Secondary aerosol formation from stress-induced biogenic emissions and possible climate feedbacks
Atmospheric aerosols impact climate by scattering and absorbing solar\nradiation and by acting as ice and cloud condensation nuclei. Biogenic\nsecondary organic aerosols (BSOAs) comprise an important component of\natmospheric aerosols. Biogenic volatile organic compounds (BVOCs)\nemitted by vegetation are the source of BSOAs. Pathogens and insect\nattacks, heat waves and droughts can induce stress to plants that may\nimpact their BVOC emissions, and hence the yield and type of formed\nBSOAs, and possibly their climatic effects. This raises questions of\nwhether stress-induced changes in BSOA formation may attenuate or\namplify effects of climate change. In this study we assess the potential\nimpact of stress-induced BVOC emissions on BSOA formation for tree\nspecies typical for mixed deciduous and Boreal Eurasian forests. We\nstudied the photochemical BSOA formation for plants infested by aphids\nin a laboratory setup under well-controlled conditions and applied in\naddition heat and drought stress. The results indicate that stress\nconditions substantially modify BSOA formation and yield. Stress-induced\nemissions of sesquiterpenes, methyl salicylate, and C-17-BVOCs increase\nBSOA yields. Mixtures including these compounds exhibit BSOA yields\nbetween 17 and 33%, significantly higher than mixtures containing\nmainly monoterpenes (4-6% yield). Green leaf volatiles suppress SOA\nformation, presumably by scavenging OH, similar to isoprene. By\nclassifying emission types, stressors and BSOA formation potential, we\ndiscuss possible climatic feedbacks regarding aerosol effects. We\nconclude that stress situations for plants due to climate change should\nbe considered in climate-vegetation feedback mechanisms.