Long term trends in aerosol optical characteristics in the Po Valley, Italy

Aerosol properties have been monitored by ground-based in situ and remote sensing measurements at the station for atmospheric research located in Ispra, on the edge of the Po Valley, for almost one decade. In situ measurements are performed according to Global Atmosphere Watch recommendations, and quality is assured through the participation in regular inter-laboratory comparisons. Sunphotometer data are produced by the Aerosol Robotic Network (AERONET). Data show significant decreasing trends over the 2004–2010 period for a number of variables, including particulate matter (PM) mass concentration, aerosol scattering, backscattering and absorption coefficients, and aerosol optical thickness (AOT). In situ measurement data show no significant trends in the aerosol backscatter ratio, but they do show a significant decreasing trend of about −0.7±0.3%yr−1 in the aerosol single scattering albedo (SSA) in the visible light range. Similar trends are observed in the SSA retrieved from sun-photometer measurements. Correlations appear between in situ PM mass concentration and aerosol scattering coefficient, on the one hand, and elemental carbon (EC) concentration and aerosol absorption coefficient, on the other hand. However, no increase in the EC /PM ratio was observed, which could have explained the decrease in SSA. The application of a simple approximation to calculate the direct radiative forcing by aerosols suggests a significant diminution in their cooling effect, mainly due to the decrease in AOT. Applying the methodology we present to those sites, where the necessary suite of measurements is available, would provide important information to inform future policies for air-quality enhancement and fast climate change mitigation.JRC.H.2-Air and Climat

JRC Ispra EMEP - GAW Regional Station for Atmospheric Research - 2005 Report

The aim of the JRC-Ispra station for atmospheric research (45°49'N, 8°38'E) is to monitor atmospheric parameters (pollutant concentrations and fluxes, atmospheric particle chemical composition, number size distribution and optical properties) to contribute in assessing the impact of European policies on air pollution and climate change. The station has been operated continuously since November 1985, with a gap in gas phase data due to a severe breakdown of the data acquisition system in 2003 though. The measurements performed in 2005 led to annual averages of ca. 43 µg m-3 O3, 4 µg m-3 SO2, 16 µg m-3 NO2, 0.8 mg m-3 CO and 41 µg m-3 PM10. Carbonaceous species (organic matter plus elemental carbon) are the main constituents of both PM10 and PM2.5 (> 50%) followed by (NH4)2SO4 and NH4NO3 (a bit less than 20% each). The measurements confirmed the seasonal variations observed over the previous years, mainly driven by meteorology rather than by changes in emissions. Aerosol physical and optical properties were measured from 2004. The average particle number (from 6 nm to 10 µm) was about 10000 cm-3 in 2005. The mean (close to dry) aerosol single scattering albedo (a key parameter for determining the aerosol direct radiative forcing) was 0.80. Long-term trends (over 20 years) show decreases in sulfur concentrations and deposition, and in extreme ozone value occurrence frequency. The decreasing trends in nitrogen oxides, reduced nitrogen species, and PM concentrations are much less marked.JRC.H.2-Climate chang

JRC Ispra EMEP-GAW Regional Station for Atmospheric Research - 2007 Report

The aim of the JRC-Ispra station for atmospheric research (45°49'N, 8°38'E) is to monitor atmospheric parameters (pollutant concentrations and fluxes, atmospheric particle chemical composition, number size distribution and optical properties) to contribute in assessing the impact of European policies on air pollution and climate change. The station has been operated continuously since November 1985, with a gap in gas phase data due to a severe breakdown of the data acquisition system in 2003 though. The measurements performed in 2007 led to annual averages of ca. 32 µg m-3 O3, 0.8 µg m-3 SO2, 21 µg m-3 NO2 and 30 µg m-3 PM10. Carbonaceous species (organic matter plus elemental carbon) are the main constituents of PM2.5 (> 55 %) followed by NH4NO3 (20-30 %) and (NH4)2SO4 (10-20 %). The measurements confirmed the seasonal variations observed over the previous years, mainly driven by meteorology rather than by changes in emissions. Aerosol physical and optical properties were also measured in 2007. The average particle number (from 10 nm to 10 µm) was about 9200 cm-3 in 2007. The mean (close to dry) aerosol single scattering albedo (0.79) was low compared to the values generally observed in Europe, which means that the cooling effect of aerosols is reduced in our region compared to others. Long-term trends (over 20 years) show consistent decreases in sulfur concentrations and deposition, PM mass concentration (-0.9 µg m-3 yr-1) and in extreme ozone value occurrence frequency. The decreasing trends in oxidised and reduced nitrogen species are much less pronounced. However, historical minimum in NO3-, NH4+, (and SO42-) wet deposition, as well as in O3 pollution indicators (AOT40 and SOMO35) were observed in 2007.JRC.H.2-Climate chang

JRC Ispra EMEP - GAW Regional Station for Atmospheric Research - 2006 Report

The aim of the JRC-Ispra station for atmospheric research (45°49'N, 8°38'E) is to monitor atmospheric parameters (pollutant concentrations and fluxes, atmospheric particle chemical composition, number size distribution and optical properties) to contribute in assessing the impact of European policies on air pollution and climate change. The station has been operated continuously since November 1985, with a gap in gas phase data due to a severe breakdown of the data acquisition system in 2003 though. The measurements performed in 2006 led to annual averages of ca. 41 µg m-3 O3, 1.1 µg m-3 SO2, 21 µg m-3 NO2 and 33 µg m-3 PM10. Carbonaceous species (organic matter plus elemental carbon) are the main constituents of PM2.5 (> 50 %) followed by (NH4)2SO4 (10-20 %) and NH4NO3 (20-30 %). The measurements confirmed the seasonal variations observed over the previous years, mainly driven by meteorology rather than by changes in emissions. Aerosol physical and optical properties were also measured in 2006. The average particle number (from 6 nm to 10 µm) was about 10000 cm-3 in 2006. The mean (close to dry) aerosol single scattering albedo (a key parameter for determining the aerosol direct radiative forcing) was 0.79. Long-term trends (over 20 years) show decreases in sulfur concentrations and deposition, and in extreme ozone value occurrence frequency, although the latter was higher in compared to the last two years The decreasing trends in nitrogen oxides, reduced nitrogen species, and PM concentrations are much less pronounced.JRC.H.2-Climate chang

JRC Ispra EMEP - GAW Regional Station for Atmospheric Research 2008 Report

The aim of the JRC-Ispra station for atmospheric research (45°49'N, 8°38'E) is to monitor atmospheric parameters (pollutant concentrations and fluxes, atmospheric particle chemical composition, number size distribution and optical properties) to contribute in assessing the impact of European policies on air pollution and climate change. The station has been operated continuously since November 1985, with a gap in gas phase data due to a severe breakdown of the data acquisition system in 2003 though. The measurements performed in 2008 led to annual averages of ca. 34 µg m-3 O3, 0.7 µg m-3 SO2, 20 µg m-3 NO2 and 27 µg m-3 PM10. Carbonaceous species (organic matter plus elemental carbon) are the main constituents of PM2.5 (~57 %) followed by NH4NO3 (20-30 %) and (NH4)2SO4 (10-20 %). The data from 2008 confirmed the seasonal variations observed over the previous years, mainly driven by meteorology rather than by changes in emissions, as revealed by the lidar measurements. Aerosol physical and optical properties were also measured in 2008. The average particle number (from 10 nm to 10 µm) was about 8000 cm-3 in 2008. The mean (close to dry) aerosol single scattering albedo (0.75) was low compared to the values generally observed in Europe, which means that the cooling effect of aerosols is reduced in our region compared to others. Long-term trends (over 20 years) show consistent decreases in sulfur concentrations and deposition, PM mass concentration (-0.9 µg m-3 yr-1), and from 2003 in ozone concentrations too. The decreasing trends in oxidised and reduced nitrogen species are much less pronounced.JRC.H.2-Climate chang

JRC Ispra EMEP - GAW Regional Station for Atmospheric Research, 2009 Report

The aim of the JRC-Ispra station for atmospheric research (45°49¿N, 8°38¿E) is to monitor atmospheric parameters (pollutant concentrations and fluxes, atmospheric particle chemical composition, number size distribution and optical properties) to contribute in assessing the impact of European policies on air pollution and climate change. The station has been operated continuously since November 1985, with a gap in gas phase data in 2003 and 2009 due to a breakdown of the data acquisition system and lack of man-power, respectively. The measurements performed in 2009 led to annual average of 26.8 µg m-3 for PM10, well below the European annual limit value of 40 µg/m³ (the European directive 1999/30/EC for the year 2005 and onwards). In addition, the measurements performed in 2009 led to annual average of 19.0 µg m-3 for PM2.5, well below the future European annual limit value of 25 µg/m³ (European directive 2008/50/EC for the year 2015 and onwards). Carbonaceous species (organic matter plus elemental carbon) are the main constituents of PM2.5 (~57 %) followed by (NH4)2SO4 (24 %) and NH4NO3 (12 %). The data from 2009 confirmed the seasonal variations observed over the previous years, mainly driven by meteorology rather than by changes in emissions, as revealed by the lidar measurements. Aerosol physical and optical properties were also measured in 2009. The average particle number (from 10 nm to 10 µm) was about 7400 cm-3 and the mean geometric diameter was 70 nm. Their hygroscopic growth at 90% RH varies from <1.2 in December to 1.25 ¿ 1.35 (size dependent) in June. The mean (close to dry) aerosol single scattering albedo at ¿ = 550 nm was 0.76, and it was low compared to the values generally observed in Europe, which means that the cooling effect of aerosols is reduced in our region compared to others. Long-term trends (over 20 years) show consistent decreases in sulfur concentrations and deposition, PM mass concentration (about -0.9 µg m-3 yr-1), and from 2003 onwards also a slight decease in ozone concentrations too. The decreasing trends in oxidised and reduced nitrogen species are much less pronounced.JRC.DDG.H.2-Climate change and air qualit

Intercomparison of 15 aerodynamic particle size spectrometers (APS 3321): uncertainties in particle sizing and number size distribution

Aerodynamic particle size spectrometers are a well-established method to measure number size distributions of coarse mode particles in the atmosphere. Quality assurance is essential for atmospheric observational aerosol networks to obtain comparable results with known uncertainties. In a laboratory study within the framework of ACTRIS (Aerosols, Clouds, and Trace gases Research Infrastructure Network), 15 aerodynamic particle size spectrometers (APS model 3321, TSI Inc., St. Paul, MN, USA) were compared with a focus on flow rates, particle sizing, and the unit-to-unit variability of the particle number size distribution. Flow rate deviations were relatively small (within a few percent), while the sizing accuracy was found to be within 10 % compared to polystyrene latex (PSL) reference particles. The unit-to-unit variability in terms of the particle number size distribution during this study was within 10 % to 20 % for particles in the range of 0.9 up to 3 µm, which is acceptable for atmospheric measurements. For particles smaller than that, the variability increased up to 60 %, probably caused by differences in the counting efficiencies of individual units. Number size distribution data for particles smaller than 0.9 µm in aerodynamic diameter should only be used with caution. For particles larger than 3 µm, the unit-to-unit variability increased as well. A possible reason is an insufficient sizing accuracy in combination with a steeply sloping particle number size distribution and the increasing uncertainty due to decreasing counting. Particularly this uncertainty of the particle number size distribution must be considered if higher moments of the size distribution such as the particle volume or mass are calculated, which require the conversion of the aerodynamic diameter measured to a volume equivalent diameter. In order to perform a quantitative quality assurance, a traceable reference method for the particle number concentration in the size range 0.5–3 µm is needed.JRC.H.2-Air and Climat

JRC-Ispra Atmosphere - Biosphere - Climate Integrated monitoring Station: 2016 report

A comprehensive set of essential atmospheric variables have been measured at the JRC-Ispra Atmosphere - Biosphere - Climate Integrated monitoring Station (ABC-IS) for several years to assess the impact of European policies and international conventions on air pollution and climate forcing. The variables we measure at the Atmospheric Observatory in Ispra include greenhouse gas concentrations (CO2, CH4, N2O, SF6), radon (222Rn) activity concentration, short-lived gaseous and particulate pollutant (CO, SO2, NO, NO2, O3, PM2.5 and its main ionic and carbonaceous constituents) concentrations, atmospheric particle micro-physical characteristics (number concentration and size distribution) and optical properties (light scattering and absorption in-situ, light scattering and extinction vertical profiles remotely), eutrophying and acidifying species (SO42-, NO3-, NH4+) wet deposition. Vegetation atmosphere exchanges (CO2, O3, H2O and heat) are measured at our Forest Flux Station of San Rossore, backed up by meteorological and pedological measurements. The ABC-IS 2016 report presents the data produced during the past year in the context of the previous years of measurements.JRC.C.5-Air and Climat

JRC – Ispra: Atmosphere – Biosphere – Climate Integrated monitoring Station: 2015 Report

A comprehensive set of essential atmospheric variables have been measured at the JRC-Ispra Atmosphere -Biosphere - Climate Integrated monitoring Station (ABC-IS) for several years to detect the impact of European policies and international conventions on air pollution and climate forcing. The variables we measure include greenhouse gas concentrations (CO2, CH4, N2O, SF6), radon (222Rn)activity concentration, short-lived gaseous and particulate pollutants (CO, SO2, NO, NO2, O3, PM2.5 and its main ionic and carbonaceous constituents), atmospheric particle micro-physical characteristics (number concentration and size distribution) and optical properties (light scattering and absorption in-situ, light scattering and extinction vertical profiles remotely), eutrophying and acidifying species (SO42-, NO3-, NH4+) wet deposition, and vegetation atmosphere exchanges (CO2, O3, H2O and heat), backed up by meteorological and pedological measurements. All the measurements performed at ABC-IS are made under international projects and programs like InGOS (Integrated non-CO2 Greenhouse gas Observation System), ACTRIS (the EU research Infra-Structure for the observation of Aerosols, Clouds and TRace gases), EMEP (co-operative Program for Monitoring and Evaluation of the long range transmission of air pollutants in Europe) and GAW (Global Atmosphere Watch), which implies the use of standard methods and scales, and the participation in quality assurance activities. The JRC has a leading role in ACTRIS and EMEP regarding the quality assurance for carbonaceous aerosol measurements. All the data obtained at ABC-IS are submitted to international open data bases (www.europe-fluxdata.eu, fluxnet.ornl.gov, www.ingos-infrastructure.eu, ebas.nilu.no,) and can be freely downloaded from these web sites. The data we produce are used in European wide assessments, for model inputs and validation, and for calibrating satellite airborne sensors. The ABC-IS 2015 report presents the data produced during the past year in the context of the previous years of measurements.JRC.C.5-Air and Climat

Intercomparison of 15 aerodynamic particle size spectrometers (APS 3321) : uncertainties in particle sizing and number size distribution

Aerodynamic particle size spectrometers are a well-established method to measure number size distributions of coarse mode particles in the atmosphere. Quality assurance is essential for atmospheric observational aerosol networks to obtain comparable results with known uncertainties. In a laboratory study within the framework of ACTRIS (Aerosols, Clouds, and Trace gases Research Infrastructure Network), 15 aerodynamic particle size spectrometers (APS model 3321, TSI Inc., St. Paul, MN, USA) were compared with a focus on flow rates, particle sizing, and the unit-tounit variability of the particle number size distribution. Flow rate deviations were relatively small (within a few percent), while the sizing accuracy was found to be within 10% compared to polystyrene latex (PSL) reference particles. The unit-to-unit variability in terms of the particle number size distribution during this study was within 10% to 20% for particles in the range of 0.9 up to 3 mu m, which is acceptable for atmospheric measurements. For particles smaller than that, the variability increased up to 60 %, probably caused by differences in the counting efficiencies of individual units. Number size distribution data for particles smaller than 0.9 mu m in aerodynamic diameter should only be used with caution. For particles larger than 3 mu m, the unit-tounit variability increased as well. A possible reason is an insufficient sizing accuracy in combination with a steeply sloping particle number size distribution and the increasing uncertainty due to decreasing counting. Particularly this uncertainty of the particle number size distribution must be considered if higher moments of the size distribution such as the particle volume or mass are calculated, which require the conversion of the aerodynamic diameter measured to a volume equivalent diameter. In order to perform a quantitative quality assurance, a traceable reference method for the particle number concentration in the size range 0.5-3 mu m is needed.Peer reviewe