DIRECT GRAVIMETRIC MEASUREMENTS OF THE MASS OF THE ANTARCTIC AEROSOL COLLECTED BY HIGH VOLUME SAMPLER:PM10 SUMMER SEASONAL VARIATION AT TERRA NOVA BAY

摘要

An on-site procedure was set up for direct gravimetric measurement of the mass of aerosol collected using high volume impactors(aerodynamic size cut point of 10 mu m,PM10);this knowledge has hitherto been unavailable.Using a computerized microbalance in a clean chemistry laboratory,under controlled temperature(+-0.5 deg C)and relative humidity(+-1 %),continuous,long time filter mass measurements(hours)were carried out before and after exposure,after a 48 h minimun equilibration at the laboratory conditions.The effect of the electrostatic charge was exhausted in 30-60 min,after which stable measurements were obtained.Measurements of filters exposed for 7-11 days(1.13m~3 min~(-1))in a coastal site near Terra Nova Bay(December 2000-February 2001),gave results for aerosol mass in the order of 10-20 mg(SD approx 2 mg),corresponding to atmospheric concentrations of 0.52-1.27 mug m~3.Data show a seasonal behaviour in the PM10 content with an increase during December-early January,followed by a net decrease.The above results compare well with estimates obtained from proxy data for the Antarctic Peninsula(0.30 mu g m~(-3)),the Ronne Ice Shelf(1.49 mug m~(-3)),and the South Pole(0.18 mug m~(-3),summer 1974-1975,and 0.37 mug m~(-3),average summer seasons 1975-1976 and 1977-1978),and from direct gravimetric measurements recently obtained from medium volume samplers at McMurdo station(downwind 3.39 mug m~(-3),upwind 4.15 mug m~(-3))and at King George Island(2.5 mug m~(-3),summer,particle diameter <20 mum).This finding opens the way to the direct measurement of the chemical composition of the Antarctic aerosol and,in turn,to a better knowledge of the snow/air relationships as required for the reconstruction of the chemical composition of past atmospheres from deep ice core data.