Phase partitioning of atmospheric formaldehyde in a suburban atmosphere

Ambient air samples (n=89) were collected between May 2003 and May 2004 in Izmir, Turkey to investigate the gas/particle partitioning of formaldehyde (HCHO). Average gas-phase formaldehyde (HCHO) concentrations (7.3±6.5 μg m−3, average±SD) were within the range previously measured at different sites around the world. Particle-phase HCHO concentrations ranged between 3 and 65 ng m−3 (average±SD, 18±12 ng m−3) and HCHO was primarily associated with gas phase (99.55%). The partitioning of HCHO between particle and gas phases was compared to the absorptive gas/particle partitioning model. The partitioning model significantly underpredicted the experimental (gas/particle partition coefficient) values. Modeled Kp values were more than five orders of magnitude smaller than the experimental ones. However, the agreement between experimental Kp values and those predicted for HCHO hydrate was very good, suggesting that HCHO hydrate formation in particles may be responsible for the measurement of anomalously large experimental Kp values for HCHO.