- Email: [email protected]
The monitoring of inhalable lead particles emitted from vehicles at different atmospheric stability classes
248
Aerosols m science, medicine and technolog? REFERENCES
NIOSH Air Saraptin 0 Instruments lor Evaluation ot .4tmospherlt Contaminants, 5th ed. Nozaki, K. (1979) Ind. HIth 21. Willeke, K. (1980) Generation of Aerosols and Facilities ]or E,:posure Experiments. Ann Arbor Science Z88 Committee for Respiratory Protection (1981) American National Standards Institute, Report, 8 Ju!) 19SI,
THE
MONITORING OF INHALABLE LEAD PARTICLES EMITTED FROM VEHICLES AT DIFFERENT ATMOSPHERIC STABILITY CLASSES M. S. EL-SHOBOKSHY Mech. Eng., Dept., College of Engineering, King Saud University, Rivadh P.O. Box 800, Saudi Arabia
Almtraet--Measurements were made of the concentrations of airborne lead particles emitted from road vehicles beside the building of the Mechanica! Engim)ering Department, King Saud University. The measurements were based on the EPA's recommendations, upon which the concentrations in two size ranges, namely; 2.5-15 #m (coarse particles) and less than 2.5 ~m (fine particlcs), were found. The concentrations were measured by means of the automatic dichotomous sampler and by virtue of their inertia, particles were separated into the two ranges of interest and theo collected on 37 mm glass fiber filters. The concentrations of the inhalable suspended particles were rneasured by means of nine ~ each over one hour period starting from 7.0 a.m. to 4.0 p.m. (The bulk of the working day.) The tiitm w m weighed hefore and after sarapling to obtain the particulate concentrations in the two size ranges. The lead in thefilters was measured by atomic absorption spectroscopy and t he concentration of the lead particulate in the two size ranges were then found. The meteorological data over the samplingpcriod were recorded by means of Texas Electronic Meteorological instrumentations and the atmospheric stability class were determined during each measuring hour. For the average traffic loading it has been found that the lead concentration is about 25 ?.0less when the atmosphere is unstable that for slightly unstable. Coarse lead particles (2.5-15/am) were increased four times due to the increase in the atmospheric unstability at the measuring location which was 4 m above the road level.
INTRODUCTION The Ix:baviour o f the penetrated aerosol particles to the respiratory system remains an area meriting major study for a variety o f reasons. Since 1971, analysis o f health studies and particle composition have shown that particles less than 15 #m (inhalable particles) can penetrate to the tracheobronchial and alveolar regions o f the lung. The health hazard of;particulates may be physical, from the clogging o f the lung sacs by the particles, a chemical from reactions of the body to very small substances that can pass through the lung membranes into the blood and thence to Other body organs. O f these hazards are the lead particles that pass efficiently to the blood streams. It has been shown (Nelson, 1981) that the body burden o f children as measured by blood lead has turned out to be a close tracer of the average level o f lead in the air o f some o f urban areas, where it followed faithfully the general decline in air conc, ntrations oflcad as the lead in gasoline was reduced. In December, 1977 a report was issued (EPA, 1977)by the American government, in which 92 scientists review critically over 1000 research papers about airborne lead from motor vehicles, and the firm conclusion is that airborne lead from motor vehicles does represent a danger to health, particularly for occupationally..expom,~d groups, pregnant women and pre-school children. The lead Content in most of the C o m m o n Market countries is now about 0,40-0,45 g/I, while in Germany is rather less, (0.15 g/l), In Saudi Arabia the lead content is fairly high at 0.57 4- 0.03 g/hr. More than 80 "o of the gasoline vehicles in Saudi Arabiaare of 2000 cm a engine capacity and greater. It may be anticipated that lead represents one of the principal hazardous pollutants in the atmospheric air in this country specially in the big cities. It was shown (Little and Wiffem 1978) that lead particles emitted from gasoline vehicles are in the range of 0.1-5.0/~m diameter. It was inferred that cars driven at normal speeds emit aerosols mainly in the nuclei mode (0.018 #m G.M. dia.). Coagulation within these aerosols and coagulation with other aerosols transfers the particles to the accumulation mode (4.9 #m). In the present work the concentration o f lead aerosol in the atmospheric air has been monitored during the time of working days. The atmospheric stability during the measurements was varying and the effect of this upon the concentration was observed.
EXPERIMENTAL The lead concentration measurements were made at a level of 4 m above the ground at the entrance of the Co!lege o f Engineering, King Saud University, The entrance lies on a road 20 m width. A previous statistical measurements showed that about 350-4(~cars per hour pass through this road with a peak of about 600/hrl All experimental work was carried out under dry weather conditions. The meteorological instrumentations (Texas Electronic) were fixed on the top o f the College at a height of 28 m. An automatic dichotomous sampler was used for measuring the particulate concentration. This is a programmable sampler that can be adjusted to take samples at any selected times and during predetermined periods. The sampler separates particles into two distinct size fractions; from 2.5 to 15 ,um (coarse) and less than 2,5/~m (fine), (Fig. 59) and all are collected on membrane filters: The sampler was adjusted to take a sample every hour, with a sample period o f one hour, and about 1.5 min was taken for the filter tray to move between each sample, The filter
The Tenth A n n u a l Conference of the Association for Aerosol Research
249
Inl, tube Inlet
__. Fine p a r t l c l e s ~ ~ - - , ~
Nozzle N C, Col lecfion
!liP'probe
Coarse
@ li:J-ql<~ -L--:~- c particle II IIv'~ I~~. _ ~ l tCoarse I ~ ,~ J ~ - - ~ e r
Fine particles I I fi,ter
~
,~ Filter holder ~ - - Plunger
Totati carousel
]~
-i T
.9
0.1
cm/hr 7.5
m
cm/hr tubing
to control
module
Fig. 59. Principles of the dichotomous dust sample.
elements were weighed before and after sampling using a precision micro-balance, with a m i n i m u m measurable mass of I/~g, therefore the mass of dust collected on each filter was determined. The air flow rates through each filter were adjusted and recorded on a circular chart flow event recorder. K n o w i n g the collected mass and the air rate, the particulate concentrations were determined. During the day the sky conditions (clearness and cloud) were recorded during every hour. This was to help in determining the stability class of the atmosphere during each hour of the experiment. The filters were then taken to the laboratory a n d the deposited particulates were dissolved using a routine program for dissolving all the expected trace elements in the atmospheric air in Riyadh such as Pb, N a * , Si + and K + . An atomic absorption unit was then used to determine the concentration of each trace element and only the lead concentrations were worked out and presented in this paper.
RESULTS AND DISCUSSION The concentrations of the total suspended particles (TSP) were measured into two fractions 2.5-15 # m and less than 2.5 #m. The percentages o f lead particles in each size range were found by means o f the atomic absorption (AA) analysis. Series o f measurements were performed, and two results are presented here. These results are for two days in which the traffic loadings were nearly the same, this implies similar average exhaust emissions. Figures 60(a) and (b) show the variation o f lead concentration with time during the day o f I March 1982 and 2 April 1982. Figure 61 shows the wind speed in these days as recorded by the meteorological instrumentations. It can be seen that the prevailing wind speed during these days varies significantly. This provides a good comparison to test the effect of atmospheric stability on the concentration o f lead. It has to be mentioned that the mean wind direction is about the same, also in these days which were north-east. K n o w i n g the wind speed and based on the cloud content in the sky, the atmospheric stability classes were found during every hour by using the flow chart of atmospheric stability class determination which is shown in Fig. 62. By comparison of Figs 60(a) and (b) it can be shown that in March measurements the mean wind speed is 5 m/sec (arithmetic average), and about 77.8 oo of the working day, the atmosphere was unstable and 22.2 oo slightly unstable. O n the other day (2 April), the mean wind speed was 3.4 m/sec and 11 oo of the working day was unstable 22.2 oo neutral and 66.7 °0 was slightly unstable. The average total lead concentration in the first day was 4.37 g/m 3 while for the other day it was 5.83 g/m a . This means that due to the increase in the atmospheric unstability the lead particulates have been dispersed, consequently the concentrations were reduced by about 25°~. O n the other hand, the concentration of the coarse particles were increased in the unstable atmosphere. This was due to the strong mixing of the air in this atmosphere which rises the coarse particles in larger a m o u n t than that in a more stable atmosphere, and were sampled at a level of 4 m above the road. The coarse particles (2.5-15 itm) showed an increase of about four times in the unstable atmosphere than that in the stable one.
250
A e r o s o l s m science, medicine a n d technolog>
~
6.0
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5.o
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4,0~3.0
:::::::::I
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12
pm
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! Time of day
]
I Morct~
I982
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1.78
2.0
1.78
4.48
8.2
C
8
C
B
B
6.7 i 6.7
B i
6.7
5.8
Prevailing wincl speed,m/sec
8
B
Atmospheric stabihty class
B
8.0
8_
7.0!:i:i:i:
f,
6.0-::i!i:::::::: ::'.:':::
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.v.v. •
,:
2c-l iiiiii:
v.v.'. v.v,'.
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particles< 2,5 #m
(b)
~:":":!
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Coarse particles 2.5-15 ,~.m
~Fine
iJilt
v.v.'.
.:.:.:.:
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8
~'~
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H
pm 2
3
4 Time of day 2April 1982
1.78
1.3,
2.70
5.,58
D
O
C
C
4.47
4,0
4.0
4.25
4,47
B
C
C
C
C
Prevailing wind speea, m/sec Atmospheric stability class
Fig. 60. Variation of lead content in the atmospheric air during working days.
so
I
60
March l , 1982
I
,
I I
4o
'
~ i .t
20 E
8~
"
60
April 2, 1982
4O 2O 0 7 am
8.0
9.0
lO.O
ll.O
12.0
l.O pm 2.0
TIME OF THE DAY Fig. 61 Variauon of the wind speed during the test period.
3.0
4.0
5.0
T h e T e n t h A n n u a l C o n f e r e n c e o f the A s s o c i a t i o n f o r A e r o s o l R e s e a r c h
©
25
1 I
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o
8 g o
o m
E t'4
6
c
E
~E •~
o
7..
6
!t 7-
w
o ).-
l
252
Aerosols in science, medicine and technology CON('LI. S1ONS
It may be concluded that the dispersion of particulate materials is enhanced in the unstable atmosphere, It tins been noticed that the concentrations of the TSP were increased with the wind speed, as there are unlimited source of dust around the area. However, the concentration of lead particles decreased as the wind speed increased, h is then concluded that due to the limited source of lead particles, the wind speed and the strong mixing of the air tends to disperse the lead particles and reduce their concentration, it may also be concluded that coarser part icles may e×lst in the higher altitudes during unstable atmospheres.
REFERENCES EPA 11977) Air quality criteria for lead and other papers. United States EPA, Technical Information Center Little, P. and Wiffen, R. D. (1978) Atmos. Eat'iron. 12, 1331. Nelson, N. (198t) Commentson the implicationsfor health of the physicaland chemicalcharacteristicsof airborne particles. Proc. 9th Conf. of the Association for Aerosol Research, 23-25 September, Duisburg, Germany.
CHARACTERIZATION
OF THE PARTICULATE EMISSION OIL-FIRED POWER PLANT
BY A L A R G E
P. BACCIz, M. DEL MONTE2, A. LONGHEI'['O3, A, PIANO3, F. PRODi4, P. REDAELLI5, C. SABBIONI~ and A. VENTURAs t CRTN-ENEL, Milano; 2Istituto Geologm. UniversitA Bologna; 3lstituto Fisica; Universit/~ Torino; '*Istituto FISBAT, CNR Bologna: sCISE, Milano
Power plants are among the largest anthropogenic point sources of particulate matter. Whilst coal-fired power plant emissions are extensively studied, relativ~y limited information is available on particulate emissions from oil-fired plants. In order to fully characterize the particulate component, the exhaust of a large power plant was sampled. The oil-fired power plant examined for this study is located in the Po Valley (Northern Italy)and consists of four units with a generating eapacity of 1365 MW. Samples were collected for elemental and particle analyses at a 320 MW power unit. The stack gas temperature was 150°C and effluent velocity 3.5 m sec. In-stack samplings have been carried out by means o f an isokinetic probe and an inertial spectrometer {SPIN) in order to collect total and size fractionated samplings. Sampling time ranged from 3 rain to 1 hour. and the power load regime was held constant for each run at 130 and 280 MW respectively. The emission concentrations range from 15 to 42 mg/m 3 and from 35 to 51 mg/m 3 for electrical loads of 130 and 280 MW respectively. Aerosol mass mediandistributions, as function of particle size. present a mass median diameter (MMD) of 0.9 pm with a geometric standard deviation Iesl of 3.9 for a 130 MW generating load, and MMD 0.75 ~m with eg 4.0 for 280 MW. The values obtained agree with data reported by Cheng et al. (1976). Data on real and aerodynamic particle size provided by the intertial spectrometer (SPIN) samplings were used to calculate particle density. For particles sized 3-5 ~m the density ranges from 1.5 to 1.9 g/m 3. The elen~ntal composition of the collected particles have been determined by means of atomic absorpuon spectrophotometry (AAS) and X.ray proton irradiation technique (PIXE). Generally, the major components were Na, Mg, S and V, the minor components were AI, K, Fe, Ni, Cu, Zn and Pb. Other elements such as Cr, Mo and Cd were also found in trace amounts. A good agreement with the data reported by Henry and Knapp (1980) have been observed. The mass median diameter for each element has also been determined. Elemental size distributions show a negligible variation at different power loads. The analysed elements show different trends as a function of diameters as follows: (a) S, V and Ni show a concentration decrease with increasing particle size: (b) Fe, Al. Na, K and Pb are constant over the whole spectrum: (c) Mg, Cu and Zn exhibit non-uniform dependence of particle size. An enrichment factor. EF. relative to average composition has been calculated using the following equation: EF
[X]AFFe]A
[-qF[Fe]F where Ix] Aand Ix] F and [Fe]^ and [Fe]v represent the concentration of element x and iron in the aerosol sample (A) and fuel oil (F) respectively (Coles et al., 1979). Average EF of S and V are 8.10- ~ and 3.1 respectively. These elements exhibit a definite increase in EF on smaller particles. Scanning electron micrographs (SEM) showed a negligible degree of agglomeration of the sampled particles. We found that 80--90 ~ of the particles collected are spherical shaped with a porous surface, internal cavities and thin external walls. Observations by minerological microscope and X-ray diffractometer show that these particles are mostly constituted by amorphous carbonaceous material and only partially by graphite. In most of the samples analysed, crystals with a prismatic hexagonal habit have been observed. X-ray diffractometry performed on bulk samples and Debye-Scherrer-Gandolfi camera performed on single crystals indicate the presence of a sodium vanadate. A careful characterization of oil-fired plant should establish the importance of this source in the complex of particulate emissions and provide the source term for the study of airborne aerosols diffusion modelling. These results can also contribute to current knowledge in planning and formulating emission control strategies for oil fuel combustion.
Aerosols m science, medicine and technolog? REFERENCES
NIOSH Air Saraptin 0 Instruments lor Evaluation ot .4tmospherlt Contaminants, 5th ed. Nozaki, K. (1979) Ind. HIth 21. Willeke, K. (1980) Generation of Aerosols and Facilities ]or E,:posure Experiments. Ann Arbor Science Z88 Committee for Respiratory Protection (1981) American National Standards Institute, Report, 8 Ju!) 19SI,
THE
MONITORING OF INHALABLE LEAD PARTICLES EMITTED FROM VEHICLES AT DIFFERENT ATMOSPHERIC STABILITY CLASSES M. S. EL-SHOBOKSHY Mech. Eng., Dept., College of Engineering, King Saud University, Rivadh P.O. Box 800, Saudi Arabia
Almtraet--Measurements were made of the concentrations of airborne lead particles emitted from road vehicles beside the building of the Mechanica! Engim)ering Department, King Saud University. The measurements were based on the EPA's recommendations, upon which the concentrations in two size ranges, namely; 2.5-15 #m (coarse particles) and less than 2.5 ~m (fine particlcs), were found. The concentrations were measured by means of the automatic dichotomous sampler and by virtue of their inertia, particles were separated into the two ranges of interest and theo collected on 37 mm glass fiber filters. The concentrations of the inhalable suspended particles were rneasured by means of nine ~ each over one hour period starting from 7.0 a.m. to 4.0 p.m. (The bulk of the working day.) The tiitm w m weighed hefore and after sarapling to obtain the particulate concentrations in the two size ranges. The lead in thefilters was measured by atomic absorption spectroscopy and t he concentration of the lead particulate in the two size ranges were then found. The meteorological data over the samplingpcriod were recorded by means of Texas Electronic Meteorological instrumentations and the atmospheric stability class were determined during each measuring hour. For the average traffic loading it has been found that the lead concentration is about 25 ?.0less when the atmosphere is unstable that for slightly unstable. Coarse lead particles (2.5-15/am) were increased four times due to the increase in the atmospheric unstability at the measuring location which was 4 m above the road level.
INTRODUCTION The Ix:baviour o f the penetrated aerosol particles to the respiratory system remains an area meriting major study for a variety o f reasons. Since 1971, analysis o f health studies and particle composition have shown that particles less than 15 #m (inhalable particles) can penetrate to the tracheobronchial and alveolar regions o f the lung. The health hazard of;particulates may be physical, from the clogging o f the lung sacs by the particles, a chemical from reactions of the body to very small substances that can pass through the lung membranes into the blood and thence to Other body organs. O f these hazards are the lead particles that pass efficiently to the blood streams. It has been shown (Nelson, 1981) that the body burden o f children as measured by blood lead has turned out to be a close tracer of the average level o f lead in the air o f some o f urban areas, where it followed faithfully the general decline in air conc, ntrations oflcad as the lead in gasoline was reduced. In December, 1977 a report was issued (EPA, 1977)by the American government, in which 92 scientists review critically over 1000 research papers about airborne lead from motor vehicles, and the firm conclusion is that airborne lead from motor vehicles does represent a danger to health, particularly for occupationally..expom,~d groups, pregnant women and pre-school children. The lead Content in most of the C o m m o n Market countries is now about 0,40-0,45 g/I, while in Germany is rather less, (0.15 g/l), In Saudi Arabia the lead content is fairly high at 0.57 4- 0.03 g/hr. More than 80 "o of the gasoline vehicles in Saudi Arabiaare of 2000 cm a engine capacity and greater. It may be anticipated that lead represents one of the principal hazardous pollutants in the atmospheric air in this country specially in the big cities. It was shown (Little and Wiffem 1978) that lead particles emitted from gasoline vehicles are in the range of 0.1-5.0/~m diameter. It was inferred that cars driven at normal speeds emit aerosols mainly in the nuclei mode (0.018 #m G.M. dia.). Coagulation within these aerosols and coagulation with other aerosols transfers the particles to the accumulation mode (4.9 #m). In the present work the concentration o f lead aerosol in the atmospheric air has been monitored during the time of working days. The atmospheric stability during the measurements was varying and the effect of this upon the concentration was observed.
EXPERIMENTAL The lead concentration measurements were made at a level of 4 m above the ground at the entrance of the Co!lege o f Engineering, King Saud University, The entrance lies on a road 20 m width. A previous statistical measurements showed that about 350-4(~cars per hour pass through this road with a peak of about 600/hrl All experimental work was carried out under dry weather conditions. The meteorological instrumentations (Texas Electronic) were fixed on the top o f the College at a height of 28 m. An automatic dichotomous sampler was used for measuring the particulate concentration. This is a programmable sampler that can be adjusted to take samples at any selected times and during predetermined periods. The sampler separates particles into two distinct size fractions; from 2.5 to 15 ,um (coarse) and less than 2,5/~m (fine), (Fig. 59) and all are collected on membrane filters: The sampler was adjusted to take a sample every hour, with a sample period o f one hour, and about 1.5 min was taken for the filter tray to move between each sample, The filter
The Tenth A n n u a l Conference of the Association for Aerosol Research
249
Inl, tube Inlet
__. Fine p a r t l c l e s ~ ~ - - , ~
Nozzle N C, Col lecfion
!liP'probe
Coarse
@ li:J-ql<~ -L--:~- c particle II IIv'~ I~~. _ ~ l tCoarse I ~ ,~ J ~ - - ~ e r
Fine particles I I fi,ter
~
,~ Filter holder ~ - - Plunger
Totati carousel
]~
-i T
.9
0.1
cm/hr 7.5
m
cm/hr tubing
to control
module
Fig. 59. Principles of the dichotomous dust sample.
elements were weighed before and after sampling using a precision micro-balance, with a m i n i m u m measurable mass of I/~g, therefore the mass of dust collected on each filter was determined. The air flow rates through each filter were adjusted and recorded on a circular chart flow event recorder. K n o w i n g the collected mass and the air rate, the particulate concentrations were determined. During the day the sky conditions (clearness and cloud) were recorded during every hour. This was to help in determining the stability class of the atmosphere during each hour of the experiment. The filters were then taken to the laboratory a n d the deposited particulates were dissolved using a routine program for dissolving all the expected trace elements in the atmospheric air in Riyadh such as Pb, N a * , Si + and K + . An atomic absorption unit was then used to determine the concentration of each trace element and only the lead concentrations were worked out and presented in this paper.
RESULTS AND DISCUSSION The concentrations of the total suspended particles (TSP) were measured into two fractions 2.5-15 # m and less than 2.5 #m. The percentages o f lead particles in each size range were found by means o f the atomic absorption (AA) analysis. Series o f measurements were performed, and two results are presented here. These results are for two days in which the traffic loadings were nearly the same, this implies similar average exhaust emissions. Figures 60(a) and (b) show the variation o f lead concentration with time during the day o f I March 1982 and 2 April 1982. Figure 61 shows the wind speed in these days as recorded by the meteorological instrumentations. It can be seen that the prevailing wind speed during these days varies significantly. This provides a good comparison to test the effect of atmospheric stability on the concentration o f lead. It has to be mentioned that the mean wind direction is about the same, also in these days which were north-east. K n o w i n g the wind speed and based on the cloud content in the sky, the atmospheric stability classes were found during every hour by using the flow chart of atmospheric stability class determination which is shown in Fig. 62. By comparison of Figs 60(a) and (b) it can be shown that in March measurements the mean wind speed is 5 m/sec (arithmetic average), and about 77.8 oo of the working day, the atmosphere was unstable and 22.2 oo slightly unstable. O n the other day (2 April), the mean wind speed was 3.4 m/sec and 11 oo of the working day was unstable 22.2 oo neutral and 66.7 °0 was slightly unstable. The average total lead concentration in the first day was 4.37 g/m 3 while for the other day it was 5.83 g/m a . This means that due to the increase in the atmospheric unstability the lead particulates have been dispersed, consequently the concentrations were reduced by about 25°~. O n the other hand, the concentration of the coarse particles were increased in the unstable atmosphere. This was due to the strong mixing of the air in this atmosphere which rises the coarse particles in larger a m o u n t than that in a more stable atmosphere, and were sampled at a level of 4 m above the road. The coarse particles (2.5-15 itm) showed an increase of about four times in the unstable atmosphere than that in the stable one.
250
A e r o s o l s m science, medicine a n d technolog>
~
6.0
~
5.o
"6 ~
4,0~3.0
:::::::::I
-~~i2°"°i!i!: !i 7
(a)
i::i::ii i
am
I0
r[
12
pm
3
~
! Time of day
]
I Morct~
I982
I
1.78
2.0
1.78
4.48
8.2
C
8
C
B
B
6.7 i 6.7
B i
6.7
5.8
Prevailing wincl speed,m/sec
8
B
Atmospheric stabihty class
B
8.0
8_
7.0!:i:i:i:
f,
6.0-::i!i:::::::: ::'.:':::
i!i !!ii!i 4.o!- !:!:!:!: i:i:!:i:i: :i:i:!:i v,-.v, 3.C - , !:i:i:i: !ii!ii!!i! Eiiii! v.v.v,v.,
iiiiii!!ii.
,v.v."
!:':,X': ,.v.v.
v.v•'. v.v.', v.v.',
!)2iiiiiiii
!:i:i:i:!:~ fiii!i~:";:':': 7
9
am
I Total leadparticles
.v.v. •
,:
2c-l iiiiii:
v.v.'. v.v,'.
[
particles< 2,5 #m
(b)
~:":":!
L
Coarse particles 2.5-15 ,~.m
~Fine
iJilt
v.v.'.
.:.:.:.:
5.0-
8
~'~
:.-,••..• ,,• •.• .• ,•,,*.v.
~r~
iO
~2
H
pm 2
3
4 Time of day 2April 1982
1.78
1.3,
2.70
5.,58
D
O
C
C
4.47
4,0
4.0
4.25
4,47
B
C
C
C
C
Prevailing wind speea, m/sec Atmospheric stability class
Fig. 60. Variation of lead content in the atmospheric air during working days.
so
I
60
March l , 1982
I
,
I I
4o
'
~ i .t
20 E
8~
"
60
April 2, 1982
4O 2O 0 7 am
8.0
9.0
lO.O
ll.O
12.0
l.O pm 2.0
TIME OF THE DAY Fig. 61 Variauon of the wind speed during the test period.
3.0
4.0
5.0
T h e T e n t h A n n u a l C o n f e r e n c e o f the A s s o c i a t i o n f o r A e r o s o l R e s e a r c h
©
25
1 I
O m
o
8 g o
o m
E t'4
6
c
E
~E •~
o
7..
6
!t 7-
w
o ).-
l
252
Aerosols in science, medicine and technology CON('LI. S1ONS
It may be concluded that the dispersion of particulate materials is enhanced in the unstable atmosphere, It tins been noticed that the concentrations of the TSP were increased with the wind speed, as there are unlimited source of dust around the area. However, the concentration of lead particles decreased as the wind speed increased, h is then concluded that due to the limited source of lead particles, the wind speed and the strong mixing of the air tends to disperse the lead particles and reduce their concentration, it may also be concluded that coarser part icles may e×lst in the higher altitudes during unstable atmospheres.
REFERENCES EPA 11977) Air quality criteria for lead and other papers. United States EPA, Technical Information Center Little, P. and Wiffen, R. D. (1978) Atmos. Eat'iron. 12, 1331. Nelson, N. (198t) Commentson the implicationsfor health of the physicaland chemicalcharacteristicsof airborne particles. Proc. 9th Conf. of the Association for Aerosol Research, 23-25 September, Duisburg, Germany.
CHARACTERIZATION
OF THE PARTICULATE EMISSION OIL-FIRED POWER PLANT
BY A L A R G E
P. BACCIz, M. DEL MONTE2, A. LONGHEI'['O3, A, PIANO3, F. PRODi4, P. REDAELLI5, C. SABBIONI~ and A. VENTURAs t CRTN-ENEL, Milano; 2Istituto Geologm. UniversitA Bologna; 3lstituto Fisica; Universit/~ Torino; '*Istituto FISBAT, CNR Bologna: sCISE, Milano
Power plants are among the largest anthropogenic point sources of particulate matter. Whilst coal-fired power plant emissions are extensively studied, relativ~y limited information is available on particulate emissions from oil-fired plants. In order to fully characterize the particulate component, the exhaust of a large power plant was sampled. The oil-fired power plant examined for this study is located in the Po Valley (Northern Italy)and consists of four units with a generating eapacity of 1365 MW. Samples were collected for elemental and particle analyses at a 320 MW power unit. The stack gas temperature was 150°C and effluent velocity 3.5 m sec. In-stack samplings have been carried out by means o f an isokinetic probe and an inertial spectrometer {SPIN) in order to collect total and size fractionated samplings. Sampling time ranged from 3 rain to 1 hour. and the power load regime was held constant for each run at 130 and 280 MW respectively. The emission concentrations range from 15 to 42 mg/m 3 and from 35 to 51 mg/m 3 for electrical loads of 130 and 280 MW respectively. Aerosol mass mediandistributions, as function of particle size. present a mass median diameter (MMD) of 0.9 pm with a geometric standard deviation Iesl of 3.9 for a 130 MW generating load, and MMD 0.75 ~m with eg 4.0 for 280 MW. The values obtained agree with data reported by Cheng et al. (1976). Data on real and aerodynamic particle size provided by the intertial spectrometer (SPIN) samplings were used to calculate particle density. For particles sized 3-5 ~m the density ranges from 1.5 to 1.9 g/m 3. The elen~ntal composition of the collected particles have been determined by means of atomic absorpuon spectrophotometry (AAS) and X.ray proton irradiation technique (PIXE). Generally, the major components were Na, Mg, S and V, the minor components were AI, K, Fe, Ni, Cu, Zn and Pb. Other elements such as Cr, Mo and Cd were also found in trace amounts. A good agreement with the data reported by Henry and Knapp (1980) have been observed. The mass median diameter for each element has also been determined. Elemental size distributions show a negligible variation at different power loads. The analysed elements show different trends as a function of diameters as follows: (a) S, V and Ni show a concentration decrease with increasing particle size: (b) Fe, Al. Na, K and Pb are constant over the whole spectrum: (c) Mg, Cu and Zn exhibit non-uniform dependence of particle size. An enrichment factor. EF. relative to average composition has been calculated using the following equation: EF
[X]AFFe]A
[-qF[Fe]F where Ix] Aand Ix] F and [Fe]^ and [Fe]v represent the concentration of element x and iron in the aerosol sample (A) and fuel oil (F) respectively (Coles et al., 1979). Average EF of S and V are 8.10- ~ and 3.1 respectively. These elements exhibit a definite increase in EF on smaller particles. Scanning electron micrographs (SEM) showed a negligible degree of agglomeration of the sampled particles. We found that 80--90 ~ of the particles collected are spherical shaped with a porous surface, internal cavities and thin external walls. Observations by minerological microscope and X-ray diffractometer show that these particles are mostly constituted by amorphous carbonaceous material and only partially by graphite. In most of the samples analysed, crystals with a prismatic hexagonal habit have been observed. X-ray diffractometry performed on bulk samples and Debye-Scherrer-Gandolfi camera performed on single crystals indicate the presence of a sodium vanadate. A careful characterization of oil-fired plant should establish the importance of this source in the complex of particulate emissions and provide the source term for the study of airborne aerosols diffusion modelling. These results can also contribute to current knowledge in planning and formulating emission control strategies for oil fuel combustion.