320
280
Tarallo prepared the draft and final versions of the manuscript. Registry No. PAN, 2278-22-0.
4
0
40
80
120
160
PAN, ppb, EC
200
240
280
320
- GC
Figure 1. Comparison of PAN measurement methods: EC-GC and dual alumina cartridge-LC-UV with thermal converter. Open squares, direct camMge measurements of PAN as total acetate; solid triangles,
acetate measurements downstream of converter; solid squares, acetate measurements by difference (total acetate - acetic acid). Acknowledgments
We thank Eric Grosjean for assistance in field operations, liquid chromatography analyses, and data reduction, and the Technical Services Division staff of the South Coast Air Quality Management District for their cooperation in the field measurements. Denise Yanez and Tina
L i t e r a t u r e Cited (1) Stephens, E. R. Adv. Environ. Sci. Technol. 1969, I, 119- 146. (2) Darley, E. F.; Kettner, K, A,; Stephens, E. R. Anal. Chem. 1963,35, 589-591. (3) Singh, H. B.; Salas, J. L. Atmos. Environ. 1989,23,231-238. (4) Grosjean, D. Environ. Sci. Technol. 1983, 17, 13-19. (5) Williams, E. L., Q Grosjean, D. Atmos. Environ. 1990,24A, 2369-2377. (6) Tuazon, E. C.; Winer, A. M.; Pitts, J. N., Jr. Environ. Sci. Technol. 1981,15, 1232-1237. (7) Hanst, P. L.; Wong, N. W.; Bragin, J. Atmos. Enuiron. 1982, 16, 969. (8) Blanchard, B.; Shepson, P. B.; So, K. W.; Schiff, H. I.; Bottenheim, J. W.; Gallant, A. J.; Drummond, J. W.; Wong, P. Atmos. Environ. 1990, 24A, 2839-2846. (9) Taylor, 0. C. J. Air Pollut. Control Assoc. 1969,19,347-351. (10) Peak, M. J.; Belser, W. L. Atmos. Environ. 1969,3,385-397. (11) Kleindienst, T. E.; Shepson, P. B.; Edney, E. 0.;Claxton, L. D. Mutat. Res. 1985, 157, 123-128. (12) Grosjean, D.; Harrison, J. Environ. Sci. Technol. 1985,19, 749-752. (13) Grosjean, D.; Van Neste, A.; Parmar, S. S. J. Liq. Chromatogr. 1989,12,3007-3017. (14) Grosjean, D. Atmos. Enoiron. 1990,24A, 2695-2698. (15) Williams, E. L., 11; Grosjean, D. Inland Areas Air Quality Study: a one-year survey of ambient levels of aldehydes, nitric acid and peroxyacetyl nitrate in Palm Springs and Perris, June 1989-June 1990. Final report to South Coast Air Quality Management District, DGA, Inc., Ventura, CA, November 1990. (16) Grosjean, D.; Williams, E. L. Acidic pollutants in the Sierra Nevada: formic acid and acetic acid. Final report to the University of Nevada Desert Research Institute, DGA, Inc., Ventura, CA, November 1990. (17) Gaffney, J. S.; Fajer, R.; Senum, G. I. Atmos. Environ. 1984, 18, 215-218. (18) Grosjean, D. Environ. Sci. Technol. 1990,24, 1428-1432. (19) Roberts, J. M.; Fajer, R. W. Environ. Sci. Technol. 1989, 23, 945-951.
Received for review December 27, 1990. Revised manuscript received June 17, 1991. Accepted June 28, 1991.
Comparability of Wet-Only Precipitation Chemistry Measurements from the United States’ National Atmospheric Deposition Program (NADP) to Those of the Canadian Network for Sampling Acid Precipitation (CANSAP) Davld S. Blgelow
Natural Resource Ecology Laboratory, Colorado State University, Fort Collins, Colorado 80523
A 3-yea.r)six-site, direct comparison between NADP and CANSAP deposition monitoring programs reveals a positive bias in reported CANSAP values over those reported by NADP. The bias is significant at most locations for most measured analytes. Reasons given for the bias include an inadequate seal on the mechanical lid of the CANSAP collector. Poor siting of the sampling equipment is further shown to exacerbate the problem. Introduction
Beginning in 1981, the National Oceanic and Atmospheric Administration (NOAA) sponsored a 3-year, direct 0013-936X/91/0925-1867$02.50/0
comparison of atmospheric deposition monitoring protocols used by the National Atmospheric Deposition Program (NADP) and the Canadian Network for Sampling Acid Precipitation [CANSAP (1-4)].At the time of the comparison, these two deposition monitoring programs represented the primary long-term deposition monitoring initiatives in both the United States and Canada. The purpose of the comparison was to determine if data from these two networks could be used as a single data set to characterize atmospheric deposition in North America. As a single data set, the networks would become a 200+ site monitoring program for North America and would improve the understanding and interpretation of the transboundary
0 1991 American Chemical Society
Environ. Sci. Technol., Vol. 25, No. 11, 1991 1867
Table I. Profile of NADPCANSAP Intercomparison Sites location
ecoregion
longitude/latitude
elevation, m
Kejimkujik National Park, NS Caribou, ME
2110 2114
65°12’20”/44025’58’’ 68°00‘53“/46052‘08’‘
152 191
Mount Forest, ON
2110
80°44’46”/43059’29’’
410
Douglas Lake, MI Lethbridge, AB
2113 3110
84”40’42”/45”33’39’’ 112°47’16”/49038’13”
238 913
Glacier National Park, MT
M2112
113°59’4”’/48030’37’’
968
transport of atmospheric pollutants between the two countries. The comparison would further provide a unique on-going peer review of the advantages and disadvantages of each network’s chosen operating protocols. The two networks differed in a number of ways. The NADP network sampled wet deposition weekly (3),using a modified HASL-style Aerochem Metrics wet/dry precipitation collector (Aerochem Metrics, Inc., Route 2, Box 112, Bushell, FL 33513). The collector used a 16-L (31/2 gal) plastic pail, a 7 5 4 rain sensor, and a mechanical lid assembly to capture wet deposition and limit sample contamination by dry deposition. A foam seal on the underside of the lid maintained a semi-gas-tight seal on the bucket to prevent sample evaporation and to limit the captured liquid’s contact with dryfall. The bucket had an opening of 678.9 cm2 and it was used as the shipping container for each collected sample. A single laboratory analyzed all samples. The CANSAP network utilized a Sangamo Model A wet/dry precipitation collector (Sangamo Co. Ltd., 215 Laird Drive, Toronto, ON, Canada M4G 3x1). Its collection vessel, a black reusable bucket with a 307-cm2 opening, was emptied after each event into a holding container. At the end of each calendar month ( 1 , 4 ) , a subsample of the accumulated liquid was shipped to a central laboratory for analysis. A flat, 300-Qprinted circuit board comprised the rain sensor, and like the HASL-style collectors, a mechanical lid assembly allowed the bucket to capture wet deposition and exclude dry fallout. Of special note was the lack of a compressible lid seal on the CANSAP collectors. (Near the end of the CANSAP monitoring program a number of the Sangamo collectors were fitted with a compressible neoprene lid insert. The effect of this retrofit would have no doubt improved the collectors’ sealing ability.) Sample integrity relied upon the weight of the lid pressing against the rim of a rigid plastic collection vessel and the frequent removal of wet deposition from the collector. Other notable differences between the networks’ protocols include the exclusion of
