AEROSOL AND TRACE GAS MEASUREMENTS DURING THE MACE HEAD EXPERIMENT

Measurements obtained between the 9th and 23rd of April 1991 at the Ma ce Head remote maritime station are presented. These measurements were obtained as part of a EUROTRAC Air Sea Exchange intensive measurement campaign. Analysis of variations in the aerosol and trace concentrati ons is based on inter-comparison of the measured species and use of lo cal meteorological data and back trajectories for the period. While ai r masses of principally maritime origin were encountered throughout th e campaign, typical background maritime conditions only occurred durin g short periods. Other periods were highly modified by mainly ''local' ' influences which included local biomass burning and Aitken nuclei (A N) production. The biomass burning was observed to contribute to eleva ted accumulation mode aerosol (0.1-1.0 mu m), black carbon mass concen tration, CO, and CH4 levels. The O-3 concentrations were variable thro ughout the measurement period. Reasonable correlations were found betw een the trace gas data except between O-3 and CO during the period inf fuenced by biomass burning when the O-3 levels were generally depleted . Very high AN concentrations (>20,000 cm(-3)) were measured on a numb er of sampling days, with a distinct ''dawn effect'' being observed. T he very high AN concentrations occurred during otherwise clean air con ditions and also in the presence of combustion aerosols and are princi pally attributed to photochemical gas-to-particle conversion processes . The conditions under which these events occurred and variations in b ackground conditions are examined. Copyright (C) 1996 Elsevier Science Ltd.