Organic acid gas and liquid-phase measurements in Po Valley fall-winter conditions in the presence of fog

Abstract

Concurrent gas and liquid phase organic acid measurements during radiation fog episodes are reported. Gas phase concentrations of HCOOH and CH 3 COOH exhibit large variations from the detection limit (5 nmol m -3 0.1 ppb) to 150 nmol m -3 (3.5 ppb). Liquid phase concentration ranges of 11-175 and 10-269 μM were observed for HCOOH and CH 3 COOH, respectively. Large deviations from Henry’s law equilibrium were observed for HCOOH when the pH of fog droplet solutions was above 5. Our hypothesis is that in this range, the bulk sample pH might not be representative of the acidity of individual droplets in equilibrium with the gas phase. The organic acids in the Po Valley fall-winter conditions seem to originate from anthropogenic processes. DOI: 10.1111/j.1600-0889.1988.tb00109.x