Snowpack concentrations and estimated fluxes of volatile organic compounds in a boreal forest

Abstract

Abstract. Soil provides an important source of volatile organic compounds (VOCs) to atmosphere, but in boreal forests these fluxes and their seasonal variations have not been characterized in detail. Especially wintertime fluxes are almost completely unstudied. In this study, we measured the VOC concentrations inside the snowpack in a boreal Scots pine (Pinus sylvestris L.) forest in southern Finland, using adsorbent tubes and air samplers installed permanently in the snow profile. Based on the VOC concentrations at three heights inside the snowpack, we estimated the fluxes of these gases. We measured 20 VOCs from the snowpack, monoterpenes being the most abundant group with concentrations varying from 0.11 to 16 µg m −3 . Sesquiterpenes and oxygencontaining monoterpenes were also detected. Inside the pristine snowpack, the concentrations of terpenoids decreased from soil surface towards the surface of the snow, suggesting soil as the source for terpenoids. Forest damages (i.e. broken treetops and branches, fallen trees) resulting from heavy snow loading during the measurement period increased the terpenoid concentrations dramatically, especially in the upper part of the snowpack. The results show that soil processes are active and efficient VOC sources also during winter, and that natural or human disturbance can increase forest floor VOC concentrations substantially. Our results stress the importance of soil as a source of VOCs during the season when other biological sources, such as plants, have lower activity.

Potential of needle trap microextraction–portable gas chromatography–mass spectrometry for measurement of atmospheric volatile compounds

“…Altogether, these observations suggest the accumulation of these compounds under or into the snow pack. The same phenomena have been verified in another study (Aaltonen et al, 2012). A similar comparison was performed for aldehydes identified and measured in the same sampling period.…”

“…Carbonyl compounds, such as aldehydes, are also important to atmospheric chemistry due to their atmospheric photolysis, reaction with hydroxyl and nitrate radicals, and their contribution to new particle formation (Atkinson, 2000;Jang and Kamens, 2001). Aldehydes can be directly emitted to the atmosphere from incomplete combustion of biomass and fossil fuels, by vegetation, when exposed to stress conditions such as ozone exposure or insect and pathogen attacks, and formed in the atmosphere as a result of photochemical oxidation of reactive compounds (Altemose et al, 2015;Wildt et al, 2003). Primary emissions of saturated C 6 -C 10 aldehydes, such as hexanal, heptanal, octanal, nonanal and decanal, were found from several particular plant species (Wildt et al, 2003).…”

Off-season biogenic volatile organic compound emissions from heath mesocosms: responses to vegetation cutting

“…However, recent studies have revealed that boreal forest floor BVOC emissions peak during early summer and autumn (Aaltonen et al, 2011) and not at midsummer even though the green plant biomass is peaking at midsummer. BVOC emissions can even be measured from the snowpack during winter (Helmig et al, 2009; Aaltonen et al, 2012). In this work we focus on BVOC emissions both from soil and the whole ecosystem in a period of the year which has hither-to been largely neglected, namely the shoulder periods between summer and winter.…”

Pan-Eurasian Experiment (PEEX): towards a holistic understanding of the feedbacks and interactions in the land–atmosphere–ocean–society continuum in the northern Eurasian region

“…Although the inhibitory effect of CO 2 on the process level may be important, Arctic greening may strongly enhance the production of BVOCs in northern ecosystems (Arneth et al, 2007;Sun et al, 2013). Open tundra may also act as a significant source for BVOCs, especially if the snow cover period changes (Aaltonen et al, 2012;Faubert et al, 2012). This would lead to negative climate feedbacks involving either aerosol-cloud or aerosol-carbon cycle interactions (M. Kulmala et al, 2013Paasonen et al, 2013).…”