Abstract
AbstractBioenergy crop production is rapidly expanding in Europe, and the potential emissions of biogenic volatile organic compounds (BVOCs) might change the chemical composition of the atmosphere, influencing in turn air quality and regional climate. The environmental impacts of bioenergy crops on air chemistry are difficult to assess due to a lack of accurate field observations. Therefore, we studied BVOC fluxes from a bioenergy maize field in North‐Eastern Germany throughout the entire reproductive growth stage of the plants. Combining automated large chambers and proton transfer reaction mass spectrometry (PTR‐MS), we successfully measured fluxes of the highly reactive hydrocarbons monoterpenes (MTs) and sesquiterpenes (SQTs), together with several other BVOCs, including alcohols, aldehydes, ketones, benzenoids, and fatty acid derivatives. Emissions of MTs and SQTs were relatively high (17.0% and 3.6% of total mean molar BVOC emission, respectively) compared to methanol emissions (17.6%). Seasonal MT and SQT fluxes were clearly associated with the flowering phase, originating mainly from the flowering tissues as shown in additional laboratory experiments. From the observations of CO2 net ecosystem exchange and evapotranspiration rates, we could exclude heat and drought stress‐induced BVOC emissions. Standard emission factors calculated for all compounds, chemical groups, and growth stages, showed that the temperature dependency of volatile terpenoid fluxes decreased distinctively with proceeding development stage. The results indicate that emissions from large‐scale bioenergy maize fields should be better differentiated and considered in regional estimates of aerosol formation. For the implementation of such relation into biogeochemical modelling, it should be considered that not only seasonal weather development but also phenological growth stages are determining the BVOC patterns and emission potentials.
Highlights
Biogenic volatile organic compounds (BVOCs) play a pivotal role for air chemistry processes and the formation of secondary organic aerosols (SOA)
Based on the meteorological data, we distinguish five phases of measurement periods: (i) late July with low daily mean temperatures and frequent precipitation events, (ii) first half of August with oscillating but high temperatures (>20 °C) and mostly dry weather, (iii) second half of August with slightly cooler temperatures but higher radiation in the first week followed by days with lower radiation, (iv) a short period beginning of September when temperatures sharply rise and decline within few days, and (v) the rest of the measurement campaign with cooler temperatures (12 to °C) and moist conditions
As the biomass of the maize plants inside the chambers could only be measured at the time of harvesting, the biomass development was determined from plants close to the chambers
Summary
Biogenic volatile organic compounds (BVOCs) play a pivotal role for air chemistry processes and the formation of secondary organic aerosols (SOA). They increase CH4 life time by removing hydroxyl radicals, participate in the formation of SOA, and are essential for photochemical ozone production (Atkinson & Arey, 2003; Makkonen et al, 2012; Calfapietra et al, 2013; Schultz et al, 2015). The effects of a changed BVOCs emission regime related to major land-use changes should not be neglected (Rosenkranz et al, 2015).
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