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. ...

From emissions to ambient mixing ratios: online seasonal field measurements of volatile organic compounds over a Norway spruce-dominated forest in central Germany

“…1). Independent of time, oxVOC dominated the ambient mixing ratios, as expected for European conditions (Oderbolz et al, 2013). Their impact in atmospheric reactivity is less profound than isoprenoids, but they still share an important portion of the total OH reactivity emission rates (Nölscher et al, 2012).…”

“…These may subsequently act as cloud condensation nuclei and affect cloud radiative properties (Pöschl et al, 2010;Siostedt et al, 2011;Paasonen et al, 2013). Isoprenoids have been a main focus due to their highly reactive nature, but some oxVOCs may also play a substantial role (Guenther et al, 1995;Kesselmeier and Staudt, 1999;Fuentes et al, 2000) and their importance should be investigated in greater detail (Oderbolz et al, 2013). In situ emission measurements of vegetation may be the real-world indicator of the variations in the biogenic source strength of these compounds, as well as of their future ambient mixing ratios.…”

“…Because of their volatility and abundance, and hence their role in atmospheric chemistry, isoprene (C 5 H 8 ), monoterpenes (MT, C 10 H 16 ) and, more recently, sesquiterpenes (SQT, C 15 H 24 ) dominate BVOC emission studies. However, plants also emit a large amount of oxygenated VOCs (oxVOC) such as methanol (CH 4 O), acetaldehyde (C 2 H 4 O), ethanol (C 2 H 6 O) and acetone (C 3 H 6 O) (Kesselmeier and Staudt, 1999), the importance of which needs to be better addressed in future studies (Oderbolz et al,2013). Short-term laboratory experiments provide valuable information under controlled conditions, but their results are not comparable with longer term field experiments (Kivimäenpää et al, 2013) due to the controlled unnatural environments they grow in.…”

“…The main goal of this study is to address the dominant factors determining the driving forces of VOC emissions from temperate-latitude Norway spruce over a seasonal snow-free period by using dynamic enclosure and online proton-transfer-reaction mass spectrometry (PTR-MS) techniques. Since oxVOCs are dominant contributors in the total annual BVOC emissions in Europe (Oderbolz et al, 2013) but are absent in more detailed models (McKinney et al, 2011), their emission rates have been investigated in parallel with isoprenoids and compared in terms of correlation, emission potential and temperature dependencies. Monthly diel emission patterns were investigated for both VOC class compounds, and a parameterization evaluation was performed for oxVOC along with monoterpenes.…”

The impact of speciated VOCs on regional ozone increment derived from measurements at the UK EMEP supersites between 1999 and 2012

“…The UK biogenic VOC emissions estimate reported to EMEP for 2011 was 91.2 Gg (cf. anthropogenic emissions of 752 Gg) but this value is uncertain and studies have estimated considerably higher UK annual biogenic VOC emissions, in excess of 200 Gg (Karl et al, 2009;Oderbolz et al, 2013). Biogenic VOC contributions to regional O 3 increments were not studied using this methodology.…”