Pergamon Atmospheric Environment Vol. 31, No. 11, pp. 1657-1666, 1997 0 1997 Elsevier Science Ltd PII: S1352-2310(96)00335-4 All rights reserved. Printed in Great Britain 1352-2310/97 117.M) + 0.00 OPTIMIZATION AND FIELD APPLICATION OF A FILTER PACK SYSTEM FOR THE SIMULTANEOUS SAMPLING OF ATMOSPHERIC HN03, NH3 AND SO2 DURAN KARAKASand SEMRA G. TUNCEL Department of Chemistry, Middle East Technical University, 06531 Ankara, Turkey (First received 15 August 1995 and injnalform 13 October 1996. Published March 1997) Abstract-Optimization and field application of a filter pack system for the simultaneous collection of atmospheric gas-phase HNOJ, NH3 and SO2 have been studied. A Teflon prefilter was used to remove particulate matter. Nylon filter, oxalic-acid-treated Whatman 41 filter and sodium-carbonate-treated Whatman 41 filter were used for the collection of HN03, NH3 and SO,, respectively. For the collection of gas-phase HNO,, nylon filters had better efficiency and capacity as compared to NaCl-impregnated Whatman 41 filters for long sampling periods of more than 30 h. All treated filters and nylon filters worked with the collection efficiencies of greater than 95%. About 2% of the gas-phase ammonia has been retained by the nylon filters during simultaneous collection experiments done in the laboratory but the retained ammonia on the nylon filter 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 filter pack system was observed during the simultaneous experiments carried out in an urban atmosphere. 0 1997 Elsevier Science Ltd. All rights reserved. Key word index: Nitric acid, ammonia, sulfur dioxide, filter pack. INTRODUCTION In atmospheric research, sampling is considerably im- portant for the first part of the study. In the sampling of gas-phase pollutants the commercial instruments that have been used are generally expensive and should be operated by trained personnel. Places where these types of instruments are not available or they cannot be installed, there will be a need for an alternative sampling, procedure, like a filter pack sys- tem, which has little maintenance problems, light weight, low cost, and the same collection efficiency as the commercial ones. Forrest et al. (1980) collected gaseous nitric acid on NaCl-impregnated paper filters. The nitric acid vapors from ambient atmospheres were collected at efficiencies of around 95% when NaCl-filters were placed downstream from pretreated quartz particle filters in a high-volume sampler. The collection efliciencies of a tandem sampling system for atmospheric aerosols and gaseous NH3 and SOZ were studied by Quinn and Bates (1989). Whatman 41 paper filters were impregnated with K&O3 or LiOH to collect SO1 and with oxalic acid to collect NHJ. The efficiencies were 100 f 21,88 + 9 and 103 &-30% for KzC03, LiOH and oxalic-acid- treated filters, respectively. Uptake of ammonia by nylon filters in filter pack system was studied iby Masia et al. (1994). Their re- sults indicated that the ambient levels of ammonia may be underestimated in filter packs if the acid- absorbing nylon filter is not analyzed for the am- monium ion. Recently, Kaneyasu et al. (1995) collected nitric acid, ammonia and sulfur dioxide simultaneously by using a filter pack system. They collected nitric acid on NaCl-impregnated filter papers; sulfur dioxide on NazC03-impregnated filter papers, and ammonia on oxalic-acid-treated filter papers. The flow rates were 6.5 emin-’ for HNOJ, and 1.8 emin-’ for SO2 and NH3. The collection efficiencies of the filters were determined by comparing the amounts on the first filter with the amounts of species collected on the second and third filters. In this study, results of optimization and field application of a filter pack system in an urban atmo- sphere for simultaneous HNO,, NH3 and SOZ samp- ling are discussed. EXPERIM ENTA L For the collection of all parameters, Whatman 41 cellulose filters (47 mm in diameter) were impregnated using different chemicals. For the collection of gaseous HN03, nylon filters (Sartorius, 47 mm in diameter aid 0.45 pm pore size) and for particulate matters Teflon filter (millipore, 0.5 pm pore size, 47 mm in diameter) were used. 1657