Sources and concentrations of volatile organic compounds

Volatile organic compounds (VOCs) have a great influence on tropospheric chemistry; they affect ozone formation and they or their reaction products are able to take part in secondary organic aerosol formation; some of the VOCs are themselves toxic. Knowing the concentrations and sources of different reactive volatile organic compounds is essential for the development of ozone control strategies and for studies of secondary organic aerosol formation. The objective of this work was to study volatile organic compounds in urban air, develop and validate determination methods for them, characterize their concentrations and estimate the contributions of different VOC sources. Of the different compound groups detected in the urban air of Helsinki, alkanes were found to have the highest concentrations, but when the concentrations were scaled against the reactivity with hydroxyl radicals (OH), aromatic hydrocarbons and alkenes were found to have the greatest effect on local chemistry. Comparisons with rural sites showed that concentrations at Utö and Hyytiälä were generally lower than those in Helsinki, especially for the alkenes and aromatic hydrocarbons, but concentrations of halogenated hydrocarbons at Utö and carbonyls at Hyytiälä were at the same level as in Helsinki. Most halogenated hydrocarbons do not have any significant sources in Helsinki, and carbonyls are formed in the atmosphere in the reactions of other VOCs, and are therefore also produced in other than urban areas. At Hyytiälä carbonyls were found to have an important role in the local chemistry. The contribution of carbonyls as an OH sink was higher than that of the monoterpenes and aromatic hydrocarbons. Based on the emission profile and concentration measurements, the contributions of different sources were estimated at urban (Helsinki) and residential (Järvenpää) sites using a chemical mass balance (CMB) receptor model. It was shown that it is possible to apply CMB in the case of a large number of different compounds with different properties. According to the CMB analysis, the major sources for these VOCs in Helsinki were traffic and distant sources. At the residential site in Järvenpää, the contribution due to traffic was minor, while distant sources, liquid gasoline and wood combustion made higher contributions. It was also shown that wood combustion can be an important source at some locations of VOCs usually considered as traffic-related compounds (e.g., benzene).Haihtuviin orgaanisiin yhdisteisiin (VOC) kuulu monentyyppisiä yhdisteitä: alkaaneja, alkeeneja, aromaattisia hiilivetyjä, halogeeneja sisältäviä hiilivetyjä ja hapettuneita yhdisteitä kuten aldehydejä ja ketoneja. Näitä yhdisteitä pääsee ilmaan monenlaisista päästölähteistä. Palaminen, fossiilisten polttoaineiden käyttö, liuottimien käyttö ja teollisuus tuottavat ilmaan suuren joukon VOC yhdisteitä, mutta niitä emittoituu myös luonnosta. Osa VOC yhdisteistä on haitallisia ihmisen terveydelle kuten esim. bentseeni, jonka vuosikeskiarvolle Euroopan Unioni on asettanut pitoisuusrajan. Lähes kaikki VOC yhdisteet reagoivat ilmassa valon vaikutuksesta ja typen oksidien läsnä ollessa saattavat muodostaa otsonia. Ilmassa reagoidessaan orgaaniset yhdisteet muodostavat huonommin haihtuvia yhdisteitä, jotka saattavat osallistua uusien hiukkasten muodostukseen tai kasvuun. Tämän työ tarkoitus oli tutkia kaupunki-ilman haihtuvia orgaanisia yhdisteitä, kehittää määritysmenetelmiä niiden mittaamiseksi ilmasta, määrittää pitoisuustasoja ja arvioida eri VOC lähteiden merkityksiä pitoisuuksiin. Eri yhdisteryhmistä alkaaneilla havaittiin olevan suurimmat pitoisuudet Helsingin ilmassa, mutta jos pitoisuuksia tarkasteltiin reaktiivisuuksien suhteen, aromaattisilla hiilivedyillä ja alkeeneilla havaittiin olevan suurin vaikutus paikalliseen ilmakemiaan. Euroopan Union asettama raja-arvo (5 μg m-3) ilmassa olevan syöpää aiheuttavan bentseenin pitoisuuden vuosikeskiarvolle alittui selkeästi kaikilla mittausasemilla. Eri VOC lähteiden merkitystä arvioitiin erityyppisissä kaupunkiympäristöissä, Helsingissä Kalliossa ja Järvenpäässä pientaloalueella, kemiallisen massatasapaino menetelmän avulla käyttäen lähtötietoina mitattuja päästölähdeprofiileja ja ilmapitoisuuksia. Päälähteet useimmille yhdisteille Helsingissä olivat liikenne ja kaukokulkeuma. Järvenpäässä liikenteen osuus oli pieni verrattuna kaukokulkeuman, bensiinin ja puunpolton osuuksiin. Tutkimuksen avulla pystyttiin toteamaan, että puunpoltto voi olla merkittävä lähde yhdisteille, joiden tavallisesti ajatellaan tulevan pääasiassa liikenteestä (esim. bentseeni)

Ozone stress as a driving force of sesquiterpene emissions: a suggested parameterisation

Sesquiterpenes (C15H24) are semi-volatile organic compounds emitted by vegetation and are of interest in atmospheric research because they influence the oxidative capacity of the atmosphere and contribute to the formation of secondary organic aerosols. However, little is known about their emission pattern and no established parameterisation is available for global emission models. The aim of this study is to investigate a Central European spruce forest and its emission response to meteorological and environmental parameters, looking for a parameterisation that incorporates heat and oxidative stress as the main driving forces of the induced emissions. Therefore, a healthy ca. 80 yr old Norway spruce (Picea abies) tree was selected and a dynamical vegetation enclosure technique was applied from April to November 2011. The emissions clearly responded to temperature changes with small variations in the β-factor along the year (βspring = 0.09 ± 0.01, βsummer = 0.12 ± 0.02, βautumn = 0.11 ± 0.02). However, daily calculated values revealed a vast amount of variability in temperature dependencies ((0.02 ± 0.002) < β < (0.27 ± 0.04)) with no distinct seasonality. By separating the complete dataset in 10 different ozone regimes, we found that in moderately or less polluted atmospheric conditions the main driving force of sesquiterpene emissions is the temperature, but when ambient ozone mixing ratios exceed a critical threshold of (36.6 ± 3.9) ppbv, the emissions become primarily correlated with ozone. Considering the complete dataset, cross correlation analysis resulted in highest correlation with ambient ozone mixing ratios (CCO3 = 0.63 ± 0.01; CCT = 0.47 ± 0.02 at t = 0 h for temperature) with a time shift 2–4 h prior to the emissions. An only temperature dependent algorithm was found to substantially underestimate the induced emissions (20% of the measured; R2 = 0.31). However, the addition of an ozone dependent term improved substantially the fitting between measured and modelled emissions (81% of the modelled emissions could be explained by the measurements; R2 = 0.63), providing confidence about the reliability of the suggested parameterisation for the spruce forest site investigated

Ozone stress as a driving force of sesquiterpene emissions: a suggested parameterization [Discussion paper]

Sesquiterpenes (C15H24) are semi-volatile organic compounds emitted by vegetation and are of interest in atmospheric research because they influence the oxidative capacity of the atmosphere and contribute to the formation of secondary organic aerosols. However, little is known about their emission pattern and no established parameterization is available for global emission models. The aim of this study is to investigate a Central European spruce forest and its emission response to meteorological and environmental parameters, looking for a parameterization that incorporates heat and oxidative stress as the main driving forces of the induced emissions. Therefore, a healthy ca. 80 yr old Norway spruce (Picea abies) tree was selected and a dynamical vegetation enclosure technique was applied from April to November 2011. The emissions clearly responded to temperature changes with small variations in the β-factor along the year (βspring=0.09 ± 0.01, βsummer=0.12 ± 0.02, βautumn=0.11 ± 0.02). However, daily calculated values revealed a vast amount of variability in temperature dependencies ((0.02 ± 0.002)< β<(0.27 ± 0.04)) with no distinct seasonality. By separating the complete dataset in 10 different ozone regimes, we found that in moderately or less polluted atmospheric conditions the main driving force of sesquiterpene emissions is the temperature, but when ambient ozone mixing ratios exceed a~critical threshold of (36.6 ± 3.9) ppbv, the emissions become primarily correlated with ozone. Considering the complete dataset, cross correlation analysis resulted in highest correlation with ambient ozone mixing ratios (CCO3=0.63 ± 0.01; CCT=0.47 ± 0.02 at t=0 h for temperature) with a time shift 2–4 h prior to the emissions. An only temperature dependent algorithm was found to substantially underestimate the induced emissions (20 % of the measured; R2=0.31). However, the addition of an ozone dependent term improved substantially the fitting between measured and modeled emissions (81 % of the measured; R2=0.63), providing confidence about the reliability of the suggested parameterization for the spruce forest site investigated

Summer concentrations of NMHCs in ambient air of the Arctic and Antarctic

Peer reviewe

Boreal forest soil is a significant and diverse source of volatile organic compounds

Vegetation emissions of volatile organic compounds (VOCs) are intensively studied world-wide, because oxidation products of VOCs contribute to atmospheric processes. The overall aim of this study was to identify and quantify the VOCs that originate from boreal podzolized forest soil at different depths, in addition to studying the association of VOC concentrations with VOC and CO2 fluxes from the boreal forest floor.Peer reviewe

Deadwood substrate and species-species interactions determine the release of volatile organic compounds by wood-decaying fungi

Wood-decaying fungi in the phylum Basidiomycota play a significant role in the global carbon cycle, as they decompose deadwood effectively. Fungi may compete for utilizable substrate and growth space by producing soluble metabolites and by releasing volatile organic compounds (VOCs). We determined the role of wood substrate (Scots pine or Norway spruce) on the generation of hyphal biomass, secreted metabolites and enzyme activities, wood decomposition rate, and fungal species-species interactions on VOC release. We studied one brown-rot species (Fomitopsis pinicola) and two white-rot species (Phlebia radiata and Trichaptum abietinum) cultivated individually or in combinations. Wood substrate quality influences VOC release by the wood-decaying fungi, with signature differences caused by the decomposition trait (brown rot or white rot) and species-species interactions. VOC release was higher in the cultures of Basidiomycota than in uncolonized sawdust. Fungal biomass, decomposition activity, iron reduction, enzyme activities, oxalate anion content, and oxalic acid production explained VOC release from decaying wood.Peer reviewe

Direktiivin 2004/107/EY mukaisen ilmanlaadun seurannan tulosten oikeellisuuden varmistaminen 2019-2020 (DIRME2019)

Kansallinen ilmanlaadun vertailulaboratorio arvioi tässä hankkeessa ensimmäisen kerran käynnissä olevien ilmanlaadun polyaromaattisten hiilivety- (PAH) ja metallimittausten tulosten oikeellisuutta ja käytettyjä laadunvarmennuskeinoja Suomessa. Hanke kokosi yhteen tiedot direktiivin 2004/107/EY mukaisesta ilmanlaadun seurannasta Suomessa 2000-luvulla. Arvioinnin kohteena oli erityisesti bentso(a)pyreeni ja muut PAH-yhdisteet sekä arseeni, kadmium ja nikkeli PM10:ssä ja laskeumassa. Lisäksi hankkeessa arvioitiin lyijyn ja muiden metallien PM10- ja laskeumamittauksia, kaasumaisen elohopean ja elohopealaskeuman mittauksia sekä lyhyesti muita Suomessa tehtyjä harvinaisempia ilmanlaadun mittauksia kuten haihtuvien orgaanisten yhdisteiden (VOC) ja PM2,5-hiukkasten kemiallisen koostumuksen mittauksia. Hankkeessa suoritettiin metalli- ja PAH-mittausten auditointeja mittauksia toteuttaviin verkkoihin sekä niiden käyttämiin analyysilaboratorioihin. Muiden mittausten osalta arviointi tehtiin suppeasti haastattelujen ja erilaisten saatavilla olevien ilmanlaaturaporttien avulla. Toteutuneita mittauksia selvitettiin myös ilmanlaadun tietojärjestelmästä sekä käyttämällä apuna ilmanlaadun mittausverkkojen asiantuntemusta ja julkaisuja, sillä kaikkia hankkeen aiheeseen liittyviä mittauksia ei ole raportoitu tietojärjestelmään. Auditointeihin osallistui kaikki seitsemän ilmanlaadun metalli- ja PAH-mittauksia vuosina 2019–2020 suorittavaa mittausverkkoa Suomessa. Auditointeja suoritettiin 11 asemalla, kun kyseisiä mittauksia suoritettiin yhteensä 22 asemalla, jakuudessa laboratoriossa. Isojen mittausverkkojen osalta valittiin yksi asema edustamaan verkon toimintaa. Auditoinnilla saatiin tietoa metalli- ja PAH-mittausten vaatimustenmukaisuudesta verrattuna ilmanlaatuasetuksiin ja eurooppalaisiin EN-menetelmästandardeihin. Samalla saatiin yleistä tietoa mittausten suorittamisesta, käytetyistä mittalaitteista ja laadunvarmistusmenettelyistä. Laboratorioauditointien tulokset ovat luottamuksellisia, mutta raportissa on esitetty yleisiä havaintoja auditoinneista, ja mittaajat ovat saaneet tiedon auditointien tuloksista laboratorioiden luvalla. Johtopäätöksenä voidaan todeta, että käytetyt mittausmenetelmät olivat pääosin referenssimenetelmiä. Kenttätoiminnassa oli siirrytty käyttämään referenssimenetelmiä, joskin ennen vuotta 2018 kolmella verkolla on ollut käytössä muita menetelmiä, jotka ovat voineet aliarvioida pitoisuuksia. Näiden mittausten osalta aiempia mittaustuloksia käsiteltäessä on huomioitava, että mittaustulokset eivät ole vertailukelpoisia referenssimenetelmään. Laboratoriomääritykset oli suoritettu referenssimenetelmällä kahta poikkeusta lukuun ottamatta, joista toinen oli tehty hyväksyttävästi ekvivalentilla menetelmällä ja toisen osalta suositeltiin siirtymistä referenssimenetelmään, mikä toteutui heti 2020 alusta. Joissain tuoreissa mittauksissa laadunvarmistustoiminta ei ollut vielä vakiintunutta. Osa mittausverkoista käytti konsulttia huolto- ja kalibrointitöihin, ja näiden osalta verkko ei ollut aina itse tietoinen tehdyistä toimenpiteistä. EN-menetelmästandardeja noudatettiin mittausverkoissa pääosin hyvin. Virtauksen tarkistuksesta 3 kk välein poikettiin kaikissa verkoissa, ja sen osalta esitettiin parannusehdotuksia useille verkoille. Mittausepävarmuusarvioiden laskentatapaa on syytä kehittää mittausverkoissa. Kunhan mittausverkot ottavat käyttöönsä auditoinneissa esitetyt parannusehdotukset, voidaan katsoa, että mittauksia suoritetaan riittävässä määrin EN-menetelmästandardien mukaan. Selviä tuloksen oikeellisuuteen vaikuttavia tekijöitä ei kenttätoiminnassa havaittu auditoinnin aikana. Sama pätee laboratorioanalyysejä vuonna 2020. Yhden suuntaa-antavia mittauksia suorittavan verkon osalta mittaustuloksia on ollut yli tavoitearvojen, ja mittausten ajallista kattavuutta olisi syytä nostaa.This project summarizes the results from 2000–2020 and evaluates the trueness and the quality control (QC) procedures of the ongoing polycyclic aromatic hydrocarbon (PAH) and trace element measurements in Finland relating to Air Quality (AQ) Directive 2004/107/EC. The evaluation was focused on benzo(a)pyrene and other PAH compounds as well as arsenic, cadmium and nickel in PM10 and deposition. Additionally, it included lead and other metals in PM10 and deposition, gaseous mercury and mercury deposition, and briefly other specific AQ measurements such as volatile organic compounds (VOC)and PM2.5 chemical composition. This project was conducted by the National Reference Laboratory on air quality and this was the first time these measurements were assessed. A major part of the project was field and laboratory audits of the ongoing PAH and metal measurements. Other measurements were briefly evaluated through interviews and available literature. In addition, the national AQ database, the expertise of local measurement networks and related publications were utilised. In total, all the seven measurement networks performing PAH and metal measurements in 2019–2020 took part in the audits. Eleven stations were audited while these measurements are performed at 22 AQ stations in Finland. For the large networks, one station was chosen to represent the performance of the network. The audits included also six laboratories performing the analysis of the collected samples. The audits revealed the compliance of the measurements with the AQ Decree 113/2017, Directive 2004/107/EC and Standards of the European Committee for Standardization (CEN). In addition, general information of the measurements, instruments and quality control procedures were gained. The results of the laboratory audits were confidential, but this report includes general findings, and the measurement networks were informed on the audit results with the permission of the participating laboratories. As a conclusion, the measurement methods used were mainly reference methods. Currently, all sampling methods were reference methods; however, before 2018 three networks used other methods that may have underestimated concentrations. Regarding these measurements, it should be noted the results are not comparable with the reference method. Laboratory methods were reference methods excluding two cases, where the first was considered an acceptable equivalent method. For the other, a change to a reference method was strongly recommended and this realized in 2020. For some new measurements, the ongoing QC procedures were not yet fully established, and advice were given. Some networks used consultant for calibration and maintenance, and thus they were not fully aware of the QC procedures. EN-Standards were mostly followed. Main concerns were related to the checks of flow and calculation of measurement uncertainty, and suggestions for improvement were given. When the measurement networks implement the recommendations given in the audits, it can be concluded that the EN-Standards are adequately followed in the networks. In the ongoing sampling, clear factors risking the trueness of the result were not found. This applies also for the laboratory analyses in 2020. One network had concentrations above the target value, and the indicative measurements should be updated to fixed measurements

Biogenic volatile organic compounds in different ecosystems in southern Kenya

Biogenic volatile organic compounds (BVOCs) have an important impact on atmospheric chemistry. Mixing ratio of BVOCs in different ecosystems have been measured and discussed in detail in recent decades. However, field measurements from tropical Africa remain scarce. In this study, we present the mixing ratio of BVOCs, including isoprene, monoterpenoids, sesquiterpenes, bornylacetate, and 2-methyl-3-buten-2-ol from typical forests, bushlands, grasslands and agricultural ecosystems in Taita Taveta County, southern Kenya. The measurements were conducted in April 2019 during the end of the dry season. The total BVOC mixing ratios in forest, agricultural, bushland and grassland ecosystems were 913 +/- 183 pptv, 1094 +/- 179 pptv, 751 +/- 47 pptv and 886 +/- 95 pptv, respectively. Isoprene represented 76%, 86%, 91% and 85%, respectively, of total mixing ratios. Monoterpenoids represented in 23%, 14%, 8% and 14% of total mixing ratios, respectively. Monoterpenoid have strong effect on the total BVOC mixing ratios, especially at the certain landscape (i.e. wattletree, pine and cypress forest, and dry grassland). The monoterpenoids were dominated by alpha-pinene, limonene and beta-pinene in all of the ecosystems. Linalool was found in a relative high mixing ratio from all lowland samples, which was likely responding to the lower soil moisture.Peer reviewe