Response of fine particulate matter concentrations to changes of emissions and temperature in Europe

<p>PMCAMx-2008, a three dimensional chemical transport model (CTM), was applied in Europe to quantify the changes in fine particle (PM_2.5) concentration in response to different emission reductions as well as to temperature increase. A summer and a winter simulation period were used, to investigate the seasonal dependence of the PM_2.5 response to 50% reductions of sulfur dioxide (SO₂), ammonia (NH₃), nitrogen oxides (NO_x), anthropogenic volatile organic compounds (VOCs) and anthropogenic primary organic aerosol (POA) emissions and also to temperature increases of 2.5 and 5 K. Reduction of NH₃ emissions seems to be the most effective control strategy for reducing PM_2.5, in both periods, resulting in a decrease of PM_2.5 up to 5.1 μg m⁻³ and 1.8 μg m⁻³ (5.5% and 4% on average) during summer and winter respectively, mainly due to reduction of ammonium nitrate (NH₄NO₃) (20% on average in both periods). The reduction of SO₂ emissions decreases PM_2.5 in both periods having a significant effect over the Balkans (up to 1.6 μg m⁻³) during the modeled summer period, mainly due to decrease of sulfate (34% on average over the Balkans). The anthropogenic POA control strategy reduces total OA by 15% during the modeled winter period and 8% in the summer period. The reduction of total OA is higher in urban areas close to its emissions sources. A slight decrease of OA (8% in the modeled summer period and 4% in the modeled winter period) is also predicted after a 50% reduction of VOCs emissions due to the decrease of anthropogenic SOA. The reduction of NO_x emissions reduces PM_2.5(up to 3.4 μg m⁻³) during the summer period, due to a decrease of NH₄NO₃, causing although an increase of ozone concentration in major urban areas and over Western Europe. Additionally, the NO_x control strategy actually increases PM_2.5 levels during the winter period, due to more oxidants becoming available to react with SO₂ and VOCs. The increase of temperature results in a decrease of PM_2.5 in both periods over Central Europe, mainly due to a decrease of NH₄NO₃ during summer (18%) and fresh POA during wintertime (35%). Significant increases of OA are predicted during the summer due mainly to the increase of biogenic VOC emissions. On the contrary, OA is predicted to decrease in the modeled winter period due to the dominance of fresh POA reduction and the small biogenic SOA contribution to OA. The resulting increase of oxidant levels from the temperature rise lead to an increase of sulfate levels in both periods, mainly over North Europe and the Atlantic Ocean. The substantial reduction of PM_2.5 components due to emissions reductions of their precursors outlines the importance of emissions for improving air quality, while the sensitivity of PM_2.5 concentrations to temperature changes indicate that climate interactions need to be considered when predicting future levels of PM, with different net effects in different parts of Europe.</p

Evaluation of a three-dimensional chemical transport model (PMCAMx) in the European domain during the EUCAARI May 2008 campaign

PMCAMx-2008, a detailed three-dimensional chemical transport model (CTM), was applied to Europe to simulate the mass concentration and chemical composition of particulate matter (PM) during May 2008. The model includes a state-of-the-art organic aerosol module which is based on the volatility basis set framework treating both primary and secondary organic components as semivolatile and photochemically reactive. The model performance is evaluated against high time resolution aerosol mass spectrometer (AMS) ground and airborne measurements. Overall, organic aerosol is predicted to account for 32% of total PM1 at ground level during May 2008, followed by sulfate (30%), crustal material and sea-salt (14%), ammonium (13%), nitrate (7%), and elemental carbon (4%). The model predicts that fresh primary OA (POA) is a small contributor to organic PM concentrations in Europe during late spring, and that oxygenated species (oxidized primary and biogenic secondary) dominate the ambient OA. The Mediterranean region is the only area in Europe where sulfate concentrations are predicted to be much higher than the OA, while organic matter is predicted to be the dominant PM1 species in central and northern Europe. The comparison of the model predictions with the ground measurements in four measurement stations is encouraging. The model reproduces more than 94% of the daily averaged data and more than 87% of the hourly data within a factor of 2 for PM1 OA. The model tends to predict relatively flat diurnal profiles for PM1 OA in many areas, both rural and urban in agreement with the available measurements. The model performance against the high time resolution airborne measurements at multiple altitudes and locations is as good as its performance against the ground level hourly measurements. There is no evidence of missing sources of OA aloft over Europe during this period.</p

Simulating ultrafine particle formation in Europe using a regional CTM: contribution of primary emissions versus secondary formation to aerosol number concentrations

<p>A three-dimensional regional chemical transport model (CTM) with detailed aerosol microphysics, PMCAMx-UF, was applied to the European domain to simulate the contribution of direct emissions and secondary formation to total particle number concentrations during May 2008. PMCAMx-UF uses the Dynamic Model for Aerosol Nucleation and the Two-Moment Aerosol Sectional (TOMAS) algorithm to track both aerosol number and mass concentration using a sectional approach. The model predicts nucleation events that occur over scales of hundreds up to thousands of kilometers especially over the Balkans and Southeast Europe. The model predictions were compared against measurements from 7 sites across Europe. The model reproduces more than 70% of the hourly concentrations of particles larger than 10 nm (<em>N</em>₁₀) within a factor of 2. About half of these particles are predicted to originate from nucleation in the lower troposphere. Regional nucleation is predicted to increase the total particle number concentration by approximately a factor of 3. For particles larger than 100 nm the effect varies from an increase of 20% in the eastern Mediterranean to a decrease of 20% in southern Spain and Portugal resulting in a small average increase of around 1% over the whole domain. Nucleation has a significant effect in the predicted<em>N</em>₅₀ levels (up to a factor of 2 increase) mainly in areas where there are condensable vapors to grow the particles to larger sizes. A semi-empirical ternary sulfuric acid-ammonia-water parameterization performs better than the activation or the kinetic parameterizations in reproducing the observations. Reducing emissions of ammonia and sulfur dioxide affects certain parts of the number size distribution.</p

The Finokalia Aerosol Measurement Experiment – 2008 (FAME-08): an overview

A month (4 May to 8 June 2008) of ambient aerosol, air ion and gas phase sampling (Finokalia Aerosol Measurement Experiment 2008, FAME-08) was conducted at Finokalia, on the island of Crete, Greece. The purpose of the study was to characterize the physical and chemical properties of aged aerosol and to investigate new particle formation. Measurements included aerosol and air ion size distributions, size-resolved chemical composition, organic aerosol thermal volatility, water uptake and particle optical properties (light scattering and absorption). Statistical analysis of the aerosol mass concentration variations revealed the absence of diurnal patterns suggesting the lack of strong local sources. Sulfates accounted for approximately half of the particulate matter less than 1 micrometer in diameter (PM1) and organics for 28%. The PM1 organic aerosol fraction was highly oxidized with 80% water soluble. The supermicrometer particles were dominated by crustal components (50%), sea salt (24%) and nitrates (16%). The organic carbon to elemental carbon (OC/EC) ratio correlated with ozone measurements but with a one-day lag. The average OC/EC ratio for the study period was equal to 5.4. For three days air masses from North Africa resulted in a 6-fold increase of particulate matter less than 10 micrometers in diameter (PM10) and a decrease of the OC/EC ratio by a factor of 2. Back trajectory analysis, based on FLEXPART footprint plots, identified five source regions (Athens, Greece, Africa, other continental and marine), each of which influenced the PM1 aerosol composition and properties. Marine air masses had the lowest PM1 concentrations and air masses from the Balkans, Turkey and Eastern Europe the highest.</p