Improvement and characterization of an automatic aerosol sampler for remote (glacier) sites

An automatic prototype aerosol sampler has been specifically revised to gain reliable year round data sets of the chemical aerosol composition at high Alpine ice core drill sites. An unattended deployment of the new aerosol sampler at the Vallot Observatory (4361 m a.s.l., French Alps) showed that previous shortcoming such as sensitivity to lightning activities and strong passive sampling effects were successfully overcome. The latter effect was almost eliminated, leading to an improvement of the detection limits by up to a factor of 30. Detailed investigations of the blank variability and sampling characteristics revealed that the new sampler allows to quantify the aerosol species NH4+, SO42−, K+, oxalate as well as total Cl− and total NO3−. In addition records of Na+, Mg2+ and Ca2+ can be provided though systematically underestimated. On the other hand unreliable results are derived for formate, acetate and SO2. Considering a bi-weekly sampling interval, detection limits range from 0.2 to 2 ng m−3 STP (except for Na+: 16 ng m−3 STP). Such a detection limit is also accessible for Na+ if PTFE filters are used. The aerosol data set gained at Vallot Observatory allowed preliminary estimates of mean firn/air ratios for NH4+, SO42− and total NO3−. The air/firn relationship appeared to be consistent compared to other high elevation ice core drilling sites. With the improved detection limits at still minimized energy consumption, a year round deployment of the automatic aerosol sampler appears now to be feasible even at polar glacier sites.