Patterns in Airborne Polynuclear Hydrocarbon Concentrations at Four Los Angeles Sites Robert J. Gordon’ and Robert J. Bryan2 Department of Pathology, University of Southern California School of Medicine, Los Angeles, Calif. 90033
Simultaneous sampling for airborne particulate matter was carried out a t four Los Angeles locations for one year. A composite for the year a t each site was extracted a n d analyzed for polynuclear aromatic hydrocarbons (PAH) a n d lead. The yields of total particulate mass, benzene solubles, lead, and coronene paralleled t h e estimated traffic densities a t the four sites. A number of PAH, other than coronene, did not parallel traffic density. The PAH patterns, normalized to coronene, were similar for three sites a n d to a fair degree, resembled patterns for auto exhaust previously published. T h e fourth site had a distinctly different pattern, reflecting local sources of nonautomotive PAH. Absolute levels of PAH are much below those found before imposition of stationary source emission controls, but have not changed much further since the late 1950’s. Polynuclear aromatic hydrocarbons (PAH) associated with airborne particles are believed to arise mainly as products of combustion (Badger, 1962). Their concentrations in t h e air may be high in areas where coal and fuel oil are used for space heating and power generation ( S a wicki et al., 1962), but they are also observed in automobile exhaust (Hoffman a n d Wynder, 1962). Since no coal is used in Los Angeles a n d much of t h e heat and power are derived from natural gas, it was of interest to compare t h e atmospheric PAH patterns a t several locations there with those in auto exhaust. PAH have been measured previously in Los Angeles and several other cities (Kotin e t al., 1954; Sawicki et al., 1962). A current study was also of interest for comparison with the earlier work. A program of large-volume air sampling for carcinogenesis studies offered a n opportunity for this comparison. Experimental Four large-scale trailer-mounted air samplers based on the design of Begeman and Colucci (1962) were sited in t h e Los Angeles basin. The locations (Figure 1) and their characteristics were as follows: 1. Near a freeway junction, heavy traffic, little heavy industry. Nearest freeway, 0.12 mile 2. Concentration of metal-working, smelting, and meatpacking industry, moderate traffic. Nearest freeway, 1.27 miles 3. Concentration of petroleum refineries and chemical plants, moderate traffic. Nearest freeway, 0.75 mile 4. Light traffic, no industry. Nearest freeway, 6.5 miles None of t h e locations is close to any known fixed combust ion source. Sampling was carried out during the 12 months from J u n e 1971 to J u n e 1972. T h e four samplers were run simultaneously for one week on, one week off, during the period. Pleated glass fiber filters with about 25 m* of effective filter area were changed monthly. T h e airflow rate was about 150 m3-min-l, resulting in a total volume to filter To whom correspondence should be addressed. Present address, Pacific Environmental Services. Inc.. S a n t a Monica. Calif. 1050
Environmental Science 8 Technology
area ratio t h a t was approximately the same as for a s t a n dard high-volume sampler run for two days. T h e airflow during the two weeks of sampling seldom dropBed as much as 15%. T h e exposed filters were sawed apart and various numbers of pleats were used for different purposes. For the work reported here, a composite of pleats from each monthly filter over a period of a year was made u p for each location and extracted in a large Soxhlet unit for 24 hr with benzene. (In earlier composites, PAH analyses on such extracts were the same within repeatability limits as those calculated by summing the analyses of extracts freshly made as t h e individual filters were collected.) T h e extract was evaporated to constant weight in a vacuum rotary evaporator a t 40°C. Aliquots of a chloroform solution of the extract were used for a PAH analysis patterned after that of Sawicki et al. (1960a). T h e extract was first rough-chromatographed on a 1 x 15-cm column of silica plus 4% water with chloroform, then evaporated and charged by valve to a column of neutral alumina (Merck) deactivated with 1% water. The alumina column (Chromatronix) was 3 x 1000 m m . The activity of the alumina column was checked before use by eluting anthracene with n-hexane. Elution volumes of 40-80 ml indicated satisfactory activity. T h e column could be reactivated several times, if necessary, by passing ethyl ether and 0.07% water through it, followed by hexane to clear t h e ether. A Milton Roy solvent pump ( u p to 200 psi) was used for a stepwise elution gradient of nhexane with increasing amounts of benzene, u p to 100% benzene, 40 ml per step. T h e eluate was collected in 5-ml fractions for direct analysis by ultraviolet spectrometry on a Cary model 15 spectrophotometer. The base line technique was used. The benzopyrene group was collected for confirmatory analysis (Spotswood, 1960). This was made on a 3 X 500-mm column of cellulose acetate (MachereyNagel) with methanol eluent. T h e sample was charged in methanol via septum. About a dozen 3.2 ml fractions sufficed to separate benzo(a)pyrene from other members of
I
Figure 1. Four Los
Angeles sampling sites with freeway network
the group and to allow an estimate by uv spectra of all the components shown in Figure 2. Mixtures of synthetic PAH were run periodically through the chromatographic and spectral analyses for calibration. The PAH were mostly obtained from commercial sources and purified by recrystallization or chromatography, if necessary, to agree with reference spectra (Sawicki et al., 1960b; Monkman, 1970). Benzo(k)fluoranthene was obtained from J . L. Monkman. Benzo(b)fluoranthene and benzo0')fluoranthene were not available. Spectra for them, as run on the same model of spectrometer (Monkman, 1970), were used for approximate estimates of their concentrations. Lead values were determined after low-temperature ashing (Trapelo RF excited oxygen generator) and acid extraction, by atomic absorption spectrometry. Total particulate weight was estimated by weighing an exposed bundle of pleats and subtracting the weight of a like number of unexposed pleats. Roberts et al. (1971) prepared a detailed 50 x 50-mile grid of Los Angeles traffic densities, summed in 2-mile square units, based on vehicle counts and street mileages. The traffic densities a t each of the four sampling sites were estimated from this grid. Each grid unit traffic density was assigned to the point center of the grid unit. The air sampling site density was calculated by interpolation among the four surrounding grid values.
to one another and to traffic density, several other PAH do not. The linear regression fit of the first four variables to traffic density is given in Table 11. The line for coronene is shown in Figure 3. The PAH values from Table I were normalized to coronene with the results shown in Figure 4. The ratios for all PAH a t sites 1 and 2 are quite similar, as are most of those a t site 4 (where concentrations are very low). Those for site 3 are obviously much 50 -
BENZO (E) PYRENE
0-
8 k
0 50
0 50
Results
0
Collected analytical d a t a are given in Table I. It is apparent by inspection t h a t although total particulate mass, benzene solubles, lead, and the PAH coronene run parallel
FRACTION NUMBER
Figure 2. Chromatograph of benzopyrene-benzofluoranthene
group 011 cellulose acetate
Table I. Components in Los Angeles Airborne Particles Composite June 1971-June 1972 Location. 1971-72 Component
Total particulate mass, p g / m 3 Benzene solubles, pg/m3 Lead, p g / m 3
Traffic density X vehicle mi /mi2/day PAH, ng/m3 Coronene Pyrene Fluoranthene Benz(a)anthracene Chrysene Benzo(e) pyrene Benzo(a) pyrene Benzo(b)fluorantheneC
1
2
3
4
21 5
131
102
40
21.7 5.35
200
1952-53"
13.2
8.3
2.6
2.50
1.97
0.50
130
1958-59'
8
95
6.4 2.0 1.9
3.2 1.4 0.8
2.8 3.8 3.4
0.20 0.18 0.12
1.1 2.6 3.0 1.1
0.8 1.6 1 .8 0.5
3.1 3.8 3.2 3.5
0.04 0.04 0.09 0.03
1.6
0.9
1 .8
0.09
0.6
0.3
0.8
0.01
0.8 0.5 0.4
0.3 0.3 0.2
1.3 1.2 1.1
0.03 0.01 0.01
9.2
4.2
7.1
0.21
1.2
0.4
0.3
0.03
7.5
31
1.3
2.3 1.6
Benzo ( j ) f luoran theneC Benzo(k)fluoranthene Perylene Anthanthrene Benzo ( g h i )perylene
1.6 0.23 0.07 21
6.4
Indene( 1,2,3-cd)-
pyrene
Kotin et al (1954) Geometric mean of fall and winter-spring composites and winter averages Based on spectra run on another instrument
'Sawicki
et al
(1962)
Geometric means of
summer
Volume 7, Number 1 1 , November 1973 1051
locations are under test for relative carcinogenic activity,
’1
to be reported elsewhere.) The PAH pattern derived from sites 1 and 2, with few exceptions, is in fair accord with published auto exhaust patterns (Table 111). The pyrene and fluoranthene differences may be due to volatility or instability when diluted in air. These tetracyclics may have enough vapor pressure to escape complete collection on the filters. The observed ratio for benzo(ghi)perylene falls between the very different values for the two patterns cited, and may reflect some difference in the type of exhaust generated in Los Angeles from those previously examined. Included in Table I are d a t a found by Sawicki et’ al. (1962) in Los Angeles 13 years earlier and by Kotin et al. (1954) 19 years earlier. The recent values are much reduced from the Kotin results, especially for benzo(a)pyrene, but not so different from the Sawicki data. (The values quoted are geometric means of the earlier averages
6-
5-
0
n
E
4-
c 0
0
80
40
120
160
200
TRAFFIC DENSITY x (ESTIMATED VEHICLE -MILES/SQUARE MILEIDAY)
Figure 3. Airborne coronene concentration vs. traffic density Sampling sites designated
~
Table I I. Observed Concentrations vs. Estimated Traffic Density ( T ) a
C=A+BT C
Total particulate mass, p g / m 3 air Benzene-solu bles, p g / m 3 air Lead, p g / m 3 air Coronene, p g / m 3 air
A
B
24.6
0.899
0.989
9.40
0.65 -0.076
0.0998 0.0245
0.984 0.964
1.23 0.47
-0.25
Vehicle miles,’mile)’day X 1 0 error of estimate for C.
0.0314
Rb
0.985
’Correlation coefficient
ScC
BBF
EJF
EKF
PER
ANT
INP
GEE
Figure 4. Concentration ratios, PAH/COR
0.38
See Table I l l for PAH identification
Standard
Table I l l . PAH Pattern Comparisons
different. The average pattern for sites 1 and 2 is compared in Table 111 to published exhaust patterns and is also used to deduct the hypothetical auto exhaust contribution to site 3, assuming that coronene arises solely from exhaust. The results shown in the last column represent a pattern for nonautomobile emissions a t site 3.
Discussion The correlation of several air pollutants with traffic density is surprisingly good, considering t h a t effects of meteorology are in no way taken into account. This suggests that the components considered are not mainly a result of any photochemical or other atmospheric process involving a time delay, but are primary emissions from the automobile. This seems to be true not only for lead, as might be expected, but also for coronene, judging from the close fit shown in Figure 3. Although several of the constituents of airborne particulate pollution given in Table I bear out the concept t h a t much of the particulate matter in Los Angeles derives from the automobile, the anomalous PAH found in excess a t site 3 show that there are other sources important to local areas. Since several of the PAH found in excess a t site 3 are known carcinogens (Hoffman and Wynder, 1968), such differences may be important. (Samples from all four 1052
Environmental Science & Technology
Concentration ratio, PAH COR Calculated nonauto PAH site Refa Refb 3 wg rn3
Av, sites 1f 2
Pyrene ( P Y R ) Fluoranthene (FLT) Benz(a)anthracene ( B A A1 Chrysene (CHY) Benzo(e)pyrene (BEP)
0.38 0.27
5.2 2.9
0.21 0.45
0.18 0.52
0.52
1.25
0 53
18
0.16
0.09
0 71
30
0.27
0.19
1 1
0.09
0.05
05
0.11 0.09 0.06
0.16
26
28 26 25 25
Benzo ( a )pyrene (BAP)
Benzo ( b )fluoranthene (BBF) Benzo(j)fluoranthene (BJF) Benzo(k)fluoranthene ( B K F ) Perylene (PER) Anthanthrene ( A N T ) Benzo(ghi) perylene (GEE) lndeno (1,2,3-cd)pyrene ( I N P )
Coronene ( C O R )
0.13
0 09 0 24
10 10 09
1.38
0.15
30
32
0.16 ( 1 .OO)
( 1 .OO)
Hoffman and Wynder (1962).
0.24
-0 1 (1 00)
Sawicki et al. (1962)
(0)
for various times of t h e year. Samples were taken a t downtown locations.) During the mid 1950’s, stringent emission controls were applied to stationary sources in Los Angeles. Since the Sawicki study, carried out in 1958 and 1959, the stationary source control program has seen fewer changes as compared t o t h e earlier time period. T h e effect of the motor vehicle emissions control program on organic particulate matter is difficult to assess. Air sampling is now under way a t other sites in t h e Los Angeles basin.
A cknolcledgm ent A sample of benzo(k)fluoranthene and reference PAH spectra from J . L. Monkman are gratefully acknowledged. H . Menck carried out the regression analyses. Technical assistance was given by C. Choa, J. Mena, R. Papa, and A. Smith. Literature Cited Badger, G. M., Natl. Cancer Instit. Monogr. S o . 9. pp 1-16 (1962).
Begeman, C. R., Collucci, J. M., ibid., pp 17-57. Hoffman, D., Wynder, E. L., ibid., p p 91-116. Hoffman, D., Wynder, E. L., “Air Pollution,” 2nd Ed., Vol. 2, Ch. 20, ed. by A. C. Stern, Academic Press, New York, N.Y. ( 1968). Kotin, P., Falk, H . L., Mader, P., Thomas, M., Arch. Ind. Hyg. Occup. Med. 9, 153-63 (1954). Monkman, J . L., Occupational Health Division, Kational Health and Welfare, Ottawa, Canada, private communication, 1970. Roberts, P . J. LV., Roth, P. M . , Nelson, C. M., Report 71 SAI-6, Systems Applications, Inc., for the Air Pollution Control Office, Environ. Protec. Admin., under contract CPA 70-148 (1971). Sawicki, E., Elbert, W . C., Stanley, T . W., Hauser, T . R., Fox, F. T.,Anal. Chem., 32,810-15 (1960a). Sawicki, E . , Hauser, T . R., Stanley, T . b’.,Intern. J . Air Pollut., 2, 253-72 (1960b). Sawicki, E., Hauser, T . R., Elbert, W. C., Fox, F. T . , Meeker, J . E . , Amer. Ind. Hyg. Assoc. J . , 23, 137-44 (1962). Spotswood. T . M., J . Chromatog., 3, 101-10 (1960).
Receiced for recieu Aprii 9, 1973. Accepted July 19. 1973. This stud?, u as conducted under Contract X o . 43-SCI-68-1030 uithin The Virus Cancer Program of the Yationai Cancer Institute, &Vutionai Institutes of Health, Public Health Sercice, L’.S. Department of Heaith, Education, and Welfare.
Particulate Lead Contamination Recorded in Sedimentary Cores from Lake Washington, Seattle Eric A. Crecelius’ and David Z. Piper Department of Oceanography, University of Washington, Seattle, Wash. 98195
The concentration of lead in two sediment cores from Lake Washington, Seattle, has increased 20 fold during the past 100 years. The sources of lead in the lake sediments are believed to be automobile combustion products and particulate matter from a copper smelter. ~
In recent years there has been considerable interest in the distribution of lead in the environment. High concentrations of lead in soils near highways (Chow, 1970; Daines e t al., 1970) and in aerosols in metropolitan areas (Chow and Earl, 1970) suggest the lead alkyl additives in gasoline are the major contributor of lead to the presentday environment. Locally, however, other sources of lead may be important. High lead concentrations have been reported in soils near smelters (John, 1971). The burning of coal may also represent locally an important source of lead. The vicinity of Seattle, Wash., may receive lead from all three of these sources. The Tacoma copper smelter, 50 km to the south of Seattle, presently releases stack dust containing approximately 80,000 kg of lead per year (Rossano, 1971). The smelter may have released much more particulate lead during the years 1890 to 1913 when the smelter produced lead bullion. The quantity of particulate lead presently released by the Tacoma smelter is small compared to the amount of lead released by automobiles in the Seattle area, approximately 500,000 kg of lead per year [based on the total lead released by automobile exhaust in the United States (Goldberg, 1971)]. Although Seattle presently burns very little coal, in the early 1900’s coal burning may have released as much as 4000 kg of lead per year to the atmosphere [assuming the lead concentration in coal was 50 ppm (Abernethy and Gibson, 196311, 3 tons of coal consumed by capita per year, and 10% of the lead escaped into the atmosphere. Until the year 1967 Lake Washington was receiving sewage effluent To whom correspondence should be addressed.
from 11 treatment plants surrounding the lake. The maximum amount of lead which could have been added to the lake before 1997 by effluent was 1500 kg of lead per year (METRO, 1973). To identify present-day sources, the distribution of lead in the needles of Douglas Fir trees (pseudotsuga m e n t iesii) in the vicinity of the Tacoma smelter and near and distant from major highways was determined. Copper was also determined in the fir needles to establish the area presently receiving particulate material from the copper smelter. To estimate past levels of lead pollution in the Seattle area from all sources. the distribution of lead was determined in two sedimentary gravity cores from Lake Washington. This lake forms the eastern boundary of Seattle (Figure 1) and is located 35 km S E E of the smelter. The aim of this study has been to evaluate the present relative contribution of lead to the environment by autos and smelter and the relative change in the overall level of lead pollution from the time of the development of the Seattle area, approximately 1880, to the present. Methods The lead concentration in lake sediment was analyzed by atomic absorption spectrometry. Samples were dried a t 90°C for 48 hr and then dissolved by treatment with hydrofluoric, perchloric, and hydrochloric acids, similar to the technique described by Bockheim et al. (1969). Lead and copper analyses of the fir needles. which represented first- and second-year growth only, also were measured by atomic absorption following drying a t 60°C for 24 hr and dissolution with perchloric and nitric acids. Collection of all fir tree samples was carried out on a single day. Drying for a period of u p to one week showed only a slight change in weight compared to a 12-hr drying period. Although uncertainty of the lead and copper analyses is largest for samples that contained low concentration of lead and copper, precision was less than 10% for all analyses. Volume 7, Number 11, November 1973
1053
