nature of the differences in the trace-element distributions found among the plumes of different copper smelters (1). However, the influence of the concentrates on this variability can be determined from the ratios of the normalized elemental concentrations in the concentrate, Le.
also thank the staff of the National Bureau of Standards reactor for their help with the irradiations and Mr. Gary Eckhardt (University of Arizona) for his assistance with the atomic absorption analysis.
EFconc = (Cx/Ccu)plume/(Cx/Ccu)conc
This double normalization has been done by using the plume data for smelters 1 , 2 , and 5 from ref 2 and the data given in Table I for the concentrates for these same smelters. The results are presented in Figure 3 for the sulfide-associated elements. If the concentrate were the only factor that determined the trace-element concentrations found in the plume particulate material, then normalizing the plume concentrations to the concentrate should remove all variation among the smelters. However, this is not the case: only some of the plume variability has been removed for some elements, most notably, Zn, Cd, In, and Au. We conclude that the differences in the elemental concentrations found in copper smelter plumes are due not only to the differences in the elemental concentrations of the concentrates, but also to the operating conditions used in smelting and the air pollution control devices installed at the smelters. Acknowledgment
We thank Mr. M. P. Scanlon, Dr. J. Dick, and Mr. F. Mendola (Phelps Dodge Corp.), Mr. D. C. Ridinger (Magma Copper), Mr. K. H. Mapheson (Kennecott Copper), Mr. F. Moninger (Inspiration Consolidated Copper Co.), and Mr. L. G. Cahill (Asarco Copper) for their help in obtaining the inplant samples and information on the smelting process. We
Literature Cited (1) Small, M.; Germani, M. S.; Small, A. M.; Zoller, W. H.; Moyers, J. L. Enuiron. Sci. Technol., preceding paper in this issue. ( 2 ) Gladney, E. S.Ph.D. Thesis, University of Maryland, College Park, MD, 1974. (3) Germani, M. S.Ph.D. Thesis, University of Maryland, College Park, MD, 1980. (4) Germani, M. S.; Gokmen, I.; Sigleo, A. C.; Kowalczyk, G. S.; Olmez, I.; Small, A.; Anderson, D. L.; Failey, M. P.; Gulovali, M. C.; Choquette, C. E.;Lepel, E. A.; Gordon, G. E.; Zoller, W. H. Anal. Chem. 1980, Fj2, 240. (5) Bernas, B. Anal. Chem. 1968,40, 1682. (6) Ranweiler. L. E.; Movers. J. L. Enuiron. Sci. Technol. 1974,8, 152. (7) Moyers, J. L. et al. 1977, Electric Power Research Institute Technical Report EA487. (8) Wedepohl, K. H. In “Origin and Distribution of the Elements”; Ahrens, L. H., Ed.; Pergammon Press: London, 1968; pp 9991016. (9) Natusch, D. F. S.; Wallace, J. R.; Evans, C. A., Jr. Science 1974, 183, 202. (10) Coles, D. C.; Ragaini, R. C.; Ondov, J. M.; Fisher, G. L.; Silberman, D.; Prentice, B. A. Enuiron. Sci. Technol. 1979, 13, 455. (11) Smith, R. D.; Campbell, J. A.; Nielson, K. K. Enuiron. Sci. Technol. 1979,13, 553. (12) Drehmel, D. C.; Gooding, C. H. Enuiron. Sei. Technol. 1978,12, 661. (13) Weast, R. C., Ed. “Handbook of Chemistry and Physics”; CRC Press: Boca Raton, FL, 1978-79.
Receiued for review October 12, 1979. Accepted November 7, 1980. This work was supported by the National Science Foundation RANN Program under Grant Nos. ENV 7ij-02667-AO3and PFR 75-02667806.
Seasonal Visibility and Pollutant Sources in the Northeastern United Statest Brian P. Leaderer’ and Jan A. Stolwijk John B. Pierce Foundation Laboratory, Department of Epidemiology and Public Health, Yale University School of Medicine, New Haven, Connecticut 06519
Seasonal visibility trends in the New York region are presented, and a hypothesis for those trends is proposed in light of recent data gathered on the optical properties of the New York City aerosol. Annual median visibility in the New York region has improved markedly since 1968 and appears to correspond to local emission control efforts. The improvement in annual median visibility, however, appears to be due principally to improvements in winter median visibility. Winter visibility was found to be related to pollutant emission from local sources. Summer median visibility has not improved markedly despite substantial reductions in local pollutant emissions. Summer median visibility appears to be principally related to aerosol transported into the region from distant sources located west and southwest of New York. Introduction
Visibility degradation is one of the most readily apparent effects of air pollution. Visibility or visual range in the urban atmosphere is dominated by the mass of fine suspended particulates in the 0.1-1.0-pm size range ( I ) . Most of the fine
t The material contained in this paper was in part presented a t the 178th National Meeting of the American Chemical Society, Division of Physical Chemistry, held in Washington, D.C. 0013-936X/81/0915-0305$01.25/0
@ 1981 American Chemical Society
particulates found in the atmosphere are directly emitted from combustion sources or are formed from the primary gaseous pollutant emissions of SOZ, NO,, and other reactant gases. A number of recent studies of the urban and nonurban ambient aerosol have identified sulfate and nitrate aerosol as major constituents of the fine particulate mass (2-7) and found that they are the dominant cause of atmospheric light scattering and extinction (visibility) (5-18). Sulfates alone at a number of locations have on average been found to account for over 50%of the light scattering and light extinction (13,17,18).The observed sulfate-light scattering relationship was found to be particularly strong in the northeast quandrant of the United States, where sulfur oxide emission densities are the highest. As a result, the records of visibility observations from airports in the Northeast, and probably those throughout most of the country, could serve as a useful indicator of levels of fine particulate mass, particularly the sulfate mass. Consequently, they could also serve as a means of assessing the effectivepess of efforts to control fine particulates through reducing emissions of fine particulates and gaseous precursors (SOs, NO,, etc.). In addition, the use of visibility data may provide insight into the air-quality impact of the reintroduction of fuels with higher sulfur and ash content (principally coal) in the Northeast. Volume 15, Number 3, March 1981 305
One visibility trend study for the northeastern United States (I&?), utilizing routinely collected airport-visibility observations from 1950 to 1972, has shown that in metropolitan locations, where annually averaged visibilities are low (median values are 8-10 mi), the averages have not changed greatly during the study period. When seasonal visibilities were examined, however, marked patterns were found. Summer visibililities were found to be decreasing slightly but were consistently lower than winter visibilities. Winter values were found to be increasing slightly in recent years. Urban/ suburban locations also exhibited lower visibilities in summer than winter with recent sharp decreases in summer values. Another study which examined trends of haziness in the eastern US. between 1948 and 1974 ( 1 9 )noted that the range and the trend of visibility among stations in the Northeast Megalopolis (Connecticut, Rhode Island, Massachusetts, New Jersey, Maryland, Delaware, and parts of Pennsylvania and New York) were consistent, suggesting a regional nature to visibility in the Northeast. Winter visibilities were found to be increasing while summer visibilities decreased. This study also noted that the observed yearly and seasonal visibility trends in many regions of the U.S. were consistent with regional changes in coal demand. This paper examines the seasonal visibility trends in the New York City area from 1948 through 1977 in conjunction with recent data collected in a series of aerosol characterization studies conducted in the New York City subregion (6,20). The impact on visibility of local sulfur oxide and particulate emission control efforts since 1967 in New York are discussed. Methods
Surface weather data collected a t La Guardia Airport in New York City from 1948 through 1977 were obtained from the National Oceanic and Atmospheric Administration ( 2 1 ) . From these data, prevailing visibility and other relevant meteorological observations taken a t 3-h intervals during daylight hours only were extracted for use. Because of the confounding effects of fog and precipitation, observations taken under these conditions were deleted from the analysis. Daily heating or cooling degree days were calculated from the surface weather data. The visibility data were summarized and analyzed over the desired time scales in terms of cumulative frequency distributions from which loth, 50th (median), and 90th percentiles were then calculated. The percentiles were chosen as the unit of observation because the visibility observations, while discrete values, are recorded over a range of unequal intervals. Visibility frequency distributions were calculated from 1948 through 1977 on a yearly basis (January through December), for the yearly heating seasons (December, January, February and March), and for the yearly cooling seasons (June, July, August, and September). Quarterly city-wide average concentrations of total suspended particulates and sulfur dioxide were obtained from the New York City Department of Environmental Protection for the period 1968-1977, the period of time for which datp exist for a number of sites in New York City. These observations provide a recent time trend for New York City of local levels of total suspended particulates (of which fine particulates are a portion) and for sulfur dioxide concentrations (a precursor of sulfate aerosol) and reflect to an extent the impact of local emission control efforts. Air-quality data for TSP and SO2 are available for New York City before 1968. However, the data are for a few scattered locations with variable sampling frequencies and as such may not be representative of city-wide averages. In addition, the findings of recent intensive aerosol characterization studies during summer and winter periods in New York City and the New York City subregion and data gathered in those studies and presented 306
Environmental Science & Technology
elsewhere are used in this analysis as a basis for explaining the trends and seasonal variability of visibility in the New York City area (6,14,20,22-26). Results and Discussion
Yearly daylight median visibilities for La Guardia Airport from 1948 through 1977 and the city-wide yearly averages of total suspended particulates (TSP)and sulfur dioxide (S02) from 1968 through 1977 are shown in Figure 1. In 1968 an improvement in median yearly visibility began which has been sustained through 1977, the most recent year for which data are available. Between 1967 and 1977 the median yearly visibility increased from 9 to almost 15 mi. This improvement parallels the decreases in yearly average ambient TSP and SO2 concentrations in New York City since 1967. In 1967, New York City initiated a program to improve air quality through the imposition of strict emission controls on major sources. Under Local Law 14 (March 1968) a specified timetable was established for reducing the percentage of sulfur in fuels, restricting the use of coal as a fuel, and upgrading or eliminating incinerators (27-29). The implementation of the emission control timetable in New York City has been associated with improvements in visibility and reductions in TSP and SO2 levels. Figure 2 shows 1948-1977 median summer visibilities, corresponding city-wide average TSP and SO2 concentrations, and cooling degree days. Figure 3 presents median visibility, TSP and SO2 averages, and heating degree days for the winters of 1948-1977. Summer median visibilities show little or no improvement in time, despite substantial reductions in ambient TSP and SO2 levels. Some improvement, however, in summer visibility appears to have occurred since 1975. Conversely, winter median visibilities and TSP and SO2 levels exhibit marked improvements since 1968. Visibility trends for the remaining months combined (April, May, October, and November) closely resemble the winter trend. Winter median visibilities for the most recent years are 50% higher than summer visibilities. The time trends for the 10th and 90th percentiles for the annual and seasonal visibilities are similar to those for the median trends. No significant corresponding trends in dew point, temperature, or relative humidity (RH) which could explain the visibility trends were observed. Segregating the summer visibilities by RH < 70% and I70% did not alter the trends observed, although median visibilities were higher for
YEARLY DAYLIGHT MEDIAN VlSlBlLlTV AVG. TSP AND 6 0 2 NEW VORK ciry
15r
ANNUAL Y E D I I N VSIBILITY
t
'48
I 52
I
I
56
60
I 64
-
CCUT REDUCTON¶ IN
sap AND
TIP
IN
miasm
I
1
I
I
68
71
76
80
YEAR
Flgure 1. Annual daylight median visibility for New York City for 1948-1977 calculated from La Guardia Airport visibility observations and city-wide annual average total suspended particulate (TSP) and sulfur dioxide (SO2)concentrations for 1968-1977.
SUMMER OAYLIOMT MEMAN VISIBILITY AV.vCi. TSP AND SO0 AND NUMBER OF COOLINO DEGREE OAYS N E W YORK CITY
t . CITY WIPE AM T¶P 0 - 0 CITY WIDE AM SO1
\
1'" 1"' 50
'"r
- A W L
M M A N SUYYtR VISIIILITY
t?
lo' 0.1
Orn-o**e
L, WARDIA AI*PORT
-
P Q C W L I N O DCORCC DbYS JUNI S I W
YEAR
Figure 2. Annual median summer (June,July, August, and September)
visibility and cooling degree days for New York City for 1948-1977 calculated from La Guardia Airport visibility observations and city-wide summer (July,August, and September) average total suspended particulate (TSP) and sulfur dioxide (SO2) concentrations for 19681977.
WINTER OAYLIGWT MEDIAN VISIBILITY AVG TSP AND 502 A m NUMBER OF HEATING DEGREE OAYS NEW YORK CITY
I 48
52
I 10
I $0
I
64
1 68
I
I
72
76
'
Jo
80
YEAR
Figure 3. Annual median winter (December, January, February, and
March) visibility and heating degree days for New York City for 1948-1977 calculated from La Guardia Airport visibility observations and city-wide winter (January, February, and March) average total suspended particulate (TSP) and sulfur dioxide (Sop)concentrations for 1968-1977.
R H < 70% and lower for R H 2 70% when compared to the overall median. There were wide variations in fuel consumption for cooling and space-heating degree days for each year, so that variations in fuel consumption could be expected. However, no long-term trend in heating or cooling demand is detectable which could explain the observed seasonal visibility trends. It is apparent then that the strong trend toward improved average annual visibility between 1967 and 1977 in the New York region is due largely to improvements in winter visibility and only small recent improvements in summer visibility (1975-77). Correlations between atmospheric light scattering (bscat, measured with an integrating nephelometer equipped with a sampling inlet drier), aerosol mass components, and gaseous pollutants measured during intensive summer and winter aerosol studies are shown in Table I. The correlation coefficients between variables in Table I do not demonstrate
cause-effect relationships between variables. The correlations cannot be used to draw quantitative conclusions but can be used to formulate hypotheses. The summer data (upper portion of Table I) demonstrate a strong intercorrelation with a high significance level ( p I 0.001) between bscat, daily maximum hourly ozone (Os), and the sulfate component of the total mass (SOq2-). Lead was weakly correlated with bscat a t a low significance level ( r = 0.41,O.Ol < p 5 0.05), and vanadium and SO2 were found not to be significantly related to light scattering ( p > 0.05). In contrast, the winter data (lower portion of Table I) are marked by a strong and highly significant ( p < 0,001) intercorrelation among light scattering, SOZ, vanadium, lead, and sulfate. Analyses of light-scattering data collected during the 1 summer and winter aerosol studies in New York showed levels of dry particulate light scattering ( 10-4b,,at m-l) in winter to be 50% lower than summer values (14 ) , corresponding with the observed differences in season visibility. Regression analyses of the summer and winter light-scattering and extinction data show variations in dry particulate light scattering for summer and RH < 70%,for summer and RH 1 70%, and for winter to account for 67,56, and 58% of the variation, respectively, in light extinction (14).Light extinction (b,,t) was calculated from prevailing visibility observation at La Guardia Airport where 10-4b,,t m-l = 24.3/visibility (Koschmieder formula). The bscat(dry)/bextratio or percent of total extinction (visibility) accounted for by dry particulate light scattering was found to be 74 f 28% for summer and R H < 7070, 59 f 26% for summer and RH 1 70%,and 59 f 19%for winter ( 1 4 ) .Dry particulate light scattering was found to dominate visibility during both high and low relative humidities. Regression analysis also showed the sulfate component of the aerosol mass to explain over 65% of the variance in light scattering and light extinction in New York during both seasons (14). The strong qualitative association between the sulfate mass light scattering and light extinction during both seasons in New York is explained by the large contribution of sulfate species mass to the submicrometer mass (an average of -45% in summer and -30% in winter) (14,22,23,25)and the strong positive association between sulfate mass and the volume of aerosol in the size range (0.1-1.0 pm), which efficiently scatters light (14,22).Lead and vanadium which were found predominantly in the light scattering efficient size range (0.1-1.0 Km) were found in concentrations typically less than 1.0 pg/m3 (30, 31). Their low concentrations preclude them from contributing significantly to the total light scattering. However, as tracers of local particulate emissions from automotive (lead) and stationary oil combustion sources (vanadium) in New York (321, they may serve as indicators of the impact of these local sources on light scattering. A regression model for apportioning the relative contribution of several sources in New York City to the observed ambient TSP levels has shown that the total ambient TSP associated with automotive emissions and fuel burning is less than the sulfate levels observed for recent years (32).The gases sulfur dioxide and ozone do not directly affect light scattering but serve as proxies for sources or formation mechanisms of light-scattering aerosol. Sulfur dioxide is associated with local emission of particulates from oil combustion while maximum daily ozone concentrations may be indicative of light-scattering aerosol formation related to photochemical activity. Lower visibilities and higher levels of light scattering, ozone, and sulfate in New York City and the New York subregion during the summers of 1976 and 1977 were found to be associated more with local resultant surface-wind directions from the south, southwest, and west (the prevailing summer directions) than with winds from other directions (14,22,23,25). Categorization of sulfate concentrations measured during the summer of 1976 and 1977 New York studies according to wind Volume 15, Number 3, March 1981 307
Table 1. Correlations of bscata and Selected Air Pollutants for New York City, Summer 1976 and Winter 1977b season
summer
variables &scat
so4*03 SO2
V
winter
bscat
So42-
so2 V
Pb
0.41 (27) n n n -0.45 (27) 0.84d (20) 0.5gd(16) 0.61 (20) 0.72d (20)
so2
V
n
n n n
n n
03
0.67 (48) 0.6gd (48)
sop 0.8gd (43)
n
0.69 (20) 0.68 (16) 0.70d (20)
0.74d (51) 0.80d(41)
0.87 (44)
a is the light-scattering coefficient measured with an integrating nephelometer equipped with an inlet drier. Number of samples given in parentheses. n = not significant, p 0.05. Sod2- is the water-soluble sulfate determined from 24-h total particulate mass samples. Trace metals (Pb and V) determined from 24-h total particulate mass samples by AA. SO2 determined by West-Gaeke colorimetric method with hourly average readings averaged over 24-h periods. 0 3 determined by chemiluminescence with the maximum daily hourly concentration used. O3 data for the winter period were not available. SO?and 03 concentrations were measured at a New York State continuous-monitoring station located on Roosevelt Island in New York City -0.25 mi from aerosol sampling site. P 5 0.05. d P 0.001,
>
trajectories has shown that high sulfate concentrations seen in New York in the summer (>7.5 pg/m3 in 1976 and >15.0 pg/m3 in 1977) are associated with a strong southwesterly and westerly flow while low sulfate concentrations (55.0 pg/m3) are associated with other wind trajectories (24, 26). High concentrations of sulfates in New York during the summer are associated with southerly to westerly flow (180-292O) on the backside of a high-pressure system which had been moving slowly over major SO2 emission density areas ( 2 5 ) .Sulfates were found to be regionally distributed (23, 24, 26), and the transport of sulfate and other submicrometer aerosol during the summer into New York was found at times to be substantial (in excess of 50%) (25, 26). No significant diurnal patterns ( p I 0.05) for light scattering, visibility, or sulfates were observed in New York during the summer even during days when ozone levels exceeded 80 and 120 ppb (14, 23). Comparisons between light scattering and the volume of aerosol in four size ranges within the light scattering efficient size range, 0.1-1.0 pm, in New York has shown that the summer volume between 0.1 and 1.0 pm is more efficient in scattering light than an equal volume of aerosol in that size range in the winter (14).This is due to a skewing of the aerosol size distribution toward smaller particles in the winter (33) and suggests that the winter aerosol is fresher in nature. The findings from the summer aerosol studies listed above and the intercorrelation among light scattering, daily maximum ozone, and sulfate shown in Table I suggests that transport of an aged aerosol enhances summer light scattering and reduces visibility in New York and the New York subregion, This aging has taken par$ in slow-moving air masses, rich in photochemical oxidants which have passed over regions southwest and west of New York which are rich in SO,/NO, sources. The insignificant ( p > 0.05) or low significance and low correlation (0.01 < p 5 0.05 and r = 0.4) between light scattering, SOz, vanadium, and lead in the summer (Table I) suggests that pollutant emissions from local stationary and mobile sources may contribute less to levels of light scattering and reduced visibility in New York during the summer than transported aerosol. Analysis of data collected during winter aerosol studies in New York and the New York subregion has shown light scattering and sulfate not to be dependent on wind direction (14, 22). There was a pronounced shift noted in the winter aerosol toward particles in the lower size within the 0.1-1.0-pm size range ( 3 3 ) ,resulting in a less efficient light-scattering volume of aerosol in the winter compared to the summer (14). The above, with the intercorrelations among bscat,sulfate, SOz, vanadium, and lead for the winter shown in Table I, suggests 308
Environmental Science & Technology
that the major source of light-scattering aerosol in the winter in New York and the New York subregion may well be pollutant emissions from local stationary and mobile sources, rather than the transport of aerosol into the region. The results noted above of the light-scattering measurements from the winter and summer aerosol studies in New York suggest an explanation for the visibility trends that are displayed in Figures 2 and 3. On the one hand, summer visibility degradation in the New York region is largely related to the efficient light-scattering fine particulate mass transported into the region, and to a lesser degree to local precursor and fine particulate emissions. On the other hand, winter visibility degradation may be largely related to the local precursor and fine particulate emissions and may be to a much smaller degree due to aerosols transported into the region. The differences in seasonal meterology play a controlling role in these relationships. During the summer and early fall the Northeast typically experiences high-pressure systems in which the overall motion of the air mass is slow, the skies are clear (high isolation), inversions are common, dispersion (mixing height X wind speed) is poor, and there is relatively little precipitation. These air masses have typically passed over high SO,/NO, emission density areas west and southwest of the New York region. Such weather systems favor the accumulation and transport of sulfate aerosol, other visibilityreducing fine particulates, and gaseous pollutants (particularly ozone) and have been shown to be associated with the evolution and transport of regional-scale hazy air masses (24, 26, 34-39). While local emissions of pollutants in the New York region do effect local summer visibility, their major impact may be felt downwind of New York. In contrast, the winter, late fall, and early spring weather systems in the Northeast typically do not favor the accumulation and transport of visibility-reducing aerosols because they move rapidly, are often cloudy (causing reduced solar radiation), are greater in dispersion capabilities, and include increased precipitation. The findings of this study could be used in developing strategies for control of visibility reduction and of pollutant concentrations. Control of local emissions of SOz, NO,, and other reactant gases or fine particulates in the New York region would not be expected to have a major impact on local summer visibility if, as it appears from the data discussed here, transport of fine particulates plays the dominant role. Thus, further reductions in local pollutant emissions which have been achieved in the New York region since 1967 would not be expected to result in major improvements in local summer visibility. Such improvements might be achieved through
reductions in precursor emissions of reactant gases from sources upwind of the region. Such emission controls may have to focus on control of sulfate precursors, since sulfate is qualitatively strongly implicated as a major aerosol species responsible for reducing visibility. This study should not be taken to suggest abandonment of summer control in the New York region since reductions in summer emissions in New York presumably benefit areas downwind of New York. The dramatic improvements in visibility since 1967 in the New York region during the winter coincide with reductions in emissions of local pollutants and ambient levels of SO2 and TSP. Control of local emissions would be expected to be more effective in improving winter visibility since the data suggest that winter visibility is related to local emissions with aerosol transport being minimal. If visibility improvement or protection becomes a goal in future pollutant control efforts in the Northeast, then there is a clear need to conduct additional aerosol sampling studies in the New York region to provide a more extensive data base which would allow for a more detailed examination of the seasonal relationship between visibility and fine particulates from local sources and those transported into the region. Of particular need is more detailed information on the chemical composition and mass size distribution of the submicrometer aerosol and its relation to visibility and light scattering. Measurements of the contribution of aerosol absorption to total extinction (visibility) and its relation to the chemical composition and size distribution of the fine aerosol are needed as is the examination of the role of water vapor in affecting visibility. The importance of light absorption in visibility reduction prior to 1968, when coal was burned, needs to be examined. A detailed examination of the relation between reductions in winter emissions of pollutants and the resulting improvements in visibility is needed so that the relationship can be better defined. Future control strategies directed toward controlling levels of fine particulates, and hence visibility, in the northeastern United States will have to consider the seasonal differences in visibility trends and their relationship to sources. The existing visibility data provide an extensive data base which would be useful in examining the effectiveness of past efforts to control levels of fine particulates and in evaluating the impact of future energy policies involving high-sulfur fuels. This readily available data base would be most useful in the areas east of the Mississippi, where 75% of the sulfur dioxide emissions in the country occur, and especially in the Northeast, which has the highest sulfate concentrations and the lowest visibilities.
Literature Cited 71) Waggoner, A. P.; Charlson, R. 3. In “Fine Particles”; Lin, B. Y. H., Ed.; Academic Press: New York, 1976. (2) Loo, B. W.; French, W. R.; Gatti, R. C.; Goulding, F. S.; Jaklevic, J. M.; Lacer, J.; Thompson, A. C. Atmos. Enuiron. 1978,12, 759. (3) Stevens, R. K.; Dzubay, T. G.; Russwurm, G.; Rickel, D. Atmos. Environ. 1978,12, 55. (4) Hidy, G. M., et al. “Characterization of Aerosols in California” (ACHEX), prepared for California Air Resources Board by Rockwell International, 1974, Vol. 1-4. (5) Macias, E. S.; Blumenthal, D. L.; Anderson, J. A.; Cantrell, B. K. Ann. N.Y. Acad. Sci. 1980,338, 233.
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Received for reuiew March 12,1980. Accepted Nouember 14,1980.
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