OPTIMIZATION AND FIELD APPLICATION OF A FILTER PACK SYSTEM FOR THE SIMULTANEOUS SAMPLING OF ATMOSPHERIC HNO3, NH3 AND SO2

Optimization and field application of a filter pack system for the sim ultaneous collection of atmospheric gas-phase HNO3, NH3 and SO2 have b een studied. A Teflon prefilter was used to remove particulate matter. Nylon filter, oxalic-acid-treated Whatman 41 filter and sodium-carbon ate-treated Whatman 41 filter were used for the collection of HNO3, NH 3 and SO2, respectively. For the collection of gas-phase HNO3, nylon f ilters had better efficiency and capacity as compared to NaCl-impregna ted Whatman 41 filters for long sampling periods of more than 30 h. Al l treated filters and nylon filters worked with the collection efficie ncies of greater than 95%. About 2% of the gas-phase ammonia has been retained by the nylon filters during simultaneous collection experimen ts done in the laboratory but the retained ammonia on the nylon tilter sometimes reached to about 25% of the gaseous total ammonia collected on the oxalic-acid-impregnated filter in the field experiments. Other than ammonia no significant retention or volatilization from the filt er pack system was observed during the simultaneous experiments carrie d out in an urban atmosphere. (C) 1997 Elsevier Science Ltd.