Influence of road traffic on volatile organic compound concentrations in and above a deep Alpine valley

Volatile organic compounds (VOCs) were measured with a motor-glider during six days of July and August, 1996, in Switzerland’s Mesolcina valley. Morning and afternoon profiles from the motor-glider reached up to 4000 m above sea level (m asl). Additional measurements were made on the valley floor with the same type of instrument. The concentration differences at various altitudes between morning and afternoon were correlated with traffic emission factors for the individual VOCs. Traffic emissions govern the concentrations of anthropogenic VOCs in this Alpine valley and above the crests. Due to vertical transport of air, VOC concentrations can increase strongly during daytime at high altitudes ( 2000–4000 m asl) over the Alps.