Variability of formaldehyde in the Antarctic troposphere

The annual cycle of formaldehyde (HCHO) was measured at a remote site in An tarctica in order to investigate seasonal and diurnal variations as well as chemical processes in the troposphere. The measurements were performed in 1997 (March 1997 to January 1998) and in February 1999 at the German Antarc tic research station Neumayer, which is located at 70 degrees 37'5, 8 degre es 22'W. The obtained time series for formaldehyde in near-surface air clea rly indicates the occurrence of diurnal and seasonal variations in Antarcti ca. It was found that HCHO concentrations vary from values below the detect ion limit (0.03 ppbv) to maximum values of 0.4 ppbv in winter and 0.7 ppbv in the austral summer. The observed concentrations show daily variations on certain days, with maxima in early afternoon and minima during the night. It was found that HCHO mixing ratios are significantly higher than those pr edicted so far by photochemical models.