Elemental carbon (EC) and black carbon (BC) measurements with a thermal method and an aethalometer at the high-alpine research station Jungfraujoch

A thermal method for the determination of ambient organic carbon (OC) and e lemental carbon (EC) concentrations in carbonaceous samples was further dev eloped. Possible artifacts were investigated and were shown to be low. Good agreement of EC data with the German VDI reference method was found and de tection limits were 1.3 mu g for EC and 1.8 mu g for OC, The method was app lied to samples obtained with an aethalometer from an ongoing campaign at t he high-alpine research station Jungfraujoch from July 1995 to June 1987, M easurements of EC concentration were used to derive a new site-specific cal ibration factor (instrumental absorption efficiency alpha(API)) for the det ermination of the black carbon (BC) concentration. Despite a distinct seaso nal cycle in BC, of around one order in magnitude with a maximum in summer and minimum in winter, alpha(API) exhibited no significant seasonality. The derived calibration factor for the Jungfraujoch, alpha(API) = 9.3 +/- 0.4 m(2) g(-1), is lower than the manufacturer calibration by a factor similar to 2. The results confirm the observation that the aethalometer determined BC concentration, underestimates the true value at remote sites, when the m anufacturer calibration is used. (C) 1999 Elsevier Science Ltd. All rights reserved.