EPISODIC REMOVAL OF NOY SPECIES FROM THE MARINE BOUNDARY-LAYER OVER THE NORTH-ATLANTIC

Measurements of ozone, carbon monoxide, NOy, NOx, HNO3, particulate NO 3-, PAN, PPN, and alkyl nitrates were made at Chebogue Point, Nova Sco tia, during July, August, and September 1993, and measurements of ozon e, carbon monoxide, NOx and NOy were made at Sable Island, Nova Scotia , during August and September 1993 as part of the North Atlantic Regio nal Experiment (NARE). Periods of photochemical pollution were observe d during which concentrations of the above species were elevated relat ive to average conditions. The best indicator of the extent of impact was found to be the sum of the C-1-C-4 alkyl nitrates. The removal of PAN and PPN by fog droplets through thermal decomposition and subseque nt uptake of the peroxyacetyl and peroxypropionyl radicals (PA and PP) was suggested by loss of PAN and PPN during fog. The effect of this c hemistry on NOy species in the marine environment will need to be cons idered. The loss of inorganic nitrate (HNO3 and particulate NO3-), PAN (and to a minor extent PPN) resulted in deviation of the O-3 versus N Oy-NOx correlations from that observed in eastern North America.