LEAD CONCENTRATION IN CAIRO ATMOSPHERE

AFTER USING UNLEADED GASOLINE

Hoda F.S. Rizk and Mamdouh I.M. Khoder

National Research Center , Air Pollution Dept., Dokki, Cairo, Egypt

Email: hrizk62@hotmailcom

Abstract

The Government of Egypt performed many efforts to reduce the lead (Pb) in the environment of Cairo. These introduced efforts caused a notable decrease in (Pb) concentration in the atmosphere of Cairo which sampled as suspended dust.

Two urban sites in Greater Cairo; one is Cairo City Centre and the other is Dokki; were chosen to represent Cairo atmosphere.

A comparative study between the results of this study during (1998-1999) and previous studies (1980's - 1996) showed a marked decrease in (Pb) concentrations at site(1).

Seasonal variations of (Pb) concentrations in the two sites as well as Nickle (Ni) concentrations have been monitored in the present study.

The decrease percentage of (Pb) concentration varied through the four seasons. The maximum decrease percentage was through the winter and the minimum decrease percentage was through the summer. It was 43.87% and 29.73%, respectively. During the four seasons of the year the annual decrease reached 39.50%.

Introduction

Although atmospheric (Pb) originates from a number of industrial sources, leaded gasoline appears to be a principal source of general environmental (Pb) pollution. Tetraethyl lead was introduced as an antinok agent in gasoline in the 1920's (EPA, 1986) and since then has played an increasingly important role as a pollutant of the general atmosphere. Murozumi et al 1968, estimated that 90% of the atmospheric (Pb) comes from automobile exhaust and that the increase in environmental (Pb) levels was due mainly to emissions from leaded gasoline.

Sources of lead (Pb) in the atmosphere according to WHO, 1977, are either natural sources e.g. rocks, volcanoes, buildings, which all give traces or very rare concentrations, or Man-Made sources. The biggest man-made source is batteries stores, the second man-made source after batteries stores is traffic and combustible fuels. The thired big source is smelting and lastly coke, paints and pencils.

Recently the Government of Egypt introduced many efforts to reduce the (Pb) concentration in the environment. Beside the use of natural gas as fuel in houses and in some vehicles, also the underground metro as a long net in Cairo City; the Egyptian Environmental Affairs Agency; has reduced significantly the lead content of gasoline sold in Cairo, where the (Pb) problem is most serious. After 1991 the tetraethyl lead as an addetive antinock agent was gradually reduced in gasoline sold in all the Cairo City stations. The plan was that through five years i.e. at 1996; the gasoline sold is completely unleaded.

Airborne lead caused by the burning of leaded gasoline represents a serious pollution problem. Many millions of adults and children suffering adverse health effects. It is very important to evaluate the lead levels in Cairo atmosphere and trace it after using unleaded gasoline. The aim of this paper is to assess the atmospheric concentrations of (Pb) in total suspended matter or particulate (TSP).

Thus (TSP) was sampled in two sites chosen to represent Cairo atmosphere.

Methodology

The (TSP) was collected from two sampling stations which were selected for their traffic densities. Site (1) is Cairo City Center and site (2) is Dokki (NRC); which represent urban areas. The first site data was compared with previous data before using unleaded gasoline.

Sampling of suspended particulate matter was collected on a membrane filter from air aspirated by a vacuum pump with a rate of 10L/min. The volume of air was determined by a gas meter connected to the vacuum pump. The sampling time was 24 hours. The numbers of samples were 10, 11 or 12 samples each season of the year. Sampling was through the four seasons at the two sites under investigation.

The membrane filter was digested to prepare a test sample; (Pb) and (Ni) were extracted from the (TSP); (Jackson, 1973); for aspirating to atomic absorption type Varian Spectra A.A. model 220. The concentrations of (Pb) and (Ni) were expressed in µg/m³.

Results and Discussions

The mean seasonal variation of lead concentrations in suspended particulate matter at sites (1) and (2) during 1998 - 1999 are shown in table (1). This table reveals that the maximum concentrations of lead (Pb) were 2.2 and 1.7 µg/m³ during the winter, while the minimum concentrations were 1.3 and 1.1 µg/m³ during the summer season at sites (1) and (2), respectively. The higher concentration of (Pb) during the winter season may be due to usual high inversion which cause low dispersion during this season.

This leads to increase the accumulation of (Pb) particulate and hence the increase of its concentration. This is in agreement with Hassanien and Harvath (1995), and Khoder (1997) who found that the highest concentration of (Pb) occurred in winter season.

The annual mean concentration of (Pb) as shown in table (1) were 1.7 and 1.4 µg/m³ at sites (1) and (2) respectively. These concentrations are much higher than those reported in Helsinki (0.05 µg/m³) and in European and North American cities (0.2 - 0.8 µg/m³), according to OECD (1993).

The annual mean concentrations of (Pb) at both sites in the present study exceeded the Egyptian standard (1 µg/m³, EE.AA., 1995). Although, the use of unleaded gasoline has started in Cairo City fuel stations, yet leaded gasoline is still used in other Egyptian governorates which surround Cairo City. So, the high concentrations of (Pb) in Cairo may be due to its emission from vehicles that still using leaded gasoline which enter Cairo every day from other governorates. Another source of lead in Cairo may be due to the resuspension of street dust (lead - bearing dust) by the wind and anthropogenic activities. This contaminated dust was emitted from using leaded gasoline before using unleaded gasoline. This was confirmed by the presence of high lead content in street dust of Cairo (Shakour et al, 1999). High level of (Pb) concentrations may be also because sites (1) and (2) are located downwind of industrial area in which smelters and foundaries beside other factories of paints and other sources of (Pb) are found. A similar behavior trends of (Pb) concentrations at site (1) through the four seasons; were observed during (1994 - 1995); before using unleaded gasoline; and during (1998 - 1999); after using unleaded gasoline; (Figure 1).

However, the seasonal and annual mean concentrations of (Pb) were decreased during (1998 - 1999) than those found during (1994-1995) for the four seasons. The lead concentration was decreased by 43.87% (as a maximum decrease) during the winter, while the minimum decreasing percentage was 29.73% in the summer, this low decrease in (Pb) concentration may be due to increase in numbers of vehicles entering the city from outside Cairo through this season. During the four seasons of the year, the annual mean decreasing percentage was 39.50%. As we expected, the decreasing percentage of (Pb) concentration was not great. This indicates that lead is still emitted in Cairo atmosphere. This may be attributed to the vehicles which enter Cairo from the other cities in Egypt using leaded gasoline and resuspension of street lead-bearing dust. So, it is expected that, after using unleaded gasoline in all the surrounding governorates, the concentration of (Pb) will be much decreased in the future.

Although the government of Egypt already has reduced significantly the lead content of gasoline sold in Cairo, where the lead problem is most serious, and the environmental action plan 1992; which lead to the decrease gradually of lead (Pb) content as shown in table (2); yet the concentration of (Pb) in Cairo atmosphere was not notably changed through 1978 to 1995 as shown in figure (2). While in table (2) the concentration of lead (Pb) in gasoline (90 octans) was 0.9 g/L during 1980's and gradually decreased to 0.15 g/L as planed to be used during 1995, and after this year unleaded gasoline was to be used; the annual mean lead concentration in an urban area in Cairo (1978 - 1979) was 2.83 µg/m³ (Shakour, 1982) and it was 2.81 µg/m³ during 1994-1995 (Khoder, 1997) (Figure 2). That result was mainly due to great increase in number of vehicles in the city.

Recently in the present study, the annual mean of lead concentration decreased from 2.81 µg/m³ (1994 - 1995) to 1.7 µg/m³ (1998 - 1999) after using unleaded gasoline. This decrease was highly significant (P < 0.001). A comparative study in Canada was conducted by Loranger and Zayed (1994), Concluded that (Pb) concentration in ambient air from unleaded gasoline showed an annual emission rate decrease reached 28%.

Recently in Cairo supposing that through the four years there was a regular decrease; the emission rate showed an annual decrease reached 13% (decrease per year). This emission rate will show much annual decrease in the future when all the governorates use unleaded gasoline.

The seasonal variation of Nickel (Ni) concentrations in suspended particulate matter at both sites (1 and 2) Juring 1998 - 1999 are shown in table (3). The seasonal mean concentrations of (Ni) at site (1) ranged from 0.13 µg/m³ (summer) to 0.23 µg/m³ (winter). The annual mean was 0.18 µg/m³ . While at site (2), it ranged from 0.11 µg/m³ (summer) to 0.18 µg/m³ (winter) and the annual mean was 0.15 µg/m³. The maximum seasonal concentration of (Ni) during the winter season at the both sites may be attributed to the same factors previously discussed for the seasonal variation of (Pb) concentration (high inversion and low dispersion).

Similar seasonal behavior trends of Nickel concentration were observed at site (1) during 1994 - 1995 and 1998 - 1999, with relatively higher concentration during 1998 - 1999 (Figure 3). This may be due to the increase of vehicles from year to year, which lead to the increase in the emission of (Ni). Nickel is one of the heavy metals usually found in parent oil (Nasralla, 1975).

The major sources of chromium (Cr) and (Ni) were via attrition of (Cr) and (Ni) plating and alloys in automobiles, and of yellow paint on roads (Madany et al., 1994).

Through autumn 1999, some days of special weathering conditions occurred. It was a high inversion which cause low dispersion of pollutants over Cairo City. Through those days some samples of suspended particulate matter showed high content of (Pb) and (Ni).

Those samples were excluded from the tabulated result tables (1) and (3); and shown in table (4).

Conclusion

This study can be concluded that the concentration of lead in ambient air of Cairo showed a notable decrease in the recent years after using unleaded gasoline. The mean amuual decrease was 13% (per year). It is expected that this decrease will be much greater after using unleaded gasoline in all the governorates of Egypt.

References

Air Quality Criteria for Lead. Research Triangle Park, NC : US. Environmental Protection Agency; (1986), EPA publication 600/8-83/028 dF.

Ali, E.A.; Nasralla M.M. and Shakour, A.A.; (1986). Environmental Pollution (Series B) 11, pp. 205-210.

Egyptian Environmental Affair Agency E.E.A.A. ( 1995 ) :

Environmental Protection Low No. 4 , 1994 .

Environmental Health Criteria 3, Lead; (1977) publications of World Health Organization (WHO), Geneva, pp. 30 - 38.

Hassanien, M.A. and Harvath, A.; (1995), Central European Journal of Occupational and Environmental Medicine, 1:1, pp. 68-77.

Jackson , M.L. ( 1973 ) : Soil Chemical Analysis , Prentice Hall , India .

Khoder, M.I.M.; (1977), Ph.D. Thesis, Ain Shams University, pp. 227-231.

Loranger, S. and Zayed, J.; (1994), Atmospheric Environment, vol. 28, No. 9 pp. 1645 - 1651.

Madany, I.M.; Akhter, M.S.; Aljowder, O.A.; (1994); Environ. Int. 20 pp. 483-492.

Murozumi, M.; Chow, T.J.; and Patterson, C.C. (1969); Geochim Cosmochim Acta; 33 pp. 1247 - 1294.

Nasralla, M.M.; (1975), Ph.D. Thesis, Leeds University, U.K. p. 155.

Organization For Economic Co-Operation and Development OECD , (1993 ):

Risk reduction monograph . No. 1 Lead , Paris .

Rhoda, R.; and Krause, K.; (1993), Lead Pollution in Cairo: Review of Available Information. Publications of USAID, pp. 1-13.

Shakour, A.A.; (1982), Ph.D. Thesis, Al-Azhar Univ. Cairo. Pp. 145-173.

Shakour, A.A. , Awad A.H. and Khoder M.I. ( 1999 ) : Central European Journal

Occupational and Environmental Medicine , 5 ( 2 ) P. P. 173 – 180 .

Table (1): Seasonal variation of lead concentrations at sites (1) and (2) during winter 1998-1999 to autumn 1999

Season	Concentration, µg/m^3
	Site 1 N mean		Site 2 N mean
Winter Spring Summer Autumn Annual mean S.D.	12 11 12 10 45	2.2 1.5 1.3 1.8 1.7 0.59	12 11 12 10 45	1.7 1.2 1.1 1.5 1.4 0.48

N : Number of samples

S.D. : Standard deviation

Table (2): Change of lead content in gasoline fuel according to publication of USAID (GOE) plan, (Rhoda & Krause, 1993)

year	Lead content in gasoline fuel
	80 Octans 80% of sales	90 Octans 20% of sales
1980's 1991 1992 1995 (Plan)	? 0.41 g/L 0.34 g/L 0.15 g/L 0.00 g/L	0.9 g/L 0.45 g/L 0.36 g/L 0.15 g/L (leaded) 0.00 g/L (unleaded)

Table (3): Seasonal variation of Nickel concentrations at sites (1) and (2) during winter 1998 - 1999 to autumn 1999

Season	Concentration, µg/m^3
	Site 1 N mean		Site 2 N mean
Winter Spring Summer Autumn Annual mean S.D.	12 11 12 10 45	0.23 0.19 0.13 0.17 0.18 0.061	12 11 12 10 45	0.18 0.16 0.11 0.13 0.15 0.050

N : Number of samples

S.D. : Standard deviation

Table (4): Seasonal variation of Nickel concentrations at sites (1) and (2) during winter 1998 - 1999 to autumn 1999

Element	Concentration, µg/m^3
	Site 1 N mean		Site 2 N mean
Lead Nickel	3 3	5.30 0.58	3 3	4.50 0.46

Figure Captions

Figure (1) : Comparison of the seasonal and annual variation of lead concentrations at site 1 during (1994 - 1995) and (1998 - 1999).

Figure (2) : Change of lead concentrations at city centre of Cairo (site 1) from (1978 - 1979) to (1998 - 1999).

Figure (3) : Comparison of the seasonal and annual variation of Nickel concentrations at site 1 during (1994 - 1995) and (1988 - 1999).

Figure (1) : Comparison of the seasonal and annual variation of lead concentrations at site 1 during (1994 - 1995) and (1998 – 1999).

Figure (2) : Change of lead concentrations at city centre of Cairo (site 1) from (1978 - 1979) to (1998 - 1999).

Figure (3) : Comparison of the seasonal and annual variation of Nickel concentrations at site 1 during (1994 - 1995) and (1988 - 1999).