Monica Crippa

Ubiquity of organic nitrates from nighttime chemistry in the European submicron aerosol

In the atmosphere night time removal of volatile organic compounds (VOC) is initiated to a large extent by reaction with the nitrate radical (NO3) forming organic nitrates which partition between gas and particulate phase. Here we show based on particle phase measurements performed at a suburban site in the Netherlands that organic nitrates contribute substantially to particulate nitrate and organic mass. Comparisons with a chemistry transport model (CTM) indicate that most of the measured particulate organic nitrates are formed by NO3 oxidation. Using aerosol composition data from three intensive observation periods at numerous measurement sites across Europe, we conclude that organic nitrates are a considerable fraction of fine particulate matter (PM1) at the continental scale. Organic nitrates represent 34% to 44% of measured submicron aerosol nitrate and are found at all urban and rural sites, implying a substantial potential of PM reduction by NOx emission control.In the atmosphere nighttime removal of volatile organic compounds is initiated to a large extent by reaction with the nitrate radical (NO3) forming organic nitrates which partition between gas and particulate phase. Here we show based on particle phase measurements performed at a suburban site in the Netherlands that organic nitrates contribute substantially to particulate nitrate and organic mass. Comparisons with a chemistry transport model indicate that most of the measured particulate organic nitrates are formed by NO3 oxidation. Using aerosol composition data from three intensive observation periods at numerous measurement sites across Europe, we conclude that organic nitrates are a considerable fraction of fine particulate matter (PM1) at the continental scale. Organic nitrates represent 34% to 44% of measured submicron aerosol nitrate and are found at all urban and rural sites, implying a substantial potential of PM reduction by NOx emission control.

EDGAR v4.3.2 Global Atlas of the three major GreenhouseGas Emissions for the period 1970–2012

The Emissions Database for Global Atmospheric Research (EDGAR) compiles anthropogenic emissions data for greenhouse gases (GHGs), and for multiple air pollutants, based on international statistics and emission factors. EDGAR data provide quantitative support for atmospheric modelling and for mitigation scenario and impact assessment analyses as well as for policy evaluation. The new version (v4.3.2) of the EDGAR emission inventory provides global estimates, broken down to IPCC-relevant source-sector levels, from 1970 (the year of the European Union’s first Air Quality Directive) to 2012 (the end year of the first commitment period of the Kyoto Protocol, KP). Strengths of EDGAR v4.3.2 include global geo-coverage (226 countries), continuity in time, and comprehensiveness in activities. Emissions of multiple chemical compounds, GHGs as well as air pollutants, from relevant sources (fossil fuel activities but also, for example, fermentation processes in agricultural activities) are compiled following a bottom-up (BU), transparent and IPCC-compliant methodology. This paper describes EDGAR v4.3.2 developments with respect to three major long-lived GHGs (CO2, CH4, and N2O) derived from a wide range of human activities apart from the land-use, land-use change and forestry (LULUCF) sector and apart from savannah burning; a companion paper quantifies and discusses emissions of air pollutants. Detailed information is included for each of the IPCC-relevant source sectors, leading to global totals for 2010 (in the middle of the first KP commitment period) (with a 95 % confidence interval in parentheses): 33.6(±5.9) Pg CO2 yr−1, 0.34(±0.16) Pg CH4 yr−1, and 7.2(±3.7) Tg N2O yr−1. We provide uncertainty factors in emissions data for the different GHGs and for three different groups of countries: OECD countries of 1990, countries with economies in transition in 1990, and the remaining countries in development (the UNFCCC nonAnnex I parties). We document trends for the major emitting countries together with the European Union in more Published by Copernicus Publications. 960 G. Janssens-Maenhout et al.: EDGAR greenhouse gas emissions detail, demonstrating that effects of fuel markets and financial instability have had greater impacts on GHG trends than effects of income or population. These data (https://doi.org/10.5281/zenodo.2658138, Janssens-Maenhout et al., 2019) are visualised with annual and monthly global emissions grid maps of 0.1× 0.1 for each source sector. 1 Historical evolution An essential component of the UN Framework Convention on Climate Change (UNFCCC, 1992) is the collection of nationally reported inventories and information on these greenhouse gas (GHG) emission inventory time series. At the time the UNFCCC was established, the 24 members of the OECD in 1990 and 16 other European countries and Russia were considered liable for “the largest share of historical and current global emissions of GHG” and taken up in Annex I to the UNFCCC. These Annex I countries and the European Union1 submit annually complete inventories of GHG emissions from the 1990 base year2 until the latest year for which full accounting is completed and reviewed (typically with a 2-year time lag), and these inventories are all reviewed to ensure transparency, completeness, comparability, consistency and accuracy3. This allows for most of these Annex I countries to track progress towards their reduction targets committed under the Kyoto Protocol (UNFCCC, 1997). Other (non-Annex I) countries are encouraged to submit their GHG inventories as part of their National Communications and Biennial Update Reports (BURs). The GHG inventories of nonAnnex I countries were required to cover CO2, CH4 and N2O emissions for 1 year (1990 or 1994), without specific documentation and only subject to a brief review. However, the Paris Agreement (UNFCCC, 2015) requires submission every 2 years of BURs4, which are subject to international consultation and analysis. Theoretically, UNFCCC should receive at the latest after 2 years national emissions inventories from each of the 197 countries, but as shown in Fig. 1a, not all countries did provide a national inventory and 154 countries did not provide a completed (i.e. year-2) time se1This includes the 28 Member States of the European Union (EU) as of 1 July 2013. 2For some economies in transition, another year such as 1988 or 1989 can be chosen under UNFCCC as the base year. These GHG emissions are mainly sources, but also include carbon stock sinks for which the human-induced part needs to be assessed with care (Grassi et al., 2018). 3These five principles of a good reporting practice are defined in the UNFCCC guidelines for national GHG inventory, e.g. https://pdfs.semanticscholar.org/3c30/ a1bd769dee5299746e0af825c7ab4ed55fba.pdf. EDGAR uses the term “comprehensiveness” to summarise these principles. 4The first BUR submitted should cover the inventory for the year no more than 4 years prior to the submission data, and subsequent BURs should be submitted every 2 years, but flexibility is given to the least developed countries and small island developing states. ries of inventories. In addition, many countries lack a welldeveloped statistical infrastructure, which is needed for an accurate bottom-up (BU) inventory. Figure 1b presents the latest year that is covered with a national inventory, with dates for quite a few countries more than 10 years ago: for most South-East Asian countries this is between 2004 and 2007 and for most African countries between 2000 and 2003. As such, the collection of national reports/communications does not provide a complete, consistent and comparable global dataset which can be used to understand the global budgets of the most important GHG emissions and their impact on climate. Very few bottom-up inventories of global anthropogenic emissions have been produced with continued effort for more than 2 decades. The Carbon Dioxide Information Analysis Centre (CDIAC) (Boden et al., 2017; Andres et al., 2014) and the Emissions Database for Global Atmospheric Research (EDGAR) (Olivier and Janssens-Maenhout, 2016; Olivier et al., 2016) provide global totals, whereas the IEA provides CO2 estimates from fuel combustion only and the FAO CH4 from agriculture only. While CDIAC ceased operation in September 2017, the Open-source Data Inventory for Anthropogenic CO2 (ODIAC) (Oda et al., 2018) continued to use the CDIAC data and combined these with geospatial proxies (including night light satellite maps) to provide CO2 grid maps, as EDGAR is also doing (using other geospatial proxies). In addition, the new Community Emissions Data System (CEDS) of Hoesly et al. (2018) builds upon existing inventories to provide a new gridded dataset of all emission species for the Climate Model Inter-comparison Programme CMIP6. The scientific community started to bring together these anthropogenic BU emissions with top-down estimates covering also the natural component to obtain the Global Carbon Budget (GCB) (Le Quéré et al., 2018) and the Global Methane Budget (Saunois et al., 2016). These budgets are important input for the periodic global stocktake that the Paris Agreement envisages from 2023 onwards (with the submitted inventories for 2021). Even though significant progress in inventory compilation has been made, the overall uncertainty of the global total has become larger over time because the share of emissions from non-Annex I countries (with less developed statistical infrastructure) increased from less than 40 % in 1990 to more than 60 % in 2012, as shown in Fig. 2. To support both science and policy making with the monitoring and verification of the GHG emissions, it is important Earth Syst. Sci. Data, 11, 959–1002, 2019 www.earth-syst-sci-data.net/11/959/2019/ G. Janssens-Maenhout et al.: EDGAR greenhouse gas emissions 961 Figure 1. (a) Inventory submission as received at UNFCCC (by January 2017) for all countries: expressed with the year of emission reporting in which the latest national communication to UNFCCC took place. (b) Inventory submission as received at UNFCCC (by January 2017) for all countries expressed with the latest year of emission that is covered in the inventory submitted to UNFCCC. Figure 2. Relative contribution of the Annex I and non-Annex I countries to the global total GHG emissions. The red, brown and orange dashed parts of the stack correspond to the non-Annex I share that increases from about 1/3 in 1990 to almost 2/3 in 2012. www.earth-syst-sci-data.net/11/959/2019/ Earth Syst. Sci. Data, 11, 959–1002, 2019 962 G. Janssens-Maenhout et al.: EDGAR greenhouse gas emissions that emissions are estimated by using comparable methodologies, consistent source allocation and comprehensive coverage of the globe. The EDGAR v4.3.2 global inventory illustrates the result of a bottom-up technology-based compilation of countryand sector-specific emission time series for 1970–2012. Furthermore, the monthly resolution and global grid maps at a spatial resolution of 0.1× 0.1 allow direct use in atmospheric models as well as in analyses of policy impacts. The first version of the Emissions Database for Global Atmospheric Research (EDGAR v2) answered the needs of the air quality community to map technological parameters of air pollution sources and was published by Olivier et al. (1996). Since then, several updated versions (Olivier, 2002) have been released (EDGAR-HYDE, EDGAR v3.2, EDGAR 3.2 FT2000). Driven by the development of scientific knowledge on emission generating processes and by the availability of more recent information, the EDGAR v4 datasets were constructed including new emission factors and additional end-of-pipe abatement measures. The specification of the combustion technology and its endof-pipe abatement is more important for air pollutants and aerosols than for GHGs. CO2 combustion emissions are fueldetermined and carbon capture and storage are not yet implemented at an opera

Novel insights on new particle formation derived from a pan-european observing system

The formation of new atmospheric particles involves an initial step forming stable clusters less than a nanometre in size (<~1 nm), followed by growth into quasi-stable aerosol particles a few nanometres (~1–10 nm) and larger (>~10 nm). Although at times, the same species can be responsible for both processes, it is thought that more generally each step comprises differing chemical contributors. Here, we present a novel analysis of measurements from a unique multi-station ground-based observing system which reveals new insights into continental-scale patterns associated with new particle formation. Statistical cluster analysis of this unique 2-year multi-station dataset comprising size distribution and chemical composition reveals that across Europe, there are different major seasonal trends depending on geographical location, concomitant with diversity in nucleating species while it seems that the growth phase is dominated by organic aerosol formation. The diversity and seasonality of these events requires an advanced observing system to elucidate the key processes and species driving particle formation, along with detecting continental scale changes in aerosol formation into the future.

Trends in chemical composition of global and regional population-weighted fine particulate matter estimated for 25 years

We interpret in situ and satellite observations with a chemical transport model (GEOS-Chem, downscaled to 0.1° × 0.1°) to understand global trends in population-weighted mean chemical composition of fine particulate matter (PM2.5). Trends in observed and simulated population-weighted mean PM2.5 composition over 1989-2013 are highly consistent for PM2.5 (-2.4 vs -2.4%/yr), secondary inorganic aerosols (-4.3 vs -4.1%/yr), organic aerosols (OA, -3.6 vs -3.0%/yr) and black carbon (-4.3 vs -3.9%/yr) over North America, as well as for sulfate (-4.7 vs -5.8%/yr) over Europe. Simulated trends over 1998-2013 also have overlapping 95% confidence intervals with satellite-derived trends in population-weighted mean PM2.5 for 20 of 21 global regions. Over 1989-2013, most (79%) of the simulated increase in global population-weighted mean PM2.5 of 0.28 μg m-3yr-1 is explained by significantly (p < 0.05) increasing OA (0.10 μg m-3yr-1), nitrate (0.05 μg m-3yr-1), sulfate (0.04 μg m-3yr-1), and ammonium (0.03 μg m-3yr-1). These four components predominantly drive trends in population-weighted mean PM2.5 over populous regions of South Asia (0.94 μg m-3yr-1), East Asia (0.66 μg m-3yr-1), Western Europe (-0.47 μg m-3yr-1), and North America (-0.32 μg m-3yr-1). Trends in area-weighted mean and population-weighted mean PM2.5 composition differ significantly.

Spatial Variation of Aerosol Chemical Composition and Organic Components Identified by Positive Matrix Factorization in the Barcelona Region.

The spatial distribution of PM1 components in the Barcelona metropolitan area was investigated using on-road mobile measurements of atmospheric particle- and gas-phase compounds during the DAURE campaign in March 2009. Positive matrix factorization (PMF) applied to organic aerosol (OA) data yielded 5 factors: hydrocarbon-like OA (HOA), cooking OA (COA), biomass burning OA (BBOA), and low volatility and semivolatile oxygenated OA (LV-OOA and SV-OOA). The area under investigation (∼500 km(2)) was divided into six zones (city center, harbor, industrial area, precoastal depression, 2 mountain ranges) for measurements and data analysis. Mean zonal OA concentrations are 4.9-9.5 μg m(-3). The area is heavily impacted by local primary emissions (HOA 14-38%, COA 10-18%, BBOA 10-12% of OA); concentrations of traffic-related components, especially black carbon, are biased high due to the on-road nature of the measurements. The formation of secondary OA adds more than half of the OA burden outside the city center (SV-OOA 14-40%, LV-OOA 17-42% of OA). A case study of one measurement drive from the shore to the precoastal mountain range furthest downwind of the city center indicates the importance of nonfossil over anthropogenic secondary OA based on OA/CO.

Influence of local production and vertical transport on the organic aerosol budget over Paris

We performed a case study of the organic aerosol (OA) budget during the MEGAPOLI campaign during summer 2009 in Paris. We combined aerosol mass spectrometer, gas-phase chemistry and atmospheric boundary layer (ABL) data, and applied the MXL/MESSy column model. We find that during daytime, vertical mixing due to ABL growth has opposing effects on secondary organic aerosol (SOA) and primary organic aerosol (POA) concentrations. POA concentrations are mainly governed by dilution due to boundary layer expansion and transport of POA-depleted air from aloft, while SOA concentrations are enhanced by entrainment of SOA-rich air from the residual layer (RL). Further, local emissions and photochemical production control the diurnal cycle of SOA. SOA from intermediate volatility organic compounds (fSOA-iv) constitutes about half of the locally formed SOA mass. Other processes that previously have been shown to influence the urban OA budget, such as aging of semi-volatile and intermediate volatility organic compounds (S/IVOC), dry deposition of S/IVOCs and IVOC emissions, are found to have minor influences on OA. Our model results show that the modern carbon content of the OA is driven by vertical and long-range transport, with a minor contribution from local cooking emissions. SOA from regional sources and resulting from aging and long-lived precursors can lead to high SOA concentrations above the ABL, which can strongly influence ground-based observations through downward transport. Sensitivity analysis shows that modeled SOA concentrations in the ABL are equally sensitive to ABL dynamics as to SOA concentrations transported from the RL.