Total Biogenic Volatile Organic Compounds Emissions Research Articles

Contribution of volatile organic compound fluxes to the ecosystem carbon budget of a poplar short-rotation plantation.

Biogenic volatile organic compounds (BVOCs) are major precursors of both ozone and secondary organic aerosols (SOA) in the troposphere and represent a non‐negligible portion of the carbon fixed by primary producers, but long‐term ecosystem‐scale measurements of their exchanges with the atmosphere are lacking. In this study, the fluxes of 46 ions corresponding to 36 BVOCs were continuously monitored along with the exchanges of mass (carbon dioxide and water vapor) and energy (sensible and latent heat) for an entire year in a poplar (Populus) short‐rotation crop (SRC), using the eddy covariance methodology. BVOC emissions mainly consisted of isoprene, acetic acid, and methanol. Total net BVOC emissions were 19.20 kg C ha−1 yr−1, which represented 0.63% of the net ecosystem exchange (NEE), resulting from −23.59 Mg C ha−1 yr−1 fixed as CO 2 and 20.55 Mg C ha−1 yr−1 respired as CO 2 from the ecosystem. Isoprene emissions represented 0.293% of NEE, being emitted at a ratio of 1 : 1709 mol isoprene per mol of CO 2 fixed. Based on annual ecosystem‐scale measurements, this study quantified for the first time that BVOC carbon emissions were lower than previously estimated in other studies (0.5–2% of NEE) on poplar trees. Furthermore, the seasonal and diurnal emission patterns of isoprene, methanol, and other BVOCs provided a better interpretation of the relationships with ecosystem CO 2 and water vapor fluxes, with air temperature, vapor pressure deficit, and photosynthetic photon flux density.

Biogenic volatile organic compound emissions from senescent maize leaves and a comparison with other leaf developmental stages

Plants are the major source of Biogenic Volatile Organic Compounds (BVOCs) which have a large influence on atmospheric chemistry and the climate system. Therefore, understanding of BVOC emissions from all abundant plant species at all developmental stages is very important. Nevertheless, investigations on BVOC emissions from even the most widespread agricultural crop species are rare and mainly confined to the healthy green leaves. Senescent leaves of grain crop species could be an important source of BVOCs as almost all the leaves senesce on the field before being harvested. For these reasons, BVOC emission measurements have been performed on maize (Zea mays L.), one of the most cultivated crop species in the world, at all the leaf developmental stages. The measurements were performed in controlled environmental conditions using dynamic enclosures and proton transfer reaction mass spectrometry (PTR-MS). The main compounds emitted by senescent maize leaves were methanol (31% of the total cumulative BVOC emission on a mass of compound basis) and acetic acid (30%), followed by acetaldehyde (11%), hexenals (9%) and m/z 59 compounds (acetone/propanal) (7%). Important differences were observed in the temporal emission profiles of the compounds, and both yellow leaves during chlorosis and dry brown leaves after chlorosis were identified as important senescence-related BVOC sources. Total cumulative BVOC emissions from senescent maize leaves were found to be among the highest for senescent Poaceae plant species. BVOC emission rates varied strongly among the different leaf developmental stages, and senescent leaves showed a larger diversity of emitted compounds than leaves at earlier stages. Methanol was the compound with the highest emissions for all the leaf developmental stages and the contribution from the young-growing, mature, and senescent stages to the total methanol emission by a typical maize leaf was 61, 13, and 26%, respectively. This study shows that BVOC emissions from senescent maize leaves cannot be neglected and further investigations in field conditions are recommended to further constrain the BVOC emissions from this important C4 crop species.

BVOC emissions from English oak (<i>Quercus robur</i>) and European beech (<i>Fagus sylvatica</i>) along a latitudinal gradient

Abstract. English oak (Quercus robur) and European beech (Fagus sylvatica) are amongst the most common tree species growing in Europe, influencing the annual biogenic volatile organic compound (BVOC) budget in this region. Studies have shown great variability in the emissions from these tree species, originating from both genetic variability and differences in climatic conditions between study sites. In this study, we examine the emission patterns for English oak and European beech in genetically identical individuals and the potential variation within and between sites. Leaf scale BVOC emissions, net assimilation rates and stomatal conductance were measured at the International Phenological Garden sites of Ljubljana (Slovenia), Grafrath (Germany) and Taastrup (Denmark). Sampling was conducted during three campaigns between May and July 2014. Our results show that English oak mainly emitted isoprene whilst European beech released monoterpenes. The relative contribution of the most emitted compounds from the two species remained stable across latitudes. The contribution of isoprene for English oak from Grafrath and Taastrup ranged between 92 and 97 % of the total BVOC emissions, whilst sabinene and limonene for European beech ranged from 30.5 to 40.5 and 9 to 15 % respectively for all three sites. The relative contribution of isoprene for English oak at Ljubljana was lower (78 %) in comparison to the other sites, most likely caused by frost damage in early spring. The variability in total leaf-level emission rates from the same site was small, whereas there were greater differences between sites. These differences were probably caused by short-term weather events and plant stress. A difference in age did not seem to affect the emission patterns for the selected trees. This study highlights the significance of within-genotypic variation of BVOC emission capacities for English oak and European beech, the influence of climatic variables such as temperature and light on emission intensities and the potential stability in relative compound contribution across a latitudinal gradient.

Shoot-level terpenoids emission in Norway spruce (Picea abies) under natural field and manipulated laboratory conditions

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 CO2 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 O3 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.

Urban stress-induced biogenic VOC emissions and SOA-forming potentials in Beijing

Abstract. Trees can significantly impact the urban air chemistry by the uptake and emission of reactive biogenic volatile organic compounds (BVOCs), which are involved in ozone and particle formation. Here we present the emission potentials of "constitutive" (cBVOCs) and "stress-induced" BVOCs (sBVOCs) from the dominant broadleaf woody plant species in the megacity of Beijing. Based on the municipal tree census and cuvette BVOC measurements on leaf level, we built an inventory of BVOC emissions, and assessed the potential impact of BVOCs on secondary organic aerosol (SOA) formation in 2005 and 2010, i.e., before and after realizing the large tree-planting program for the 2008 Olympic Games. We found that sBVOCs, such as fatty acid derivatives, benzenoids, and sesquiterpenes, constituted a significant fraction ( ∼ 40 %) of the total annual BVOC emissions, and we estimated that the overall annual BVOC budget may have doubled from ∼ 4.8 × 109 g C year−1 in 2005 to ∼ 10.3 × 109 g C year−1 in 2010 due to the increase in urban greening, while at the same time the emission of anthropogenic VOCs (AVOCs) decreased by 24 %. Based on the BVOC emission assessment, we estimated the biological impact on SOA mass formation potential in Beijing. Constitutive and stress-induced BVOCs might produce similar amounts of secondary aerosol in Beijing. However, the main contributors of SOA-mass formations originated from anthropogenic sources (> 90 %). This study demonstrates the general importance to include sBVOCs when studying BVOC emissions. Although the main problems regarding air quality in Beijing still originate from anthropogenic activities, the present survey suggests that in urban plantation programs, the selection of low-emitting plant species has some potential beneficial effects on urban air quality.

Global data set of biogenic VOC emissions calculated by the MEGAN model over the last 30 years

Abstract. The Model of Emissions of Gases and Aerosols from Nature (MEGANv2.1) together with the Modern-Era Retrospective Analysis for Research and Applications (MERRA) meteorological fields were used to create a global emission data set of biogenic volatile organic compounds (BVOC) available on a monthly basis for the time period of 1980–2010. This data set, developed under the Monitoring Atmospheric Composition and Climate project (MACC), is called MEGAN–MACC. The model estimated mean annual total BVOC emission of 760 Tg (C) yr−1 consisting of isoprene (70%), monoterpenes (11%), methanol (6%), acetone (3%), sesquiterpenes (2.5%) and other BVOC species each contributing less than 2%. Several sensitivity model runs were performed to study the impact of different model input and model settings on isoprene estimates and resulted in differences of up to ±17% of the reference isoprene total. A greater impact was observed for a sensitivity run applying parameterization of soil moisture deficit that led to a 50% reduction of isoprene emissions on a global scale, most significantly in specific regions of Africa, South America and Australia. MEGAN–MACC estimates are comparable to results of previous studies. More detailed comparison with other isoprene inventories indicated significant spatial and temporal differences between the data sets especially for Australia, Southeast Asia and South America. MEGAN–MACC estimates of isoprene, α-pinene and group of monoterpenes showed a reasonable agreement with surface flux measurements at sites located in tropical forests in the Amazon and Malaysia. The model was able to capture the seasonal variation of isoprene emissions in the Amazon forest.

Biogenic volatile organic compound (BVOC) emissions from forested areas in Turkey: Determination of specific emission rates for thirty-one tree species

Normalized biogenic volatile organic compound (BVOC) emission rates for thirty one tree species that cover the 98% of national forested areas in Turkey were determined. Field samplings were performed at fourteen different forested areas in Turkey using a specific dynamic enclosure system. The selected branches of tree species were enclosed in a chamber consisted of a transparent Nalofan bag. The air-flows were sampled from both inlet and outlet of the chamber by Tenax-filled sorbent tubes during photosynthesis of trees under the presence of sunlight. Several environmental parameters (temperature, humidity, photosynthetically active radiation-PAR, and CO2) were continuously monitored inside and outside the enclosure chamber during the samplings. Collected samples were analyzed using a gas chromatography mass spectrometry (GC/MS) system equipped with a thermal desorber (TD). Sixty five BVOCs classified in five major groups (isoprene, monoterpenes, sesquiterpenes, oxygenated sesquiterpenes, and other oxygenated compounds) were analyzed. Emission rates were determined by normalization to standard conditions (1000μmol/m2s PAR and 30°C temperature for isoprene and 30°C temperature for the remaining compounds). In agreement with the literature, isoprene was mostly emitted by broad-leaved trees while coniferous species mainly emitted monoterpenes. Several tree species such as Sweet Chestnut, Silver Lime, and European Alder had higher monoterpene emissions although they are broad-leaved species. High isoprene emissions were also observed for a few coniferous species such as Nordmann Fir and Oriental Spruce. The highest normalized total BVOC emission rate of 27.1μg/gh was observed for Oriental Plane while South European Flowering Ash was the weakest BVOC emitter with a total normalized emission rate of 0.031μg/gh. Monoterpene emissions of broad-leaved species mainly consisted of sabinene, limonene and trans-beta-ocimene, while alpha-pinene, beta-pinene and beta-myrcene were generally emitted by coniferous species. Oxygenated compounds were the third most prominent BVOC group and sesquiterpenes had slightly lower contributions.

Spatio-temporal variation of biogenic volatile organic compounds emissions in China

Aiming to reduce the large uncertainties of biogenic volatile organic compounds (BVOCs) emissions estimation, the emission inventory of BVOCs in China at a high spatial and temporal resolution of 36 km × 36 km and 1 h was established using MEGANv2.1 with MM5 providing high-resolution meteorological data, based on the most detailed and latest vegetation investigations. BVOC emissions from 82 plant functional types in China were computed firstly. More local species-specific emission rates were developed combining statistical analysis and category classification, and the leaf biomass was estimated based on vegetation volume and production with biomass-apportion models. The total annual BVOC emissions in 2003 were 42.5 Tg, including isoprene 23.4 Tg, monoterpene 5.6 Tg, sesquiterpene 1.0 Tg, and other VOCs (OVOCs) 12.5 Tg. Subtropical and tropical evergreen and deciduous broadleaf shrubs, Quercus, and bamboo contributed more than 45% to the total BVOC emissions. The highest biogenic emissions were found over northeastern, southeastern, and southwestern China. Strong seasonal pattern was observed with the highest BVOC emissions in July and the lowest in January and December, with daily emission peaked at approximately 13:00 or 14:00 local time.

A comprehensive emission inventory of biogenic volatile organic compounds in Europe: improved seasonality and land-cover

Abstract. Biogenic volatile organic compounds (BVOC) emitted from vegetation are important for the formation of secondary pollutants such as ozone and secondary organic aerosols (SOA) in the atmosphere. Therefore, BVOC emission are an important input for air quality models. To model these emissions with high spatial resolution, the accuracy of the underlying vegetation inventory is crucial. We present a BVOC emission model that accommodates different vegetation inventories and uses satellite-based measurements of greenness instead of pre-defined vegetation periods. This approach to seasonality implicitly treats effects caused by water or nutrient availability, altitude and latitude on a plant stand. Additionally, we test the influence of proposed seasonal variability in enzyme activity on BVOC emissions. In its present setup, the emission model calculates hourly emissions of isoprene, monoterpenes, sesquiterpenes and the oxygenated volatile organic compounds (OVOC) methanol, formaldehyde, formic acid, ethanol, acetaldehyde, acetone and acetic acid. In this study, emissions based on three different vegetation inventories are compared with each other and diurnal and seasonal variations in Europe are investigated for the year 2006. Two of these vegetation inventories require information on tree-cover as an input. We compare three different land-cover inventories (USGS GLCC, GLC2000 and Globcover 2.2) with respect to tree-cover. The often-used USGS GLCC land-cover inventory leads to a severe reduction of BVOC emissions due to a potential miss-attribution of broad-leaved trees and reduced tree-cover compared to the two other land-cover inventories. To account for uncertainties in the land-cover classification, we introduce land-cover correction factors for each relevant land-use category to adjust the tree-cover. The results are very sensitive to these factors within the plausible range. For June 2006, total monthly BVOC emissions decreased up to −27% with minimal and increased up to +71% with maximal factors, while in January 2006, the changes in monthly BVOC emissions were −54 and +56% with minimal and maximal factors, respectively. The new seasonality approach leads to a reduction in the annual emissions compared with non-adjusted data. The strongest reduction occurs in OVOC (up to −32%), the weakest in isoprene (as little as −19%). If also enzyme seasonality is taken into account, however, isoprene reacts with the steepest decrease of annual emissions, which are reduced by −44% to −49%, annual emissions of monoterpenes reduce between −30 and −35%. The sensitivity of the model to changes in temperature depends on the climatic zone but not on the vegetation inventory. The sensitivity is higher for temperature increases of 3 K (+31% to +64%) than decreases by the same amount (−20 to −35%). The climatic zones "Cold except summer" and "arid" are most sensitive to temperature changes in January for isoprene and monoterpenes, respectively, while in June, "polar" is most sensitive to temperature for both isoprene and monoterpenes. Our model predicts the oxygenated volatile organic compounds to be the most abundant fraction of the annual European emissions (3571–5328 Gg yr−1), followed by monoterpenes (2964–4124 Gg yr−1), isoprene (1450–2650 Gg yr−1) and sesquiterpenes (150–257 Gg yr−1). We find regions with high isoprene emissions (most notably the Iberian Peninsula), but overall, oxygenated VOC dominate with 43–45% (depending on the vegetation inventory) contribution to the total annual BVOC emissions in Europe. Isoprene contributes between 18–21%, monoterpenes 33–36% and sesquiterpenes contribute 1–2%. We compare the concentrations of biogenic species simulated by an air quality model with measurements of isoprene and monoterpenes in Hohenpeissenberg (Germany) for both summer and winter. The agreement between observed and modelled concentrations is better in summer than in winter. This can partly be explained with the difficulty to model weather conditions in winter accurately, but also with the increased anthropogenic influence on the concentrations of BVOC compounds in winter. Our results suggest that land-cover inventories used to derive tree-cover must be chosen with care. Also, uncertainties in the classification of land-cover pixels must be taken into account and remain high. This problem must be addressed together with the remote sensing community. Our new approach using a greenness index for addressing seasonality of vegetation can be implemented easily in existing models. The importance of OVOC for air quality should be more deeply addressed by future studies, especially in smog chambers. Also, the fate of BVOC from the dominant region of the Iberian Peninsula should be studied more in detail.

The Model of Emissions of Gases and Aerosols from Nature version 2.1 (MEGAN2.1): an extended and updated framework for modeling biogenic emissions

Abstract. The Model of Emissions of Gases and Aerosols from Nature version 2.1 (MEGAN2.1) is a modeling framework for estimating fluxes of biogenic compounds between terrestrial ecosystems and the atmosphere using simple mechanistic algorithms to account for the major known processes controlling biogenic emissions. It is available as an offline code and has also been coupled into land surface and atmospheric chemistry models. MEGAN2.1 is an update from the previous versions including MEGAN2.0, which was described for isoprene emissions by Guenther et al. (2006) and MEGAN2.02, which was described for monoterpene and sesquiterpene emissions by Sakulyanontvittaya et al. (2008). Isoprene comprises about half of the total global biogenic volatile organic compound (BVOC) emission of 1 Pg (1000 Tg or 1015 g) estimated using MEGAN2.1. Methanol, ethanol, acetaldehyde, acetone, α-pinene, β-pinene, t-β-ocimene, limonene, ethene, and propene together contribute another 30% of the MEGAN2.1 estimated emission. An additional 20 compounds (mostly terpenoids) are associated with the MEGAN2.1 estimates of another 17% of the total emission with the remaining 3% distributed among >100 compounds. Emissions of 41 monoterpenes and 32 sesquiterpenes together comprise about 15% and 3%, respectively, of the estimated total global BVOC emission. Tropical trees cover about 18% of the global land surface and are estimated to be responsible for ~80% of terpenoid emissions and ~50% of other VOC emissions. Other trees cover about the same area but are estimated to contribute only about 10% of total emissions. The magnitude of the emissions estimated with MEGAN2.1 are within the range of estimates reported using other approaches and much of the differences between reported values can be attributed to land cover and meteorological driving variables. The offline version of MEGAN2.1 source code and driving variables is available from

Isoprene and terpenoid emissions from Abies alba: Identification and emission rates under ambient conditions

In this study, biogenic volatile organic compound (BVOC) emissions from Abies alba were studied under ambient conditions in Flanders (Belgium). Emission patterns and rates were investigated from April till November 2010 by using the dynamic branch enclosure technique. The present work revealed that A. alba is an isoprene emitter, with isoprene accounting for 86–93% of total BVOC emissions, except during budburst (67%) in May. The emission spectrum of A. alba consisted of 27 compounds. Next to isoprene, the main emitted compounds were α-pinene, β-pinene, camphene and limonene. BVOC emissions showed a peak in June after development of the young needles, followed by a constant emission during summer months and September and a decrease in October. In all the samples isoprene was the most abundant compound with standardized emission rates between 27 μg g(dw)−1 h−1 in June and 4.6 μg g(dw)−1 h−1 in October, while the total standardized terpenoid emission rates ranged from 2.85 μg g(dw)−1 h−1 in June to 0.26 μg g(dw)−1 h−1 in October. The obtained average β coefficients according to the temperature dependent algorithm of Guenther et al. (1993) during April–June, July, August and September–October were as follows: for terpenoids 0.12 ± 0.03, 0.11 ± 0.05, 0.12 ± 0.04, 0.24 ± 0.01 K−1 and sesquiterpenes (SQTs) 0.09 ± 0.02, 0.11 ± 0.01, 0.10 ± 0.05, 0 K−1, respectively. Overall, isoprene detected in this study was never quantified in previous studies on A. alba and this finding could have a significant impact on the regional BVOCs budget. Therefore, the result of this study is very important for modeling and local air quality.

An inventory of biogenic volatile organic compounds for a subtropical urban–rural complex

Increases in atmospheric volatile organic compounds (VOC), especially in relation to biogenic VOC (BVOC), and haze days that affect the built-up areas are believed to be closely correlated. The present study aims to provide a spatially and temporally resolved BVOC inventory of a subtropical urban–rural complex, the Greater Hangzhou Area (GHA) in China. Urban green space was subdivided into block green space and linear green space; rural areas were classified into four primary forest types. A field survey was conducted to assess the vegetation composition (species, size) and foliar mass of each tree species. BVOC emission potentials were obtained from measurement and literature. Results showed (1) the emission intensity (annual BVOC emissions per land area) in the entire GHA is 3.37 × 106 g C km−2 yr−1, and rural forest (excluding bamboo forest) exhibits lower average emission intensity (2.74 × 106 g C km−2 yr−1) than that of urban green space (3.13 × 106 g C km−2 yr−1); (2) Within the built-up area, the block green space has higher emission intensity (3.93 × 106 g C km−2 yr−1) than the linear green space (2.63 × 106 g C km−2 yr−1); (3) in Hangzhou city, BVOC emissions of native and exotic trees exhibited no differences; and (4) in rural areas, bamboo forests and coniferous forests were the major contributors of BVOC emissions, whereas the original vegetation type of this region, evergreen broad-leaved forest, possessed lower BVOC emissions. The results suggest that total BVOC emission can be controlled to low levels by planting low-emitting species in built-up areas while restoring original broad-leaved forest vegetation in rural areas.

Seasonal Variations of BVOCs Emission from <i>Ginkgo biloba</i> Linn in Urban Area

In this study, seasonal biogenic volatile organic compound (BVOC) emission rates and emission patterns of Ginkgo biloba linn are estimated. The released volatiles were collected from branches onto cartridges filled with Tenax TA, and quantified by thermal desorption gas chromatography mass spectrometry (GC-MS). The result showed that the main BVOCs emitted from Ginkgo biloba linn were alkanes, aldehydes, alkenes, aromatic compounds, esters, terpenes and ketones. The total BVOC emission rate increased from May, and reached its maximum 27.96 μg C g-1dw h-1 in July, then decreased quickly. The emissions of α-pinene, isoprene, cyclohexane, methyl-cyclohexane and 2-methyl-hexane were significantly correlated to both temperature (p<0.05) and light (p<0.05).

Few long-term effects of simulated climate change on volatile organic compound emissions and leaf chemistry of three subarctic dwarf shrubs

Climate change is exposing arctic ecosystems to higher temperature, increased nutrient availability and shading due to the increasing cloud cover and the expanding forests. In this work, we assessed how these factors affect the emissions of biogenic volatile organic compounds (BVOCs) from three subarctic dwarf shrub species in a field experiment after 18 treatment years. Of the studied species the willow Salix phylicifolia L. was the only isoprene-emitter with an emission potential of 16.1 ± 8.4 μg g −1 dw h −1 (at 30 °C and photosynthetic photon flux density of 1000 μmol m −2 s −1). The dwarf birch Betula nana L. had significant emissions of various reactive BVOCs, including monoterpenes and sesquiterpenes. The evergreen Cassiope tetragona (L.) D. Don emitted high amounts of mono- and sesquiterpenes. Due to chance, the temperature in the warming treatment (employing open-top plastic tents) and the unwarmed treatments was similar at the time of the measurements, and therefore long-term indirect effects of warming could be assessed without interference of temperature differences at the time of measurement. The long-term warming had not altered foliar N, P or condensed tannin concentrations, but it had led to other chemical changes detected in the near-infrared reflectance spectra of the leaves. Nevertheless, there were no significant differences in the BVOC emissions per unit leaf mass measured by the dynamic enclosure method and gas chromatography-mass spectrometry. Annual additions of NPK fertilizer, which mimicked increased nutrient availability, had accumulated P in the leaves of all species. In addition, fertilization marginally increased the leaf N concentration of B. nana. The only significant fertilization effect on BVOC emissions was a stimulation of emission of the sesquiterpene β-selinene from S. phylicifolia. The shading treatment obtained by dome-shaped hessian tents did not cause clear long-term changes in leaf chemistry or BVOC emissions. The only observed change was a marginally significant increase in sesquiterpene emissions from B. nana. When the treatment effects on long-term biomass changes in the different treatments were taken into account by proportioning the BVOC emissions to the biomass of each species in the field treatments, warming led to a significant increase and shading to a decrease in the total BVOC emissions per unit ground area from B. nana. These results highlight the importance of an integrated approach for realistic assessment of responses to climate change.

Temporal, spatial characteristics and uncertainty of biogenic VOC emissions in the Pearl River Delta region, China

Using the Global Biosphere Emissions and Interactions System model (GloBEIS), 3 × 3 km gridded and hourly biogenic volatile organic compound (BVOC) emissions in the Pearl River Delta (PRD) were estimated for the year 2006. The study used newly available land cover database, observed meteorological data, and recent measurements of emission rates for tree species in China. The results show that the total BVOC emission in the PRD region in 2006 was 296 kt (2.2 × 10 11 gC), of which isoprene contributes about 25% (73 kt, 6.4 × 10 10 gC), monoterpenes about 34% (102 kt, 8.9 × 10 10 gC), and other VOCs (OVOC) about 41% (121 kt, 6.8 × 10 10 gC). BVOC emissions in the PRD region exhibit a marked seasonal pattern with the peak emission in July and the lowest emission in January, and are mainly distributed over the outlying areas of the PRD region, where the economy and land use are less developed. The uncertainties in BVOC emission estimates were quantified using Monte Carlo simulation; the results indicate high uncertainties in isoprene emission estimates, with a relative error of −82 to +177%, ranging from 12.4 to 186.4 kt; −41 to +58% uncertainty for monoterpenes emissions, ranging from 67.7 to 181.9 kt; and −26 to +30% uncertainty in OVOC emissions, ranging from 88.8 to 156.2 kt on the 95% confidence intervals. The key uncertainty sources include emission factors and the model empirical coefficients α, C T1, C L, and E opt for estimating isoprene emission, and emission factors and foliar density for estimating monoterpenes and OVOC emissions. This implies that determining these empirical coefficient values properly and conducting more field measurements of emission rates of tree species are key approaches for reducing uncertainties in BVOC emission estimates. Improving future BVOC emission inventory work in the PRD region requires giving priority to research on shrub land, coniferous forests, and irrigated cropland and pasture.

Improved land cover and emission factors for modeling biogenic volatile organic compounds emissions from Hong Kong

This paper describes a study of local biogenic volatile organic compounds (BVOC) emissions from the Hong Kong Special Administrative Region (HKSAR). An improved land cover and emission factor database was developed to estimate Hong Kong emissions using MEGAN, a BVOC emission model developed by Guenther et al. (2006). Field surveys of plant species composition and laboratory measurements of emission factors were combined with other data to improve existing land cover and emission factor data. The BVOC emissions from Hong Kong were calculated for 12 consecutive years from 1995 to 2006. For the year 2006, the total annual BVOC emissions were determined to be 12,400 metric tons or 9.82 × 10 9 g C (BVOC carbon). Isoprene emission accounts for 72%, monoterpene emissions account for 8%, and other VOCs emissions account for the remaining 20%. As expected, seasonal variation results in a higher emission in the summer and a lower emission in the winter, with emission predominantly in day time. A high emission of isoprene occurs for regions, such as Lowest Forest-NT North, dominated by broadleaf trees. The spatial variation of total BVOC is similar to the isoprene spatial variation due to its high contribution. The year to year variability in emissions due to weather was small over the twelve-year period (−1.4%, 2006 to 1995 trendline), but an increasing trend in the annual variation due to an increase in forest land cover can be observed (+7%, 2006 to 1995 trendline). The results of this study demonstrate the importance of accurate land cover inputs for biogenic emission models and indicate that land cover change should be considered for these models.

Reassessment of biogenic volatile organic compound emissions in the Atlanta area

Localized estimates of biogenic volatile organic compound (BVOC) emissions are important inputs for photochemical oxidant simulation models. Since forest tree species are the primary emitters of BVOCs, it is important to develop reliable estimates of their areal coverage and BVOC emission rates. A new system is used to estimate these emissions in the Atlanta area for specific tree genera at hourly and county levels. The U.S. Department of Agriculture, Forest Service Forest Inventory and Analysis data and an associated urban vegetation survey are used to estimate canopy occupancy by genus in the Atlanta area. A simple canopy model is used to adjust photosynthetically active solar radiation at five vertical levels in the canopy. Lraf temperature and photosynthetically active radiation derived from ambient conditions above the forest canopy are then used to drive empirical equations to estimate genus level emission rates of BVOCs vertically through forest canopies. These genera-level estimates are then aggregated to county and regional levels for input into air quality models and for comparison with (1) the regulatory model currently used and (2) previous estimates for the Atlanta area by local researchers. Estimated hourly emissions from the three approaches during a documented ozone event day are compared. The proposed model yields peak diurnal isoprene emission rates that are over a factor of three times higher than previous estimates. This results in total BVOC emission rates that are roughly a factor of two times higher than previous estimates. These emissions are compared with observed emissions from forests of similar composition. Possible implications for oxidant events are discussed.

An improved model for estimating emissions of volatile organic compounds from forests in the eastern United States

Regional estimates of biogenic volatile organic compound (BVOC) emissions are important inputs for models of atmospheric chemistry and carbon budgets. Since forests are the primary emitters of BVOCs, it is important to develop reliable estimates of their areal coverage and BVOC emission rate. A new system is developed to estimate these emissions for specific tree genera at hourly and county level resolution. The U.S. Department of Agriculture, Forest Service Forest Inventory and Analysis Eastwide Database is used to describe the areal extent, species composition, and tree diameter distributions of United States forests. Horizontal canopy occupancy by genera is then estimated as a function of diameter at breast height. Growing season peak foliar masses are derived from the empirical literature for canopies of deciduous and coniferous genera. A simple canopy model is used to adjust photosynthetically active solar radiation at five vertical levels in the canopy. Leaf temperature and photosynthetically active radiation derived from ambient conditions above the forest canopy are then used to drive empirical equations to estimate genus level emission rates of BVOCs vertically through forest canopies. These genera level estimates are then aggregated to regional levels for comparison with the regulatory model currently used and for input into air quality models. The proposed model yields isoprene emission rate estimates for specific countries that are 5 to 10 times higher (and total BVOC emission rates that are 3 to 5 times higher) than the Environmental Protection Agency BVOC emission rate model currently used. Emission estimates of isoprene and monoterpenes from the new system compare favorably with rates measured at various forested sites in the United States.