- Email: [email protected]
Urban and rural ambient air measurements in Schenectady, New York and on Whiteface mountain, New York∗
1975
Discussions The corrected portion of the table is reproduced in Table 3 above (corrected values underling). Figure 10 of our paper used the correct numbers. L. L. AsHBAW~~* *California Air Resources Board L. 0. MYRUP+ P.O. Box 28 15 R. G. FLOCCHINI+ Sacromunto, CA 988 It, U.S.A. tDept. of Land Air and Warer Resources Unit;ersity of California Dacis. CA 95616, U.S.A. REFERENCES
Ashbaugh L. L., Myrup L. 0. and Flocchini R. G. (1984a)A principal component analysis of sulfur concentrations in the western United States. Atmospheric Encironment 1% 783791. Cattell R. B. and Dickman K. W. ( 1962)A dynamic model of physical inffuenrrs demonstrat~g the necessity of oblique simple structure. Psychol. Bult. 59, 389-400. Coan R. W. (1959) A comparison of oblique and orthogonal factor solutions. J. exp. Ed. 27, 151-166. Cohen S. 1. (1983) Classification of 500 mb height anomalies using obliquely rotated principal components. J. Cfimute appt. Met. 22, 1975-1988. Harman H. H. (1976) .&&dern Factor Analysis. The University of Chicago Press, Chicago, fllinois. Lamb P. J. and Richman M. B. I19831An analysis of the sDace and time variation of growing s&on rainf& in the central United States. Preprints Eighth Conference on Probability and Statistics in Atmospheric Sciences, Hot Springs, AR, American Meteorologi~l Society, pp. 49-54. Lorenz E. N. (1956) Empirical orthogonal functions and statistical weather prediction. Scientific Report I, Statistical Massachusetts Institute of Forecasting Project, Technology. (Available NTIS AD1 10268.) Mufaik S. A. (1972) The Fou~ar~o~ of Facror Analysis. McGraw-Hill, New York. Overland J, E. and Preisendorfer R. W. (1982) A significance test for principal components applied to a cyclone climatology. Mon. Weath. &XL 110, l-4. Preisendorfer R. W. (1984) Principal Component Analysis in Meteorology and Oceanography. Contribution No. 713, Pacific Marine Environmental Laboratory (NOAA), 461 Pr%endorfer R. W. and Barnett ‘f. P. (1977) Significance test for empirical orthogonal functions. Preprints Fifth Conference on Probability and Statistics in Atmospheric Sciences, Las Vegas, NV, American Meteorological Society, pp. 169-172. Richman M, B. (1981) Obliquely rotated principa1 components: an improved meteorological map typing technique? /. appl. Met. 20, I14~1159. Richman M. B. (1983a) Rotation of principal components in climatological research. Part I: Theoretical considerations, suitable applications and advantages over unrotated solutions. Preprints Eighth Conference on Probability and Statistics in Atmospheric Sciences, Hot Springs, AR, American Meteorological Society, pp. 59-68. Richman M. B. (1983b) Rotation of principal components in climatological research-II. How the various analytic simple structure rotations on the major statistical packages compare on different types of data. Preprints Eighth Conference on Probability and Statistics in Atmospheric Sciences, Hot Springs. AR, American Meteorological Society, pp. 115-i24. _ Richman M. B. 119851Rotation of o&c&l . _ components. J. Climuiolo~y (in press). Richman M. B. and Lamb P. J. (1985) On the climatic pattern analysis of short-period (37 days) summer rainfall in the central United States: some methodological considerations and a regionalization. J. CIimare uppl. Met. (in press).
Rummel R. J. (1970) Applied Facror Analysis. Northwestern University Press, Evanston, Illinois. Walsh J. E, Richman M. 8. and Allen D. W. (1982) Spatial coherence of monthly precipitation in the United States. Non. Weath. Rer. 110. 272-286.
URBAN AND RURAL AMBIENT AIR MEASUREMENTS IN SCHENECTADY, NEW YORK AND ON WHITEFACE MOUNTAIN, NEW YORK* Afdehydes play a criticaf role in the chemistry of the global troposphere and in urban phot~hemi~l smog. Schulam and coworkers (1985) have recently measured ambient levels of formaldehyde and acetaldehyde in Schenectady and on W~~tef~e Mountain, NY. Their study, while limited in scope, provides useful information concerning levels of HCHO (along with some data for CH,CHO) in urban and rural air. 1.would like to comment on two aspects of the work of Schulam et al. (1985). First, they state that “There are no studies of aidehyde concentrations in smaller urban areas or regions that would be expected to have very low or background concentrations of aldehydes”. In fact, a substantial body of literature is avaitable concerning formaldehyde and other carbonyls in the troposphere. Second, the authors conclude, after comparing their data to some of our results for Los Angeles (Grosjean, 1982; Grosjean et at., 1983). that “there may be a fundamental difference in that higher aldehydesareabsent from theSchenectady and Whitefacedata”. f suggest that no “fundamental difference” need to be invoked, and that higher carbonyls were not seen by Schulam er al. simply because the ambient levels of these carbonyls were below the authors’ detection limits. Aldehyde concentrations in smaller urban areas and in the .back~rou~ tro~spkere
While a detailed review is not appropriate here, a few examples are given below of rhe abundant literature on this topic. A comprehensive review recently appeared in this journal (Altschuller, 1983)and include several tables compiling carbonyl levels in urban, suburban, and rural air. i&lore recent work includes, for example, the study of Tanner and Meng (1984) and the references therein. 1Measurements of tropospheric formaldehyde include those of Fushimi and Miyake (1980), Zafiriou et al. (1980), Klippel and Warneck (1980) and Lowe and Schmidt (1983). Grosjean and Wright (1983)have measured formaldehyde, acetaldehyde, propanal, n-butanal, acetone, acrolein, 2-butanone, n-pentanal, nhexanal and benzaidehyde in fog, cloudwater, rainwater and ice fog samples. Their study included urban areas, both large and small (e.g. Los Angeles. CA. Fairbanks. AK. and Camarillo, CA) as well & n&urban locations (e.g. San Nicholas Istand, CA). Comparison ofSchenectady and Los Angeles data In Los Angeles, ambient levels of carbonyls reffect the contribution of (a) direct emissions and (b) atmospheric reactions, the latter including carbonyl formation from precursor hydrocarbons, and carbonyl removal by photolysis and by reactions with the hydroxyl radical (daytime)and with the nitrare radical (night-time). The relative importance of emissions and photochemistry in Los Angeles has been discussed in detail elsewhere (Grosjean et ai., 1983). In Schenectady, photochemistry is expected (0 be less important
*Schulam
P. Newbold
R. and
Atmospheric Encironment 19, 623-626.
Hull L. A. (1985)
than m Los Angeles. and dlrecr smwons Indeed, the HCHO diurnal protileshown
u iii predommate.
in Fig. 2 of Schulam et ai. (1985) exhibit dtstincr ‘rush hour’ maxima. Direct emissions in Schenectadr are obvtously much lower than those for a large metropolitan area such as Los Angeles. Data for higher aldehydes in early morning Los .Angeles air (i.e. when direct emissions predominate over photochemistry) are available from GrosJean and Fung (1984). It is evident that the same compounds, with the much !ower emission rates expected for Schenectady, would be present in Schenectady air but at levels generally below the derrcrion limits oJSchulam er al. (1985). Thus. no “fundamental difference” need to be
W: also feel that I[ would be desirable to simultaneously detcrmme hydrocarbons, carbonyl compounds and the products of gas phase reactions as well as their scavenging by clouds at Whirsface Mountain. To that end we have begun monitoring cloudwater concentrations of aldehydes tBcrtman et ui.. 1985). Depurrmrnr o~‘ChrmistrJ
L. A.
HLLL
Lnion College
Schrnecrady, .VY 12308, U.S.A.
invoked to explain the failure of Schulam er ai. (1985) to identify and measure higher aldehydes in Schenectady air.
AidehJde concentrations on lthirefacr ~llounratn
In the absence of local anthropogentc influences. tropospheric concentrations of aldehydes are closely related to those of their precursor hydrocarbons. Precursors of formaldehyde include methane and ethylene (e.g. Graedel. 1979;Aikin et al., 1982; Lowe and Schmidt, 1983). Ethane yields acetaldehyde (Cronn and Robinson, 1979; Aikin et a/., 1982) and propane yields acetone (Singh and Hanst, 198I). Acetaldehyde (major) and acetone (minor) are in turn precursors of peroxyacetyl nitrate, PAN (Singh and Hanst, 1981). Benzaldehyde may also form from toluene (e.g. Leone rr u[.. 1985),and toluene has been measured at remote locations (Rasmussen and Khalil, 1983).With the detection limits reported by Schulam et al. (1985). tropospheric levels of formaldehyde would be barely measurable. and acetaldehyde, acetone. benzaldehyde. etc. would go undetected. Much lower detection limits than those of Schulam rt al. (1985) are needed for measurements of these carbonyls in the troposphere. Finally, the HCHO (0.8-2.6 ppb) and CH,CHO (0.2-0.8 ppb) data of Schulam rt al. (1985) for Whiteface Mountain indicate that air quality at this ‘rural’ site was heavily impacted by nearby (regional) anthropogenic emissions. A more quantitative study would require simultaneous measurements of carbonyls, their precursor hydrocarbons. their gas phase reaction products (e.g. PAN) and their scavenging by fog and clouds. Daniel Grosjean and Associures, Inc.
DANIEL GROSJEAN
Suite 645, 350 i?. Lantuna Street Cumarillo, CA 93010, L’.S.A.
AUTHOR’S
REPLY
At the time of submission of the revised version of our paper (Schulam, et ul., 1985) in August 1984, the work reported in the literature for rural and small urban areas was either for formaldehyde or total aldehydes. Altschuller (1983) summarizes several formaldehyde determinations in nonurban areas and, exclusive of Grosjean’s work (1982, 1983). total aldehydes (by MBTH), formaldehyde and, in a limited number of cases, acrolein for urban areas. The Tanner and Meng work (1984) appeared during the usual prepublication delays. We agree with Grosjean’s comments that it is likely there is a relatively greater importance of emissions over photochemistry in the Schenectady levels of aldehydes. The “fundamental difference” is that very point. Smaller eastern urban areas are unlikely to exhibit the wide range of aldehydes found by Grosjean because of the more limited contribution of photochemistry. It is interesting that Tanner and Meng also find a near exclusive predominance of formaldehyde and acetaidehyde for determinations at Brookhaven National Laboratories (Long Island. NY).
REFERENCES
Aikin A. C., Herman J. R.. Maier E. J. and McQuillan C. J. (1983) Atmospheric chemistry of ethane and ethylene. J. geophys. Res. CS7, 3105-3118. Altschuller A. P. (1983) Measurements of the products of atmospheric photochemical reactions in laboratory studies and in ambient air. Relationships between ozone and other products. Armospheric Environment 17, 23832427. Bertman S., Carroll M. and Hull L. A. (1985) Aldehyde levels in rural cloudwater. Paper presentation, American Chemical Society Meeting, Miami, FL, April 1985. Cronn D. and Robinson E. (1979) Tropospheric and lower stratospheric vertical profiles of ethane and acetylene. Geophps. Rrr. Left. 6, 641-644. Fushimi K. and Miyake Y. (1980) Contents of formaldehyde in the air above the surface of the ocean. J. geophJs. Res. CSS, 7533-7536. Graedel T. E. (1979) The kinetic photochemistry of the marine atmosphere. J. geophys. Res. C&l, 273286. Grosjean D. (1982)Formaldehyde and other carbonyls in Los Angeles ambient air. Envir. Sci. Technol. 16, 254-262. Grosjean D.. Swanson R. and Ellis C. (1983)Carbonyls in Los Angles air: contribution of direct emissions and photochemistry. Sci. Toto1 Enrir. 29, 65-85. Grosjean D. and Wright B. (1983) Carbonyls in urban fog, ice fog, cloudwater and rainwater. Atmospheric Ent+onmenf 17, 2093-2096. Grosjean D. and Fung K. (1984) Hydrocarbons and carbonyls in Los Angeles air. J. Air Polk. Conrrof ASS. 34, 537-543. Klippel W. and Warneck P. (1980)The formaldehyde content of the atmosoheric aerosol. Armosoheric EnLtironmenr 14, sO9-818. . Leone J. A., Flagan R. C., Grosjean D. and Seinfeld J. H. (1985) An outdoor smog chamber and modeling study of toluene-NO, photooxidation. Int. J. Chem. Kinerks. 17, 177-216. Lowe D. C. and Schmidt U. (1983) Formaldehyde (HCHO) measurements in the nonurban atmosphere. J. geophys. Res. C&3, 10844-10858. Rasmussen R. A. and Khalil M. A. K. (1983) Atmospheric benzene and toluene. Geophps. Res. Lat. 10, 10961G99. Schulam P., Newbold R. and Hull L. A. (1985) Urban and rural ambient air measurements in Schenectady, New York and on Whiteface Mountain, New York. Atmospheric Encironmenr 19, 623-626. Singh H. B. and Hanst P. L. (1981) Peroxyacetyl nitrate (PAN) in the unpolluted atmosphere: an important reservoir for nitrogen oxides. Geophys. Res. Lerr. 8,941-944. Tanner R. L. and Meng 2. (1984) Seasonal variations in ambient atmospheric levels of formaldehyde and acetaldehyde. Encir. Sci. Technol. 18, 723726. Zafiriou 0. C., Alford J., Herrera M., Paltzer E. T., Gagosian R. B. and Liu S. C. (1980) Formaldehyde in remote marine air and rain: flux measurements and estimates. Geophys. Rex Lerr. 7. 341-344.
Discussions The corrected portion of the table is reproduced in Table 3 above (corrected values underling). Figure 10 of our paper used the correct numbers. L. L. AsHBAW~~* *California Air Resources Board L. 0. MYRUP+ P.O. Box 28 15 R. G. FLOCCHINI+ Sacromunto, CA 988 It, U.S.A. tDept. of Land Air and Warer Resources Unit;ersity of California Dacis. CA 95616, U.S.A. REFERENCES
Ashbaugh L. L., Myrup L. 0. and Flocchini R. G. (1984a)A principal component analysis of sulfur concentrations in the western United States. Atmospheric Encironment 1% 783791. Cattell R. B. and Dickman K. W. ( 1962)A dynamic model of physical inffuenrrs demonstrat~g the necessity of oblique simple structure. Psychol. Bult. 59, 389-400. Coan R. W. (1959) A comparison of oblique and orthogonal factor solutions. J. exp. Ed. 27, 151-166. Cohen S. 1. (1983) Classification of 500 mb height anomalies using obliquely rotated principal components. J. Cfimute appt. Met. 22, 1975-1988. Harman H. H. (1976) .&&dern Factor Analysis. The University of Chicago Press, Chicago, fllinois. Lamb P. J. and Richman M. B. I19831An analysis of the sDace and time variation of growing s&on rainf& in the central United States. Preprints Eighth Conference on Probability and Statistics in Atmospheric Sciences, Hot Springs, AR, American Meteorologi~l Society, pp. 49-54. Lorenz E. N. (1956) Empirical orthogonal functions and statistical weather prediction. Scientific Report I, Statistical Massachusetts Institute of Forecasting Project, Technology. (Available NTIS AD1 10268.) Mufaik S. A. (1972) The Fou~ar~o~ of Facror Analysis. McGraw-Hill, New York. Overland J, E. and Preisendorfer R. W. (1982) A significance test for principal components applied to a cyclone climatology. Mon. Weath. &XL 110, l-4. Preisendorfer R. W. (1984) Principal Component Analysis in Meteorology and Oceanography. Contribution No. 713, Pacific Marine Environmental Laboratory (NOAA), 461 Pr%endorfer R. W. and Barnett ‘f. P. (1977) Significance test for empirical orthogonal functions. Preprints Fifth Conference on Probability and Statistics in Atmospheric Sciences, Las Vegas, NV, American Meteorological Society, pp. 169-172. Richman M, B. (1981) Obliquely rotated principa1 components: an improved meteorological map typing technique? /. appl. Met. 20, I14~1159. Richman M. B. (1983a) Rotation of principal components in climatological research. Part I: Theoretical considerations, suitable applications and advantages over unrotated solutions. Preprints Eighth Conference on Probability and Statistics in Atmospheric Sciences, Hot Springs, AR, American Meteorological Society, pp. 59-68. Richman M. B. (1983b) Rotation of principal components in climatological research-II. How the various analytic simple structure rotations on the major statistical packages compare on different types of data. Preprints Eighth Conference on Probability and Statistics in Atmospheric Sciences, Hot Springs. AR, American Meteorological Society, pp. 115-i24. _ Richman M. B. 119851Rotation of o&c&l . _ components. J. Climuiolo~y (in press). Richman M. B. and Lamb P. J. (1985) On the climatic pattern analysis of short-period (37 days) summer rainfall in the central United States: some methodological considerations and a regionalization. J. CIimare uppl. Met. (in press).
Rummel R. J. (1970) Applied Facror Analysis. Northwestern University Press, Evanston, Illinois. Walsh J. E, Richman M. 8. and Allen D. W. (1982) Spatial coherence of monthly precipitation in the United States. Non. Weath. Rer. 110. 272-286.
URBAN AND RURAL AMBIENT AIR MEASUREMENTS IN SCHENECTADY, NEW YORK AND ON WHITEFACE MOUNTAIN, NEW YORK* Afdehydes play a criticaf role in the chemistry of the global troposphere and in urban phot~hemi~l smog. Schulam and coworkers (1985) have recently measured ambient levels of formaldehyde and acetaldehyde in Schenectady and on W~~tef~e Mountain, NY. Their study, while limited in scope, provides useful information concerning levels of HCHO (along with some data for CH,CHO) in urban and rural air. 1.would like to comment on two aspects of the work of Schulam et al. (1985). First, they state that “There are no studies of aidehyde concentrations in smaller urban areas or regions that would be expected to have very low or background concentrations of aldehydes”. In fact, a substantial body of literature is avaitable concerning formaldehyde and other carbonyls in the troposphere. Second, the authors conclude, after comparing their data to some of our results for Los Angeles (Grosjean, 1982; Grosjean et at., 1983). that “there may be a fundamental difference in that higher aldehydesareabsent from theSchenectady and Whitefacedata”. f suggest that no “fundamental difference” need to be invoked, and that higher carbonyls were not seen by Schulam er al. simply because the ambient levels of these carbonyls were below the authors’ detection limits. Aldehyde concentrations in smaller urban areas and in the .back~rou~ tro~spkere
While a detailed review is not appropriate here, a few examples are given below of rhe abundant literature on this topic. A comprehensive review recently appeared in this journal (Altschuller, 1983)and include several tables compiling carbonyl levels in urban, suburban, and rural air. i&lore recent work includes, for example, the study of Tanner and Meng (1984) and the references therein. 1Measurements of tropospheric formaldehyde include those of Fushimi and Miyake (1980), Zafiriou et al. (1980), Klippel and Warneck (1980) and Lowe and Schmidt (1983). Grosjean and Wright (1983)have measured formaldehyde, acetaldehyde, propanal, n-butanal, acetone, acrolein, 2-butanone, n-pentanal, nhexanal and benzaidehyde in fog, cloudwater, rainwater and ice fog samples. Their study included urban areas, both large and small (e.g. Los Angeles. CA. Fairbanks. AK. and Camarillo, CA) as well & n&urban locations (e.g. San Nicholas Istand, CA). Comparison ofSchenectady and Los Angeles data In Los Angeles, ambient levels of carbonyls reffect the contribution of (a) direct emissions and (b) atmospheric reactions, the latter including carbonyl formation from precursor hydrocarbons, and carbonyl removal by photolysis and by reactions with the hydroxyl radical (daytime)and with the nitrare radical (night-time). The relative importance of emissions and photochemistry in Los Angeles has been discussed in detail elsewhere (Grosjean et ai., 1983). In Schenectady, photochemistry is expected (0 be less important
*Schulam
P. Newbold
R. and
Atmospheric Encironment 19, 623-626.
Hull L. A. (1985)
than m Los Angeles. and dlrecr smwons Indeed, the HCHO diurnal protileshown
u iii predommate.
in Fig. 2 of Schulam et ai. (1985) exhibit dtstincr ‘rush hour’ maxima. Direct emissions in Schenectadr are obvtously much lower than those for a large metropolitan area such as Los Angeles. Data for higher aldehydes in early morning Los .Angeles air (i.e. when direct emissions predominate over photochemistry) are available from GrosJean and Fung (1984). It is evident that the same compounds, with the much !ower emission rates expected for Schenectady, would be present in Schenectady air but at levels generally below the derrcrion limits oJSchulam er al. (1985). Thus. no “fundamental difference” need to be
W: also feel that I[ would be desirable to simultaneously detcrmme hydrocarbons, carbonyl compounds and the products of gas phase reactions as well as their scavenging by clouds at Whirsface Mountain. To that end we have begun monitoring cloudwater concentrations of aldehydes tBcrtman et ui.. 1985). Depurrmrnr o~‘ChrmistrJ
L. A.
HLLL
Lnion College
Schrnecrady, .VY 12308, U.S.A.
invoked to explain the failure of Schulam er ai. (1985) to identify and measure higher aldehydes in Schenectady air.
AidehJde concentrations on lthirefacr ~llounratn
In the absence of local anthropogentc influences. tropospheric concentrations of aldehydes are closely related to those of their precursor hydrocarbons. Precursors of formaldehyde include methane and ethylene (e.g. Graedel. 1979;Aikin et al., 1982; Lowe and Schmidt, 1983). Ethane yields acetaldehyde (Cronn and Robinson, 1979; Aikin et a/., 1982) and propane yields acetone (Singh and Hanst, 198I). Acetaldehyde (major) and acetone (minor) are in turn precursors of peroxyacetyl nitrate, PAN (Singh and Hanst, 1981). Benzaldehyde may also form from toluene (e.g. Leone rr u[.. 1985),and toluene has been measured at remote locations (Rasmussen and Khalil, 1983).With the detection limits reported by Schulam et al. (1985). tropospheric levels of formaldehyde would be barely measurable. and acetaldehyde, acetone. benzaldehyde. etc. would go undetected. Much lower detection limits than those of Schulam rt al. (1985) are needed for measurements of these carbonyls in the troposphere. Finally, the HCHO (0.8-2.6 ppb) and CH,CHO (0.2-0.8 ppb) data of Schulam rt al. (1985) for Whiteface Mountain indicate that air quality at this ‘rural’ site was heavily impacted by nearby (regional) anthropogenic emissions. A more quantitative study would require simultaneous measurements of carbonyls, their precursor hydrocarbons. their gas phase reaction products (e.g. PAN) and their scavenging by fog and clouds. Daniel Grosjean and Associures, Inc.
DANIEL GROSJEAN
Suite 645, 350 i?. Lantuna Street Cumarillo, CA 93010, L’.S.A.
AUTHOR’S
REPLY
At the time of submission of the revised version of our paper (Schulam, et ul., 1985) in August 1984, the work reported in the literature for rural and small urban areas was either for formaldehyde or total aldehydes. Altschuller (1983) summarizes several formaldehyde determinations in nonurban areas and, exclusive of Grosjean’s work (1982, 1983). total aldehydes (by MBTH), formaldehyde and, in a limited number of cases, acrolein for urban areas. The Tanner and Meng work (1984) appeared during the usual prepublication delays. We agree with Grosjean’s comments that it is likely there is a relatively greater importance of emissions over photochemistry in the Schenectady levels of aldehydes. The “fundamental difference” is that very point. Smaller eastern urban areas are unlikely to exhibit the wide range of aldehydes found by Grosjean because of the more limited contribution of photochemistry. It is interesting that Tanner and Meng also find a near exclusive predominance of formaldehyde and acetaidehyde for determinations at Brookhaven National Laboratories (Long Island. NY).
REFERENCES
Aikin A. C., Herman J. R.. Maier E. J. and McQuillan C. J. (1983) Atmospheric chemistry of ethane and ethylene. J. geophys. Res. CS7, 3105-3118. Altschuller A. P. (1983) Measurements of the products of atmospheric photochemical reactions in laboratory studies and in ambient air. Relationships between ozone and other products. Armospheric Environment 17, 23832427. Bertman S., Carroll M. and Hull L. A. (1985) Aldehyde levels in rural cloudwater. Paper presentation, American Chemical Society Meeting, Miami, FL, April 1985. Cronn D. and Robinson E. (1979) Tropospheric and lower stratospheric vertical profiles of ethane and acetylene. Geophps. Rrr. Left. 6, 641-644. Fushimi K. and Miyake Y. (1980) Contents of formaldehyde in the air above the surface of the ocean. J. geophJs. Res. CSS, 7533-7536. Graedel T. E. (1979) The kinetic photochemistry of the marine atmosphere. J. geophys. Res. C&l, 273286. Grosjean D. (1982)Formaldehyde and other carbonyls in Los Angeles ambient air. Envir. Sci. Technol. 16, 254-262. Grosjean D.. Swanson R. and Ellis C. (1983)Carbonyls in Los Angles air: contribution of direct emissions and photochemistry. Sci. Toto1 Enrir. 29, 65-85. Grosjean D. and Wright B. (1983) Carbonyls in urban fog, ice fog, cloudwater and rainwater. Atmospheric Ent+onmenf 17, 2093-2096. Grosjean D. and Fung K. (1984) Hydrocarbons and carbonyls in Los Angeles air. J. Air Polk. Conrrof ASS. 34, 537-543. Klippel W. and Warneck P. (1980)The formaldehyde content of the atmosoheric aerosol. Armosoheric EnLtironmenr 14, sO9-818. . Leone J. A., Flagan R. C., Grosjean D. and Seinfeld J. H. (1985) An outdoor smog chamber and modeling study of toluene-NO, photooxidation. Int. J. Chem. Kinerks. 17, 177-216. Lowe D. C. and Schmidt U. (1983) Formaldehyde (HCHO) measurements in the nonurban atmosphere. J. geophys. Res. C&3, 10844-10858. Rasmussen R. A. and Khalil M. A. K. (1983) Atmospheric benzene and toluene. Geophps. Res. Lat. 10, 10961G99. Schulam P., Newbold R. and Hull L. A. (1985) Urban and rural ambient air measurements in Schenectady, New York and on Whiteface Mountain, New York. Atmospheric Encironmenr 19, 623-626. Singh H. B. and Hanst P. L. (1981) Peroxyacetyl nitrate (PAN) in the unpolluted atmosphere: an important reservoir for nitrogen oxides. Geophys. Res. Lerr. 8,941-944. Tanner R. L. and Meng 2. (1984) Seasonal variations in ambient atmospheric levels of formaldehyde and acetaldehyde. Encir. Sci. Technol. 18, 723726. Zafiriou 0. C., Alford J., Herrera M., Paltzer E. T., Gagosian R. B. and Liu S. C. (1980) Formaldehyde in remote marine air and rain: flux measurements and estimates. Geophys. Rex Lerr. 7. 341-344.