Search

Biogenic volatile organic compounds (BVOC) are known as hydrocarbons emitted into the atmosphere from the biosphere. They have physiological and ecological functions such as communication within the plant and plant – plant, protection against environmental stress factors and defense against herbivores attack. Coniferous forests are known to produce larger quantities of BVOCs, especially terpenes, where isoprene and the group of monoterpenes are the main compounds. Emitted BVOCs are highly reactive and have an impact on the atmospheric chemistry where it contributes to particle formation and growth. Hence, BVOCs mediate the relationship between the biosphere and atmosphere. Produced BVOCs are affected by environmental factors, among these factors are temperature, stress and light. Emissions may be induced in response to biotic and abiotic factors such as increased temperature, damage done by other organisms or air pollutants. The analysis of this thesis presents the relationship between BVOC emissions and the photosynthetic rate, and how the different compounds are affected by different environmental factors such as light. This was achieved by using a flow-through conifer chamber technique combined with a portable photosynthesis system combined with adsorbent tubes to trap the BVOC emissions. Where the result revealed the differences in compounds, emission rate and photosynthetic activity. Isoprene and the group of monoterpenes, including nine different compounds were then chosen BVOCs for this study. The results from this thesis were then compared to other published literature focusing on Norway spruce (Picea abies) stands during the growing season. This study based on measurements in 2019 showed increased emission rates compared to another study from the same stand four years prior to this, indicating induced emission from stress. The emission rates for the seasonal average were 2.35 (± 3.83 std) for isoprene and 3.59 (± 3.24 std) for monoterpenes, these results we

Traditionally, biogenic volatile organic compound (BVOC) emissions are often considered a unidirectional flux, from the ecosystem to the atmosphere, but recent studies clearly show the potential for bidirectional exchange. Here we aimed to investigate how warming and leaf litter addition affect the bidirectional exchange (flux) of BVOCs in a long-term field experiment in the Subarctic. We also assessed changes in net BVOC fluxes in relation to the time of day and the influence of different plant phenological stages. The study was conducted in a full factorial experiment with open top chamber warming and annual litter addition treatments in a tundra heath in Abisko, Northern Sweden. After 18 years of treatments, ecosystem-level net BVOC fluxes were measured in the experimental plots using proton-transfer-reaction time-of-flight mass spectrometry (PTR–ToF–MS). The warming treatment increased monoterpene and isoprene emissions by ≈50%. Increasing temperature, due to diurnal variations, can both increase BVOC emission and simultaneously, increase ecosystem uptake. For any given treatment, monoterpene, isoprene, and acetone emissions also increased with increasing ambient air temperatures caused by diurnal variability. Acetaldehyde, methanol, and sesquiterpenes decreased likely due to a deposition flux. For litter addition, only a significant indirect effect on isoprene and monoterpene fluxes (decrease by ~50%–75%) was observed. Litter addition may change soil moisture conditions, leading to changes in plant species composition and biomass, which could subsequently result in changes to BVOC emission compositions. Phenological stages significantly affected fluxes of methanol, isoprene and monoterpenes. We suggest that plant phenological stages differ in impacts on BVOC net emissions, but ambient air temperature and photosynthetically active radiation (PAR) also interact and influence BVOC net emissions differently. Our results may also suggest that BVOC fluxes are not

Traditionally, biogenic volatile organic compound (BVOC) emissions are often considered a unidirectional flux, from the ecosystem to the atmosphere, but recent studies clearly show the potential for bidirectional exchange. Here we aimed to investigate how warming and leaf litter addition affect the bidirectional exchange (flux) of BVOCs in a long-term field experiment in the Subarctic. We also assessed changes in net BVOC fluxes in relation to the time of day and the influence of different plant phenological stages. The study was conducted in a full factorial experiment with open top chamber warming and annual litter addition treatments in a tundra heath in Abisko, Northern Sweden. After 18 years of treatments, ecosystem-level net BVOC fluxes were measured in the experimental plots using proton-transfer-reaction time-of-flight mass spectrometry (PTR-ToF-MS). The warming treatment increased monoterpene and isoprene emissions by ≈50%. Increasing temperature, due to diurnal variations, can both increase BVOC emission and simultaneously, increase ecosystem uptake. For any given treatment, monoterpene, isoprene, and acetone emissions also increased with increasing ambient air temperatures caused by diurnal variability. Acetaldehyde, methanol, and sesquiterpenes decreased likely due to a deposition flux. For litter addition, only a significant indirect effect on isoprene and monoterpene fluxes (decrease by ~50%-75%) was observed. Litter addition may change soil moisture conditions, leading to changes in plant species composition and biomass, which could subsequently result in changes to BVOC emission compositions. Phenological stages significantly affected fluxes of methanol, isoprene and monoterpenes. We suggest that plant phenological stages differ in impacts on BVOC net emissions, but ambient air temperature and photosynthetically active radiation (PAR) also interact and influence BVOC net emissions differently. Our results may also suggest that BVOC fluxes are not onl

Willow (Salix spp.) trees are commonly used in short rotation coppices (SRC) to produce renewable energy. However, these plants are also known to emit high concentrations of biogenic volatile organic compounds (BVOCs), which have a large influence on air quality. Many different clones of commercially used Salix varieties exist today, but only a few studies have focused on BVOC emissions from these newer varieties. In this study, four varieties commercially propagated for biofuel production have been studied on a leaf-scale in the southern part of Sweden. The trees had either their first or second growing season, and measurements on BVOC emissions were done during the growing season in 2017 from the end of May to the beginning of September. Isoprene was the dominant emitted compound for all varieties but the average emission amongst varieties varied from 4.00 to 12.66 μg gdw-1 h-1. Average monoterpene (MT) (0.78-1.87 μg gdw -1 h-1) and sesquiterpene (SQT) emission rates (0.22-0.57 μg gdw -1 h-1) differed as well among the varieties. Besides isoprene, other compounds like ocimene, linalool and caryophyllene also showed a response to light but not for all varieties. Younger plants had several times higher emissions of non-isoprenoids (other VOCs) than the corresponding 1-year-old trees. The conclusions from this study show that the choice of variety can have a large impact on the regional BVOC emission budget. Genetics, together with stand age, should be taken into account when modelling BVOC emissions on a regional scale, for example, for air quality assessments.

Emissions of biogenic volatile organic compounds (BVOCs) from natural ecosystems impact atmospheric chemistry as well as biological interactions and even soil biogeochemical processes. Plant litter emits substantial amounts of BVOCs. These emissions may contribute to total ecosystem emissions especially in the Arctic where the living plant biomass is low and the amount of litter is expected to increase as the deciduous shrubs expand in response to a warmer climate. Here, we incubated in the laboratory litter from the evergreen Cassiope tetragona and deciduous Salix spp. from a high arctic and a low arctic location. The 8-week-long incubation was conducted with temperature increasing from 5 °C to 26 °C, mimicking the transition from winter to summer. BVOC emissions from the decomposing litter were sampled weekly in adsorbent cartridges and analyzed using gas chromatography–mass spectrometry, and the bacterial community composition was investigated by sequencing of PCR amplified 16S rRNA gene fragments. Our results showed that litter from C. tetragona, which is a terpenoid storing species, had higher BVOC emission rates (mainly terpenoids) than the Salix litter, which does not have specialized BVOC storing compartments. The C. tetragona litter emissions were higher in the high arctic than the low arctic samples. The emission rates from the C. tetragona litter increased during the incubation period, whereas emission rates from the Salix litter decreased, suggesting that the emissions originated from different sources and/or processes. The bacterial community composition in the Salix litter, but not in the C. tetragona litter, changed in parallel with the changes in the BVOC emissions during the incubation period. Therefore, we suggest that bacteria may be more important for the BVOC emissions from decomposing Salix litter than C. tetragona litter.

Plants emit large quantities of isoprene and monoterpenes, the main components of global biogenic volatile organic compound (BVOC) emissions. BVOCs have an important impact on the atmospheric composition of methane, and of short-lived radiative forcing agents (e.g. ozone, aerosols etc.). It is therefore necessary to know how isoprene and monoterpene emissions have changed over the past and how future changes in climate, land-use and other factors will impact them. Here we present emission estimates of isoprene and monoterpenes over the period 1901–2 100 based on the dynamic global vegetation model LPJ-GUESS, including the effects of all known important drivers. We find that both isoprene and monoterpene emissions at the beginning of the 20th century were higher than at present. While anthropogenic land-use change largely drives the global decreasing trend for isoprene over the 20th century, changes in natural vegetation composition caused a decreasing trend for monoterpene emissions. Future global isoprene and monoterpene emissions depend strongly on the climate and land-use scenarios considered. Over the 21st century, global isoprene emissions are simulated to either remain stable (RCP 4.5), or decrease further (RCP 8.5), with important differences depending on the underlying land-use scenario. Future monoterpene emissions are expected to continue their present decreasing trend for all scenarios, possibly stabilizing from 2050 onwards (RCP 4.5). These results demonstrate the importance to take both natural vegetation dynamics and anthropogenic changes in land-use into account when estimating past and future BVOC emissions. They also indicate that a future global increase in BVOC emissions is improbable.

Secondary organic aerosol (SOA) plays a significant role in climate change by altering the global atmospheric radiation budget. Biogenic volatile organic compounds (BVOCs) are major sources for the formation of SOA. Their relationship is critical to understand the continental biosphere-aerosol-cloud-climate (COBACC) feedback mechanism but receives less attention in previous studies. In this study, a long time-series dataset (2008-2014) of SOA and monoterpene (the dominant biogenic precursor at the site) concentrations measured at the SMEAR II station in Hyytiälä, Finland, was analyzed to quantify the correlation between SOA and monoterpene concentrations. Climate factors including wind direction, temperature and relative humidity are studied to investigate their effects on the correlation. Overall, there was a significant and moderate linear correlation between SOA and monoterpene concentration with the Pearson correlation coefficient R of 0.66. To rule out the anthropogenic influence, the dataset was filtered by selecting the data at the wind direction 270-360°, based on the air trajectory analysis. The correlation coefficient was improved from 0.66 to 0.68. Temperature has been found not only to affect monoterpene emission but also their oxidation and partition processes. Therefore, the correlation between SOA and monoterpene concentration was scrutinized from a number of temperature windows to study the temperature influence. The linear regression slopes at different temperature windows showed a strong temperature dependence (R=0.75), indicating an increasing SOA yield with temperature. Following the same method, a negative correlation was found between the regression slopes and relative humidity(R=-0.88), suggesting a decreasing SOA yield as relative humidity increased. However, this might be due to the anti-correlation between temperature and relative humidity. Finally, the correlations between the SOA concentration increase rates and the monoterpenes oxidation, Aerosols affect the climate by scattering and absorbing light to change the global radiation balance. They can also take part in the cloud formation process to modify cloud properties and the earth’s hydrological cycle. A notable fraction of aerosols is consisted of secondary organic aerosols (SOA), which are predominately from organic compounds emitted by plants. It is suggested that the SOA-cloud interaction will cause a cooling effect under a warmer climate. Therefore, a better understanding of the link between SOA and these compounds would help us understand more about the mechanisms behind the SOA formation and the cooling impact. The aim of this study is to reveal the link between SOA and monoterpenes (the major organic compounds emitted by the trees at the site) behind the measurement data from 2008 to 2014 at a boreal forest site in Hyytiälä, Finland. How wind direction, temperature, relative humidity and oxidants affected the monoterpenes-SOA relation were also studied. In the results, we found a positive link between SOA and monoterpenes, implying that SOA concentration increased with monoterpene concentration. Temperature had a strong and positive impact on the rate at which SOA was formed from monoterpenes, suggesting a more efficient SOA formation at higher temperature. Humidity, on the contrary, exhibited a strong and negative impact on this rate. It was questionable if this negative influence was indirectly affected by temperature as well. Wind direction associated human pollutions showed very weak impact in this study and the night time oxidation was mainly driven by O3. Our findings suggested that in a warmer climate, SOA concentration is likely to increase and hence may mitigate the warming through the SOA-cloud interactions. Keywords: Physical Geography, Ecosystem Analysis, BVOC, Monoterpenes, SOA, Temperature, Relative humidity, Wind direction

Biogenic volatile organic compounds (BVOCs) are trace gases other than CO2 and CH4 produced and emitted by the vegetation. The group consists of thousands of compounds in various shapes and sizes and with short atmospheric lifetimes. Some of the most common BVOC groups are called isoprene, monoterpenes and sesquiterpenes. For the plant, the emission of BVOCs is used for plant communication, attracting pollinators, to deter herbivores and to enhance abiotic stress defense against for example high temperatures, irradiation or oxidative stresses. But once released into the atmosphere, they are affecting the atmospheric chemistry which in effect alters our climate. Depending on the atmospheric composition, BVOC emissions can either enhance tropospheric ozone and indirectly prolong the lifetimes of greenhouse gases such as methane by reducing the concentration of hydroxyl radicals, or increase the formation of aerosols and cloud condensation nuclei which may mitigate the effect of greenhouse gases on global warming.It is fairly well known that BVOCs have an impact on the climate. However, whether the BVOC emissions have a warming or cooling effect on the overall climate is difficult to determine due to existing emission pattern variations both between individuals of the same species and between species. Some of the reasons which are often discussed to be influential and where there is relatively little data available are within-species genetic variation, stress response, adaptation to different weather and climatic conditions and seasonality. In this thesis, focus has been given to the importance of genetic diversity and adaptation to different growing conditions. Studies have been conducted on three European tree species with genetically identical individuals across a latitudinal gradient, stretching from Slovenia to southern Finland. The main results were that even though the emission amounts varied between sites due to differences in weather events, the progression of

The biogenic volatile organic compound (BVOC) emissions from plants impact atmosphere and climate. The species-specific emissions, and thereby the atmospheric impact, of many plant species are still unknown. Knowledge of BVOC emission from arctic plants is particularly limited. The vast area and relatively high leaf temperature give the Arctic potential for emissions that cannot be neglected. This field study aimed to elucidate the BVOC emission profiles for four common arctic plant species in their natural environment during the growing season. BVOCs were sampled from aboveground parts of Empetrum hermaphroditum, Salix glauca, Salix arctophila and Betula nana using the dynamic enclosure technique and collection of volatiles in adsorbent cartridges, analyzed by gas chromatography-mass spectrometry. Sampling occurred three times: in late June/early July, in mid-July and in early August. E. hermaphroditum emitted the least BVOCs, dominated by sesquiterpenes (SQTs) and non-isoprenoid BVOCs. The Salix spp. emitted the most, dominated by isoprene. The emissions of B. nana were composed of about two-thirds non-isoprenoid BVOCs, with moderate amounts of monoterpenes (MTs) and SQTs. The total B. nana emissions and the MT and SQT emissions standardized to 30 °C were highest in the first measurement in early July, while the other species had the highest emissions in the last measurement in early August. As climate change is expected to increase plant biomass and change vegetation composition in the Arctic, the BVOC emissions from arctic ecosystems will also change. Our results suggest that if the abundance of deciduous shrubs like Betula and Salix spp. increases at the expense of slower growing evergreens like E. hermaphroditum, there is the potential for increased emissions of isoprene, MTs and non-isoprenoid BVOCs in the Arctic.

In August 2012, emissions of biogenic volatile organic compounds (BVOCs) from willow (Salix) trees were measured in Lund, southern Sweden. Sweden has more than 16000 ha of short rotation willow plantations for biofuel production and willow trees are suspected to emit substantial amounts of BVOC to the atmosphere. BVOC emission measurements were carried out on two Salix fragilis trees and one Salix phylicifolia tree. The measurements were conducted using a dynamic flow through chamber covered with Teflon film. Salix trees were found to emit large amounts of isoprene. Especially Salix phylicifolia emitted 98% isoprene of total BVOC emission, whereas Salix fragilis trees released about 85% of the total BVOC mass as isoprene. Apart from isoprene, willow trees were found to emit significant amounts of ocimene as well. Emission rates of different BVOCs were found to vary between different individuals of the same species of willow trees as well as between the subspecies of willow trees. Emissions of BVOCs were detected to depend on temperature and photosynthetically active radiation. Isoprene emission potential for Salix phylicifolia was 56.4 µg g-1dw h-1 whereas 16.9 µg g-1dw h-1 and 44.4 µg g-1dw h-1 were measured for the Salix fragilis trees., Popular science Biogenic volatile organic compounds (BVOCs) are a versatile group of non-methane hydrocarbons (chemical compounds made of carbon and hydrogen) emitted by vegetation. The most common BVOCs from plants are some chemical compounds like isoprene, monoterpenes and sesquiterpenes. BVOCs are involved in plant growth, reproduction and defense mechanisms. Besides, BVOC play an important role in tropospheric (lower portion of atmosphere) chemistry and could increase methane’s lifetime, form tropospheric ozone and increase CO2 concentration. In August 2012, emissions of biogenic volatile organic compounds (BVOCs) from willow (Salix) trees were measured in Lund, southern Sweden. For the last 25 years willow has been cultivated as an agricultural crop for bioenergy production and played an important role in Swedish energy sector by producing wood fuel. During this period, more than 16000 ha of short rotation willow plantations have been planted in Sweden. But willow trees are suspected to emit substantial amounts of BVOC to the atmosphere. BVOC emission measurements were carried out on two Salix fragilis trees and one Salix phylicifolia tree. Emission rates of different BVOCs were found to vary between different individuals of the same species of willow trees as well as between the subspecies of willow trees. Emissions of BVOCs were detected to depend on temperature and light intensity. Salix trees were found to emit large amounts of isoprene. Especially Salix phylicifolia emitted 98% isoprene of total BVOC emission, whereas Salix fragilis trees released about 85% of the total BVOC mass as isoprene. But isoprene is an extremely reactive compound and reacts with other atmospheric gases. Isoprene emission potential for Salix phylicifolia was 56.4 µg g-1dw h-1 (microgram per gram dry weight of leaves per hour) whereas 16.9 µg g-1dw h-1 and 44.4 µg g-1dw h-1 were measured for the Salix fragilis trees. Isoprene emission potentials for Willows were higher compared to o

Biogenic volatile organic compounds (BVOC) are one of the most important chemical classes in tropospheric chemistry associated with ozone and secondary organic aerosol formation. Nevertheless, their emission and deposition rates remain unknown for many potentially important plant species due to lack of measurements. Moreover, the number of BVOC species reported for flux measurement by current techniques has been limited to a small fraction of the number of compounds actually emitted or deposited. Thus, large uncertainties still exist in estimating the ecosystem-scale fluxes of BVOCs and their oxidation products (OVOC). Two intensive field observation campaigns in different vegetation ecosystems took place in summer 2009 and 2010. The Biosphere Effects on AeRosols and Photochemistry EXperiment field campaign during summer 2009 (BEARPEX 2009, June 15 - July 31) was made in a Ponderosa pine plantation on the western slope of the Sierra Nevada Mountain range in California. During summer 2010 (June 25 - July 26), another intensive BVOC concentration and flux measurement campaign was conducted as part of a one-year continuous field campaign (CITRUS 2010, October 2009 - November 2010) in an orange orchard in the Central Valley of California near Visalia. Through these two field campaigns, this dissertation presents the ecosystem-atmosphere exchange of a wide range of BVOC and OVOC by coupling state of the art VOC measurement techniques (proton transfer reaction mass spectrometry; PTR-MS, and proton transfer reaction - time of flight - mass spectrometry; PTR-TOF-MS) with a well-established micrometeorological approach (eddy-covariance method; EC). Ambient concentrations of BVOC and OVOC were simultaneously measured for investigating fluxes and vertical gradients in both field sites along with the meteorological parameters. From BEARPEX 2009, I developed an approach of using the flux and gradient relationship from species which could be measured quickly enough to use the EC

Flyktiga organiska föreningar som släpps ut från växter (BVOC- Biogenic volatile organic compounds) kan ha en stor påverkan på atmosfärisk kemi genom reaktioner som leder till ökad eller minskad ozonproduktion, och genom att de kan vara ett förstadium till aerosoler. De vanligaste flyktiga organiska föreningarna är isopren (2-metyl, 1,3-butadien) och dess derivat, terpener och terpenoider (isoprenoider). Dessa används av växter som t.ex. uppbyggnad av cellmembran, steroider m.m., men är också ett sätt för växten att kommunicera och försvara sig mot yttre påverkan. Utsläpp av flyktiga föreningar har visat sig gynnsamt under vissa situtationer, såsom förhöjd temperatur och solinstrålning, insektsangrepp och fysiska skador. Doften från många växter och blommor består i hög grad av isoprenoider, och används för att kommunicera och locka pollinatorer. Förångning av kemiska föreningar står i korrelation till temperaturen, men växters produktion är beroende av produkter från fotosyntesen, vilket gör att utsläppen även är beroende av solljus. Hur växter reglerar produktionen av specifika kemiska föreningar är dock i hög grad okänt. Utsläppen av flyktiga föreningar från växter är inte stora i subarktiska ekosystem, men kommer troligen förändras under en klimatuppvärmning som kommer att påverka nordliga latituders ekosystem betydligt. Därför är forskning på BVOC-området, som involverar kol- och strålningsbudgetar, av stor betydelse. Den här studien är en analys av rådata från en tredagars mätning av BVOCutsläpp från en Fjällbjörk (Betula pubescens ssp. czerepanovii) i juli 2008. Rådatan omvandlades till flöden, och analyserades med avseende på korrelationen mot temperatur, ljus och fotosyntes. Utsläppen var betydligt lägre än i en tidigare studie på Fjällbjörkar i samma område, men det är möjligt att vissa kemiska föreningar som släpptes ut inte identifierades. Ett stort utbrott av en växtätare år 2004, tros ha triggat en ökning av utsläppen under efterföljande år. Tidigare s, Biogenic volatile organic compounds (BVOCs) can have a large affect on atmospheric chemistry by the production or degradation of ozone and by acting as precursors to secondary organic aerosols (SOA). The most common BVOCs are isoprene and its derivatives, terpenes and terpenoids (isoprenoids). These are used by the plant in cell membranes and as steroids, but are also a means of communication and defence. Emissions of BVOCs have proved advantageous in stressful situations such as elevated temperatures and radiation, herbivore attacks and physical damage. Many of the volatile isoprenoids are the main compound in plant scents that are used to communicate and attract pollinators. The volatilization of compounds is correlated to temperature, but production of BVOCs is dependent on photosynthetic products, and hence light. How plants regulate the production of specific compounds is largely unknown. Emissions of BVOCs are not large in subarctic ecosystems, but are likely to change in the course of a climate warming that will affect high latitude ecosystems significantly. Research on BVOCs, that involves both carbon and radiation budgets, at northern sites, is therefore of high importance. This study is an analysis of raw data obtained in a three day monitoring of BVOC emissions from a Mountain birch (Betula pubescens ssp. czerepanovii) during July, 2008. The raw data was converted into fluxes and analyzed with regards to correlation to temperature, light and photosynthesis. Emission potentials were calculated using the common algorithms developed by Alex Guenther. Emissions were significantly lower than found in a previous study on the Mountain birches in the same area (maximum total emission rate at 300 ng gdw -1 h-1), although some compounds that were emitted might not have been identified due to lack of references in the GC-MS analysis. Linalool was the main compound emitted with an emission potential of 28,5 ng gdw -1 h-1 (standard temperature 20°C). A severe herbivor

Biogenic volatile organic compounds (BVOCs) in the atmosphere react to form ozone and secondary organic aerosols, which deteriorate air quality, affect human health, and indirectly influence global climate changes. The present study aims to provide a preliminary assessment of BVOC emissions in Hong Kong (HKSAR). Thriteen local tree species were measured for their isoprene emission potential. Tree distribution was estimated for country park areas based on field survey data. Plant emission data obtained from measurements and the literature, tree distribution estimation data, land use information, and meteorological data were combined to estimate annual BVOC emissions of 8.6×109 g C for Hong Kong. Isoprene, monoterpenes, and other VOCs contributed about 30%, 40%, and 30% of the estimated total annual emissions, respectively. Although hundreds of plant species are found in Hong Kong country parks, the model results indicate that only 10 tree species contribute about 76% of total annual VOC emissions. Prominent seasonal and diurnal variations in emissions were also predicted by the model. The present study lays a solid foundation for future local research, and results can be applied for studying BVOC emissions in nearby southern China and Asian regions that share similar climate and plant distributions. © 2008 Elsevier Ltd. All rights reserved.