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Chemical composition of Pasadena aerosol by particle size and time of day. IV. Carbonate and noncarbonate carbon content
Chemical Composition of Pasadena Aerosol by Particle Size and Time of Day IV. Carbonate and NoncarbonateCarbon Content P. K. M U E L L E R , R. W. M O S L E Y , AND L. B. P I E R C E Air and Industrial Hygiene Laboratory, California State Department of Public Health, Berkeley, California
t~eceived January 24, 1972; accepted January 27, 1972 The carbon content of atmospheric particles is in the form of the element, organic compounds and carbonates. In urban aerosol the noncarbonate carbon is probably of anthropogenic origin. Carbonates more likely result from surface erosion. To obtain information on these matters we have developed a method for measuring 10#g or more of carbon in size-segregated collections. The results of a preliminary study conducted during photochemical smog episodes in Pasadena, California, indicate that carbon in particulate matter measured as a function of size and time of day may be a useful indicator of aerosol origin. The carbonate C was consistently less than 1.0 ~g/m~. The noncarbonate C ranged from about 20 to 35 ~g/m ~ and constituted from 18 to 44% of the total particulate matter. INTRODUCTION The carbon content of the atmospheric aerosol may be an important criterion of its origin. The carbon content of particles is in the form of the element, organic compounds, biological particles and carbonates. In the urban aerosol, most of the noncarbonate carbon is probably of anthropogenic origin (2). Carbonates more likely result from surface erosion or cement manufacture. Despite the fact t h a t source inventories indicate carbon is one of the major dements occurring in particulate emissions (1), and that at least 30 % of the total particulate m a t t e r consists of noncarbonate carbon compounds in Los Angeles smog (2), very little work has actually been done on the carbon content of airborne particulate matter. Mader et al. (3) cited Fudakowski (4) as having established in 1873 t h a t petroleum fractions may be oxidized to form particulate m a t t e r when exposed to sunlight and air. Mader et al. showed in 1952 t h a t gasoline vapors in air, when irradiated ~4th or ~4thout the addition of nitrogen dioxide, formed an aerosol, the ether soluble portion of which Copyright © 1972 b y Academic Press, Inc.
had very nearly the same elemental composition, functional group reactions, and infrared spectrum as the ether soluble material extracted from particles collected from the atmosphere. T h e y also demonstrated a strong negative correlation between organic ether soluble aerosol and visibility indicating this material is concentrated in the 0.1-1 ~m diameter size range. Unfortunately, they did not obtain or publish data on the total particulate m a t t e r content, and it is not clear whether or not the ratio of ether soluble material increases with increasing photochemical aerosol formation. In addition to ether solubles, the aerosol formation process from hydrocarbons yielda insoluble resins. Goetz (5) has shown expertmentally that traces of ammonia and sulfur dioxide can accelerate the process and that water vapor readily condenses on the particles. The particle size distribution of the total organic particulate matter in the urban aerosol could therefore be expected to shift diurnally. Such changes, if substantial, should also be apparent from analysis of the total non-carbonate content of the collected parJournal of Colloid and Interface Science, Vot. 39, No. 1, .~kpril 1972
235
236
MUELLER, MOSLEY, AND PIERCE
ticles. The magnitude of these changes in relation to total particulate matter, lead, :silica or iron content, might serve to estimate the total amount of particulate mass created photochemically. When sampling aerosol as a function of size and time, only micrograms of particulate matter are available for analysis. For such small quantities, a carbon analysis would provide information on the total carbonaceous matter content, and would be a more direct and sensitive means of obtaining preliminary information than the analysis of only ether solubles. To avoid possible interferences, carbonate carbon was also determined. We have described and validated the analytical procedure previously (6). This paper reports preliminary findings on the diurnal changes of the size distribution of carbon containing particles. SAMPLE C O L L E C T I O N AND ANALYSIS The Lundgren impactor (7) along with other instrumentation was used in a colloborative research study (8) in Pasadena, California, during September, 1969. The impaetors and total mass samplers were located at the bottom of a vertical sampling line to minimize losses of large particles. The collection drums of the four stages of the impaetor for chemical analysis were coated witha thin film of aluminum foil held to the drum with cellophane tape. The taped end of the aluminum film was cut off before chemical analysis to prevent contamination from the tape itself or from dirt it may have picked up. A 4-in. diameter glass fiber filter pad was used as the fifth stage. The sampling rate was about 79 liters/min. A parallel impactor operating simultaneously and coated with Teflon film held in place with a mechanical clamp was used for weight determinations of the size segregated particles. In this case a Teflon filter was used as a fifth stage to collect particulate matter passing the impactor's fourth stage. Other elements have been determined on the deposits on the Teflon films and filters and data for these are presented in companion papers [9, 10). Particleswere segregated during collection ~)n the impactor stages according to mass Journal of Colloid and Interface Science, Vol. 39, No. 1, April 1972
median diameters assuming spheres of unit density as follows: 17-30 ~m for stage one, 5-17 ~m on stage two, 2-5 t~m on stage three, 0.6-2 gm on stage four and less than 0.6 ~m on stage five. Strips of the aluminum foil or glass fiber filters containing the particulate samples were placed in combustion boats. A boat was inserted into a train designed to generate carbon dioxide from a single sample first by acidification and then by combustion. The respective quantities of carbon dioxide were swept with a purified oxygen stream through a trap for water to a freeze-out trap for carbon dioxide. The concentrated carbon dioxide was moved to a gas chromatograph for separating residual oxygen, water, and acid gases, and was then quantitated by thermal conductivity. The amount of C02 measured was corrected for losses and blank values obtained from clean foils and filters, respectively. Three sets of cascade impactor samples were analyzed. Each aluminum foil was cut in half and each half analyzed separately. Each glass fiber filter was cut into one-eighth sections and two such sections analyzed separately. Although visual inspection indicated the deposits may not have been always uniformly distributed, the precision demonstrated by Table I indicates there were no serious relative errors in the analytical procedure. CARBON CONTENT OF PASADENA AEROSOL Three sets of cascade impactor samples obtained during the 1969 aerosol study in Pasadena have been analyzed for carbonate and noncarbonate carbon. The results are given in Tables II, III and IV. Two sets were obtained during 4 hr in the afternoon and one set during 11 hr in the daytime. The lower limit of measurement was a difference of 1 #g carbon between the blank values and the sample, thus leading to the inequality statements in these tables. The carbonates are consistently quite low compared to the noncarbonate carbon. The data in Table III indicate a tendency for the carbonate containing particles to be concentrated in size ranges greater than 2 t~m. Most
237
C A R B O N IN P A S A D E N A AEROSOL of t h e t o t a l m a s s of p a r t i c l e s c o l l e c t e d a p p e a r e d o n t h e f i f t h s t a g e i n all cases a n d c a r b o n a t e s c o n s t i t u t e d less t h a n 2 % of t h e
total particulate matter on that stage. It is striking that no carbonate was found in the ll-hr sample (Table IV) even though more mass was available for analysis. The detection limit for the carbonate content of the particulate matter was 0.03 %. This finding
Stage ~ 1b
SAMPLES
8/22 Sample
8/26 Sample
- - -
, ~ - - -
co~- non-CO~-! CO a-
/ 4.2 2b 3.0 4.8 3b 4.0 3.0 4b 3.4 3.0 5~ 5.5 7.2
22.0 37.6 33.8 21.2 25.3 NA 32.2 62.0 62.0
9/3 Sample ,
- - - -
inon-CO~CO~-
3.5 13.4 2.8 8.4 3.7 4.3 6.2 4.8 NA
2 non-CO Z
24.0 27.5 21.0 39.2 32.2 57.0 65.0 91.8 86.0
~ 4.7 NA 3.3 4.0 4.5 3.5 3.0 3.0 3.0
19.5 26.0 24.8 34.3 26.3 78.8 71.0 124 146
° Blank values not subtracted. b Each number refers to 30.6 cm ~ aluminum foil, i.e., ~ of the total foil. Blank was 4.8 ~g (±.06) for CO~- ; 26.2/~g (±5) for non-CO~-. Each number refers to 7.9 cm" glass fiber filter, i.e., 1/~ of the total filter, blank was 4.4 ~g (±0.6) for CO~-; 17.3 (4-2) for non-COl-. e NA--Data not available. TABLE II I969 PASADENA AEROSOL SAMPLE ANALYSISa #g C / m a as Size class
Stage
Total ]
% C of Total Particles b y weight as
par-
(~m) coF
o~-COy
tides ~ug/ma'.
non-
co~-
co~-
<2 <2.8 <0.6 <0.7 1.4
<2 53.5 <0.6 7.9 32.6
__I
17-30 5-17 2-5 0.6-2 0.1-0.6
7 1
4 5
0.06 ~0.056 2.5 O.O6 1.07 2.0 0.06 ~0.056 9.5 0.06 0.67 8.5 0.88 20.1 61.8
/~g C / m a as Size class
!non-CO~-
Sample collected on Lundgren Impactor Saturday, August 22, 1969, 1200-1600 hours, 17.8 m ~sample volume collected.
ticles [
non-
F
coF
(~g/ma) CO~J
17-30
1 2 3 4 5
[<0.05 0.34 I O. 13 i 0.05 0.17
% C of total particles by weight as
Total par-
St~e COF
5-17 I 2-5 0.6-2 0.1-0.6
TABLE I TOTAL 1V[ICROGaAMS~ CAZEON ON TWO SECTIONS OF ANALYZED
TABLE III 1969 PASADENA AEROSOL SAMPLE ANALYSISa
J-U <2
0.05 0.99 3.65 29.80
4.4! 13.3 31:3 67.7
7.7 1.0 0.2 0.3
<2 <1,2 7.4 11.7 44.0
Sample collected on Lundgren Impactor Wednesday, August 26, 1969, 1200-1600 hours, 19.2 m a sample volume collected. T A B L E IV 1969 PASADENA AEROSOL SAMPLE ANALYSISa
Size class
Stage g i
f~m)
17-30 5-17 2-5 0.6-2 0.1-0.6
~g C / m s as
par-
non-CO~
1 2 3 4 5
% C of total partldes b y weight as
Total
/ <0.02 <0.02 <0.O2 <0.02 <0.02 0.17 <0.02 2.05 <0.02 19.8 '
tides ~g lm a
non-
coF 4.6 5.7 12.5 20.3 72.8
co~-
<0.5 <0.5 <0.4 I <0.4 <0.2 1.4 .<0.1 I 10.1 <0.03 i 27.3 t
a Sample collected on Lundgren Impactor Thursday, September 3, 1969, 0900-2000 hours 47.5 m 3 sample volume collected.
suggests that acid particles or gases also present during sampling destroyed the carbonates. In other samples obtained by this laboratory, evidence of acid droplets using methods such as have been described by Waller (ii) or by Lodge (12) has not been found. Thus, the relative roles of trace carbonates and acids in the atmosphere become interesting problems for investigation. The noncarbonate carbon containing particles cnsistently comprised a substantial fraction of the total in the size class less than 0.6 ~m. Summing the data within each size class given in Tables II-IV, the mass distribution function was calculated and plotted in Fig. i. This presentation of the size distribution was suggested by analogy to the volume Journal of Colloid and Interface Science, Vol. 39, No. 1, April 1972
MUELLER, MOSLEY, AND PIERCE
238
1.20 :x~o~l. O0
°J • 80
.60
-Q
,40
.20 o
o.1
1.0
10
100
P a r t i c l e Diameter, Dp, firm
FIG. 1. Noncarbonate carbon mass distribution by particle size Pasadena, California, AugustSeptember, 1969. M=26.1z/m3. distribution flmetion of Whitby et al. (13). AM is the amount weighed on each stage, and M is the sum of the weights obtained on the five cascade impaetor stages. Alog Dp represents the size interval specified for each stage. The upper size cutoff for the first stage was taken at 30 gm because particles larger than that would have a poor capture efficiency at the entrance of the sampling duct (14). The lower size cutoff was taken as 0.1 gm because the occurrence of substantial mass in the smaller particles in the Pasadena aerosol seemed unlikely according to the available volume spectra (13). Figure 1 shows dramatically that almost 90 % of the noncarbonate carbon occurred in particles less than 1 gm. During the 4-hr sampling period on Aug-ast 22, the NO2 corrected oxidant concentrations ranged from a high of 41 pphm at 1300 hours to 8 pphm at 1600 hours. Meteorological range as measured by nephe. !ometry at 546 nm ranged from a low a t 1300 hours of 14 km to a high of 60 k'm at 1600 hr. During the 4-hour period on August 26 the oxidant values ranged from a low at 1200 hr of 18 pphm to a high at 1330 hours of 35 pphm. This generally high level of oxidants persisted until 1600 hours. The meteorological range remained analogously low, ranging from 4.4 km at 1240 hours to 9.8 km at 1600 hours. The 11-hr sampling on 9/3/69 included a Journal of Colloid and Interface Science, Vo]. 39, No. 1, April 1972
4-hr period between 1200 to 1600 hours quite similar to the conditions prevailing on 8/26/ 69. However, during the 3-hr period from 0900 to 1200 hours the oxidant increased from 10 to 28 pphm and the meteorological range decreased from 9.3 to 7.3 km. Between 1600 and 2000 hr the oxidant decreased from 20 to 4 pphm and the meteorological range increased from 17 to 205 km. Although increases in oxidant and decreases in meteorological range coincide, disparate factors govern the level of occurrence of these two indices of air quality. In this particular situation they indicate independently the intensity of the photochemical smog. In Table V, we have summarized the indices corresponding to the periods of carbon analysis. Also, listed are the values of % C (noncarbonate) in the particles less than 0.6 ~m. While the peal: oxidant value on 8/22 was the highest, the episode was of shorter duration in that 4-hr period than in others, so that the smog intensity was considered to be less than that on 8/26 when the episode spanned the entire 4-hr period and the visibility was restricted severely. Coincident with this increase in smog intensity the carbonaceous carbon content of the particles sampled on 8/26 was also higher. The carbon content of the particles obtained in 11 hr on 9/3 (Table IV) was substantially lower and again there was a clearcut concentration of carbon containing particles in the smallest size range. Since the 1200-1600 hour period was similar in smog intensity to 8/26, a dilution effect from nonTABLE V AI~ QUALITYINDICES C O R R E S P O N D I N G TO t~ERIODS OF C A R B O N A N A L Y S I S
Date
Period (hr)
Oxl:tant nean
'8/22/69 8/26/69 9/3/69 9/8/69
12-1600 12-1600 12-1600 09-2000
22 26 30 22
Meteorological Range, km % C a ia <0.6 particles ~¢iea_~a o_~_w L
41 35 38 38
Noncarbonates. b NA-Data not available.
"
32 / 14
s
25 [ 5
33 44 NAb 27
CARBON IN PASADENA AEROSOL
239
carbon containing particles added during as a function of size and time of day is a usethe morning and evening hours is apparent. ful approximate indicator of aerosol origin. Thus, the comparison of the three sets of ACKNOWLEDGMENTS data show a consistency with the expectation of substantial carbonaceous aerosol formaThe conscientious technical assistance from a tion from the atmospheric photochemical number of individuals made the outcome of the smog reaction. Our findings indicate that a study possible. Dale Lundgren of Environmental carbon analysis of size segregated particulate Research Inc., engineered and supervised the collections for many 4-hr periods obtained collection of the samples. J. Husar and S. Forbes consecutively during very low as well as very collected the specimens. SuzAnne Twiss assisted high photochemical smog days would pro- considerably with the reduction of the data. This work was supported in part by California vide information for estimating the quantity Air Resources Board, Mr. John Maga, Executive of aerosol formed photoehemically. Officer. W hile our data indicate there is a shift in REFERENCES the carbon content of particles diurnally in the less than 0.6 vm size range, much more 1. DANIELSON,J. A., ed, "Air Pollution Engineering Manual." Nat. Air Pollut. Contr. data are needed. In cooperation with Dr. A1 Admin. Publ. No. 999-AF-40, Cincinnati, Boekian of the California Air Resources OH (1967). Board, we have completed total carbon 2. CADIm, R. D., "Particles in the Atmosphere analysis on a set of total particulate samples and Space." Reinhold, New York (1966). collected by him in Los Angeles and Azusa 3. MADER, P. P., Ind. Eng. Chem. 44, 1352 (1952). during daylight hours in September, 1969. 4. FIJDAKGWSKI,H., Berichte 6, 106 (1873). The location showing the highest range of 5. GOETZ, A., Staub 29, 357 (1969). particulate carbon was Pasadena with 186. MUELLER, P. K., MOSLEY, R. W., AND PIERCE, 44%. Los Angeles was intermediate with L. B., "Carbonate and Noncarbonate 11-36%, and Azusa lowest with 6-32%. Carbon in Atmospheric Particles," Proco This indicates there may be a difference in 2nd Int. Clean Air Congr. (1970). 7. LUNDGREN,D. A., or. A i r Pollut. Contr. Ass. carbon content as a function of location in 17, 225 (1967). the Los Angeles basin. SUMMARY AND CONCLUSIONS
Preliminary findings on the diurnal changes in carbon containing particles, obtained as a function of size in Pasadena, California in August and September, 1969 are consistent with the expectation that a substantial fraction of the photochemically formed aerosol results from conversion of volatile organics. Much more data are needed to estimate reliably the quantity of carbonaceous aerosol formed photochemically. The findings reported here indicate that carbon in particulate matter measured
8. WHITBV, K. T., ed, "Aerosol IYIeasurements in Los Angeles Smog," Vol. I. U.S. Environmental Protection Agency, NC (1971). 9. MUELImR, P. K., W~.SOLOWSKI, J. J., and ALCECER, A. E. J. Colloid Interface Sci., in press. 10. MUELLER, P. K., CAHILL, T. A. AND ALCOCER, A. E., or. Colloid Interface Sci., in press. 11. WALLER, R. E., J. Air Water Pollut. 7, 773 (1963). 12. LODGE, J. P., AND FRANK, E. R., or. Microsc. 6, 449 (1967). 13. WHITEr, K. T., HUSAR, R. B., AND LIU, B. Y . H., J. Colloid Interface Sci. 39, 177 (1972). 14. WHITBV, K. T., private communication, 1971.
Journal of Colloidand Interface Science, ¥oi. 39, No. 1, April I972
t~eceived January 24, 1972; accepted January 27, 1972 The carbon content of atmospheric particles is in the form of the element, organic compounds and carbonates. In urban aerosol the noncarbonate carbon is probably of anthropogenic origin. Carbonates more likely result from surface erosion. To obtain information on these matters we have developed a method for measuring 10#g or more of carbon in size-segregated collections. The results of a preliminary study conducted during photochemical smog episodes in Pasadena, California, indicate that carbon in particulate matter measured as a function of size and time of day may be a useful indicator of aerosol origin. The carbonate C was consistently less than 1.0 ~g/m~. The noncarbonate C ranged from about 20 to 35 ~g/m ~ and constituted from 18 to 44% of the total particulate matter. INTRODUCTION The carbon content of the atmospheric aerosol may be an important criterion of its origin. The carbon content of particles is in the form of the element, organic compounds, biological particles and carbonates. In the urban aerosol, most of the noncarbonate carbon is probably of anthropogenic origin (2). Carbonates more likely result from surface erosion or cement manufacture. Despite the fact t h a t source inventories indicate carbon is one of the major dements occurring in particulate emissions (1), and that at least 30 % of the total particulate m a t t e r consists of noncarbonate carbon compounds in Los Angeles smog (2), very little work has actually been done on the carbon content of airborne particulate matter. Mader et al. (3) cited Fudakowski (4) as having established in 1873 t h a t petroleum fractions may be oxidized to form particulate m a t t e r when exposed to sunlight and air. Mader et al. showed in 1952 t h a t gasoline vapors in air, when irradiated ~4th or ~4thout the addition of nitrogen dioxide, formed an aerosol, the ether soluble portion of which Copyright © 1972 b y Academic Press, Inc.
had very nearly the same elemental composition, functional group reactions, and infrared spectrum as the ether soluble material extracted from particles collected from the atmosphere. T h e y also demonstrated a strong negative correlation between organic ether soluble aerosol and visibility indicating this material is concentrated in the 0.1-1 ~m diameter size range. Unfortunately, they did not obtain or publish data on the total particulate m a t t e r content, and it is not clear whether or not the ratio of ether soluble material increases with increasing photochemical aerosol formation. In addition to ether solubles, the aerosol formation process from hydrocarbons yielda insoluble resins. Goetz (5) has shown expertmentally that traces of ammonia and sulfur dioxide can accelerate the process and that water vapor readily condenses on the particles. The particle size distribution of the total organic particulate matter in the urban aerosol could therefore be expected to shift diurnally. Such changes, if substantial, should also be apparent from analysis of the total non-carbonate content of the collected parJournal of Colloid and Interface Science, Vot. 39, No. 1, .~kpril 1972
235
236
MUELLER, MOSLEY, AND PIERCE
ticles. The magnitude of these changes in relation to total particulate matter, lead, :silica or iron content, might serve to estimate the total amount of particulate mass created photochemically. When sampling aerosol as a function of size and time, only micrograms of particulate matter are available for analysis. For such small quantities, a carbon analysis would provide information on the total carbonaceous matter content, and would be a more direct and sensitive means of obtaining preliminary information than the analysis of only ether solubles. To avoid possible interferences, carbonate carbon was also determined. We have described and validated the analytical procedure previously (6). This paper reports preliminary findings on the diurnal changes of the size distribution of carbon containing particles. SAMPLE C O L L E C T I O N AND ANALYSIS The Lundgren impactor (7) along with other instrumentation was used in a colloborative research study (8) in Pasadena, California, during September, 1969. The impaetors and total mass samplers were located at the bottom of a vertical sampling line to minimize losses of large particles. The collection drums of the four stages of the impaetor for chemical analysis were coated witha thin film of aluminum foil held to the drum with cellophane tape. The taped end of the aluminum film was cut off before chemical analysis to prevent contamination from the tape itself or from dirt it may have picked up. A 4-in. diameter glass fiber filter pad was used as the fifth stage. The sampling rate was about 79 liters/min. A parallel impactor operating simultaneously and coated with Teflon film held in place with a mechanical clamp was used for weight determinations of the size segregated particles. In this case a Teflon filter was used as a fifth stage to collect particulate matter passing the impactor's fourth stage. Other elements have been determined on the deposits on the Teflon films and filters and data for these are presented in companion papers [9, 10). Particleswere segregated during collection ~)n the impactor stages according to mass Journal of Colloid and Interface Science, Vol. 39, No. 1, April 1972
median diameters assuming spheres of unit density as follows: 17-30 ~m for stage one, 5-17 ~m on stage two, 2-5 t~m on stage three, 0.6-2 gm on stage four and less than 0.6 ~m on stage five. Strips of the aluminum foil or glass fiber filters containing the particulate samples were placed in combustion boats. A boat was inserted into a train designed to generate carbon dioxide from a single sample first by acidification and then by combustion. The respective quantities of carbon dioxide were swept with a purified oxygen stream through a trap for water to a freeze-out trap for carbon dioxide. The concentrated carbon dioxide was moved to a gas chromatograph for separating residual oxygen, water, and acid gases, and was then quantitated by thermal conductivity. The amount of C02 measured was corrected for losses and blank values obtained from clean foils and filters, respectively. Three sets of cascade impactor samples were analyzed. Each aluminum foil was cut in half and each half analyzed separately. Each glass fiber filter was cut into one-eighth sections and two such sections analyzed separately. Although visual inspection indicated the deposits may not have been always uniformly distributed, the precision demonstrated by Table I indicates there were no serious relative errors in the analytical procedure. CARBON CONTENT OF PASADENA AEROSOL Three sets of cascade impactor samples obtained during the 1969 aerosol study in Pasadena have been analyzed for carbonate and noncarbonate carbon. The results are given in Tables II, III and IV. Two sets were obtained during 4 hr in the afternoon and one set during 11 hr in the daytime. The lower limit of measurement was a difference of 1 #g carbon between the blank values and the sample, thus leading to the inequality statements in these tables. The carbonates are consistently quite low compared to the noncarbonate carbon. The data in Table III indicate a tendency for the carbonate containing particles to be concentrated in size ranges greater than 2 t~m. Most
237
C A R B O N IN P A S A D E N A AEROSOL of t h e t o t a l m a s s of p a r t i c l e s c o l l e c t e d a p p e a r e d o n t h e f i f t h s t a g e i n all cases a n d c a r b o n a t e s c o n s t i t u t e d less t h a n 2 % of t h e
total particulate matter on that stage. It is striking that no carbonate was found in the ll-hr sample (Table IV) even though more mass was available for analysis. The detection limit for the carbonate content of the particulate matter was 0.03 %. This finding
Stage ~ 1b
SAMPLES
8/22 Sample
8/26 Sample
- - -
, ~ - - -
co~- non-CO~-! CO a-
/ 4.2 2b 3.0 4.8 3b 4.0 3.0 4b 3.4 3.0 5~ 5.5 7.2
22.0 37.6 33.8 21.2 25.3 NA 32.2 62.0 62.0
9/3 Sample ,
- - - -
inon-CO~CO~-
3.5 13.4 2.8 8.4 3.7 4.3 6.2 4.8 NA
2 non-CO Z
24.0 27.5 21.0 39.2 32.2 57.0 65.0 91.8 86.0
~ 4.7 NA 3.3 4.0 4.5 3.5 3.0 3.0 3.0
19.5 26.0 24.8 34.3 26.3 78.8 71.0 124 146
° Blank values not subtracted. b Each number refers to 30.6 cm ~ aluminum foil, i.e., ~ of the total foil. Blank was 4.8 ~g (±.06) for CO~- ; 26.2/~g (±5) for non-CO~-. Each number refers to 7.9 cm" glass fiber filter, i.e., 1/~ of the total filter, blank was 4.4 ~g (±0.6) for CO~-; 17.3 (4-2) for non-COl-. e NA--Data not available. TABLE II I969 PASADENA AEROSOL SAMPLE ANALYSISa #g C / m a as Size class
Stage
Total ]
% C of Total Particles b y weight as
par-
(~m) coF
o~-COy
tides ~ug/ma'.
non-
co~-
co~-
<2 <2.8 <0.6 <0.7 1.4
<2 53.5 <0.6 7.9 32.6
__I
17-30 5-17 2-5 0.6-2 0.1-0.6
7 1
4 5
0.06 ~0.056 2.5 O.O6 1.07 2.0 0.06 ~0.056 9.5 0.06 0.67 8.5 0.88 20.1 61.8
/~g C / m a as Size class
!non-CO~-
Sample collected on Lundgren Impactor Saturday, August 22, 1969, 1200-1600 hours, 17.8 m ~sample volume collected.
ticles [
non-
F
coF
(~g/ma) CO~J
17-30
1 2 3 4 5
[<0.05 0.34 I O. 13 i 0.05 0.17
% C of total particles by weight as
Total par-
St~e COF
5-17 I 2-5 0.6-2 0.1-0.6
TABLE I TOTAL 1V[ICROGaAMS~ CAZEON ON TWO SECTIONS OF ANALYZED
TABLE III 1969 PASADENA AEROSOL SAMPLE ANALYSISa
J-U <2
0.05 0.99 3.65 29.80
4.4! 13.3 31:3 67.7
7.7 1.0 0.2 0.3
<2 <1,2 7.4 11.7 44.0
Sample collected on Lundgren Impactor Wednesday, August 26, 1969, 1200-1600 hours, 19.2 m a sample volume collected. T A B L E IV 1969 PASADENA AEROSOL SAMPLE ANALYSISa
Size class
Stage g i
f~m)
17-30 5-17 2-5 0.6-2 0.1-0.6
~g C / m s as
par-
non-CO~
1 2 3 4 5
% C of total partldes b y weight as
Total
/ <0.02 <0.02 <0.O2 <0.02 <0.02 0.17 <0.02 2.05 <0.02 19.8 '
tides ~g lm a
non-
coF 4.6 5.7 12.5 20.3 72.8
co~-
<0.5 <0.5 <0.4 I <0.4 <0.2 1.4 .<0.1 I 10.1 <0.03 i 27.3 t
a Sample collected on Lundgren Impactor Thursday, September 3, 1969, 0900-2000 hours 47.5 m 3 sample volume collected.
suggests that acid particles or gases also present during sampling destroyed the carbonates. In other samples obtained by this laboratory, evidence of acid droplets using methods such as have been described by Waller (ii) or by Lodge (12) has not been found. Thus, the relative roles of trace carbonates and acids in the atmosphere become interesting problems for investigation. The noncarbonate carbon containing particles cnsistently comprised a substantial fraction of the total in the size class less than 0.6 ~m. Summing the data within each size class given in Tables II-IV, the mass distribution function was calculated and plotted in Fig. i. This presentation of the size distribution was suggested by analogy to the volume Journal of Colloid and Interface Science, Vol. 39, No. 1, April 1972
MUELLER, MOSLEY, AND PIERCE
238
1.20 :x~o~l. O0
°J • 80
.60
-Q
,40
.20 o
o.1
1.0
10
100
P a r t i c l e Diameter, Dp, firm
FIG. 1. Noncarbonate carbon mass distribution by particle size Pasadena, California, AugustSeptember, 1969. M=26.1z/m3. distribution flmetion of Whitby et al. (13). AM is the amount weighed on each stage, and M is the sum of the weights obtained on the five cascade impaetor stages. Alog Dp represents the size interval specified for each stage. The upper size cutoff for the first stage was taken at 30 gm because particles larger than that would have a poor capture efficiency at the entrance of the sampling duct (14). The lower size cutoff was taken as 0.1 gm because the occurrence of substantial mass in the smaller particles in the Pasadena aerosol seemed unlikely according to the available volume spectra (13). Figure 1 shows dramatically that almost 90 % of the noncarbonate carbon occurred in particles less than 1 gm. During the 4-hr sampling period on Aug-ast 22, the NO2 corrected oxidant concentrations ranged from a high of 41 pphm at 1300 hours to 8 pphm at 1600 hours. Meteorological range as measured by nephe. !ometry at 546 nm ranged from a low a t 1300 hours of 14 km to a high of 60 k'm at 1600 hr. During the 4-hour period on August 26 the oxidant values ranged from a low at 1200 hr of 18 pphm to a high at 1330 hours of 35 pphm. This generally high level of oxidants persisted until 1600 hours. The meteorological range remained analogously low, ranging from 4.4 km at 1240 hours to 9.8 km at 1600 hours. The 11-hr sampling on 9/3/69 included a Journal of Colloid and Interface Science, Vo]. 39, No. 1, April 1972
4-hr period between 1200 to 1600 hours quite similar to the conditions prevailing on 8/26/ 69. However, during the 3-hr period from 0900 to 1200 hours the oxidant increased from 10 to 28 pphm and the meteorological range decreased from 9.3 to 7.3 km. Between 1600 and 2000 hr the oxidant decreased from 20 to 4 pphm and the meteorological range increased from 17 to 205 km. Although increases in oxidant and decreases in meteorological range coincide, disparate factors govern the level of occurrence of these two indices of air quality. In this particular situation they indicate independently the intensity of the photochemical smog. In Table V, we have summarized the indices corresponding to the periods of carbon analysis. Also, listed are the values of % C (noncarbonate) in the particles less than 0.6 ~m. While the peal: oxidant value on 8/22 was the highest, the episode was of shorter duration in that 4-hr period than in others, so that the smog intensity was considered to be less than that on 8/26 when the episode spanned the entire 4-hr period and the visibility was restricted severely. Coincident with this increase in smog intensity the carbonaceous carbon content of the particles sampled on 8/26 was also higher. The carbon content of the particles obtained in 11 hr on 9/3 (Table IV) was substantially lower and again there was a clearcut concentration of carbon containing particles in the smallest size range. Since the 1200-1600 hour period was similar in smog intensity to 8/26, a dilution effect from nonTABLE V AI~ QUALITYINDICES C O R R E S P O N D I N G TO t~ERIODS OF C A R B O N A N A L Y S I S
Date
Period (hr)
Oxl:tant nean
'8/22/69 8/26/69 9/3/69 9/8/69
12-1600 12-1600 12-1600 09-2000
22 26 30 22
Meteorological Range, km % C a ia <0.6 particles ~¢iea_~a o_~_w L
41 35 38 38
Noncarbonates. b NA-Data not available.
"
32 / 14
s
25 [ 5
33 44 NAb 27
CARBON IN PASADENA AEROSOL
239
carbon containing particles added during as a function of size and time of day is a usethe morning and evening hours is apparent. ful approximate indicator of aerosol origin. Thus, the comparison of the three sets of ACKNOWLEDGMENTS data show a consistency with the expectation of substantial carbonaceous aerosol formaThe conscientious technical assistance from a tion from the atmospheric photochemical number of individuals made the outcome of the smog reaction. Our findings indicate that a study possible. Dale Lundgren of Environmental carbon analysis of size segregated particulate Research Inc., engineered and supervised the collections for many 4-hr periods obtained collection of the samples. J. Husar and S. Forbes consecutively during very low as well as very collected the specimens. SuzAnne Twiss assisted high photochemical smog days would pro- considerably with the reduction of the data. This work was supported in part by California vide information for estimating the quantity Air Resources Board, Mr. John Maga, Executive of aerosol formed photoehemically. Officer. W hile our data indicate there is a shift in REFERENCES the carbon content of particles diurnally in the less than 0.6 vm size range, much more 1. DANIELSON,J. A., ed, "Air Pollution Engineering Manual." Nat. Air Pollut. Contr. data are needed. In cooperation with Dr. A1 Admin. Publ. No. 999-AF-40, Cincinnati, Boekian of the California Air Resources OH (1967). Board, we have completed total carbon 2. CADIm, R. D., "Particles in the Atmosphere analysis on a set of total particulate samples and Space." Reinhold, New York (1966). collected by him in Los Angeles and Azusa 3. MADER, P. P., Ind. Eng. Chem. 44, 1352 (1952). during daylight hours in September, 1969. 4. FIJDAKGWSKI,H., Berichte 6, 106 (1873). The location showing the highest range of 5. GOETZ, A., Staub 29, 357 (1969). particulate carbon was Pasadena with 186. MUELLER, P. K., MOSLEY, R. W., AND PIERCE, 44%. Los Angeles was intermediate with L. B., "Carbonate and Noncarbonate 11-36%, and Azusa lowest with 6-32%. Carbon in Atmospheric Particles," Proco This indicates there may be a difference in 2nd Int. Clean Air Congr. (1970). 7. LUNDGREN,D. A., or. A i r Pollut. Contr. Ass. carbon content as a function of location in 17, 225 (1967). the Los Angeles basin. SUMMARY AND CONCLUSIONS
Preliminary findings on the diurnal changes in carbon containing particles, obtained as a function of size in Pasadena, California in August and September, 1969 are consistent with the expectation that a substantial fraction of the photochemically formed aerosol results from conversion of volatile organics. Much more data are needed to estimate reliably the quantity of carbonaceous aerosol formed photochemically. The findings reported here indicate that carbon in particulate matter measured
8. WHITBV, K. T., ed, "Aerosol IYIeasurements in Los Angeles Smog," Vol. I. U.S. Environmental Protection Agency, NC (1971). 9. MUELImR, P. K., W~.SOLOWSKI, J. J., and ALCECER, A. E. J. Colloid Interface Sci., in press. 10. MUELLER, P. K., CAHILL, T. A. AND ALCOCER, A. E., or. Colloid Interface Sci., in press. 11. WALLER, R. E., J. Air Water Pollut. 7, 773 (1963). 12. LODGE, J. P., AND FRANK, E. R., or. Microsc. 6, 449 (1967). 13. WHITEr, K. T., HUSAR, R. B., AND LIU, B. Y . H., J. Colloid Interface Sci. 39, 177 (1972). 14. WHITBV, K. T., private communication, 1971.
Journal of Colloidand Interface Science, ¥oi. 39, No. 1, April I972