Real-Time Detection of Arsenic Cations from Ambient Air in Boreal Forest and Lake Environments

We present the first observation of airborne organic and inorganic arsenic cations, detected in real time within the boreal forest in Hyytiala, Finland, and over nearby Lake Kuivajarvi. The technique of atmospheric-pressure interface time-of-flight mass spectrometry provides online, in situ monitoring as well as chemical information about the arsenic species, identified as protonated trimethylarsine oxide (AsC3H10O+) and AsO(H2O)(n)(+) clusters (n = 0-4). Quantum chemical calculations confirm that the proposed cations are stable under atmospheric conditions. Our most remarkable discovery is that minimal arsenic appeared during spring 2011 until after the ground began to thaw, triggering a sharp increase in airborne arsenic levels as snowmelt flooded the soil with water and stimulated microbial activity. These findings reveal that volatile arsenic species, detected here as atmospheric ions, link the biogeochemical cycling of arsenic through air, soil, water, and living organisms.