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Biogenic volatile organic compounds (BVOCs) contribute to the formation of secondary organic aerosol (SOA) through atmospheric oxidation. Previously detected SOA-markers in northern hemisphere ice cores from Alaska, Greenland, Russia, and Switzerland indicate the transportation of isoprene and monoterpene oxidation products from their forestry sources to these glacial regions. Antarctica is geographically further removed from the BVOC's source, indicating significantly lower SOA-marker concentrations are likely in southern hemisphere ice cores. The aim of this study was to develop a sensitive mass-spectrometric method to detect and quantify low-abundance SOA-markers of isoprene and monoterpenes in ice core samples. Employment of a triple quadrupole HPLC-MS method enabled limit of detections in the range of 0.4-10 ppt for nine terrestrial SOA-markers and a marker of biomass burning, levoglucosan. Quantification was conducted in the multiple reaction monitoring mode with two specific transitions monitored for each target compound. Application of the developed method onto a section of a Jurassic ice core from Antarctica revealed the presence of seven of the target compounds: 2-methylerythritol, 2-methylglyceric acid, cis -pinonic acid, 3-methyl-1,2,3-butanetricarboxylic acid, pinolic acid, cis -norpinonic acid, and pinic acid. Repeatability ranged between 2.2% and 6.2%. This is the first time that such SOA-markers have been discovered and quantified in Antarctic ice.

Isoprene and monoterpenes (MTs) are among the most abundant and reactive volatile organic compounds produced by plants (biogenic volatile organic compounds). We conducted a meta-analysis to quantify the mean effect of environmental factors associated to climate change (warming, drought, elevated CO 2 , and O 3 ) on the emission of isoprene and MTs. Results indicated that all single factors except warming inhibited isoprene emission. When subsets of data collected in experiments run under similar change of a given environmental factor were compared, isoprene and photosynthesis responded negatively to elevated O 3 (-8% and -10%, respectively) and drought (-15% and -42%), and in opposite ways to elevated CO 2 (-23% and +55%) and warming (+53% and -23%, respectively). Effects on MTs emission were usually not significant, with the exceptions of a significant stimulation caused by warming (+39%) and by elevated O 3 (limited to O 3 -insensitive plants, and evergreen species with storage organs). Our results clearly highlight individual effects of environmental factors on isoprene and MT emissions, and an overall uncoupling between these secondary metabolites produced by the same methylerythritol 4-phosphate pathway. Future results from manipulative experiments and long-term observations may help untangling the interactive effects of these factors and filling gaps featured in the current meta-analysis., (© 2019 John Wiley & Sons Ltd.)

Emissions of biogenic volatile organic compounds (BVOC) by boreal evergreen trees have strong seasonality, with low emission rates during photosynthetically inactive winter and increasing rates towards summer. Yet, the regulation of this seasonality remains unclear. We measured in situ monoterpene emissions from Scots pine shoots during several spring periods and analysed their dynamics in connection with the spring recovery of photosynthesis. We found high emission peaks caused by enhanced monoterpene synthesis consistently during every spring period (monoterpene emission bursts, MEB). The timing of the MEBs varied relatively little between the spring periods. The timing of the MEBs showed good agreement with the photosynthetic spring recovery, which was studied with simultaneous measurements of chlorophyll fluorescence, CO2 exchange and a simple, temperature history-based proxy for state of photosynthetic acclimation, S. We conclude that the MEBs were related to the early stages of photosynthetic recovery, when the efficiency of photosynthetic carbon reactions is still low whereas the light harvesting machinery actively absorbs light energy. This suggests that the MEBs may serve a protective functional role for the foliage during this critical transitory state and that these high emission peaks may contribute to atmospheric chemistry in the boreal forest in springtime., (© 2015 John Wiley & Sons Ltd.)

The aromatic plant Hedeoma multiflora Benth. is endangered by the overexploitation and the advance of agricultural and urban borders. The objective of this work was to establish an in vitro multiplication protocol for the species without using plant growth regulators (PGRs) and to compare both the morphology and the ability to produce volatile metabolites of the in vitro plants toward wild populations. We were successful in establishing two in vitro plant lines, one initiated from seeds and other from binodal segments. Neither the addition of 1-naphthylacetic acid, kinetin or their combinations improved either growth or multiplication rates which reached 26.4 stems per initial explant after 12 weeks. A comparison toward three wild populations, harvested at both early and late summer time, showed that the morpho-anatomical characteristics of the aerial parts were fairly preserved although in vitro plants displayed more abundant but shorter roots. The profiles of volatile compounds from in vivo and in vitro specimens were quite similar, although hydrocarbon monoterpenes' fraction was more important in the latter. Pulegone was by far the main volatile metabolite in all the assessed populations while its proportion dropped in the in vitro and in the in vivo plants from late summer with respect to in vivo plants from December. The concentration of the biomarkers, menthone, isomenthone, pulegone and isopulegone, was approximately an order of magnitude lower in the in vitro than in the in vivo plants. Overall, the in vitro biomass production in a PGR-free medium is an appropriate technology for reducing the overexploitation of wild endangered populations and avoiding health safety issues related to the edible consumption of the species. Key Message: High multiplication rates are achieved by the in vitro propagation of Hedeoma multiflora Benth. in a PGR-free media. Morpho-anatomical and chemical features are quite similar to those of wild specimens. [ABSTRACT FROM AUTHOR]

We present reactive VOC observations over the North Pacific and the Arctic Ocean from airborne and shipborne measurements, investigating, in particular, distributions of biogenic volatile organic compounds that may be emitted from phytoplankton. In contrast to terrestrial observations, isoprene (C5H8), the most dominant BVOC emission from the terrestrial ecosystem, was mostly present under the lower detection limit along with monoterpenes (C10H16), the second largest emission from the terrestrial ecosystem. However, we consistently detected sesquiterpenes (C15H24) over the Arctic Ocean for the two Arctic cruises. The results of the analysis of sorbent cartridge samplings conducted over the Arctic Ocean on Korean icebreaker R/V Araon in 2016 and 2017 illustrate that few tens ppt levels of sesquiterpenes were present over the Arctic Ocean. Moreover, the concentration variation was positively correlated with the quantitative indicators of ocean biological activities, such as chlorophyll-a, dissolved DMS, and the ratio of dissolved O2 and Ar. This suggests that further investigations on sesquiterpene's emission and atmospheric transformation processes over the marine boundary layer are required. [ABSTRACT FROM AUTHOR]

Aims: Biogenic volatile organic compound (BVOC) research has been mostly focused on foliar emissions. In this experiment, the main focus was on rhizosphere BVOC emissions of Scots pine seedlings under changing growth conditions. Methods: Soil-growing Scots pines were exposed to increased air (0.5°C) and soil (4.0°C) temperature and N addition (30 kg N ha− 1 yr− 1) for three growing seasons in a field experiment. In addition to these factors, seedlings were exposed to bark herbivory by large pine weevils in two last seasons. Gas-chromatography and mass-spectrometry was used for analyzing the BVOC samples collected from pine rhizosphere. Results: Almost 98 % of BVOCs were non-oxygenated monoterpenes (nMTs), 1 % oxygenated monoterpenes (oMTs), 0.5 % sesquiterpenes (SQTs), and 1 % other BVOCs. In both years, there was an interaction of warming, N addition and bark herbivory on rhizosphere BVOC emissions. In 2015, warming and N addition in single exposures decreased oMT emissions, while herbivory in single exposure increased oMT emissions. In 2016, the three-way interaction showed that the effects of warming, N addition and herbivory on BVOCs were mainly detected in single exposures. In 2016, warming decreased nMT, oMT, SQT and other BVOC emissions; N addition decreased oMT and SQT emissions; and herbivory decreased SQT and other BVOC emissions. Conclusions: Warming and N addition in single exposures decreased the rhizosphere BVOC emissions. The effect of bark herbivory on BVOC emissions varied between the years from increase to decrease. It seems that under altered growth conditions Scots pine seedlings may reduce carbon investment to rhizosphere BVOCs. [ABSTRACT FROM AUTHOR]

Volatile isoprenoids produced by plants are emitted in vast quantities into the atmosphere, with substantial effects on global carbon cycling. Yet, the molecular mechanisms regulating the balance between volatile and non-volatile isoprenoid production remain unknown. Isoprenoids are synthesised via sequential condensation of isopentenyl pyrophosphate (IPP) to dimethylallyl pyrophosphate (DMAPP), with volatile isoprenoids containing fewer isopentenyl subunits. The DMAPP:IPP ratio could affect the balance between volatile and non-volatile isoprenoids, but the plastidic DMAPP:IPP ratio is generally believed to be similar across different species. Here we demonstrate that the ratio of DMAPP:IPP produced by hydroxymethylbutenyl diphosphate reductase (HDR/IspH), the final step of the plastidic isoprenoid production pathway, is not fixed. Instead, this ratio varies greatly across HDRs from phylogenetically distinct plants, correlating with isoprenoid production patterns. Our findings suggest that adaptation of HDR plays a previously unrecognised role in determining in vivo carbon availability for isoprenoid emissions, directly shaping global biosphere-atmosphere interactions.

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.

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. [ABSTRACT FROM AUTHOR]

Background: Biogenic volatile organic compounds (BVOC) emitted by plants play an important role for ecological and physiological processes, for example as response to stressors. These emitted compounds are involved in chemical processes within the atmosphere and contribute to the formation of aerosols and ozone. Direct measurement of BVOC emissions requires a specialized sample system in order to obtain repeatable and comparable results. These systems need to be constructed carefully since BVOC measurements may be disturbed by several side effects, e.g., due to wrong material selection and lacking system stability. Results: In order to assess BVOC emission rates, a four plant chamber system was constructed, implemented and throughout evaluated by synthetic tests and in two case studies on 3-year-old sweet chestnut seedlings. Synthetic system test showed a stable sampling with good repeatability and low memory effects. The first case study demonstrated the capability of the system to screen multiple trees within a few days and revealed three different emission patterns of sweet chestnut trees. The second case study comprised an application of drought stress on two seedlings compared to two in parallel assessed seedlings of a control. Here, a clear reduction of BVOC emissions during drought stress was observed. Conclusion: The developed system allows assessing BVOC as well as CO2 and water vapor gas exchange of four tree specimens automatically and in parallel with repeatable results. A canopy volume of 30 l can be investigated, which constitutes in case of tree seedlings the whole canopy. Longer lasting experiments of e.g., 1-3 weeks can be performed easily without any significant plant interference. [ABSTRACT FROM AUTHOR]

Background and aims: Isoprene and monoterpenes account for approximately two thirds of the biogenic volatile organic compounds (BVOC) emitted annually by vegetation into the atmosphere. Previous research focussed on the magnitude of and controls on emissions of these two compounds by emitting plant species, while the role of soils and non-emitting plant species as potential sinks has been mostly ignored. The objective of the present study is to characterize the deposition of isoprene and α-pinene (a monoterpene) to non-emitting grassland plant mesocosms. Methods: We conducted a laboratory experiment with mesocosms of two forb and one graminoid plant species. Plants and soils together and bare soils only were subject to increasing ambient isoprene and α-pinene concentrations (0-10 ppbv) and the corresponding BVOC exchange rates were quantified. Results: Our major findings are that (i) soils were the dominant sink for the deposition of α-pinene and isoprene in grassland mesocosms, (ii) the presence of above-ground biomass of non-emitting plant species decreased the isoprene and α-pinene deposition in the majority of all cases, and (iii) the net deposition correlated inversely with the ambient concentrations. Conclusions: Our results call for a more in-depth analysis of soil BVOC exchange to better estimate the contribution of soils to the ecosystem-atmosphere BVOC exchange. [ABSTRACT FROM AUTHOR]

Emissions of biogenic volatile organic compounds (BVOCs) from terrestrial ecosystems are important for the atmospheric chemistry and the formation of secondary organic aerosols, and may therefore influence the climate. Global warming is predicted to change patterns in precipitation and plant species compositions, especially in arctic regions where the temperature increase will be most pronounced. These changes are potentially highly important for the BVOC emissions but studies investigating the effects are lacking. The aim of this study was to investigate the quality and quantity of BVOC emissions from a high arctic soil moisture gradient extending from dry tundra to a wet fen. Ecosystem BVOC emissions were sampled five times in the July-August period using a push-pull enclosure technique, and BVOCs trapped in absorbent cartridges were analyzed using gas chromatography–mass spectrometry. Plant species compositions were estimated using the point intercept method. In order to take into account important underlying ecosystem processes, gross ecosystem production, ecosystem respiration and net ecosystem production were measured in connection with chamber-based BVOC measurements. Highest emissions of BVOCs were found from vegetation communities dominated by Salix arctica and Cassiope tetragona , which had emission profiles dominated by isoprene and monoterpenes, respectively. These results show that emissions of BVOCs are highly dependent on the plant cover supported by the varying soil moisture, suggesting that high arctic BVOC emissions may affect the climate differently if soil water content and plant cover change. [ABSTRACT FROM AUTHOR]

Norway spruce ( Picea abies ) is a strong emitter of biogenic volatile organic compounds (BVOCs). In the present study we investigated how shoot canopy position and high levels of stressors such as high temperature and ozone concentration, affect BVOC emission rates by means of in-situ and ex-situ experimental measurements. Therefore, BVOC emission from current-year spruce shoots was investigated under field and manipulated (temperature, ozone) laboratory conditions. Emitted BVOCs were sampled on desorption tubes, coupled with gas-exchange measurements of CO 2 assimilation rate and stomatal conductance, and detected by gas chromatography coupled with mass spectrometry. Total BVOC emission rates from sun shoots under standard conditions were higher than those from shade shoots, although this was significant only in July, on the contrary, only α-pinene and γ-terpinene emission rates showed significant differences between sun and shade acclimated shoots in August. Limonene , α-pinene , β-pinene , and myrcene were identified as the most abundant BVOCs in both campaigns with emission rates above 0.2 nmol m −2 s −1 . Ex-situ measurements revealed a significantly higher total BVOC emissions under high temperature level (40 °C) by ca. 175% as compared with standard temperature (30 °C), while a short-term fumigation of acute O 3 concentration (200 ppb) had no effect on BVOC emissions and its spectrum. These findings might have a relevance considering the role of these compounds in protecting against oxidative stress and their possible stimulation in particular stressful conditions. Implication of such results into emission models may contribute to a more accurate estimation of BVOC emissions for Central European mountain regions dominated by Norway spruce forests and their rate under predicted climate change. [ABSTRACT FROM AUTHOR]

Abstract: Determining which volatile organic compounds (VOCs) are synthesized by plants and emitted into the atmosphere and at what rates is a critical component of our understanding of the Earth system, as is understanding how these emissions respond to environmental controls and how they may change in the future. Here, we review the methods used to sample biogenic VOC emissions, from the leaf scale to the regional scale, and focus on the challenges that this task presents. [Copyright &y& Elsevier]

Abstract: The interest in quantitative analysis of biogenic volatile organic compounds (BVOCs) emissions stems from their importance in atmospheric chemistry. In order to compare the most frequently used BVOC measurement techniques, simultaneous on-line PTR-MS and off-line GC-MS data collection was performed on a 3 years old Fagus sylvatica L. tree placed in a growth chamber. Using an internal standard (deuterated toluene) and applying the selective ion mode (SIM) resulted in significant improvements of monoterpene (MT) quantification by TD-GC-MS. PTR-MS quantification of MTs was based on the ion signal at m/z 137. In the course of the experiments the relative contribution of linalool compared to that of MTs was found to be up to 84%. Since this compound has also a PTR-MS signature at m/z 137, quantification of MT emission rates by PTR-MS was disturbed. Comparison of GC-MS and PTR-MS data allowed an estimation of the ratio of the PTR-MS sensitivity for linalool to the one for MTs at m/z 137. This ratio of sensitivities, combined with the information of the relative contribution of linalool to the sum of linalool and MTs obtained by GC-MS, resulted in accurate derivation of the sum of emission rates of linalool and MTs by PTR-MS. The results indicate that fast and on-line PTR-MS measurements of BVOCs are best accompanied by off-line GC measurements to detect possible interferences or to use the additional information for properly quantifying the sum of emission rates of several compounds. [Copyright &y& Elsevier]

The standard biogenic volatile organic compound (BVOC) emissions from 10 Japanese plant species (Quercus serrata, Quercus crispula, Fagus crenata, Quercus acutissima Carruthers, Quercus glauca, Quercus myrsinaefolia, Cryptomeria japonica, Chamaecyparis obtusa, Pinus densiflora, and rice [Oryza sativa]) were measured. These species were selected due to their abundance in the estimated domain (47,000km2) of the Kinki region. BVOC emission experiments were conducted in a growth chamber where temperature and light intensity can be controlled. Temperature was set at the average summer temperature in Osaka and at 5°C above average. Light intensity was set at 1000, 335, and 0μmolm−2 s−1 during day time. The amount of BVOC emission was high around noon due to the rise of ambient temperature. It was also found that the total emission rates and compositions of BVOC varied significantly among the plant species. Q. serrata, Q. crispula, F. crenata, Q. acutissima Carruthers, Q. glauca, and Q. myrsinaefolia emitted isoprene and showed emission dependence on light intensity and temperature. C. japonica, P. densiflora, C. obtusa, and O. sativa emitted monoterpenes and also showed emission dependence on temperature; however, only C. japonica and P. densiflora showed emission dependence on light intensity. Using BVOC emissions data from 10 plant species and forest data, BVOC emission potential maps were made. The emission of isoprene and monoterpenes from the Kinki region were estimated to be 596 and 54tonh−1, respectively. Seasonal and diurnal variations of BVOC emissions potential were also estimated. Of note, though the amount of monoterpenes from O. sativa is small, it contributes approximately 5% to the total monoterpene emissions due to the huge land area covered by paddy fields. [Copyright &y& Elsevier]

The effects of water deficit stress and plant water potential (ψ) on monoterpene and sesquiterpene leaf emissions from Rosmarinus officinalis, Pinus halepensis, Cistus albidus and Quercus coccifera were studied over 11 days of water withholding (from t 1 to t 11), after substrates had achieved their field capacity (control pots: t 0). Volatile compounds were sampled from the same twig per plant all throughout the study, using a dynamic bag enclosure system. Volatiles, collected in Tenax TA, were studied by means of GC-FID and GC-MS. Monoterpene emissions of water stressed plants (t 1–t 11) were either similar to those of control seedlings (R. officinalis and Q. coccifera) or higher (P. halepensis and C. albidus). By contrast, sesquiterpene emissions were strongly reduced or inhibited after four days of water withholding, particularly for R. officinalis, thus altering terpene emission composition. Despite the positive effect of water stress on leaf monoterpene emissions of P. halepensis and C. albidus, the significant correlation between these emissions and ψ showed a slow decrease of these emissions over long term water deficit periods. This contrasted with the rapid decline of sesquiterpene emissions of R. officinalis according to lower values of ψ. These results provide an overall picture of the different responses of monoterpene and sesquiterpene emissions to progressive water loss. They also reveal the utility of using ψ for estimating some emission rates of some species according to drought conditions. [Copyright &y& Elsevier]

Biogenic volatile organic carbon (BVOC) emissions are an important component of the global BVOC budget, contributing more than 90%. Emissions vary with species and vegetation type; therefore to produce accurate global budgets data is required from different vegetation types. This study investigates BVOC emissions from savannas, Kalahari woodlands, Kalahari open shrublands and Mopane woodlands in southern Africa. BVOC emission samples from individual species were collected using leaf cuvettes and the BVOC concentrations were determined by GC-FID/MS. Ten of the 14 woodland species measured were high isoprene emitters, while two showed high monoterpene emission capacities. Landscape average isoprene emission capacities were estimated to be as high as 9, 8 and 1 mg C m−2 h−1 for savannas, woodlands and shrub lands, respectively. The monoterpene emission capacity for Mopane woodlands were estimated at almost 3 mg C m−2 h−1, while for other landscapes it varied between 0.04 and 3 mg C m−2 h−1. Isoprene and monoterpene emissions at a savanna site in South Africa showed a seasonal variation, which is more pronounced for isoprene. During the winter (June–September) estimated emissions were <10 mg C m−2 d−1, with peak emissions (ranging between 20 and 80 mg C m−2 d−1) occurring during the summer months (December–March) when foliar density peaked. The total BVOC emission from southern African (south of the Equator) savannas was estimated to be in the range of 18–74 Tg C yr−1. [Copyright &y& Elsevier]