Atmospheric Environment Vol. 24B, No. 3, pp. 413~417, 1990 0957-1272/90 $3.00+0.00 printed in Great Britain. © 1990 Pergamon Press plc

CORRELATION BETWEEN PETROL LEAD ADDITIVE CONSUMPTION AND ATMOSPHERIC LEAD

CONCENTRATIONS IN PERTH, WESTERN AUSTRALIA

B. H. O'CONNOR Department of Applied Physics, Curtin University of Technology, Bentley, Western Australia, Australia

I. CAMERON and D. J. MARTIN Pollution Control Division, Environmental Protection Authority (WA), 57 Murray Street, Perth,

Western Australia, Australia

(First received 1 February 1989 and in final form 5 April 1990)

Abstract--The impact of unleaded petrol (ULP), and the variation in lead (Pb) content of leaded petrol (LP), on air quality in Perth, Western Australia, has been assessed using correlations between atmospheric Pb concentrations and petrol Pb consumption figures for the period 1982-1987 during which ULP was introduced in 1985. The study underlines the importance of taking into account the variability in the Pb content of LP when predicting atmospheric lead concentrations from petrol consumption data.

Key word index: Atmospheric lead, petrol lead additive.

INTRODUCTION

O'Connor et al. (1989) have described a study of the variation in 24-h average atmospheric lead (Pb) and total suspended particulate (TSP) concentrations for three air quality monitoring stations in the Central Business District (CBD) of Perth, Western Australia. This study provided information on the degree of compliance with existing Australian Air Quality Cri- teria, on the possible influence of the introduction of unleaded petrol (ULP) on atmospheric Pb and TSP concentrations, and on the extent to which temporal variations follow a consistent pattern at each moni- toring station.

The study results showed that the annual average atmospheric Pb concentrations fell steadily over the period, 1982-1987, with the exception of a small increase in 1987 (O'Connor et al., 1989). The introduc- tion of ULP in 1985 did not appear to have had a marked influence on the annual average atmospheric Pb concentrations. Prediction of the total petrol Pb consumed annually in Western Australia, by assuming fixed Pb concentrations in premium and regular pe- trol as determined in a study of petrol Pb levels by O'Connor et al. (1977), did not result in a petrol Pb consumption pattern consistent with the measured data for atmospheric Pb concentration. O'Connor et al. (1989) therefore postulated that variations in Pb additive concentration might account for the anomaly.

Since completion of the O'Connor et al. (1989) study the authors gained access to extensive petrol Pb data from the oil refinery which serves Western Australia.

As this refinery is the only petrol source in Western Australia, temporal variations in petrol Pb consump- tion and meteorological influences should therefore control atmospheric Pb concentrations for the Perth CBD in view of the observation by O'Connor et al. (1977) that atmospheric Pb in the Perth CBD must be predominantly due to emitted vehicular lead. The present paper presents a linear regression relation between the petrol Pb data and the atmospheric Pb concentration data of O'Connor et al. (1989) which might be used to assess the impact of ULP and variations in the Pb content of leaded petrol (LP) on atmospheric Pb concentrations.

ATMOSPHERIC Pb AND PETROL Pb DATA

The procedures and results for the atmospheric Pb data are described by O'Connor et al. (1989). The data were measured by X-ray fluorescence spectrochemical (XRFS) analysis of discs cut from HI-VOL fibreglass filter papers of area 254 mm x 203 mm through which air had been drawn at 1.0 m 3 min- ,. The discs used for XRFS analysis were 23 mm in diameter. The atmospheric Pb data from the study are given in Fig. 1.

The petrol Pb concentrations have been provided by BP Refinery (Kwinana) Proprietary Limited which operates the only oil refinery supplying the west coast of Australia. Alkyl Pb and associated scavenger ma- terial are added at the refinery rather than by the various petrol distributors. Therefore Pb concentra- tion figures for the refinery can be used to infer the

413 AE(BI 24:3-D

414 B.H. O'CONNOR et al.

ATMOSPHERIC LEAD CONCENTRATION (24 HOUR MEAN)

4.0

2.0

0.0

4.0

2.0

0.0

E ca 4.0 E

ca 2.0 o

• 0.0

4.0

~: 2.0

0 0.0 0

4.0

2.0;

0.0

4.0

2.0

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1982 O B

L,k hL L nllhllllllL II I I,l,I I

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1984 QB

PC

,,ll ,,l,lhd, hllii, i lib I111,, 1986 O B

Jl ]lJ, iJ,, ,i iI It,l, IIi !J

100 2OO 3OO

Julian Day

1987 Q B

PC

1 0 0 ~ 2 0 0 ~ 3 0 0 ~

Fig. 1. Daily average airborne Pb concentrations at the two sampling stations. Data recorded every sixth day for 24-h periods. Values taken from

O'Connor et al. (1989).

total consumption of vehicular Pb for the State of Western Australia.

Monthly concentration data for petrol Pb (highest, lowest and average), as supplied by the refinery, are available in a Curtin University of Technology tech- nical report which will be supplied on request (O'Connor, 1988). Part of the petrol Pb data set is plotted in Fig. 2 which shows the monthly average Pb concentrations for premium grade petrol for 1986. Note from this plot the substantial variations which occurred during the year. Significant variations were observed for all years of the data set, 1982-1987, which are attributed to the requirement to control the level of Pb additive according to the quality of the feedstock being refined. Thus, even within a single month, the Pb additive level may change substantially--for example

between 0.39 g E- t and 0.80 g ~- 1 for premium grade petrol in September 1986. The existence of such tem- poral variations in petrol Pb concentrations under- lines the importance of taking into account these variations when assessing the impact of ULP on atmospheric Pb concentrations.

Table 1 gives the annual average petrol Pb concen- trations for premium and regular grades, the annual petrol sales for Western Australia and the estimated annual petrol Pb consumption data. The petrol consumption data are taken from the Australian Government publication 'Major Energy Statistics'. Table 2 presents the annual average atmospheric Pb concentrations, and mean values, for each of two CBD sampling stations. The agreement between corres- ponding annual average Pb levels for the two air

Petrol lead additive consumption and atmospheric lead concentrations 415

1.0

0.9

~_~- 0.8

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MONTHLY AVERAGES OF LEAD IN PREMIUM PETROL : 1986

I I I I I I ' I I ' I I I I

JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC

Fig. 2. Variation in the monthly minimum, maximum and average Pb concentrations in premium petrol for 1986.

Table 1. Petrol concentrations and estimated petrol lead consumption

Petrol Pb conc. (g , , - 1)

Premium Regular

Annual Annual petrol petrol sales Pb consumption (m 3 x 10 -6) (tonnes x 10 -3)

Premium Regular ULP Premium Regular Total

1982 0.745 0.423 1983 0.798 0.564 1984 0.735 0.344 1985 0.672 0.300 1986 0.605 1987 0.682

1.405 0.059 - - 1.047 0.025 1.072 1.398 0.048 - 1.116 0.027 1.143 1.456 0.043 - - 1.056 0.015 1.071 1.480 0.014 0.019 0.995 0.004 0.999 1.476 <0.001 0.076 0.893 <0.001 0.893 1.415 - - 0.172 0.965 - - 0.965

Table 2. Annual average atmospheric lead concentrations. The estimated standard deviations are enclosed in parenth- eses. Values for the individual stations are given by tr = [Z(£

- x ) 2 / n (n - 1)] 1/2; mean values by a = (tr 2 + o2)1/2/2

Annual average atmospheric Pb* (Fgm -3)

Station Station QB (1) PC (2) Mean (3) Regr (4)

1982 2.59 2.63 2.61 2.31 (0.14) (0.15) (0.10) (0.10)

1983 2.51 2.49 2.50 2.58 (0.16) (0.14) (0.11) (0.11)

1984 2.07 2.28 2.18 2.30 (0.11) (0.12) (0.08) (0.10)

1985 1.82 2.05 1.94 2.02 (0.11) (0.11) (0.08) (0.10)

1986 1.61 1.67 1.64 1.63 (0.11) (0.12) (0.08) (0.10)

1987 1.84 1.88 1.86 1.90 (0.13) (0.12) (0.09) (O.lO)

* See O'Connor e t al. (1989) for details. Notes:

(1) Queens Building, 97 William Street, Perth (CBD). (2) Pollution Control Division Building, 57 Murray

Street, Perth (CBD). (3) Arithmetic mean for the stations. (4) According to regression equation using the annual

petrol Pb consumption data.

sampling stations is considered to be sufficiently close for the mean values to be used for correlation calcu- lations between airborne and fuel Pb da ta - - the max- imum difference, 0.23 # g m -3 for 1985, gives a value 1.5 for the ratio 'difference/(standard deviation of difference)'. The mean for each pair of atmospheric Pb levels is taken to be representative of annual average airborne Pb for the CBD in view of the locations of the stations and the agreement for each pair. Figure 3 shows the temporal variation in premium grade petrol Pb concentration, annual petrol volume consumption, estimated annual Pb consumption and atmospheric Pb concentration. Inspection of the data suggests that variation in petrol Pb concentration is an important factor influencing atmospheric Pb concentration for the study period.

CORRELATION BETWEEN ANNUAL AVERAGE DATA

VALUES FOR ATMOSPHERIC AND PETROL Pb

A plot of mean annual average atmospheric Pb concentration vs annual average petrol Pb consump- tion is shown in Fig. 4. The linear regression line indicates that the atmospheric Pb concentration cor- relates strongly with petrol Pb. The regression line is

416 B.H. O'CONNOR et al.

3.0

2.8

8..~ 1.5

UJ 3: el. 0.5 (n 0

O.O

1981

i i i i i i !

1982 1983 1984 1985 1986 1987

UJ | 1.6

1.4

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,=J

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0 .

1988

N

Z 0 ~ , 120 [ , ~ Z

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1981

Premium Petrol Consumption

ntratlon

Regular_~ Petrol Consumption ~ ~ U k P Petrol . Consumption

i i , i ' [ , 1 ~ i •

1982 1983 1984 1985 1986 1987 1988

0 . 9

- I z O Z m <

0.8 ~

W [

Fig. 3. Variation in annual average premium petrol Pb concentrations, annual petrol consumption, estimated annual Pb consumption and atmospheric Pb

concentrations. Error bars indicate + la.

Z _o I.- .< B: I- Z i,i (3 Z O (3

2 " W a.

O

<

2.8

2.0

1.5

1982

1987

1986

' o19 ' 11o ' 1:1 ' 1.2

PETROL LEAD CONSUMPTION X 10 .3 TONNE

Fig. 4. Regression plot of annual average atmospheric Pb concentration vs annual average vehicular Pb. Error bars indicate + hr.

Petrol lead additive consumption and atmospheric lead concentrations 417

described by the relation

Pb (atm) = a. Pb (petrol) + b

where Pb (atm) is the mean annual average atmo- spheric concentration in/~g m - s and Pb (petrol) is the annual petrol Pb consumption in tonnes for Western Australia. The regression values for coefficients a and b are 3.86 (0.07) x 10- 3 and - 1.83 (0.07), respectively, where the values in parentheses are the esd estimates. The 95% confidence level for both coefficients is 0.14. The coefficient of correlation for the regression line is 0.83. The authors are unable to account for the substantial deviation of the 1982 data point from the regression line. The high degree of correlation con- firms the claim by O'Connor et al. (1977) that atmo- spheric Pb in the Perth CBD must be dominated by vehicular emitted Pb. Clearly, therefore, petrol Pb concentrations and petrol consumption data may be used to infer temporal variations in annual mean atmospheric Pb concentration for the Perth CBD.

Table 2 compares the measured values of atmo- spheric Pb concentration with corresponding values computed using petrol Pb data and the regression equation. It is noted that the estimated standard deviations in the two sets of atmospheric Pb values, which are relatively high due to the variability in the 24-h measured data, need to be considered when using the regression equation for modelling.

CONCLUSIONS

The results have shown the need to take into account temporal variations in petrol Pb concentra-

tions when assessing the impact of ULP on air quality. The close correlation between total Pb consumption and mean annual atmospheric Pb level shows that the petrol Pb concentration and consumption figures may be used to predict annual average atmospheric Pb levels. The important role played by the petrol refining practices in determining atmospheric lead levels is clearly shown in this study.

Acknowledgments--We are grateful to BP Refinery (Kwinana) Proprietary Limited for supplying the petrol Pb data, in particular Mr G. Whitfield for compiling the data. We also thank Mr H. Johnstone of the EPA and Mr L. Hammond of Curtin University for assisting with data analysis.

REFERENCES

Major Energy Statistics. Monthly publication of the Austra- lian Department of Resources and Energy, GPO Box 858, Canberra, ACT 2601, Australia.

O'Connor B. H. (1988) Lead concentration in petrol mar- keted by BP Refinery, Kwinana, Western Australia, 1982-1987. Curtin University of Technology, School of Physics and Geosciences--Technical Report SPG 497/1988/AP158.

O'Connor B. H., Hammond L. C., Cameron I., Martin D. J. and Powell R. (1989) Variation in atmospheric particulate lead and total suspended particulate concentrations for Perth, Western Australia (1982-87). Clean Air 23, 156-161.

O'Connor B. H., Kerrigan G. C., Thomas W. W. and Pearce A. T. (1977) Use of bromine levels in airborne particulate samples to infer vehicular lead concentrations in the atmosphere. Atmospheric Environment 11, 635-638.