Elemental Composition of Suspended Particulate Matter in Metropolitan New York Norman L. Morrow' and Richard S. Brief Esso Research and Engineering Co., Linden, N. J. 07036
Suspended particulate matter was collected every sixth day at five stations in the New York metropolitan area for one year using high-volume samplers and Whatman no. 41 filters. These samples were analyzed by emission spectrography for calcium, lead, iron, copper, aluminum, silicon, nickel, vanadium, sodium, and magnesium. This sampling and analysis procedure has the advantage of eliminating the acid extraction step common t o methods in which glass-fiber collection media are employed, and of permitting Si, AI, and other elements present in glass to be determined without high blank corrections. In general, trends in the concentrations of the elements are not obvious, though most of the elements seem to follow approximately the same pattern over the year.
A
s part of a continuing program of environmental studies, ambient particulate matter samples were collected, using high-volume samplers, at five sites in the New York City metropolitan area. The main intent of this program was to further elucidate the elemental composition of urban particulate matter and to obtain composition data by a different analysis procedure than used in previously published work. Ambient levels for elements not heretofore reported in the New York metropolitan region were determined, including aluminum, silicon, sodium, magnesium, and calcium. N o previous report of ambient silicon concentrations could be found for any urban locale. Experimental Five high-volume samplers manufactured by the Research Appliance Co. (Model GMWLH 2000) were used to collect 24-hour samples every sixth day at the locations shown in Figure 1. These sites are in generally urban environments but are not center city and so do not reflect maximum urbanization. Four of the stations can be considered to be in partially industralized surroundings. Sample volumes were determined by a calibrated fixedorifice pressure transducer and recorder attached permanently to each unit. Volumes sampled averaged 1600 + 400 m 3 depending on filter loading and exact sampling time. Whatman no. 41 filter paper in 8 in. x 10 in. sheets was used as the filter medium. The sampler fits in an aluminum shelter which prevents direct settling of dust onto the filter. Particles must traverse a tortuous path for which the maximum theoretical size has been calculated to be 70 pm (particle specific gravity = 2). However, Whitby and Liu (1970), studying high-volume samplers, believe the upper limit of particle sizes actually collected by the high-volume sampler is 15 to 20 pm. The sample period reported here was September 21, 1969 through September 24, 1970. Nickel and vanadium were added to the list on October 3. 1969. Author to whom correspondence should be addressed. Present address: Enjay Chemical Co., Baton Rouge, La. 70821. 786 Environmental Science & Technolog,
Each 8 in. X 10 in. filter was cut in half using a specially constructed steel cutting guide to ensure reproducibility. One half was placed in a tared platinum dish, moistened with H 2 S 0 4(to prevent loss of Pb) and ashed at 1000° F. The weight of ash was obtained and the ash was then blended with LizB,Oi and fused at 1000° C. The resulting solid solution was ground, sieved, mixed with graphite, and pressed into a pellet. The pellet was excited in the low inductance spark discharge of an Applied Research Laboratories' Quantometer. The intensity of the emission line characteristic of each element was measured photometrically. Calibration curves were prepared by carrying out this procedure for synthetic mixtures prepared from the C.P. oxides or other suitable salts. Randomly chosen samples were run in duplicate. N o significant inconsistencies were found. From knowledge of the volume of air sampled and the weight and the composition of the ash, the ambient concentrations of the various constituents were calculated. Data were handled by computer (Univac 1108) using standard statistical procedures (STAT-PACK). Arithmetic and geometric means were calculated and 95 confidence intervals were determined assuming the data are log normally distributed, which is common practice when analyzing air pollution data. Results which fell below the lowest calibration point for an element were not included in the averages. Only for two days of Ni data did all five stations yield undetermined values. Five point moving averages were calculated for each element by taking the first five daily averages, fitting a second order polynomial to them by least squares, and using the polynomial to determine the smoothed value for the average in the middle of the range. This operation was then repeated after dropping the first daily average and including the sixth, and so on until the entire set of averages was treated. The two missing daily averages for Ni were filled by interpolation of the neighboring values. Following the example of Spirtas and Levin (1970), an attempt was made to assess trends in the data by application of Whittaker-Henderson smoothing techniques (Miller,
&=
BROCK-YN
Figure 1. Sampling locations
1946; Henderson, 1924). Due to the large variations in the data and the relatively short time span studied no conclusions could be drawn from this effort.
:::I\
Results and Discussion
1.8
The mean ambient concentrations of the ten elements measured are shown in Table I. The mean value for nickel of 0.18 pg/m3 was based o n discarding all values which were below the lowest spectrographic calibration point. About 15% of the nickel data fell into this category. If these data were handled differently, a slightly different mean would result. For example, if the discarded data were considered equal to the Concentration of the lowest calibration point the mean would be unchanged, while if all of the discarded data were set equal to zero, the mean value would be reduced to 0.16 pg/m3. The indicated approach was considered best. About 6 % of the vanadium data was below the lowest calibration point. As with the nickel data these values were discarded for computation purposes. If they had been included at the concentration of the lowest calibration point the mean would remain the same at 0.17 pg/m3. If they had been included as zero the mean would drop to 0.16 pgim3. All of the other data for the various elements were above the lowest calibration points, so this aspect of the data handling was restricted to nickel and vanadium only. Table I1 compares the arithmetic means found in this work with previously published data for the New York area. The data of Kneip et al. (1970) and the National Air Sampling Network (NASN)(USDHEW, 1966) were obtained with highvolume samplers using glass-fiber filter media (though the samplers used by the former were not of standard design). Kneip et al. conducted their analyses by ashing, acid extraction, and atomic absorption. NASN used a similar preparation but employed an emission spectrographic analysis step. In both cases the desire to obtain total particulate weight makes use of glass-fiber paper mandatory. This, in turn, makes the extraction procedure necessary. To simplify sample handling and because it was not clear how interference-free the extraction is, particularly for the determination of elements present in glass (e.g., Al, Na, and Si), ashless paper was used in this study. No particulate weight measurements were made. In order to evaluate the data it is necessary to have an understanding of the wind patterns of the area. General wind patterns for metropolitan New York are from the westerly directions. Thus at the station located in Linden, N. J. (the only one for which detailed meteorological data are available) the wind comes from the west, northwest or southwest over 50
Element Ca Pb Fe
cu
A1 Si Na Mg Ni V
No. of samples 263 290 283 263 295 296 262 295 259 270
Mean (ws/m3) 1.17 1.37 2.98 0.29 2.04 4.84 1 .os 0.49 0.18 0.17
II
1
-I
0.8 '.Ol
U
0.6 "
0.4
I
' '
I
"
!
"
' '
! ' ' 1
"
I
"
1
"
0.35 m- 0.305 0.25 0.20
' '
!" !
'
"
R
0.45 0.40
u
!
-
0.10 -
0.15
0.05 515 25 I5 25 I5 25 I5 25 515 25 5L525 I525 51525515 25 515 25 I5 25 515 2551525 5 5 5 5 SEPT OCT NOV. DEC. JAN. FEB. MAR APR MAY JUNE JULY AUG. SEPT. 1969 1970
Figure 2. Five point moving averages for Cu and P b of the time. Therefore, emissions from center-city elevated sources would not be expected to be major factors in locations west of the city, where four of our five sampling sites are located. This effect is reflected in our five-station network in that the average vanadium concentration found at our Bronx station was significantly higher than the network averagc Figures 2 to 5 show five point running averages for each element. They reflect the extreme variations found from week to week, but they still suggest some trends. The dotted lines in the Ni data represent two days for which averages were not obtained due to analytical difficulties. The mean copper concentration is higher than that found in both previous studies. Interestingly, the copper level follows the same pattern as found by Kneip et al. That is, the copper concentration is high in the summer and low in the winter. Since the primary source of copper is industrial emissions it is difficult to explain the variation with the seasons, though it does explain the elevated mean concentration because most of the sampling stations are in industrial areas. The mean value for lead is appreciably lower than that reported by Kneip et al. Extensive experience with, and testing of, the sulfated ashing procedure used here indicates that
Table I. Ambient Concentrations Arithmetic Standard 9 7 7 s Mean deviation dence limits (~g/m~) 0.53 0.14-2.21 1.06 0.86 0-3.06 1.13 1.32 0.39-5.58 2.71 0.63 0-1.51 0.20 0.96 0.15-3.92 1.84 2.35 0,23-9.46 4.25 0.66 0-2.38 0.91 0.21 0.07-0.91 0.44 0.09 0-0,36 0.16 0.09 0-0.35 0.15
Geometric Standard deviation 1.58 1.88 1.56 2.23 1.59 1.80 1.84 1.57 1.69 1.71
-
95% Confi-
dence limits 0.43-2 60 0.33-3.90 1 .14-6.46 0.04-1 96 0,74-4,53 1.35-13.40 0,28-2.99 0.18-1.08 0.06-0,44 0,05-0.43
Volume 5, Number 9, September 1971 787
Table 11. Comparative Data-Metropolitan New York Arithmetic Mean Values, pg/m3 Kneip et al. (1970)
a
USDHEW-NASN
Element
This work
Bronx
Manhattan
Tuxedo
Lead Iron Copper Nickel Vanadium
1.37 2.98 0.29 0.18 0.17
3.82
2.99
0.41
1 . 9
0.21 0.16 1.19
1.7 0.11 0.140 0.442
0.13 0.15 1.46
0.21 0.16 1.19
N.Y.C. (1962-1963)
These values are believed to be low due to losses during the high temperature ashing step in the analysis procedure
losses of lead by volatilization d o not occur. The extreme dependence of ambient lead concentrations on local environment is well known (Colucci and Begeman, 1969; Daines et ai., 1970; Working Group on Lead Contamination, 1965) and so this discrepancy is not completely unexpected. The mean vanadium concentration found in this work agrees with the mean value reported by NASN for Newark, N. J., though the vanadium concentrations found in the center of New York City are significantly higher than these values. This is understandable when the sources of vanadium and wind patterns are considered. In addition to that used in power plants, vanadium-containing residual fuel is widely used in apartment houses and office buildings in New York City. As a result, high stack emissions, characteristic of power
(1966) Newark (1964) 1.2. 1.3 0.16 0.093 0.187
(USDHEW,
1968).
plants, are not the major factor in localized vanadium levels. Gases and particulates from fuel oil combustion are released from the apartment houses and office buildings near rooftop level and are grossly influenced by the building itself. As a result, these emissions are not widely dispersed, and local, center-city vanadium concentrations would be expected to be high. Since winter and summer fuel consumption by tall stack sources in New York is similar, no large peak in the vanadium concentration would be seen in noncentral locations. The mean value for nickel is similar to those found in both previous studies. The small increase in this mean compared to the previous work is explainable in terms of the same industrial contributions as found for Cu. These emissions increase the nickel concentration over the level associated with the burning of coal, which is the primary center-city source, and our results reflect the sum of both of these sources. Iron concentrations are higher than reported by NASN for New York, but are consistent with values reported in other urban centers (Brar et ai., 1969; Lee et ai., 1968). On inspection of the moving averages for Fe and Ni, it becomes apparent that, with the exception of one peak in late February, there is good correspondence between the plots. In particular, the maximums in both cases occur in early May and are about twice their respective means. This correspondence lends strong credence to the idea that the dominant source of both metals is the same. No previous data on calcium, aluminum, silicon, magnesium, and sodium for the New York area could be found. Furthermore, no data on ambient concentrations of silicon could be found for any urban location. We believe the lack of data on this prevalent element is attributable to the widely used sampling scheme involving glass-fiber filters. 0.30 As would be expected the Ca, AI, Si, and Mg concentrations correlate with each other. This supports the contention that even at our relatively urban sampling locations these elements are mineralogical in origin. The relative proportions of the elements Si, AI, Ca, and Mg (10:4:2:1) agree surprisingly well with the relative proportions of these elements in the total lithosphere (13:4:1,5:1). In the atmosphere, as in the total lithosphere, silicon retains its position as second most abundant element (after oxygen). 0.32 Except for sodium all of the moving average plots show Pl R roughly similar patterns. On high pollution days all the elements tend to have high concentrations and conversely on low pollution days the reverse is true. For example, during the Christmas-New Year week, low levels of all pollutants were experienced. On the other hand in late February 1970 515 25~1525j1525j1525 ;I5 25 $2541525 ;I5 2 5 ~ 1 5 2 5 ~ 1 5 ~ ~ 1 5 2 5 ~ 1 5 2 5 ~ l 5 2 5high levels were observed. From the trends of the running averages we conclude that the concentrations of the various eleSEPT OCT NOV. DEC. JAN. F E R . MAR. APR. MAY JUNE JULY AUG.SEPT 1969 1970 ments studied depend primarily on meteorological conditions. Sodium occurs in the New York area as ocean-generated Figure 3. Five point moving averages for Fe, Ni, and V
788
/-
1
t
i
Environmental Science & Technology
.-
l.7 I,$?
e 1.1 P
3
s
0.8
---
0.7
-
0.7
1
1.0
0.9
0.2
8,01 70
/I
1
'
-
"I
Y
1
0. I 515 2 5 ; ~25 515 s i 1 5 25; I5 25 ;I5 25; I5 25 A15 25 515 25 515 E 5 I 5 25 515 25 5 E 25
4
4
v,
-1
301
SEPT. OCT. NOV. DEC. JAN, FEB. MAR, APR MAY JUNE JULY AUG SEPT.
1969
1970
1525615 25515 25 51525515 25 51525515 25 515Z551525515 26515 2551525 515 25
NaCl aerosol. This is reflected by the relatively high sodium concentration found here, 1.08 pg/m3, as compared, for example, t o the 0.31 pg!m3 found by Brar ef a/. in Chicago. It is the different nature of the Na source and its different location relative to New York that results in the unique behavior of this element compared to the others studied. The high winter N a concentrations are readily explainable in terms of the greatly increased NaCl aerosol generation from ocean sources during these months, the action of high winds, and increased atmospheric turbulence. Acknowledgtnent
We expres'i our appreciation to C. R. Hodgkins for the emission spectrographic analysis and to William Reilly for collecting thl: samples and maintaining the samplers.
"i 1.4
1.2
0.8
'
3 0.6 0.4
I ' 'I
0+ 2 -,l
"
!
'
'
!
"
~
"
I-, ' !
"
I
'
i 1
5 1525515255 152551525515 25515 %I525 5 1 5 2 5 5 I 5 2 5 5 1 5 2 5 5 E 25515 25 515 25 SEPT O C T NOV. DEC. JAN. FEB. MAR, APR MAY JUNE JULY AUG. SEPT
1969
1,
20
Figure 4. Five point moving averages for Ca, Mg, Si, AI
1970
Figure 5. Five point moving averages for Na
SEPT OCT NOV DEC
1969
J A N FEB MAR APR
MAY JUNE JULY AUG SEPT.
1970
Literature Cited
Brar, S. J., Nelson, D. M., Kanabrocki, E. L., Moore, C. E., Burnham, C. D., Hattori, D. M., "Modern Trends in Activation Analysis," Proceedings of the 1968 International Conference, Gaithersburg, Md., 1969, p 43. Colucci. J. M.. Begeman. C. R . . J . Air Pollut. Contr. Ass. 19. 225 (1969). Daines, R. H., Motto, H . , Chilko, D . M., ENVIRON. SCI. TECHNOL. 4. 318 (1970). Henderson, K., Aciuurial SOC.Amer. 25, 29 (1924); 25, 292 (1924). Kneip, T. J., Eisenbud, M . , Strehlow, C . D., Freudenthal, P . C., J . Air Pollut. Contr. Ass. 20, 144 (1970). Lee, R . E., Jr., Patterson, R. K., Wagman, ENVIRON. Scr. TECHNOL. 2,288 (1968). Miller, M. D., "Elements of Graduation," Actuarial Society of America, Philadelphia, Pa., 1946. Spirtas, R., Levin, H. J., "Characteristics of Particulate Patterns, 1957-1966," NAPCA Publ. AP-61, 1970. U. S. Department of Health, Education and Welfare, Public Health Service, "Air Quality Data from the National Air Sampling Neworks and Contributing State and Local Networks, 1964-1965," Washington, D.C., 1966. U. S. Department of Health, Education and Welfare, Public Health Service, "Air Quality Data from the National Air Sampling Networks and Contributing State and Local Networks, 1966," Washington, D.C.,1968. Whitby, K . T., Liu, B. Y., presented at 11th Conference on Methods in Air Pollution and Industrial Hygiene Studies, Berkeley, Calif., April 1, 1970. Working Group on Lead Contamination, "Survey of Lead in the Urban Atmosphere of Three Urban Communities," Public Health Service Publication 999-AP-12,1965. Receiced for reciew July 9 , 1970. Accepted Februury 16, 1971. Volume 5, Number 9, September 1971 789
