Aerosolihiukkasten kemiallisen koostumuksen vuodenaikaisvaihtelu pohjoisessa havumetsässä

Ilmakehän pienhiukkaset, eli aerosolihiukkaset, vaikuttavat maapallon säteilypakotteeseen riippuen hiukkasen kemiallisesta koostumuksesta. Kemiallinen koostumus ohjaa yli 50 nanometristen hiukkasten taipumusta joko sirottaa tai absorboida auringonsäteilyä. Toisaalta hiukkaset voivat myös osallistua pilvenmuodostukseen, jos ne ovat koostumukseltaan kyllin hapettuneita ja siksi pystyvät sitomaan ympärilleen vesimolekyylejä. Ilman aerosolihiukkasia maapallo olisi varmasti paljon lämpimämpi, sillä sekä suora säteilyn sirottaminen että epäsuora sirottaminen pilvien kautta ovat tärkeitä ilmakehän viilennysmekanismeja. Auringonsäteilyn määrä ja siten pintalämpötilat ohjaavat ilmakehän pienhiukkasten pitoisuuksia ihmisten ja luonnon kautta. Hiukkasten primäärilähteitä ja lähtöaineita on valtava kirjo, joka luo laajan hiukkasten fysiokemiallisten ominaisuuksien kokoelman. Tässä työssä esitellään tutkimus aerosolihiukkasten kemiallisen koostumuksen vuodenaikaisvaihtelusta SMEAR II -asemalla, Etelä-Suomessa, jossa lämpötilan vuodenaikaisvaihtelu on suurta. Työhön liittyvissä mittauksissa hyödynnettiin massaspektrometriaa ja in situ -suodatinmittauksia. Aerosolikemiamittaukset kuuluvat SMEAR II -aseman rutiinimittauksiin, ja niitä on tehty jatkuvasti vuodesta 2012 lähtien. Tässä tutkielmassa analysoinnin kohteena ovat vuoden 2014 neljä termistä vuodenaikaa, jotka sijoittuivat tarkemmin ajanjaksolle 23.1. - 27.10.2014. Tutkimuksen analyysimenetelmät todettiin hyödyllisiksi ja niitä sovelletaan tulevaisuudessa koko nelivuotisen aikasarjan (2012 - 2015) analyysiin. Työssä todettiin aerosolihiukkasten koostuvan kesällä pääasiassa luontoperäisistä orgaanisista yhdisteistä (~77 %) ja talvella enimmäkseen epäorgaanisista yhdisteistä (~54 % ), jotka olivat kaukokulkeumaa kaupungeista. Sulfaatti dominoi tasaisesti epäorgaanista massaa vuodenajasta riippumatta. Ilmakehän hapetuskapasiteetti heijastui kesällä orgaanisen aerosolin haihtuvuustasoon madaltaen sitä huomattavasti. Kesällä puolihaihtuvalla orgaanisella aerosolilla ja nitraatilla oli selkeä vuorokausisykli, jossa valtaosa massasta oli hiukkasfaasissa yöllä ja katosi kaasufaasiin keskipäivällä. Vastaavanlaista käyttäytymistä ei orgaanisilla aerosolityypeillä ollut havaittavissa talvella, mikä johtui toisaalta kylmemmistä lämpötiloista ja toisaalta myös orgaanisen aerosolin erilaisesta koostumuksesta. Epäorgaanisten yhdisteiden vuorokausisyklien tulkinta oli haastavaa, johtuen kaukokulkeuman ajallisten vaihteluiden runsaudesta, joka tulevaisuuden laajemmassa analyysissä saadaan minimoitua

The second ACTRIS inter-comparison (2016) for Aerosol Chemical Speciation Monitors (ACSM) : Calibration protocols and instrument performance evaluations

AbstractThis work describes results obtained from the 2016 Aerosol Chemical Speciation Monitor (ACSM) intercomparison exercise performed at the Aerosol Chemical Monitor Calibration Center (ACMCC, France). Fifteen quadrupole ACSMs (Q_ACSM) from the European Research Infrastructure for the observation of Aerosols, Clouds and Trace gases (ACTRIS) network were calibrated using a new procedure that acquires calibration data under the same operating conditions as those used during sampling and hence gets information representative of instrument performance. The new calibration procedure notably resulted in a decrease in the spread of the measured sulfate mass concentrations, improving the reproducibility of inorganic species measurements between ACSMs as well as the consistency with co-located independent instruments. Tested calibration procedures also allowed for the investigation of artifacts in individual instruments, such as the overestimation of m/z 44 from organic aerosol. This effect was quantified by the m/z (mass-to-charge) 44 to nitrate ratio measured during ammonium nitrate calibrations, with values ranging from 0.03 to 0.26, showing that it can be significant for some instruments. The fragmentation table correction previously proposed to account for this artifact was applied to the measurements acquired during this study. For some instruments (those with high artifacts), this fragmentation table adjustment led to an ?overcorrection? of the f44 (m/z 44/Org) signal. This correction based on measurements made with pure NH4NO3, assumes that the magnitude of the artifact is independent of chemical composition. Using data acquired at different NH4NO3 mixing ratios (from solutions of NH4NO3 and (NH4)2SO4) we observe that the magnitude of the artifact varies as a function of composition. Here we applied an updated correction, dependent on the ambient NO3 mass fraction, which resulted in an improved agreement in organic signal among instruments. This work illustrates the benefits of integrating new calibration procedures and artifact corrections, but also highlights the benefits of these intercomparison exercises to continue to improve our knowledge of how these instruments operate, and assist us in interpreting atmospheric chemistry.Peer reviewe

Tropical and Boreal Forest Atmosphere Interactions: A Review

This review presents how the boreal and the tropical forests affect the atmosphere, its chemical composition, its function, and further how that affects the climate and, in return, the ecosystems through feedback processes. Observations from key tower sites standing out due to their long-term comprehensive observations: The Amazon Tall Tower Observatory in Central Amazonia, the Zotino Tall Tower Observatory in Siberia, and the Station to Measure Ecosystem-Atmosphere Relations at Hyytiala in Finland. The review is complemented by short-term observations from networks and large experiments.The review discusses atmospheric chemistry observations, aerosol formation and processing, physiochemical aerosol, and cloud condensation nuclei properties and finds surprising similarities and important differences in the two ecosystems. The aerosol concentrations and chemistry are similar, particularly concerning the main chemical components, both dominated by an organic fraction, while the boreal ecosystem has generally higher concentrations of inorganics, due to higher influence of long-range transported air pollution. The emissions of biogenic volatile organic compounds are dominated by isoprene and monoterpene in the tropical and boreal regions, respectively, being the main precursors of the organic aerosol fraction.Observations and modeling studies show that climate change and deforestation affect the ecosystems such that the carbon and hydrological cycles in Amazonia are changing to carbon neutrality and affect precipitation downwind. In Africa, the tropical forests are so far maintaining their carbon sink.It is urgent to better understand the interaction between these major ecosystems, the atmosphere, and climate, which calls for more observation sites, providing long-term data on water, carbon, and other biogeochemical cycles. This is essential in finding a sustainable balance between forest preservation and reforestation versus a potential increase in food production and biofuels, which are critical in maintaining ecosystem services and global climate stability. Reducing global warming and deforestation is vital for tropical forests

Tropical and Boreal Forest Atmosphere Interactions : A Review

This review presents how the boreal and the tropical forests affect the atmosphere, its chemical composition, its function, and further how that affects the climate and, in return, the ecosystems through feedback processes. Observations from key tower sites standing out due to their long-term comprehensive observations: The Amazon Tall Tower Observatory in Central Amazonia, the Zotino Tall Tower Observatory in Siberia, and the Station to Measure Ecosystem-Atmosphere Relations at Hyytiala in Finland. The review is complemented by short-term observations from networks and large experiments. The review discusses atmospheric chemistry observations, aerosol formation and processing, physiochemical aerosol, and cloud condensation nuclei properties and finds surprising similarities and important differences in the two ecosystems. The aerosol concentrations and chemistry are similar, particularly concerning the main chemical components, both dominated by an organic fraction, while the boreal ecosystem has generally higher concentrations of inorganics, due to higher influence of long-range transported air pollution. The emissions of biogenic volatile organic compounds are dominated by isoprene and monoterpene in the tropical and boreal regions, respectively, being the main precursors of the organic aerosol fraction. Observations and modeling studies show that climate change and deforestation affect the ecosystems such that the carbon and hydrological cycles in Amazonia are changing to carbon neutrality and affect precipitation downwind. In Africa, the tropical forests are so far maintaining their carbon sink. It is urgent to better understand the interaction between these major ecosystems, the atmosphere, and climate, which calls for more observation sites, providing long-term data on water, carbon, and other biogeochemical cycles. This is essential in finding a sustainable balance between forest preservation and reforestation versus a potential increase in food production and biofuels, which are critical in maintaining ecosystem services and global climate stability. Reducing global warming and deforestation is vital for tropical forests.Peer reviewe

Tropical and Boreal Forest Atmosphere Interactions : A Review

This review presents how the boreal and the tropical forests affect the atmosphere, its chemical composition, its function, and further how that affects the climate and, in return, the ecosystems through feedback processes. Observations from key tower sites standing out due to their long-term comprehensive observations: The Amazon Tall Tower Observatory in Central Amazonia, the Zotino Tall Tower Observatory in Siberia, and the Station to Measure Ecosystem-Atmosphere Relations at Hyytiala in Finland. The review is complemented by short-term observations from networks and large experiments. The review discusses atmospheric chemistry observations, aerosol formation and processing, physiochemical aerosol, and cloud condensation nuclei properties and finds surprising similarities and important differences in the two ecosystems. The aerosol concentrations and chemistry are similar, particularly concerning the main chemical components, both dominated by an organic fraction, while the boreal ecosystem has generally higher concentrations of inorganics, due to higher influence of long-range transported air pollution. The emissions of biogenic volatile organic compounds are dominated by isoprene and monoterpene in the tropical and boreal regions, respectively, being the main precursors of the organic aerosol fraction. Observations and modeling studies show that climate change and deforestation affect the ecosystems such that the carbon and hydrological cycles in Amazonia are changing to carbon neutrality and affect precipitation downwind. In Africa, the tropical forests are so far maintaining their carbon sink. It is urgent to better understand the interaction between these major ecosystems, the atmosphere, and climate, which calls for more observation sites, providing long-term data on water, carbon, and other biogeochemical cycles. This is essential in finding a sustainable balance between forest preservation and reforestation versus a potential increase in food production and biofuels, which are critical in maintaining ecosystem services and global climate stability. Reducing global warming and deforestation is vital for tropical forests.Peer reviewe

European aerosol phenomenology - 8 : Harmonised source apportionment of organic aerosol using 22 Year-long ACSM/AMS datasets

Organic aerosol (OA) is a key component of total submicron particulate matter (PM1), and comprehensive knowledge of OA sources across Europe is crucial to mitigate PM1 levels. Europe has a well-established air quality research infrastructure from which yearlong datasets using 21 aerosol chemical speciation monitors (ACSMs) and 1 aerosol mass spectrometer (AMS) were gathered during 2013-2019. It includes 9 non-urban and 13 urban sites. This study developed a state-of-the-art source apportionment protocol to analyse long-term OA mass spectrum data by applying the most advanced source apportionment strategies (i.e., rolling PMF, ME-2, and bootstrap). This harmonised protocol was followed strictly for all 22 datasets, making the source apportionment results more comparable. In addition, it enables quantification of the most common OA components such as hydrocarbon-like OA (HOA), biomass burning OA (BBOA), cooking-like OA (COA), more oxidised-oxygenated OA (MO-OOA), and less oxidised-oxygenated OA (LO-OOA). Other components such as coal combustion OA (CCOA), solid fuel OA (SFOA: mainly mixture of coal and peat combustion), cigarette smoke OA (CSOA), sea salt (mostly inorganic but part of the OA mass spectrum), coffee OA, and ship industry OA could also be separated at a few specific sites. Oxygenated OA (OOA) components make up most of the submicron OA mass (average = 71.1%, range from 43.7 to 100%). Solid fuel combustion-related OA components (i.e., BBOA, CCOA, and SFOA) are still considerable with in total 16.0% yearly contribution to the OA, yet mainly during winter months (21.4%). Overall, this comprehensive protocol works effectively across all sites governed by different sources and generates robust and consistent source apportionment results. Our work presents a comprehensive overview of OA sources in Europe with a unique combination of high time resolution (30-240 min) and long-term data coverage (9-36 months), providing essential information to improve/validate air quality, health impact, and climate models.Peer reviewe

Data Descriptor : Collocated observations of cloud condensation nuclei, particle size distributions, and chemical composition

Cloud condensation nuclei (CCN) number concentrations alongside with submicrometer particle number size distributions and particle chemical composition have been measured at atmospheric observatories of the Aerosols, Clouds, and Trace gases Research InfraStructure (ACTRIS) as well as other international sites over multiple years. Here, harmonized data records from 11 observatories are summarized, spanning 98,677 instrument hours for CCN data, 157,880 for particle number size distributions, and 70,817 for chemical composition data. The observatories represent nine different environments, e.g., Arctic, Atlantic, Pacific and Mediterranean maritime, boreal forest, or high alpine atmospheric conditions. This is a unique collection of aerosol particle properties most relevant for studying aerosol-cloud interactions which constitute the largest uncertainty in anthropogenic radiative forcing of the climate. The dataset is appropriate for comprehensive aerosol characterization (e.g., closure studies of CCN), model-measurement intercomparison and satellite retrieval method evaluation, among others. Data have been acquired and processed following international recommendations for quality assurance and have undergone multiple stages of quality assessment.Peer reviewe

Intercomparison of AMS and ACSM Measurements for Particulate Organic Nitrates (pON)

Particulate organic nitrates (pON) are important atmospheric species that are formed through the reactions of volatile organic compounds (VOCs) with atmospheric oxidants (OH/NO3 radicals) and NOx. They may account for a considerable fraction of fine particulate matter (PM2.5) but their concentrations, sources and formation processes remain nearly unexplored aspects of atmospheric chemistry. Recently, a methodology based on time-of-flight aerosol mass spectrometer (ToF-AMS) measurements of NO+ and NO2+ fragments of nitrate aerosol has been proposed to distinguish between inorganic nitrates and pON. However, this methodology has not been applied to quadrupole or time-of-flight Aerosol Chemical Speciation Monitors (Q-ACSM/ToF-ACSM) or to anthropogenic pON. In the present study, the response of 8 different ACSM, and 1 Long-ToF-AMS, instruments to pON was explored through a unique experimental setup under controlled conditions at the Aerosol Chemical Monitor Calibration Centre (ACMCC). pON were generated in a Potential Aerosol Mass (PAM) oxidation flow reactor from the reaction of NO3 radical with single VOC precursors, two biogenic (limonene and b-pinene) and two anthropogenic (acenaphthylene and guaiacol). The results of this intercomparison will be presented, with a focus on variations in the mass spectra of pON (NO+/NO2+, organics fragments and organic-to-nitrate ratios) as a function of: (1) instrumental configuration (AMS vs ACSM, Q-ACSM vs ToF-ACSM, standard vs capture vaporizers) (2) pON precursor (3) particle size and (4) particle mass concentration. Possible improvements of the default fragmentation table used to calculate the contributions to the signal for organic and nitrates will be proposed in order to account for interfering signals from other species. The impact of the observed variabilities on the NO+/NO2+ methodology will also be investigated

Overview of the ACMCC particulate organonitrates (pON) intercomparison

Particulate organonitrates (pON) account for significant fraction (5-80% by mass) of total OA in ambient air. They are formed from the reactions of volatile organic compounds (VOCs) with atmospheric oxidants (OH/NO3 radicals) and NOx. Their quantification can be achieved using aerosol mass spectrometry (AMS), based on the characteristic mass fragment ratio (NO2+/NO+) allowing the distinction from inorganic nitrate. However, the accuracy of the low-resolution aerosol chemical speciation monitor (ACSM) to determine pON has not yet been evaluated. At the Aerosol Chemical Monitor Calibration Centre (AMCC), an intercomparison for the measurements of pON has been performed in order to obtain a stable and constant generation of pON, so to compare simultaneously the response of nine different AMS/ACSM systems (long-TOF-AMS vs ACSMs; Quads vs TOFs; standard vs capture vaporizers), as well as to investigate the pON physical properties and chemical composition..

The second ACTRIS inter-comparison (2016) for Aerosol Chemical Speciation Monitors (ACSM): Calibration protocols and instrument performance evaluations

This work describes results obtained from the 2016 Aerosol Chemical Speciation Monitor (ACSM) intercomparison exercise performed at the Aerosol Chemical Monitor Calibration Center (ACMCC, France). Fifteen quadrupole ACSMs (Q_ACSM) from the European Research Infrastructure for the observation of Aerosols, Clouds and Trace gases (ACTRIS) network were calibrated using a new procedure that acquires calibration data under the same operating conditions as those used during sampling and hence gets information representative of instrument performance. The new calibration procedure notably resulted in a decrease in the spread of the measured sulfate mass concentrations, improving the reproducibility of inorganic species measurements between ACSMs as well as the consistency with co-located independent instruments. Tested calibration procedures also allowed for the investigation of artifacts in individual instruments, such as the overestimation of m/z 44 from organic aerosol. This effect was quantified by the m/z (mass-to-charge) 44 to nitrate ratio measured during ammonium nitrate calibrations, with values ranging from 0.03 to 0.26, showing that it can be significant for some instruments. The fragmentation table correction previously proposed to account for this artifact was applied to the measurements acquired during this study. For some instruments (those with high artifacts), this fragmentation table adjustment led to an “overcorrection” of the f44 (m/z 44/Org) signal. This correction based on measurements made with pure NH4NO3, assumes that the magnitude of the artifact is independent of chemical composition. Using data acquired at different NH4NO3 mixing ratios (from solutions of NH4NO3 and (NH4)2SO4) we observe that the magnitude of the artifact varies as a function of composition. Here we applied an updated correction, dependent on the ambient NO3 mass fraction, which resulted in an improved agreement in organic signal among instruments. This work illustrates the benefits of integrating new calibration procedures and artifact corrections, but also highlights the benefits of these intercomparison exercises to continue to improve our knowledge of how these instruments operate, and assist us in interpreting atmospheric chemistry. © 2019, © 2019 Author(s). Published with license by Taylor & Francis Group, LLC