accumulation mode particle number concentration (0.1–0.8 μm) and black carbon mass concentration as well as several meteorological parameters. Vertical profiles of total aerosol number concentration up to 10 km are compared to vertical profiles probed during previous studies. During the first half of May 2008 an anticyclonic blocking event dominated the weather over Central Europe. It led to increased pollutant concentrations within the centre of the high pressure inside the boundary layer. Due to long-range transport the accumulated pollution was partly advected towards Western and Northern Europe. The measured aerosol number concentrations over Central Europe showed in the boundary layer high values up to 14 000 cm−3 for particles in diameter larger 10 nm and 2300 cm−3 for accumulation mode particles during the high pressure period, whereas the middle free troposphere showed rather low concentrations of particulates. Thus a strong negative gradient of aerosol concentrations between the well mixed boundary layer and the clean middle troposphere occurred.