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

[摘要] Soil provides an important source of volatile organic compounds (VOCs) toatmosphere, but in boreal forests these fluxes and their seasonal variationshave not been characterized in detail. Especially wintertime fluxes arealmost completely unstudied. In this study, we measured the VOCconcentrations inside the snowpack in a boreal Scots pine (Pinus sylvestris L.) forest insouthern Finland, using adsorbent tubes and air samplers installedpermanently in the snow profile. Based on the VOC concentrations at threeheights inside the snowpack, we estimated the fluxes of these gases. Wemeasured 20 VOCs from the snowpack, monoterpenes being the most abundantgroup with concentrations varying from 0.11 to 16 μg m⁻³.Sesquiterpenes and oxygen-containing monoterpenes were also detected. Insidethe pristine snowpack, the concentrations of terpenoids decreased from soilsurface towards the surface of the snow, suggesting soil as the source forterpenoids. Forest damages (i.e. broken treetops and branches, fallen trees)resulting from heavy snow loading during the measurement period increasedthe terpenoid concentrations dramatically, especially in the upper part ofthe snowpack. The results show that soil processes are active and efficientVOC sources also during winter, and that natural or human disturbance canincrease forest floor VOC concentrations substantially. Our results stressthe importance of soil as a source of VOCs during the season when otherbiological sources, such as plants, have lower activity.

[学科分类] 地球化学与岩石