The European Commission Atmospheric Observatory 2019 report

A comprehensive set of essential atmospheric variables have been measured in 2019 at the European Commission Atmospheric Observatory on the site of the historical EMEP-GAW station of the JRC in Ispra to continue the assessment of the impact of European policies and international conventions on air pollution and climate forcing that started in 1985. The variables measured at the Atmospheric Observatory in Ispra included greenhouse gas concentrations (CO2, CH4), radon (222Rn) activity concentration, short-lived gaseous and particulate pollutant concentrations (CO, SO2, NO, NO2, O3, NMHCs, PM2.5 and its main ionic and carbonaceous constituents), atmospheric particle micro-physical characteristics (number concentration and size distribution) and optical properties (light scattering absorption and extinction in-situ, light scattering and extinction vertical profiles remotely), and eutrophying and acidifying species (SO42-, NO3-, NH4+) wet deposition. On-line measurements data are visible in real time at http://abc-is.jrc.ec.europa.eu/. Vegetation atmosphere exchanges (CO2, O3, H2O and heat) were measured at our Mediterranean Forest Flux Station of San Rossore, backed up by meteorological and pedological measurements. All measurements are performed under international projects and programmes including ICOS (Integrated Carbon Observation System), ACTRIS (Aerosols, Clouds and Trace gases Research Infra-Structure), EMEP (co-operative Programme for Monitoring and Evaluation of the long range transmission of air pollutants in Europe) and GAW (Global Atmosphere Watch), each of which requires 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. Data obtained at the Atmospheric Observatory are submitted to international open data bases (www.europe-fluxdata.eu, fluxnet.ornl.gov, www.ingos-infrastructure.eu, ACTRIS Data Portal) and can be freely downloaded (partly in real-time) 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 European Commission Atmospheric Observatory 2019 report presents the data produced during the past year in the context of the previous years of measurements. All the essential in-situ and remote sensing measurements scheduled for 2019 were regularly performed across the year, except for short periods due to breakdowns or needed for maintaining and calibrating the equipment. Greenhouse gas (GHG) measurements have been performed at the JRC Ispra site since October 2007. Minimum values of CH4, N2O and SF6 measured in Ispra under clean air conditions are close to marine background values, while CO2 levels can even be lower than the Mace Head baseline due to the continental biospheric CO2 sink. Deviations from baseline concentrations provide information about regional and larger scale European greenhouse gas sources. ICOS-compliant GHG concentration measurements from the Atmospheric Observatory 100 m high tower started in December 2016. The new GHG laboratory received the ICOS certificate on 30 November 2018. For CH4 concentration, we derived a mean increasing trend of +7.3 ppb yr-1 between 2017 and 2019, in line with the observed global CH4 trend of +8.5 ± 1.6 ppb yr-1 during this period. For CO2 concentrations, we calculated a mean increasing trend of +1.4 ppm yr-1 between 2017 and 2019, compared to a global trend of +2.3 ± 0.5 ppm yr-1. The calculation of the CO2 trends at Ispra is however complicated by large seasonal variations in the biospheric CO2 fluxes. Atmospheric pollution has been characterised at the JRC-Ispra site since 1986. In 2019, the annual mean concentrations of SO2, NO2 and CO were similar to or less than during the previous years, which confirms the general trend of improvement in these air quality indicators over the last 3 decades. The concentrations of anthropogenic volatile hydrocarbons like benzene and toluene also dropped down by a factor of 2 compared to 20 years ago. In contrast, most O3 exposure indicators did not significantly improve in 2019 (in line with the trend observed since 2010), which can certainly not be explained only by the warm and sunny conditions occurring during several months this year. The concentration of PM2.5 mass and of most of its components (NO3-, SO42-, NH4+, POM and EC) further decreased in 2019 compared to 2018, and reached historical minima. PM2.5 average chemical composition was dominated by carbonaceous species (POM: 44%, EC: 6%), followed by secondary inorganics (NH4+: 8%, NO3-: 12%, SO42-: 12%). As previously observed, there was a clear increase of NO3- contribution to PM2.5 when shifting from cleaner (PM2.5 < 10 μg/m³) to more polluted periods (PM2.5 > 25 μg/m³) during both cold and warmer months. PM2.5 (from gravimetric analyses at 20% RH) annual mean mass concentration (13 μg/m³) was well below the EU annual limit value (25 μg/m³). The long-term time series of PM concentrations still suggests a decreasing trend of - 1.0 μg m-3 yr-1 over the last 3 decades. The increase in particle number concentration observed since 2014 (following a net decrease till 2011) stopped after winter 2017, and the annual average (7000 cm-3) was in 2019 less than during previous years. The trends in aerosol physics and chemistry are reflected in the aerosol properties: The aerosol single scattering albedo (0.79 in 2019) has increased since 2014. The annual wet deposition fluxes of the main acidifying and eutrophying species NH4+, NO3-, and SO42- (1.5, 3.4, and 1.5 g m-2, respectively) was quite larger than during the previous years, and similar to the values during the 2000’s. Nine rain samples with pH vegetation net ecosystem exchange (NEE) data obtained in 2019 suggest that the pine tree forest was a smaller net sink for CO2 in 2019 (82 gC/m²) compared to previous years. Although NEE is directly measured, this result is still preliminary and need a thorough re-analysis before conclusions can be drawn.
JRC.C.5-Air and Climate