Vertical transport and degradation of polycyclic aromatic hydrocarbons in an Alpine Valley

Polycyclic aromatic hydrocarbons (PAHs) are mostly emitted into the atmosphere by anthropogenic combustion sources and are of concern due to their mutagenic and carcinogenic properties. Here we present results from field measurements performed in a Swiss Alpine valley in summer 2001 during the CHAPOP campaign (Characterization of High Alpine Pollution Plumes). Aerosol filter samples were collected at two sites, one close to a freeway that runs at the ground of the valley and one at the top of a mountain, about above the lower station. The large majority of the PAHs detected are alkylated. Concentration changes of parent and alkylated PAHs between were measured with two-step laser mass spectrometry (L2MS) over 3 days with a time resolution of 2– . This technique is orders of magnitudes more sensitive than conventional chromatographic methods; however, it does not allow distinguishing isomers. Generally much lower PAH concentrations at the mountain site were observed than in the valley, whereas alkylated PAHs were more depleted relative to their respective parent PAHs. Transport times between two stations for an individual day were estimated from meteorological observations and were used to calculate reaction rates of PAHs. Lifetimes of PAHs varied between 3.3 and , whereas often alkylated PAHs were more reactive than the corresponding parent PAHs.