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The distribution and transport of airborne particulate matter and inorganic components in Great Britain
THE DISTRIBUTION AND TRANSPORT OF AIRBORNE PARTICULATE MATTER AND INORGANIC COMPONENTS IN GREAT BRITAIN ROBERT
E. LEE, JR., JIM CALDWELL,GERALD G. AKLAND and ROBERT U.S. Environmental Protection Agency, National Environmental Research Research Triangle Park, North Carolina 27711, U.S.A. (First receiord
FANKHAUSER Center.
26 June 1973 und hjinal firm 14 February 1974)
Abstract-Daily measurements of total suspended particulate matter, sulfate, nitrate, ammonium and fluoride components were made during the heating and nonheating season at 6 primary and 5 secondary sites in Great Britain. Samples were collected with high volume air samplers operating for 24-h periods. The degree of association between the inorganic components was markedly influenced by the total suspended particulate concentration. A strong relationship was found between sulfate and ammonium concentrations at the primary sites. Wind direction was the most important factor in the particulate concentration levels in Great Britain. During stagnation conditions or when the wind was predominantly from an easterly or southern direction, i.e. from the northern European continent, particulate levels were highest. However, when the wind was predominantly from a westerly direction, i.e. the Atlantic Ocean, particulate levels were lowest. A discussion of particle size and particulate transport is given.
INTRODUCTION
No individual community or country can consider itself isolated from the influence of air pollutants emitted outside its boundary area. The transport of air pollutants across broad areas is gaining increasing attention and concern, especially within international organizations such as the World Health Organization and the World Meteorological Organization. A recent example is the threat to Scandanavian forest areas from acid rainfall that originates from distant SO, emissions (Oden, 1968). Similarly, Brosset and Akerstrom (1972) found evidence of long-distance transport of black airborne particulate. One of the major difficulties in assessing the transport of pollutants is gathering a sufficient amount of reliable air quality and meteorological data over a prolonged time period. This report describes the results of an indepth air monitoring study in which daily particulate measurements were made at sites throughout Great Britain with a view toward understanding atmospheric transport of aerosols. In the first half of 1970, the U.S. Environmental Protection Agency (EPA) in cooperation with the British Ministry of Technology conducted a project to compare methods for measuring suspended particulate matter in air, Lee, Caldwell and Morgan (1972). Various sampling devices were operated for 24-h intervals over a 5-month period at six primary locations in Britain and for shorter periods at five secondary sites. As part of that study, air samples were collected on glass fiber filters with high volume samplers, Jutze and Foster (1967) at all locations for the gravimetric determination of total suspended particulate matter in air. Sufficient material was collected with the high volume samplers to also permit measurement of selected particulate components. 1095
The concentration \H,) particulatcs stations.
of soluble sullltc. nitrate. Iluoridc and ammonium (SO,. NO,,. F and ~21s determined; meteorological data wt’rc obtained from nearby
Details of the sampling locations have been published previousI>. Let, Caldwell and Morgan (1972) but arc summarized briefly hcrc. Figure I shows the sampling locations ~l‘the six prima-q sites at London. Kcw. Harlow. Manchester (Salford). Kinder and Eskdalcmuir (Scotland); samples tvcrc opcrated for 31-h periods at these sites from the end 01 .I;~IILI;II.\ 1970 until cart! .lunc 1970. Secondal-\ sitcs. also shown in Fig. I. were selected 101. :liort-term 24-h sampling at Harnslcy (21 Februar\ I I March I970), Birmingham (14 .i I March 1970). Middlesbrough (3 30 April 1970). Swansea (2X April 2 May 1970) and Lastbourne (I 8 Ma!, x June 1970).
*PRIMARY SITES lSECONDARY SITES
FRANCE
.j_",.c,-3
I ,
Meteorological data from nearby weather stations were made available by the British Meteorological Office: howevcr. the amount of detailed wind speed and wind direction information was limited at most stations. Consequently, meteorological measurements made at Heathrow Airport outside London were used with the London. Harlow and Kew air sampling measurements; meteorological mcasuremcnts made at Manchester airport \\cre used with the air sampling measurements from Snlford. Kinder and Eskdalemuir.
Airborne
particulate
1097
matter
Suspended particulate samples were collected over a 24-h period with high volume air samplers, Jutze and Foster (1967) which draw air at a rate of 1.1-1.7 m3 min- ’ (40-60 ft3 min- ‘) through a 20- x 25cm (8- x IO-in.) glass fiber filter capable of removing nearly 100 per cent of all particles 0.3 pm or greater in dia. Before and after sampling, the filters are conditioned for at least 24-h at 15-35°C and at r.h. less than 50 per cent and weighed on an analytical balance having a sensitivity of + 0. I mg. The mass concentration of suspended particulate matter in ambient air (pg mm3) is computed from the weight of particulates collected on the glass fiber filter and the volume of air sampled (average of the initial and final air flow rate multiplied by the sampling time).
A 1.9- x 20-cm (3/4- x &in.) strip of the filter (8.3 per cent) is placed in a 125-cm3 erlenmeyer flask, 50 cm3 of distilled water is added and the sample is refluxed for 30 min. After cooling, the water is decanted into a 50-cm3 graduated cylinder and the sample flask is rinsed twice with distilled water. The graduated cylinder is then filled to volume. This solution is saved for the analysis of ammonium, sulfate, nitrate and fluoride. Fluoride concentrations were determined with an Orion Specific Ion Electrode* using methods described by Thompson et al. (1971). Ammonium ion was determined using sodium phenolate and hypochlorite, Weatherburn (1967). Nitrate was reduced to nitrite by alkaline hydrazine and analyzed by diazotizing with sulfanilamide; (see A~tornatio~ irr Analytical Chemistry, 1967) all data was reported as nitrate uncorrected for trace levels of background nitrite that may have been present originally.
RESULTS
As in the previous study, Lee, Caldwell and Morgan (1972) analytical data were grouped in terms of the heating season (January-15 April) and the nonheating season (16 AprilJune) to assess the contribution from heating activities. Average concentrations of total suspended particulates (TSP) and the measured components are summarized in Table 1 for the six primary sites and in Table 2 for the five secondary sites. As pointed out in the previous study, Lee, Caldwell and Morgan (1972) unexpectedly high levels of TSP were observed at most of the primary sites during the nonheating season. For example, Table 1 and Figs. 2-7 show the weekly TSP concentrations ranged from 18 to 209 pg me3 during season. the heating season, but from 11 to 296 pg m- 3 during the nonheating Of the components measured, the largest portion was sulfate, which ranged from 14.4 to 24.3 per cent of the TSP during the heating season and from 10.3 to 26.4 per cent during the nonheating season as shown in Table 1. Throughout the 5-month sampling period, the average nitrate concentration ranged from 1.3 to 4.3 per cent, ammonium from 0.7 to 1.5 per cent and fluoride from 0.04 to 0.13 per cent. Examination of Table 1 reveals that no common pattern appears in the variation of component composition with the heating and nonheating season at all sites. For example, the average sulfate concentration was higher in the heating season at Harlow and Salford but lower at the other primary sites. Overall for the primary sites, the components measured (sulfate, nitrate, ammonium and fluoride) accounted for 17.0-28.3 per cent of the TSP concentration during the heating season and 14.3-30.6 per cent during the nonheating season. * Mention ofcommercial Protection Agency.
products
or company
names does not constitute
endorsement
by the Environmental
11.7 12.x 14.7 14.0 23 0 ‘i 7 _.
_. ’ I 2.0 ’ i
Y.5 I .: i),i I s 0.b (i-1 1..?
0 5 !,.2
0 00
0.0;
NO‘! (I.07 i).OO t1.112
The average weekly c~~~lcc~ltrat~ons of’ TSP. sulfate, nitrate and ~~n~~~~o~~~l~rn fix the six primary sampling sites are presented in Figs. It 7: lluoridc c(~ticclltr~~tiolls wcrc too tow to show ~raphicafly. In general. the average weekly concentrations of’ TSP, sulfate. nrtrate and ammonium components followed similar patterns. Sharp increases and decreases in the average weekly TSP concentrations were accompanied by corresponding increases and decreases in the other measured components at most sites. During the heating season, however. the component co~lcentratiolls at Harlow (Fig. 3) and to some extent Kinder (Fig. 6) did not follow the TSP concentrations as well as the other sites, reflecting the influence of nearby emission sources. A consistent pattern between TSP and measured components was observed at all primary sites during the nonheating season.
Barnsley Birmingham Middlesbraugh Swansea Eastbourne
Site
24 February-1 I March 14-3 I March 3-20 April 28 April-12 May 16 May-8 June
Sampling period IO 19 16 15 13
No. samples 154 132 131 90 111 1.9 1.6 2.4 2.8 3.1
1.2 1.2 1.8 3.1 2.8
NO3 Cone % of (pg mW3) total
2 s:2 12.9 6.9
12.4 11.7 10.7 11.6 1.7
SO, Cone % of (1*gmm3) total
I.0 1.3 0.5
1.0 1.3 1.2 0.6
0.8
0.8
1.3
NH, Cone % of (pgme3) total
of suspended particulate components at the secondary sites
TSP cone (pgms3)
Table 2. Average concentration
0.10 0.17 0.11 0.05 0.06
Cone (pgme3)
F
0.06 0.13 0.08 0.06 0.05
% of total
ij 3 c B
E‘
& ;. g z TI $ 2. B
Ftg. 3. Average weekly concentrations wind direction at Harlow during
oCTSP. sulfate, nitrntc and ammomum. and the prcvaitlng the heating and nonheating SCWOIIS. JanuaryJunc 1970.
Airborne particulate matter
Fig. 4. Average weekly concent~tions ofTSP, sulfate. nitrate and ammonium. and the prevailing wind direction at Kew during the heating and nonheating seasons, January-June 1970.
Fig. 5. Average weekly concentrations of TSP, sulfate, nitrate and ammonium, and the prevailing wind direction at Manchester (Salford) during the heating and nonheating seasons, January-June 1970.
1101
II02
T-T-T--T
I
I
/
T-T-l-T I7T-i-71
Fig. 7. Average weekly concelltr~tions oJ’TSP, sull:dtc, nitrate and ~~~,~,,~~,,~~~.,~nd the prcvailrng wind direction at Eskdalemuir during the heating and nonheating seasons. January June 1970.
Airborne
particulate
matter
1103
A weekly prevailing wind direction was calculated from 24-h prevailing values obtained from the Heathrow and Manchester Airport meteorological stations. A unit value was assigned to each daily wind direction; the wind direction that obtained the highest summation value was designated the weekly prevailing direction. For example, at Heathrow Airport for the week ending 21 February, the daily prevailing wind directions were W, W, S, W, SW, W and SW. Unit value assignments produced 4 for W, 2 for SW and 1 for S thereby indicating a weekly prevailing wind direction from the W. The weekly wind direction values were plotted in Figs. 2-7 and compared with the corresponding pollutant concentrations. Some judgment was occasionally required in arriving at a weekly prevailing wind direction. The worst case was for the week ending 14 February at Manchester Airport where the daily wind directions were W, W, W, N, NE, N, N thereby resulting in a N weekly designation by virtue of the NE daily value. Since it is difficult to quantitate wind direction, it should be recognized that the weekly prevailing designations represent estimates of the dominant wind direction which may be partially influenced by other wind directions during that period. A striking relationship between the prevailing weekly wind direction and the average weekly particulate concentration at the primary sampling sites can also be seen in Figs. 2-7. For the week ending 9 May, when the prevailing wind direction was from an easterly direction an unusually sharp increase was observed in the TSP concentration at the primary sites. A similar relationship was observed for the weeks ending 14 March and 18 April when the wind direction was from a southerly or northeasterly direction. Figure 1 shows that easterly or southern winds come from the direction of the European continent. On the other hand, decreases in the TSP concentrations were observed when the prevailing wind direction was from a westerly or northwesterly direction. This relationship was especially apparent in the weeks ending on 21 March, 4 April, 23 May, 30 May, 23 February, 7 March and 2 May. Westerly winds, as shown in Fig. 1 emanate from the Atlantic Ocean. DISCUSSION
Corur7tratiom
qf’measuwd
inorgar7ic ions
As can be seen from Table 1, concentrations of the water soluble inorganic ions vary markedly from site to site, with the highest concentrations occurring in London and the lowest in Scotland. With the exception of samples collected at Harlow and Salford, all measured inorganic concentrations, except fluoride which remained relatively constant, were higher during the nonheating season. In addition, the percentage inorganic fraction to the total suspended particulate concentration remained approximately the same throughout the heating and nonheating periods, as can be seen in Table 1. It should be noted that suspended sulfate constitutes a greater percentage of the sample in London, Kinder and Eskdalemuir (25 per cent) than in Kew, Harlow and Salford (15 per cent). In comparison, urban U.S. concentrations of water soluble inorganic fractions other than fluoride, based on 19661967 data (McMullen, Foaro and Morgan 1969), reveal that averages for nitrates, sulfates and ammonium are 2.4 pg m- 3, 10.1 pg m- 3 and 0.9 pg m- 3. Thus, the England sulfate concentrations appear to be somewhat higher than corresponding U.S. levels. The U.S. percentage of inorganics to the total TSP sample is approximately the same for nitrates (2.4 per cent) and ammonium (0.9 per cent), but lower for sulfate (9.9 per cent).
C’ortdutioti
uttul~5i.s
Thefol~rcomponentsmeasuredwerecornparedbycorrelatio~~analysis(Gucnther, 1965)by each site for the heating and nonheating seasons. This analytical technique was employed in an attempt to determine if the patterns associated with the collstituellt components were similar. thereby suggesting a common source. In particular, the comparison of the heating and nonheating seasons. if noticably different. would indicate the influence contributed by space heating. assuming that the meteorological paramctcrs did not change drastically. Table 3 presents the simple correlations between the four components and also TSP. It is ~vorttl~hil~ to note that the correlation bctwccn the suli’atc and ~ill~nlor~iLini ion is aiways strong~-ranging from + 0.73 for Salford during the heating scion to -t- 0.9 1 in Salford during the nonheating season. The weakest correlatiolls. in 5~~eneral. arc with the tluoridc ion. In addition. the correlations arc slightly weaker during the heating seas011 than during the nonheating season. The effect due to partial loading was determined by partial correlation analysis. Table I presents these resuits. It can be observed that p~lrt~c~ll~~teloading is definitely affecting the degree ofassociation bctwcan the ions. In general, the initial correlations tend to drop from the simple correlation value. Note that there arc 10 ( 19 per cent) negative correlations between the ions in Table 3: however. this number increases to 56 negative correlations (52 per cent) in Table 4. Ignoring the magnitude of negative correlation. this means that as one ion conce~ltr~~tion increases. the other decreases. holding the effect ciuc to particulate matter constant. It should be cmphasizcd that the strong relatiolls]liJ~ hetwccn suff:,ltes and ammonium still exist. even though in some cases the relationship is weakened by the variability in particulate loading. M~~troroloUi~al cott.sitletur iotts The most sig]liJ~cant finding in this study is the common association bt’fw~n wind direction and the conc~ntrati~~n of suspended particuJate matter and chemical components at sites widely distributed throughout Britain. This is graphically prcsentcd in Fig. X. which shows the average TSP concentration at each sampling site as a function of wind direction. At all sites. concentrations arc lowest when the wind direction is from the WUI and highest when the wind direction is from the southeast or cast. The Lllliforn~ wind direction ~lssoc~~~tiol~ is especially r~in~lrk~~~~lcwhen the Kinder and Harlow sites arc examined. As shown in Fig. I. Kinder is Iocatcd about 15 miles southeast oi‘Manchester (Salford), which can be expected to contribute a significant quantity ofparticulate matter to the Kinder atmosphere. Yet. the lowest average TSP concentration occurred when the wind direction was from the northwest, i.e. from Manchester. The highest average TSP concentration occurred in Kinder when the wind direction was from the southeast. Similarly, the TSP Icvels in Harlow should be partialJy inlluenccd by emissions from London. which is located about 20 miles to the southwest. However. the highest avcrage TSP levels in Harlow occurred when the wind direction was from the cast or the south. not from the southwest (Fig. 8). A verv similar relationship was observed by Lovelock (1972) who ti)uncl that atmospheric turbidity in southern England during 1970 and 1971 increased sharply when the wind direction was from the east, He concluded that continental Europe was the majot source of the observed aerosol. Atkins, Cox and Eggleton (1972) also observed increases in ozone concentration in Britain when the wind direction was predominantly from cast and
SOuthtxlSt.
Airborne particulate matter
Table 4. Partial
correlations
by city and by season between components Heatmg
Total period Location KC%
London
Harlow
Salford
Kinder
Scotland
Ion
SO+ I .!
NO, SO, NH,
-0.
NO, SO, NH, NO, SO, NH, NO, SO, NH, NO, SO, NH, NO, SO, NH,
- 0.39
0.57
0.29
- 0.08 -0.16
NH, - 0.30 0.54 - 0.42 0.62 0.4’) 0x3 WY 0.5x - 0.44 0.6X 0.24 0.41
F 0.37 - 0.32 ~ 0.34 0.4 I
so, 0.06
- 0.50 - 0.3.: 0.1I 0.07 - 0.07 -().I!, 0.11I -0.32 0.40 - 0.79 - 0.4 I 0.13 -0.39 -0.33
season
Nonhcatmg
NH, -0,l‘l
0.73 - O.hi
with TSP held fined
- 0.50 0.5.1
F
SO,
03) il.JS
-0.18
-0.5s
II.54 -0.37
- 0.17 0.54
NH,
0.:2 -0.33 - 0.43
0.70
-O.-II
o.si
0.64
.x7 --O.-Ii
-0.5x - 0.34 ~~~ 0. I3
-
0
(1.56
0 1.: --o.o(l - 0.0:
O.-I4 0.84
o.is -021 (L-141
- 0.00
-0.3 I - 0.45 0.14 - 0.37 -0..31
--0.3x 0.X2
0.2x
0.64 0.50
?
concentrations
of TSP (pg m -“) as :I functlotl umpling sites.
-~0.23 -0.17 --0.0x ~- o..w
KEW
Fig. X. Average
I-
--0.25
0.23
0.54
season
of wind dwcctlon
for the prtmarq
- 0.3’) -. 0.43 -0 2s -0.37 0.04 0.08 --0.10
Airborne
particulate
matter
1107
Our finding that the highest TSP levels were associated with easterly or southern winds in southern England and with southeasterly winds in the center of the island even when the greatest source of pollution appears to be in other directions requires that there be further examination of meteorological data One factor undoubtedly operating is that southerly winds are usually warmer than the surface over which they are moving. This produces a stable atmospheric condition so that pollutants which are inserted into the airstream are not mixed vertically to any great extent. The pollutants are held in the lower levels and can move great distances with much less dilution. Another factor which seemed to be important were meteorological conditions which favored transport of pollution from industrial areas of the continent. Figures 2-7 show two important periods when peak particulate levels were measured at the primary sites the week ending 14 March and the weeks ending 9 and 16 May. Examination of synoptic weather maps published by The British Meteorological Office (1970) show that between 12 and 13 March a low pressure system moved over London from a south-southwesterly direction thereby inducing an air flow from northern Europe for a period of about 30 h. A more extensive slower moving air system caused a flow of air from northern Europe to Britain during parts of the 2-week period of 2-16 May. The weather maps show that during all of the 1st week (ending 9 May) there was low pressure to the west and south of England. Most of the time the gradient over England and especially over northern Europe was weak. At noon on 4 May winds at London were 15 knots from the southeast, but were ligher and more easterly at stations over northern Europe. From then until noon of 8 May each succeeding map (6-h intervals) showed east or southeast winds over northern Europe and southern England. Most of the time the pressure gradient increased to the north of London and curved so as to cause the air moving into the London area to swing north toward Birmingham and Manchester. At noon of 8 May the elongated north-south low was west of England with a second center on the west coast of Spain. The how of TSP from the continent ended when a third low center formed north of Switzerland and the air flow was diverted from the northern coast of Europe toward the west coast of France. The pressure gradient and therefore the winds remained light so that even though northern Europe was cut off as a pollution source, the air over southern and central England probably continued to carry high concentrations of TSP. From the 10th to noon of the 13th there was a changing pattern which brought little air directly from the continent. But at noon on the 13th, there was a low west of France and another low over the Ukraine with a ridge from Italy up over the British Isles. Along this pressure ridge winds were light. During the night the stagnant area extended across Belgium and Holland into Germany. The low to the west then began to move very slowly east and generated a southeast flow from the stagnant area toward England. By evening of the 14th the wind over northern Europe was becoming more easterly which would still bring air from industrial areas to southern England. This continued into the morning of the I5th, when again the continental source of pollution was cut off. Pollution is usually dispersed in relatively short distances to become weak and unnoticeable. However, special meteorological conditions can frequently occur which channel air from an industrial source to a point quite some distance away. The period from 4-8 May lasted longer than usual resulting in high average values for the week ending the 9th. The episode which brought continental air to England during the week ending 16 May lasted for a much shorter time, but the previous history was that of almost calm conditions for
about 30 h ova- ;t highly industrialiad area. The separation 01‘the British Isles I?om the continent offers little barrier to the transport of air pollutants especially during the spring and summer seasons because the water is colder than the air. This ckerts a stabilizing atmospheric effect by cooling the lower level of the air: the resulting temperature inversion inhibits vertical dispersion.
In order to dctcrminc whether the long-distance transport ol‘ particulate mattct- from northern Europe is reasonable, it is necessary to consider the aerodynamic particle size OII ;I mass basis. Particles that have ;I Stokes equivalent diameter larger than about 20 Ltrn settle out rapidly and are probably not transported long distances. However. particles having ;I Stokes equivalent diameter near and below the submicron range approach the beha\,ior ol’gascs and can. therel’ore. be expected to be transported over greater distances b! wind currents and diffusion. As part 01‘ the previous study. Lee. C’alducll and Morgan (1972) II total oi ovctotlc hundred samples were collected at Kew. London and Eskdalemuir with cascade impactors I‘or determining the aerodynamic particle sire distribution on :I mass basis (Lee and Goranson. IO73). During the heating season, 7 I 85 per cent of’ the particulate mass was less than or equal to I pm dia.. compared to 67 79 per cent during the nonheating season. These data show that the mass 01‘suspended particulate matter in British air during this stud> was predominantly less than 1 jtrn dia.. a finding that is consistent wtth particle size n~c;tsurcnients in the I[.S. (Let. 1972). Las cotnpletc data have been coliected on the particle aia of nitrate. sultate and ;tmmonium aerosol components in the I.lnited States. These studies have shown that 6.3 to 6X per cent of nitrate components (Lee and Patterson, 1969). 65 X7 per cent of‘ ~ttllhte components. (Wagman. Let and Axt. 1967) and 70 X3 per cent 01‘ the ammonium cotnponcnls (Lee and Patterson. 1069) bq weight arc associated with particles that arc less than or qua1 to I /ml in Stokes cquivalcnt dia. No particle sire data arc available on Iluoridc comp”ll”tlts.
appears. thcr&rc. that the particlc sizes of TSP and the other aerosol components in this stud! are suflicientlq- small to account for their long-distance transport ii-on1 >ourccs outside 01’ (;rcat Britain. This finding is especially significant since sulfate and nitrate arc ttsuallk associated with combustion processes. i.c. condensation products l’ortned l?om gaseous sull‘ur oxides and nitrogen oxides. I[
tl~casut-cd
The concentration of TSP throughout Great Britain varies horn site to site: however. this stud) has shown that long-distance transport can account for a portion of’ the TSP levels. Variations in the concentration of particulate inorganic constituents appear to be site-dependent. reilecting local sources. Transport of’ TSP liom northern Europe appears to be evidenced by wind direction measurements. The levels of TSP increased sharply when the wind was predominantly rrom a11 easterly or southern direction but diminished when the wind direction was from the west, i.e. the Atlantic Ocean. This study clearly shows the value ol‘ meteorological measurements. especially of wind direction. in understanding the possible transport of particulate pollutants over long dis-
Airborne
particulate
matter
1109
tances. Further studies should be made to more clearly define the extent of TSP transport, especially in conjunction with monitoring networks established through the World Health Organization and the World Meteorological Organization. REFERENCES Atkins D. H. F., Cox R. A. and Eggleton A. E. J. (1972) Photochemical ozone and sulfuric acid aerosol formation in the atmosphere over southern England. Nuturr 235, 273-276. Automarkm in Analytical Chemistry. Technician Symposia 1966 (1967), Vol. I, pp. 534-541. Mediad Incorp., White Plains, N.Y. British Meteorological Office, The Daily Weather Report (January-June 1970), Bracknell. Berkshire, Great Britain. Brosset C. and Akerstrom A. (1972) Long distance transport of air pollutants-measurements of black air borne particulate matter (soot) and particle-borne sulphur in Sweden during the period of September-December 1969. Atmospheric Ewironmrvt 6, 661-673. Guenther W. C. (1965) Concepts in Statistical Z@rmce. McGraw-Hill, New York. Jutze G. A. and Foster K. E. (1967) Recommended standard method for sampling of fine particulate matter by filter media--High-volume sampler. J. AC Pollut. Control Ass. 17, 17-25. Lee R. E., Jr. (1972) The size of suspended particulate matter in air. Science 178, 567-575. Lee R. E., Jr., Caldwell J. S. and Morgan G. B. (1972) The evaluation of methods for measuring suspended particulates in air. Atmospheric Enuironment 6, 593-622. Lee R. E., Jr. and Goranson S. (1972) National air surveillance cascade impactor network--I. Size distribution measurements of suspended particulate matter in air. Environ. Sci. Trchnol. 6, 1019-1024. Lee R. E., Jr. and Patterson R. K. (1969) Size determination of atmospheric phosphate, nitrate, chloride and ammonium particulate in several urban areas. Afmosphrric Environment 3, 249-255. Lovelock J. E. (1972) Atmospheric turbidity and CCI,F concentrations in rural southern England and southern Ireland. Armospheric Ewirormwt 6, 9 17-925. McMullen T. B., Foaro R. B. and Morgan G. B. (1969) Profile of pollutant fractions in non-urban suspended particulate matter. Presented at the Air Pollution Control Assoc., Paper No. 69-165. Oden S. (1968) The Acid$cation of‘ Air and Precipitation and its Corwqur~e.s on the National Enuironmerlf. The State National Science Research Council, Sveavagent 166, Stockholm 23, pp. I-I 17. Thompson R. J., McMullen T. B. and Morgan G. B. (1971) Fluoride concentrations in the ambient air. _I. Air Pollur.
Control
Ass. 21, 484487.
Wagman J., Lee R. E., Jr. and Axt C. J. (1967) Influence of some atmospheric variables on the concentration and particle size distribution of sulfate in urban air. Atmosphrric Em.Gror~mer~t 1, 479-489. Weatherburn M. W. (1967) Phenaldehypochlorite reaction for determination of ammonia. Anal. Chem. 39, 971973.
E. LEE, JR., JIM CALDWELL,GERALD G. AKLAND and ROBERT U.S. Environmental Protection Agency, National Environmental Research Research Triangle Park, North Carolina 27711, U.S.A. (First receiord
FANKHAUSER Center.
26 June 1973 und hjinal firm 14 February 1974)
Abstract-Daily measurements of total suspended particulate matter, sulfate, nitrate, ammonium and fluoride components were made during the heating and nonheating season at 6 primary and 5 secondary sites in Great Britain. Samples were collected with high volume air samplers operating for 24-h periods. The degree of association between the inorganic components was markedly influenced by the total suspended particulate concentration. A strong relationship was found between sulfate and ammonium concentrations at the primary sites. Wind direction was the most important factor in the particulate concentration levels in Great Britain. During stagnation conditions or when the wind was predominantly from an easterly or southern direction, i.e. from the northern European continent, particulate levels were highest. However, when the wind was predominantly from a westerly direction, i.e. the Atlantic Ocean, particulate levels were lowest. A discussion of particle size and particulate transport is given.
INTRODUCTION
No individual community or country can consider itself isolated from the influence of air pollutants emitted outside its boundary area. The transport of air pollutants across broad areas is gaining increasing attention and concern, especially within international organizations such as the World Health Organization and the World Meteorological Organization. A recent example is the threat to Scandanavian forest areas from acid rainfall that originates from distant SO, emissions (Oden, 1968). Similarly, Brosset and Akerstrom (1972) found evidence of long-distance transport of black airborne particulate. One of the major difficulties in assessing the transport of pollutants is gathering a sufficient amount of reliable air quality and meteorological data over a prolonged time period. This report describes the results of an indepth air monitoring study in which daily particulate measurements were made at sites throughout Great Britain with a view toward understanding atmospheric transport of aerosols. In the first half of 1970, the U.S. Environmental Protection Agency (EPA) in cooperation with the British Ministry of Technology conducted a project to compare methods for measuring suspended particulate matter in air, Lee, Caldwell and Morgan (1972). Various sampling devices were operated for 24-h intervals over a 5-month period at six primary locations in Britain and for shorter periods at five secondary sites. As part of that study, air samples were collected on glass fiber filters with high volume samplers, Jutze and Foster (1967) at all locations for the gravimetric determination of total suspended particulate matter in air. Sufficient material was collected with the high volume samplers to also permit measurement of selected particulate components. 1095
The concentration \H,) particulatcs stations.
of soluble sullltc. nitrate. Iluoridc and ammonium (SO,. NO,,. F and ~21s determined; meteorological data wt’rc obtained from nearby
Details of the sampling locations have been published previousI>. Let, Caldwell and Morgan (1972) but arc summarized briefly hcrc. Figure I shows the sampling locations ~l‘the six prima-q sites at London. Kcw. Harlow. Manchester (Salford). Kinder and Eskdalcmuir (Scotland); samples tvcrc opcrated for 31-h periods at these sites from the end 01 .I;~IILI;II.\ 1970 until cart! .lunc 1970. Secondal-\ sitcs. also shown in Fig. I. were selected 101. :liort-term 24-h sampling at Harnslcy (21 Februar\ I I March I970), Birmingham (14 .i I March 1970). Middlesbrough (3 30 April 1970). Swansea (2X April 2 May 1970) and Lastbourne (I 8 Ma!, x June 1970).
*PRIMARY SITES lSECONDARY SITES
FRANCE
.j_",.c,-3
I ,
Meteorological data from nearby weather stations were made available by the British Meteorological Office: howevcr. the amount of detailed wind speed and wind direction information was limited at most stations. Consequently, meteorological measurements made at Heathrow Airport outside London were used with the London. Harlow and Kew air sampling measurements; meteorological mcasuremcnts made at Manchester airport \\cre used with the air sampling measurements from Snlford. Kinder and Eskdalemuir.
Airborne
particulate
1097
matter
Suspended particulate samples were collected over a 24-h period with high volume air samplers, Jutze and Foster (1967) which draw air at a rate of 1.1-1.7 m3 min- ’ (40-60 ft3 min- ‘) through a 20- x 25cm (8- x IO-in.) glass fiber filter capable of removing nearly 100 per cent of all particles 0.3 pm or greater in dia. Before and after sampling, the filters are conditioned for at least 24-h at 15-35°C and at r.h. less than 50 per cent and weighed on an analytical balance having a sensitivity of + 0. I mg. The mass concentration of suspended particulate matter in ambient air (pg mm3) is computed from the weight of particulates collected on the glass fiber filter and the volume of air sampled (average of the initial and final air flow rate multiplied by the sampling time).
A 1.9- x 20-cm (3/4- x &in.) strip of the filter (8.3 per cent) is placed in a 125-cm3 erlenmeyer flask, 50 cm3 of distilled water is added and the sample is refluxed for 30 min. After cooling, the water is decanted into a 50-cm3 graduated cylinder and the sample flask is rinsed twice with distilled water. The graduated cylinder is then filled to volume. This solution is saved for the analysis of ammonium, sulfate, nitrate and fluoride. Fluoride concentrations were determined with an Orion Specific Ion Electrode* using methods described by Thompson et al. (1971). Ammonium ion was determined using sodium phenolate and hypochlorite, Weatherburn (1967). Nitrate was reduced to nitrite by alkaline hydrazine and analyzed by diazotizing with sulfanilamide; (see A~tornatio~ irr Analytical Chemistry, 1967) all data was reported as nitrate uncorrected for trace levels of background nitrite that may have been present originally.
RESULTS
As in the previous study, Lee, Caldwell and Morgan (1972) analytical data were grouped in terms of the heating season (January-15 April) and the nonheating season (16 AprilJune) to assess the contribution from heating activities. Average concentrations of total suspended particulates (TSP) and the measured components are summarized in Table 1 for the six primary sites and in Table 2 for the five secondary sites. As pointed out in the previous study, Lee, Caldwell and Morgan (1972) unexpectedly high levels of TSP were observed at most of the primary sites during the nonheating season. For example, Table 1 and Figs. 2-7 show the weekly TSP concentrations ranged from 18 to 209 pg me3 during season. the heating season, but from 11 to 296 pg m- 3 during the nonheating Of the components measured, the largest portion was sulfate, which ranged from 14.4 to 24.3 per cent of the TSP during the heating season and from 10.3 to 26.4 per cent during the nonheating season as shown in Table 1. Throughout the 5-month sampling period, the average nitrate concentration ranged from 1.3 to 4.3 per cent, ammonium from 0.7 to 1.5 per cent and fluoride from 0.04 to 0.13 per cent. Examination of Table 1 reveals that no common pattern appears in the variation of component composition with the heating and nonheating season at all sites. For example, the average sulfate concentration was higher in the heating season at Harlow and Salford but lower at the other primary sites. Overall for the primary sites, the components measured (sulfate, nitrate, ammonium and fluoride) accounted for 17.0-28.3 per cent of the TSP concentration during the heating season and 14.3-30.6 per cent during the nonheating season. * Mention ofcommercial Protection Agency.
products
or company
names does not constitute
endorsement
by the Environmental
11.7 12.x 14.7 14.0 23 0 ‘i 7 _.
_. ’ I 2.0 ’ i
Y.5 I .: i),i I s 0.b (i-1 1..?
0 5 !,.2
0 00
0.0;
NO‘! (I.07 i).OO t1.112
The average weekly c~~~lcc~ltrat~ons of’ TSP. sulfate, nitrate and ~~n~~~~o~~~l~rn fix the six primary sampling sites are presented in Figs. It 7: lluoridc c(~ticclltr~~tiolls wcrc too tow to show ~raphicafly. In general. the average weekly concentrations of’ TSP, sulfate. nrtrate and ammonium components followed similar patterns. Sharp increases and decreases in the average weekly TSP concentrations were accompanied by corresponding increases and decreases in the other measured components at most sites. During the heating season, however. the component co~lcentratiolls at Harlow (Fig. 3) and to some extent Kinder (Fig. 6) did not follow the TSP concentrations as well as the other sites, reflecting the influence of nearby emission sources. A consistent pattern between TSP and measured components was observed at all primary sites during the nonheating season.
Barnsley Birmingham Middlesbraugh Swansea Eastbourne
Site
24 February-1 I March 14-3 I March 3-20 April 28 April-12 May 16 May-8 June
Sampling period IO 19 16 15 13
No. samples 154 132 131 90 111 1.9 1.6 2.4 2.8 3.1
1.2 1.2 1.8 3.1 2.8
NO3 Cone % of (pg mW3) total
2 s:2 12.9 6.9
12.4 11.7 10.7 11.6 1.7
SO, Cone % of (1*gmm3) total
I.0 1.3 0.5
1.0 1.3 1.2 0.6
0.8
0.8
1.3
NH, Cone % of (pgme3) total
of suspended particulate components at the secondary sites
TSP cone (pgms3)
Table 2. Average concentration
0.10 0.17 0.11 0.05 0.06
Cone (pgme3)
F
0.06 0.13 0.08 0.06 0.05
% of total
ij 3 c B
E‘
& ;. g z TI $ 2. B
Ftg. 3. Average weekly concentrations wind direction at Harlow during
oCTSP. sulfate, nitrntc and ammomum. and the prcvaitlng the heating and nonheating SCWOIIS. JanuaryJunc 1970.
Airborne particulate matter
Fig. 4. Average weekly concent~tions ofTSP, sulfate. nitrate and ammonium. and the prevailing wind direction at Kew during the heating and nonheating seasons, January-June 1970.
Fig. 5. Average weekly concentrations of TSP, sulfate, nitrate and ammonium, and the prevailing wind direction at Manchester (Salford) during the heating and nonheating seasons, January-June 1970.
1101
II02
T-T-T--T
I
I
/
T-T-l-T I7T-i-71
Fig. 7. Average weekly concelltr~tions oJ’TSP, sull:dtc, nitrate and ~~~,~,,~~,,~~~.,~nd the prcvailrng wind direction at Eskdalemuir during the heating and nonheating seasons. January June 1970.
Airborne
particulate
matter
1103
A weekly prevailing wind direction was calculated from 24-h prevailing values obtained from the Heathrow and Manchester Airport meteorological stations. A unit value was assigned to each daily wind direction; the wind direction that obtained the highest summation value was designated the weekly prevailing direction. For example, at Heathrow Airport for the week ending 21 February, the daily prevailing wind directions were W, W, S, W, SW, W and SW. Unit value assignments produced 4 for W, 2 for SW and 1 for S thereby indicating a weekly prevailing wind direction from the W. The weekly wind direction values were plotted in Figs. 2-7 and compared with the corresponding pollutant concentrations. Some judgment was occasionally required in arriving at a weekly prevailing wind direction. The worst case was for the week ending 14 February at Manchester Airport where the daily wind directions were W, W, W, N, NE, N, N thereby resulting in a N weekly designation by virtue of the NE daily value. Since it is difficult to quantitate wind direction, it should be recognized that the weekly prevailing designations represent estimates of the dominant wind direction which may be partially influenced by other wind directions during that period. A striking relationship between the prevailing weekly wind direction and the average weekly particulate concentration at the primary sampling sites can also be seen in Figs. 2-7. For the week ending 9 May, when the prevailing wind direction was from an easterly direction an unusually sharp increase was observed in the TSP concentration at the primary sites. A similar relationship was observed for the weeks ending 14 March and 18 April when the wind direction was from a southerly or northeasterly direction. Figure 1 shows that easterly or southern winds come from the direction of the European continent. On the other hand, decreases in the TSP concentrations were observed when the prevailing wind direction was from a westerly or northwesterly direction. This relationship was especially apparent in the weeks ending on 21 March, 4 April, 23 May, 30 May, 23 February, 7 March and 2 May. Westerly winds, as shown in Fig. 1 emanate from the Atlantic Ocean. DISCUSSION
Corur7tratiom
qf’measuwd
inorgar7ic ions
As can be seen from Table 1, concentrations of the water soluble inorganic ions vary markedly from site to site, with the highest concentrations occurring in London and the lowest in Scotland. With the exception of samples collected at Harlow and Salford, all measured inorganic concentrations, except fluoride which remained relatively constant, were higher during the nonheating season. In addition, the percentage inorganic fraction to the total suspended particulate concentration remained approximately the same throughout the heating and nonheating periods, as can be seen in Table 1. It should be noted that suspended sulfate constitutes a greater percentage of the sample in London, Kinder and Eskdalemuir (25 per cent) than in Kew, Harlow and Salford (15 per cent). In comparison, urban U.S. concentrations of water soluble inorganic fractions other than fluoride, based on 19661967 data (McMullen, Foaro and Morgan 1969), reveal that averages for nitrates, sulfates and ammonium are 2.4 pg m- 3, 10.1 pg m- 3 and 0.9 pg m- 3. Thus, the England sulfate concentrations appear to be somewhat higher than corresponding U.S. levels. The U.S. percentage of inorganics to the total TSP sample is approximately the same for nitrates (2.4 per cent) and ammonium (0.9 per cent), but lower for sulfate (9.9 per cent).
C’ortdutioti
uttul~5i.s
Thefol~rcomponentsmeasuredwerecornparedbycorrelatio~~analysis(Gucnther, 1965)by each site for the heating and nonheating seasons. This analytical technique was employed in an attempt to determine if the patterns associated with the collstituellt components were similar. thereby suggesting a common source. In particular, the comparison of the heating and nonheating seasons. if noticably different. would indicate the influence contributed by space heating. assuming that the meteorological paramctcrs did not change drastically. Table 3 presents the simple correlations between the four components and also TSP. It is ~vorttl~hil~ to note that the correlation bctwccn the suli’atc and ~ill~nlor~iLini ion is aiways strong~-ranging from + 0.73 for Salford during the heating scion to -t- 0.9 1 in Salford during the nonheating season. The weakest correlatiolls. in 5~~eneral. arc with the tluoridc ion. In addition. the correlations arc slightly weaker during the heating seas011 than during the nonheating season. The effect due to partial loading was determined by partial correlation analysis. Table I presents these resuits. It can be observed that p~lrt~c~ll~~teloading is definitely affecting the degree ofassociation bctwcan the ions. In general, the initial correlations tend to drop from the simple correlation value. Note that there arc 10 ( 19 per cent) negative correlations between the ions in Table 3: however. this number increases to 56 negative correlations (52 per cent) in Table 4. Ignoring the magnitude of negative correlation. this means that as one ion conce~ltr~~tion increases. the other decreases. holding the effect ciuc to particulate matter constant. It should be cmphasizcd that the strong relatiolls]liJ~ hetwccn suff:,ltes and ammonium still exist. even though in some cases the relationship is weakened by the variability in particulate loading. M~~troroloUi~al cott.sitletur iotts The most sig]liJ~cant finding in this study is the common association bt’fw~n wind direction and the conc~ntrati~~n of suspended particuJate matter and chemical components at sites widely distributed throughout Britain. This is graphically prcsentcd in Fig. X. which shows the average TSP concentration at each sampling site as a function of wind direction. At all sites. concentrations arc lowest when the wind direction is from the WUI and highest when the wind direction is from the southeast or cast. The Lllliforn~ wind direction ~lssoc~~~tiol~ is especially r~in~lrk~~~~lcwhen the Kinder and Harlow sites arc examined. As shown in Fig. I. Kinder is Iocatcd about 15 miles southeast oi‘Manchester (Salford), which can be expected to contribute a significant quantity ofparticulate matter to the Kinder atmosphere. Yet. the lowest average TSP concentration occurred when the wind direction was from the northwest, i.e. from Manchester. The highest average TSP concentration occurred in Kinder when the wind direction was from the southeast. Similarly, the TSP Icvels in Harlow should be partialJy inlluenccd by emissions from London. which is located about 20 miles to the southwest. However. the highest avcrage TSP levels in Harlow occurred when the wind direction was from the cast or the south. not from the southwest (Fig. 8). A verv similar relationship was observed by Lovelock (1972) who ti)uncl that atmospheric turbidity in southern England during 1970 and 1971 increased sharply when the wind direction was from the east, He concluded that continental Europe was the majot source of the observed aerosol. Atkins, Cox and Eggleton (1972) also observed increases in ozone concentration in Britain when the wind direction was predominantly from cast and
SOuthtxlSt.
Airborne particulate matter
Table 4. Partial
correlations
by city and by season between components Heatmg
Total period Location KC%
London
Harlow
Salford
Kinder
Scotland
Ion
SO+ I .!
NO, SO, NH,
-0.
NO, SO, NH, NO, SO, NH, NO, SO, NH, NO, SO, NH, NO, SO, NH,
- 0.39
0.57
0.29
- 0.08 -0.16
NH, - 0.30 0.54 - 0.42 0.62 0.4’) 0x3 WY 0.5x - 0.44 0.6X 0.24 0.41
F 0.37 - 0.32 ~ 0.34 0.4 I
so, 0.06
- 0.50 - 0.3.: 0.1I 0.07 - 0.07 -().I!, 0.11I -0.32 0.40 - 0.79 - 0.4 I 0.13 -0.39 -0.33
season
Nonhcatmg
NH, -0,l‘l
0.73 - O.hi
with TSP held fined
- 0.50 0.5.1
F
SO,
03) il.JS
-0.18
-0.5s
II.54 -0.37
- 0.17 0.54
NH,
0.:2 -0.33 - 0.43
0.70
-O.-II
o.si
0.64
.x7 --O.-Ii
-0.5x - 0.34 ~~~ 0. I3
-
0
(1.56
0 1.: --o.o(l - 0.0:
O.-I4 0.84
o.is -021 (L-141
- 0.00
-0.3 I - 0.45 0.14 - 0.37 -0..31
--0.3x 0.X2
0.2x
0.64 0.50
?
concentrations
of TSP (pg m -“) as :I functlotl umpling sites.
-~0.23 -0.17 --0.0x ~- o..w
KEW
Fig. X. Average
I-
--0.25
0.23
0.54
season
of wind dwcctlon
for the prtmarq
- 0.3’) -. 0.43 -0 2s -0.37 0.04 0.08 --0.10
Airborne
particulate
matter
1107
Our finding that the highest TSP levels were associated with easterly or southern winds in southern England and with southeasterly winds in the center of the island even when the greatest source of pollution appears to be in other directions requires that there be further examination of meteorological data One factor undoubtedly operating is that southerly winds are usually warmer than the surface over which they are moving. This produces a stable atmospheric condition so that pollutants which are inserted into the airstream are not mixed vertically to any great extent. The pollutants are held in the lower levels and can move great distances with much less dilution. Another factor which seemed to be important were meteorological conditions which favored transport of pollution from industrial areas of the continent. Figures 2-7 show two important periods when peak particulate levels were measured at the primary sites the week ending 14 March and the weeks ending 9 and 16 May. Examination of synoptic weather maps published by The British Meteorological Office (1970) show that between 12 and 13 March a low pressure system moved over London from a south-southwesterly direction thereby inducing an air flow from northern Europe for a period of about 30 h. A more extensive slower moving air system caused a flow of air from northern Europe to Britain during parts of the 2-week period of 2-16 May. The weather maps show that during all of the 1st week (ending 9 May) there was low pressure to the west and south of England. Most of the time the gradient over England and especially over northern Europe was weak. At noon on 4 May winds at London were 15 knots from the southeast, but were ligher and more easterly at stations over northern Europe. From then until noon of 8 May each succeeding map (6-h intervals) showed east or southeast winds over northern Europe and southern England. Most of the time the pressure gradient increased to the north of London and curved so as to cause the air moving into the London area to swing north toward Birmingham and Manchester. At noon of 8 May the elongated north-south low was west of England with a second center on the west coast of Spain. The how of TSP from the continent ended when a third low center formed north of Switzerland and the air flow was diverted from the northern coast of Europe toward the west coast of France. The pressure gradient and therefore the winds remained light so that even though northern Europe was cut off as a pollution source, the air over southern and central England probably continued to carry high concentrations of TSP. From the 10th to noon of the 13th there was a changing pattern which brought little air directly from the continent. But at noon on the 13th, there was a low west of France and another low over the Ukraine with a ridge from Italy up over the British Isles. Along this pressure ridge winds were light. During the night the stagnant area extended across Belgium and Holland into Germany. The low to the west then began to move very slowly east and generated a southeast flow from the stagnant area toward England. By evening of the 14th the wind over northern Europe was becoming more easterly which would still bring air from industrial areas to southern England. This continued into the morning of the I5th, when again the continental source of pollution was cut off. Pollution is usually dispersed in relatively short distances to become weak and unnoticeable. However, special meteorological conditions can frequently occur which channel air from an industrial source to a point quite some distance away. The period from 4-8 May lasted longer than usual resulting in high average values for the week ending the 9th. The episode which brought continental air to England during the week ending 16 May lasted for a much shorter time, but the previous history was that of almost calm conditions for
about 30 h ova- ;t highly industrialiad area. The separation 01‘the British Isles I?om the continent offers little barrier to the transport of air pollutants especially during the spring and summer seasons because the water is colder than the air. This ckerts a stabilizing atmospheric effect by cooling the lower level of the air: the resulting temperature inversion inhibits vertical dispersion.
In order to dctcrminc whether the long-distance transport ol‘ particulate mattct- from northern Europe is reasonable, it is necessary to consider the aerodynamic particle size OII ;I mass basis. Particles that have ;I Stokes equivalent diameter larger than about 20 Ltrn settle out rapidly and are probably not transported long distances. However. particles having ;I Stokes equivalent diameter near and below the submicron range approach the beha\,ior ol’gascs and can. therel’ore. be expected to be transported over greater distances b! wind currents and diffusion. As part 01‘ the previous study. Lee. C’alducll and Morgan (1972) II total oi ovctotlc hundred samples were collected at Kew. London and Eskdalemuir with cascade impactors I‘or determining the aerodynamic particle sire distribution on :I mass basis (Lee and Goranson. IO73). During the heating season, 7 I 85 per cent of’ the particulate mass was less than or equal to I pm dia.. compared to 67 79 per cent during the nonheating season. These data show that the mass 01‘suspended particulate matter in British air during this stud> was predominantly less than 1 jtrn dia.. a finding that is consistent wtth particle size n~c;tsurcnients in the I[.S. (Let. 1972). Las cotnpletc data have been coliected on the particle aia of nitrate. sultate and ;tmmonium aerosol components in the I.lnited States. These studies have shown that 6.3 to 6X per cent of nitrate components (Lee and Patterson, 1969). 65 X7 per cent of‘ ~ttllhte components. (Wagman. Let and Axt. 1967) and 70 X3 per cent 01‘ the ammonium cotnponcnls (Lee and Patterson. 1069) bq weight arc associated with particles that arc less than or qua1 to I /ml in Stokes cquivalcnt dia. No particle sire data arc available on Iluoridc comp”ll”tlts.
appears. thcr&rc. that the particlc sizes of TSP and the other aerosol components in this stud! are suflicientlq- small to account for their long-distance transport ii-on1 >ourccs outside 01’ (;rcat Britain. This finding is especially significant since sulfate and nitrate arc ttsuallk associated with combustion processes. i.c. condensation products l’ortned l?om gaseous sull‘ur oxides and nitrogen oxides. I[
tl~casut-cd
The concentration of TSP throughout Great Britain varies horn site to site: however. this stud) has shown that long-distance transport can account for a portion of’ the TSP levels. Variations in the concentration of particulate inorganic constituents appear to be site-dependent. reilecting local sources. Transport of’ TSP liom northern Europe appears to be evidenced by wind direction measurements. The levels of TSP increased sharply when the wind was predominantly rrom a11 easterly or southern direction but diminished when the wind direction was from the west, i.e. the Atlantic Ocean. This study clearly shows the value ol‘ meteorological measurements. especially of wind direction. in understanding the possible transport of particulate pollutants over long dis-
Airborne
particulate
matter
1109
tances. Further studies should be made to more clearly define the extent of TSP transport, especially in conjunction with monitoring networks established through the World Health Organization and the World Meteorological Organization. REFERENCES Atkins D. H. F., Cox R. A. and Eggleton A. E. J. (1972) Photochemical ozone and sulfuric acid aerosol formation in the atmosphere over southern England. Nuturr 235, 273-276. Automarkm in Analytical Chemistry. Technician Symposia 1966 (1967), Vol. I, pp. 534-541. Mediad Incorp., White Plains, N.Y. British Meteorological Office, The Daily Weather Report (January-June 1970), Bracknell. Berkshire, Great Britain. Brosset C. and Akerstrom A. (1972) Long distance transport of air pollutants-measurements of black air borne particulate matter (soot) and particle-borne sulphur in Sweden during the period of September-December 1969. Atmospheric Ewironmrvt 6, 661-673. Guenther W. C. (1965) Concepts in Statistical Z@rmce. McGraw-Hill, New York. Jutze G. A. and Foster K. E. (1967) Recommended standard method for sampling of fine particulate matter by filter media--High-volume sampler. J. AC Pollut. Control Ass. 17, 17-25. Lee R. E., Jr. (1972) The size of suspended particulate matter in air. Science 178, 567-575. Lee R. E., Jr., Caldwell J. S. and Morgan G. B. (1972) The evaluation of methods for measuring suspended particulates in air. Atmospheric Enuironment 6, 593-622. Lee R. E., Jr. and Goranson S. (1972) National air surveillance cascade impactor network--I. Size distribution measurements of suspended particulate matter in air. Environ. Sci. Trchnol. 6, 1019-1024. Lee R. E., Jr. and Patterson R. K. (1969) Size determination of atmospheric phosphate, nitrate, chloride and ammonium particulate in several urban areas. Afmosphrric Environment 3, 249-255. Lovelock J. E. (1972) Atmospheric turbidity and CCI,F concentrations in rural southern England and southern Ireland. Armospheric Ewirormwt 6, 9 17-925. McMullen T. B., Foaro R. B. and Morgan G. B. (1969) Profile of pollutant fractions in non-urban suspended particulate matter. Presented at the Air Pollution Control Assoc., Paper No. 69-165. Oden S. (1968) The Acid$cation of‘ Air and Precipitation and its Corwqur~e.s on the National Enuironmerlf. The State National Science Research Council, Sveavagent 166, Stockholm 23, pp. I-I 17. Thompson R. J., McMullen T. B. and Morgan G. B. (1971) Fluoride concentrations in the ambient air. _I. Air Pollur.
Control
Ass. 21, 484487.
Wagman J., Lee R. E., Jr. and Axt C. J. (1967) Influence of some atmospheric variables on the concentration and particle size distribution of sulfate in urban air. Atmosphrric Em.Gror~mer~t 1, 479-489. Weatherburn M. W. (1967) Phenaldehypochlorite reaction for determination of ammonia. Anal. Chem. 39, 971973.