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New particle formation (NPF) provides a large source of atmospheric aerosols, which affect the climate and human health. In recent chamber studies, ion-induced nucleation (IIN) has been discovered as an important pathway of forming particles; however, atmospheric investigation remains incomplete. For this study, we investigated the air anion compositions in the boreal forest in southern Finland for three consecutive springs, with a special focus on H2SO4-NH3 anion clusters. We found that the ratio between the concentrations of highly oxygenated organic molecules (HOMs) and H2SO4 controlled the appearance of H2SO4-NH3 clusters (3

We present ambient observations of dimeric monoterpene oxidation products (C16-20HyO6-9) in gas and particle phases in the boreal forest in Finland in spring 2013 and 2014, detected with a chemical ionization mass spectrometer with a filter inlet for gases and aerosols employing acetate and iodide as reagent ions. These are among the first online dual-phase observations of such dimers in the atmosphere. Estimated saturation concentrations of 10(-15) to 10(-6)mu gm(-3) (based on observed thermal desorptions and group-contribution methods) and measured gas-phase concentrations of 10(-3) to 10(-2)mu gm(-3) (similar to 10(6)-10(7)moleculescm(-3)) corroborate a gas-phase formation mechanism. Regular new particle formation (NPF) events allowed insights into the potential role dimers may play for atmospheric NPF and growth. The observationally constrained Model for Acid-Base chemistry in NAnoparticle Growth indicates a contribution of similar to 5% to early stage particle growth from the similar to 60 gaseous dimer compounds. Plain Language Summary Atmospheric aerosol particles influence climate and air quality. We present new insights into how emissions of volatile organic compounds from trees are transformed in the atmosphere to contribute to the formation and growth of aerosol particles. We detected for the first time over a forest, a group of organic molecules, known to grow particles, in the gas phase at levels far higher than expected. Previous measurements had only measured them in the particles. This finding provides guidance on how models of aerosol formation and growth should describe their appearance and fate in the atmosphere.

Itämeren pahimpana ongelmana pidetään typpi- ja fosforikuormituksen aiheuttamaa rehevöitymistä. Typpeä ja fosforia joutuu Itämereen paitsi valumana rantavaltioista myös merkittävissä määrin ilman kautta. Ilmaperäisen typpilaskeuman määrää ja sen kehitystä on selvitetty mittauksin ja mallinnuksen avulla 1980-luvulta lähtien, mutta ilmaperäistä fosforikuormaa Itämereen on mitattu vain sateen mukana laskeutuvan märkälaskeuman osalta muutamilla asemilla. Hiukkasiin sitoutuneesta kuivalaskeumasta ei mittaustietoa ole julkaistu lainkaan, eikä Itämeren ympärysvaltioilla ole käytettävissään menetelmää ilmaperäisen fosforikuorman hiukkasosuuden seuraamiseksi. Tässä työssä kehitettiin ja testattiin menetelmät ilmakehästä sadeveden mukana tulevan sekä ilmakehän hiukkasiin sitoutuneen fosfaatin sekä kokonaisfosforin määrittämiseksi. Menetelmäkehitys sisälsi näytteenkeruumenetelmät, näytteen esikäsittelymenetelmät sekä kemialliset analyysimenetelmät. Menetelmiä testattiin Utön saarella Saaristomeren ulkolaidalla vuosien 2013–2015 aikana. Utön saarella toimii Ilmatieteen laitoksen mittausasema, jonka mittaustulokset edustavat ilmanlaadun tausta-arvoja pohjoisella Itämerellä. Testattuina fosforin ja fosfaatin kuiva- ja märkälaskeuman näytteenkeruumenetelminä toimivat olemassa olevat ja laajasti käyttöönotetut EMEP-protokolliin perustuvat menetelmät. Näytteiden kokonaisfosforipitoisuuden määritysmenetelmään sovellettiin olemassa olevaa ISO-standardiin perustuvaa spektrometristä menetelmää. Vesiliukoisen fosfaatin pitoisuuden määrittämiseen hyödynnettiin käytössä olevaa ISO-standardiin perustuvaa ionikromatografista menetelmää, jota laajennettiin sisältämään fosfaatin määritys muiden epäorgaanisten ionien kanssa samassa analyysissä. Havaittiin, että sekä märkä- että kuivalaskeumanäytteiden sisältämät kokonaisfosfori- ja fosfaattipitoisuudet olivat erittäin alhaisia, usein pitoisuudet olivat lähellä analyysimenetelmien määritysrajoja tai niiden alle. Kuitenkin mittausjakson ajalta saatiin riittävä määrä määritystuloksia, joiden avulla voidaan laskea aiempaa luotettavampi arvio vuotuisesta ilmaperäisestä fosforikuormituksesta Itämereen. Työssä tutkittiin Utön saaren mittausasemalla suoritetun intensiivikampanjan aikana mahdollisuutta määrittää hiukkasissa olevan fosfaatin pitoisuutta jatkuvatoimisella ionikromatografilla. Menetelmän herkkyys osoittautui kuitenkin riittämättömäksi ilmakehän hiukkasten fosfaattipitoisuuden määrittämiseen. Käytetyt menetelmät on esitelty tässä raportissa siten, että menetelmät voidaan ottaa käyttöön muillakin mittausasemilla ja laboratorioissa sadeveden ja ilmakehän hiukkasten sisältämien fosfaatin ja kokonaisfosforin pitoisuuksien määrittämiseksi, ja siten ilmaperäisen fosforin kuormitusta voidaan arvioida luotettavammin ja laajemmin Itämeren alueella. Eutrophication caused by nitrogen and phosphorus load is generally thought as the most severe problem of the Baltic Sea. Nitrogen and phosphorus end up in the Baltic Sea not only by run-off from the coastal countries of the Baltic Sea but to an important extent also from the atmosphere. The amount of atmospheric nitrogen load and its development have been determined using measurements and models since the 1980’s. The atmospheric phosphorus load to the Baltic Sea has been measured earlier only from the wet deposition from the collected rain water samples from a few sites around the Baltic Sea; no published data exists about the particle bound dry deposition of phosphorus. The coastal countries of the Baltic Sea haven’t got any method in use to measure the particle bound phosphorus deposition. In this work, methods for determining the concentrations of phosphate and total phosphorus in atmospheric precipitation and particulate matter were developed and tested. The method development included the sampling, sample pre-treatment, and chemical analysis techniques. The methods were tested onsite on the Utö Island in the outskirts of the Archipelago Sea during the years 2013–2015. The monitoring station on the Utö Island is operated by the Finnish Meteorological Institute. The measurements on the station represent the background air quality of the northern Baltic Sea area. The existing and widely used sampling methods based on the EMEP protocols were tested for the sampling of dry and wet deposition of phosphorus and phosphate. A spectrometric method based on an ISO standard was applied for determination of the total phosphorus concentration of the samples. For the determination of dissolved phosphate, an ion chromatographic method based on an ISO standard was extended to include the analysis of phosphate with the main inorganic ions. It was discovered that the concentrations of total phosphorus and dissolved phosphate in the dry and wet deposition samples were very low; the concentrations were often close to the determination limits of the used analytical methods or even below those. Nevertheless, a sufficiency of samples were determined to be able to estimate the yearly atmospheric phosphorus load to the Baltic Sea more reliably than earlier. In addition, feasibility of measuring the concentration of particle-bound phosphate using a semi-continuous ion chromatograph was tested in the Utö Island during an intensive campaign. However, the sensitivity of the analyser was not sufficient to measure the low atmospheric concentrations of phosphate. The used methods are presented in this report so that they can be taken into use in other sampling sites and laboratories to determine the concentrations of phosphate and total phosphorus in the precipitation and in the atmospheric particulate matter. Thus, more reliable estimates of the atmospheric phosphorus load to the Baltic Sea could be calculated more widely.

The objective of this thesis was to study the variability of inorganic gases and the chemical composition of particulate matter in ambient air, and to study the comparability of results obtained using novel online techniques and older measurements. In recent decades, emissions of sulphur dioxide have decreased all over Europe and, consequently, ambient concentrations have decreased in Finland. A declining trend was also found in the concentrations of reduced nitrogen during the past years. It was found that, in addition to concentrations in air masses coming from central Europe, the transport pathways of air masses are important factors affecting concentrations in Finland. Decreasing concentrations place greater demands on measurement techniques. To ensure the comparability of the SO2 data obtained earlier, we compared older methods to newer measurement methods. We identified the inorganic main elements, trace elements and polycyclic hydrocarbons in PM1, PM2.5 and PM10 samples collected at the background station in Virolahti, Finland. About 70–80% of the toxic trace elements (lead, cadmium, arsenic and nickel) as well as polycyclic hydrocarbons were found in submicron particles. In practice, all the PAHs found in PM10 were actually present in the PM2.5 fraction. Analysing the PM2.5 or even the PM1 fraction instead of PM10 would prove more beneficial for PAHs and trace elements, because excluding the large particles reduces the effects of the matrix during analysis. During wildfire episodes, the concentrations of the smallest particles (PM1, PM2.5) in particular rose. On the fire days, the potassium concentration rose in all particle fractions, but ammonium and nitrate rose only in PM1. One of the objectives of this thesis was to determine whether the online ion chromatograph with a one-hour time resolution could replace the filter sampling method. We successfully measured the concentrations of gases (HCl, HNO3, HONO, NH3, SO2) and the major inorganic ions in particles (Cl-, NO3-, SO42-, NH4+, Na+, K+, Mg2+, Ca2+) with a MARGA 2S online ion chromatograph in two size ranges in both urban and background environments. We used these short-time resolution measurements to study diurnal cycles of nitrogen-containing gases. In Hyytiälä, we found clear diurnal cycles for all the nitrogen-containing gases, especially in summer, when there is enough sunlight for photochemical reactions and possibly additional emission sources from the boreal forest environment. In winter, however, we found no diurnal cycles in either Hyytiälä or Helsinki, but in spring, diurnal cycles for HONO, HNO3 andNH3 resumed. In Helsinki, the results of the particles were used to study sources using trajectory analysis showing that,although continental aerosols were mostly neutralized, marine aerosols from the Norwegian Sea were not. Tämän väitöskirjan tavoitteena oli tutkia epäorgaanisia kaasuja ja hiukkasten kemiallista koostumusta ulkoilmassa sekä verrata uudenlaista jatkuvatoimista ionikromatografia aikaisemmin ilmanlaadun tutkimuksessa käytettyihin menetelmiin. Viime vuosikymmenten kuluessa Euroopan rikkidioksidin emissiot ovat vähentyneet huomattavasti ja sen seurauksena pitoisuudet ovat laskeneet Suomessa. Trendianalyysin perusteella myös pelkistyneen typen pitoisuudet ovat vähentyneet. Suomeen Keski-Euroopasta tulevien ilmamassojen pitoisuuksien lisäksi havaittiin, että ilmamassojen tulosuuntien vaihtelut, vaikuttavat Suomen vuosittaisiin keskiarvopitoisuuksiin ja siten trendeihin. Alentuneet ilmapitoisuudet lisäävät vaatimuksia mittausmenetelmien herkkyydelle. Aiemmin käytettyjä keräys- ja analysointimenetelmiä verrattiin uudempiin määritysmenetelmiin, jotta varmistuttiin pitkien aikasarjojenvertailukelpoisuudesta. Virolahden tausta-asemalla määritettiin eri kokoluokkien hiukkasten (PM1, PM2,5 ja PM10) pääionien, hivenalkuaineidenja polysyklisten aromaattisten hiilivetyjen pitoisuudet (PAH). Tässä tutkimuksessa n. 70-80 % toksisista alkuaineista (lyijy, kadmium, arseeni, nikkeli) sekä PAH-yhdisteistä oli pienimmässä (halkaisija < 1 μm) hiukkasissa. Käytännössä PM10-hiukkasissa oleva pitoisuus oli sama kuin alle 2,5 μm hiukkasissa. Raskasmetallien ja PAH-yhdisteiden analysointi olisi kannattavampaa PM2,5-hiukkasista, koska se vähentäisi matriisin vaikutusta. Maastopalojen aikana erityisesti pienten hiukkasten (PM1, PM2,5) pitoisuudet kohosivat. Samaan aikaan kaliumin pitoisuudet kohosivat sekä pienissä että karkeissa hiukkasissa. Ammonium- ja nitraattipitoisuudet kohosivat vain pienimmissä alle 1 μm hiukkasissa. Tutkimuksessa selvitettiin myös, soveltuuko jatkuvatoiminen laitteisto korvaamaan suodatinkeräysmenetelmien käytönilmanäytteiden määrityksissä. Jatkuvatoimisella MARGA 2S-ionikromatografilla määritettiin kaasujen (HCl, HNO3, HONO, NH3, SO2) ja epäorgaanisten ionien (Cl−, NO3−, SO42−, NH4+, Na+, K+, Mg2+, Ca2+) pitoisuuksia alle 2,5 μm ja alle 10 μm hiukkasissa kaupunkiympäristössä sekä Hyytiälän tausta-asemalla. Lyhyellä aikaresoluutiolla saaduista tuloksista voitiin määrittää typpihapon, typpihapokkeen ja ammoniakin vuorokausisyklit. Talvella vuorokausisyliä ei esiintynyt, mutta keväällä sekä kaupunki- että taustailman mittauksissa havaittiin vuorokausivaihtelua. Hyytiälässä kesäaikaan havaitut syklit olivat voimakkaimpia johtuen valokemiallisista reaktiosta ja mahdollisesti metsäympäristön emissioista. Helsingissä mitattujen hiukkasten kemiallista koostumusta ja trajektorianalyysia käyttäen havaittiin, että Keski-Euroopasta tulleet hiukkaset olivat yleensä neutraloituneita, mutta Norjan mereltä saapuneet hiukkaset olivat happamia.

Residential wood combustion is a significant particulate emission source in many European countries. Especially for fine particle emissions in wood combustions, the lacking knowledge of emission factors (F-E) makes assessment of their contribution to ambient concentrations difficult. One reason for the discrepancy between modeled and measured contributions is many variables involved in combustion process. In this study, the fine particulate matter (PM) emissions coming from batch combustion of birch wood in a small masonry heater were investigated. The experiments were carried out in the specified conditions (normal and smouldering combustion, NC and SC, respectively). To enable various chemical analytical techniques, two sampling combinations for PM2.5 (particle diameter < 2.5 mu m), and size-segregated sampling were used. The samples were analyzed for gravimetric mass, major ions, monosaccharide anhydrides (MA, including levoglucosan, galactosan and mannosan), trace elements, elemental carbon (EC) and water-insoluble and -soluble particulate organic matter (WISPOM and WSPOM, respectively). F-E of PM2.5 based on gravimetric mass was three times higher for SC than for NC. Particulate organic matter (POM = 1.6 x OC) accounted for approximately 30% and 70% of F-E of PM2.5 in NC and SC, respectively. The corresponding values for EC were 32% and 25%. About 30% of the OC was water-soluble. Ions constituted about 20% of the F-E of PM2.5 in NC but only a few percents in SC. Potassium comprised around 60% of the analyzed ions. The fraction of trace elements consisting 94% of Zn was only about 1% of the total PM2.5 emissions. This study showed strong influence of combustion practice on emissions of the major chemical components from the small-scale wood combustion.

Mass concentrations of PM1, PM2.5 and PM10 in air were measured at four EMEP stations in the Nordic countries during 2006. All stations used the same low-cost equipment for sampling PM1, but used different techniques for the other size fractions. The PM1 filters were analysed for inorganic ions for the first half of June. PM1 constituted on average more than half of the PM2.5 concentrations, but was on average less than half of the PM10 concentrations. There were two episodes of high PM1 concentrations during the year, one in May-June and another one in August-September. The highest PM1 concentrations were found during South-Easterly wind trajectories and lowest concentrations during northerly trajectories.Even though the annual average mass relations between the three size fractions were rather independent of the trajectory sectors, the fine and the coarse particle masses were not correlated on a daily basis. The PM2.5 concentration, which is the parameter that should be measured within EU, correlated fairly well with the concentration of accumulation mode particles (PM1). In June only a minor fraction of PM1 consisted of inorganic ions. Only ammonium and sulphate ions of the measured ions in PM1 were well correlated with one another.

Mass concentrations of PM1, PM2.5 and PM10 in air were measured at four EMEP stations in the Nordic countries during 2006. All stations used the same low-cost equipment for sampling PM1, but used different techniques for the other size fractions. The PM1 filters were analysed for inorganic ions for the first half of June. PM1 constituted on average more than half of the PM2.5 concentrations, but was on average less than half of the PM10 concentrations. There were two episodes of high PM1 concentrations during the year, one in May-June and another one in August-September. The highest PM1 concentrations were found during South-Easterly wind trajectories and lowest concentrations during northerly trajectories. Even though the annual average mass relations between the three size fractions were rather independent of the trajectory sectors, the fine and the coarse particle masses were not correlated on a daily basis. The PM2.5 concentration, which is the parameter that should be measured within EU, correlated fairly well with the concentration of accumulation mode particles (PM1). In June only a minor fraction of PM1 consisted of inorganic ions. Only ammonium and sulphate ions of the measured ions in PM1 were well correlated with one another. Mass concentrations of PM1, PM2.5 and PM10 in air were measured at four EMEP stations in the Nordic countries during 2006. All stations used the same low-cost equipment for sampling PM1, but used different techniques for the other size fractions. The PM1 filters were analysed for inorganic ions for the first half of June. PM1 constituted on average more than half of the PM2.5 concentrations, but was on average less than half of the PM10 concentrations. There were two episodes of high PM1 concentrations during the year, one in May-June and another one in August-September. The highest PM1 concentrations were found during South-Easterly wind trajectories and lowest concentrations during northerly trajectories. Even though the annual average mass relations between the three size fractions were rather independent of the trajectory sectors, the fine and the coarse particle masses were not correlated on a daily basis. The PM2.5 concentration, which is the parameter that should be measured within EU, correlated fairly well with the concentration of accumulation mode particles (PM1). In June only a minor fraction of PM1 consisted of inorganic ions. Only ammonium and sulphate ions of the measured ions in PM1 were well correlated with one another.

The EMEP filter pack for measuring gaseous and particulate reduced and oxidised nitrogen compounds in air has been modified with a PM10 inlet to meet the EU air quality directive for particle measurements. The filter pack also collects sulphur compounds as well as base cations and sodium chloride. The EMEP filter pack has been used for 20 years now and it is important that the PM10 inlet doesn't affect the results. The cut-off for the filter pack recommended by EMEP is unknown and may be affected by wind. Here it was found that the cut-off for the EMEP filter pack is larger than it is for PM10. This implies that higher calcium concentrations will be obtained with the original EMEP filter pack without a PM10 inlet. All comparisons of the two filter packs show excellent agreement for sulphur dioxide and man made sulphate particles. Some losses of total nitrate have been found with the PM10 inlet especially of particulate nitrate. Some losses of particulate ammonium also take place but do not affect the total concentration. The EMEP filter pack for measuring gaseous and particulate reduced and oxidised nitrogen compounds in air has been modified with a PM10 inlet to meet the EU air quality directive for particle measurements. The filter pack also collects sulphur compounds as well as base cations and sodium chloride. The EMEP filter pack has been used for 20 years now and it is important that the PM10 inlet doesn't affect the results. The cut-off for the filter pack recommended by EMEP is unknown and may be affected by wind. Here it was found that the cut-off for the EMEP filter pack is larger than it is for PM10. This implies that higher calcium concentrations will be obtained with the original EMEP filter pack without a PM10 inlet. All comparisons of the two filter packs show excellent agreement for sulphur dioxide and man made sulphate particles. Some losses of total nitrate have been found with the PM10 inlet especially of particulate nitrate. Some losses of particulate ammonium also take place but do not affect the total concentration.