The impact of the gulf war on the Arabian environment—I. Particulate pollution and reduction of solar irradiance

Atmospheric Environment Vol. 27A, No. 1, pp. 95-108, 1993. Printed in Great Britain.

0~4-6981/93 $6.00+0.00 © 1993 Perpmon Press Ltd

THE IMPACT OF THE GULF WAR ON THE ARABIAN ENVIRONMENT--I. PARTICULATE POLLUTION AND REDUCTION OF SOLAR IRRADIANCE MOHAMMAD S. EL-SHOBOKSHY Mechanical Engineering Department, College of Engineering King Saud University, P.O. Box 800, Riyadh 11421, Saudi Arabia

and YASEEN G. AL-SAED! King Abdulaziz City for Science and Technology, P.O. Box 6086, Riyadh 11442, Saudi Arabia (First received 4 October 1991 and in final form 1 June 1992)

Abstract--This paper investigatessome of the air pollution problems which have been created as a result of the Gulf war in early 1991.Temporary periods of increased dust storm activity have been observed in Saudi Arabia. This is presumably due to disturbance of the desert surface by the extremely large number of tanks and other war machines before and during the war. The concentrations of inhalable dust particles ( < 15 #m) increased during the months just after the war by a factor of about 1.5 of their valuesduring the same months of the previous year, 1990. The total horizontal solar energy flux in Riyadh has been significantlyreduced during dry days with no clouds. This is attributed to the presence of soot particles, which have been generated at an extremely high rate from the fired oil fields in Kuwait. The direct normal solar insolation were also measured at the photovoltaic solar power plant in Riyadh during these days and significantreductions were observed due to the effectiveabsorption of solar radiation by soot particles. The generated power from the plant has been reduced during days with a polluted atmosphere by about 50-80% of the expected value for such days, if the atmosphere were dry and clear. Key word index: Particulate pollution, dust storm, solar radiation.

INTRODUCTION

By the beginning of 1991 thousand of tanks, vehicles and war machines were actively running in the Gulf area and desert surfaces were strongly disturbed where the crusts (aggregation) were severely pulverized. These circumstances created favourable conditions for fine dust and sand particles to be easily suspended under normal meteorological conditions. A similar situation was investigated by Oliver (1945). He reported an increase in the annual number of dust storms in the Western Desert of Egypt during the early years of the second world war, presumably due to disturbances of the desert surfaces by tanks and shelling. The frequency of dust storms was three or four per year before the war; this increased to 40 per year in 1944. A similar increase in dust storm frequency due to tank manoeuvres occurred in Arizona during the second world war when General Patton had his desert training camp in the Desert Center-Parker area (Clement et al., 1963). The frequency of dust storms increased there from 5 to 50 per year. Dust storms usually occur as a result of high speed winds which are able to entrain large amounts of dust 95

and sand particulates. In general, the threshold velocity for soil movement is the velocity at which aerodynamic forces are sufficient to dislodge particles from the soil and initiate movement. Experimental studies of threshold velocities for single soil systems consisting of beds of loose, monodisperse, and similar particles are reported by Bagnold (1941), Ishihara and Iwagaki (1952), Cbepil (1951) and Greeley et al. (1973). Marshall (1971) and Lyles and Allison (1976) have studied the increase of threshold wind velocity due to nonerodible roughness. The dust pollution problem, as briefly discussed above, as well as general environmental conditions in the Gulf, soon became much worse and more complicated as the disaster of the burning oil fields in Kuwait was initiated. The precise quantity of oil burning every day was not known. However, oil-field experts roughly estimated that about 4-5 × 106 barrels per day were burning at the beginning of this disaster. This unique combustion process produced a huge amount of smoke and gas which covered wide areas of the sky in Kuwait. Also in the city of Riyadh, Saudi Arabia, 500kin west-southwest of Kuwait, dark smoke

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M.S. EL-SHOBOKSHYand Y. G. AL-SAEDI

plumes at high altitudes were frequently observed. During rainy days, high concentrations of soot particulates in rain water were also detected. The amount of soot particulate emitted from burning oil depends mainly on the type and quality ofoil as well as the rate at which oil is burning. However, if an emission factor of about 120 kg per 103 barrels (EPA, 1990) is considered, this means that about 600 tons of soot particulates were emitted every day. This, indeed, is an extremely large quantity. The soot particulates are very small and fluffy, and are known to absorb solar radiation very effectively. This paper investigates some effects of the Gulf war and associated events, like the burning of oil fields in Kuwait, on the environment and air quality of the Arabian area. The study is mainly focussed on the particulate pollution problem and the degradation of solar energy flux, and the resulting loss in power output from the existing solar power plant in the city of Riyadh is given as an example.

L O C A L VARIATIONS IN CLIMATIC A N D

W I N D SPEED LEVELS IN RIYADH BEFORE AND AFTER T H E G U L F WAR

The wind data were collected from a weather station in Riyadh. The characteristics of wind over the past 10 years are shown in Fig. 1, where the wind data for these years were analysed and presented in the form of wind roses. The average wind speed during the test months (March-June) for the years 1981 to 1991 are shown in Fig. 2. The results show that the wind speeds during the year 1991 are indeed anomalous. Figure 3 shows the measured daily average wind speed during the months March to June for the years 1991 and 1990. It is easily noticed from this figure that the wind speed level for the months after the war is generally higher than that for the same months of the year before the war. During the colder month, March, a higher thermal gradient between the oil field in Kuwait and remote areas was established, consequently stronger horizontal winds developed. As the atmospheric temperature increased in Riyadh during the following months, the thermal gradient was reduced gradually, as did the wind speed, which may be seen from Fig. 3.

E N V I R O N M E N T A L C O N D I T I O N S AFTER T H E G U L F WAR

Soon after the war was over, the area experiencdd some variations in climatic and environmental conditions. The variations were easily detected both by measurements and visual observation, and the more pronounced are: (a) the increase in wind speed above the usual expected levels for the same time as other years; (b) the increase in the frequency of occurrence of blowing dust, and an increase in the fine particulate concentration in the atmosphere; (c) the appearance of black smoke clouds at varying altitudes. There are of course many other variations in the air quality due to the presence of gaseous pollutants of varying concentrations. The present investigation will, however, be concerned with the three above-mentioned variations and their impact on the environment in Riyadh.

THE EFFECT OF OIL-FIELD FIRING ON THE WIND

In the latter stages of the Gulf war it was announced that fires had been set in above 730 oil wells and that about 4-5 million barrels were burning every day. The thermal energy released from oil fields burning 4-5 million barrels per day is indeed huge (about 1.5x 1013 kJd-1). The physical phenomena taking place due to this event and affecting the wind speed variation may be explained as follows: the localized very hot areas within the oil fields produce strong vertical velocities, which in turn produce strong convergence of the horizontal winds.

T H E E F F E C T O F PARTICULATE P O L L U T I O N LEVEL A N D F R E Q U E N C Y O F DUST STORMS

The kingdom of Saudi Arabia is surrounded by vast areas of desert and the whole area is classified as arid. Desert areas are known here to be the main source of atmospheric dust with some minor contribution from industrial and other sources. Dust storms in Saudi Arabia are highly seasonal in their occurrence reflecting the occurrence of strong dust-transporting winds. Figure 4 shows the percentage frequency of dust storms (Goudie, 1983; Middleton, 1986). The highest frequency of dust storms occurs in the months with strongest winds; March-May in Saudi Arabia. In theory, movement of particles at rest on a bed can be initiated by different mechanisms acting alone or in combination, including (a) the drag exerted by the wind; (b) aerodynamic lift; (c) impacts by rolling or bouncing particles; and (d) mechanical disturbance by vehicles, tractors, etc. Previous studies (EI-Shobokshy and Hussein, 1988; EI-Shobokshy et al., 1990) have shown that inhalable particulate (0-15 #m) concentration in the atmosphere of Riyadh is a function of wind speed and atmospheric pressure. More recently, E1-Shobokshy and Hussein (1991) developed four predictive equations for estimating the seasonal inhalable dust concentration in Riyadh as a function of wind speed and atmospheric pressure. The equations were obtained by means of regression analysis using the experimental data which had been collected over the past few years. These investigations confirmed that the meteorological conditions (mainly wind speed and atmospheric

Environmental impact of the Gulf war

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Environmental impact of the Gulf war

pressure) are the principal factors affecting the atmospheric dust concentration in the area. The monthly average inhalable dust concentration in Riyadh during the years 1980-1984 is shown in Fig. 4. It is noticed that higher concentrations of inhalable dust are observed in the months February, March and

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May, consistent with Goudie (1983) and Middleton (1986). During the Gulf war and the preparation period, tank manoeuvres pulverized the surface crust (aggregation), and broke the interparticle cohesive forces. These actions significantly reduced the threshold velo-

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cities for entraining dust and sand particles from the dust surfaces, so that larger amounts of dust particles would be deflated from the desert surfaces at relatively lower wind speeds. Soon after the fires had been set in the oil fields in Kuwait, a marked increase in wind speed was observed in Riyadh. These two main factors (pulverization of the desert surfaces and increasing wind speed) created favourable conditions for entraining and dispersing (to far distances) large quantities of fine dust, resulting in severe particulate pollution problems. The concentrations of inhaiable dust particles in the atmosphere of Riyadh were measured directly after the war during the months March-June, and the results were then compared with those of the previous year, 1990, for the same months. For this purpose an

automatic dichotomous sampler was used. The sampler separates the airborne particles into two distinct size fractions: from 2.5 to 15/~m (coarse) and less than 2.5 Izm (fine). Figures 5a and 5b show the concentrations of fine (0-2.5/an), coarse (3-15 ~m), and the total inhalable particulates for the months MarchJune in 1990 and 1991. The figures show that the concentrations of fine particles are higher than those of the coarse particles by a factor of about two. This is due to the longer time that fine particles can survive in the atmosphere than coarser ones because of the difference in their settling velocities. If the averages are taken for both years, it can be shown that the concentration of inhalable dust partides has increased from about 380 to 580 g m - 3, i.e. it has increased by a factor of about 1.5.

Environmental impact of the Gulf war

101

There were also emissions of sulphur dioxide, carbon monoxide and dioxide, as well as water vapor. Based on the roughly estimated amount ofoii which The emission of such pollutants at these high rates was burning per day and using the emission factors will certainly affect the amount of solar energy reavailable (EPA, 1990), the following pollutants were ceived by the areas of the Earth's surface over which believed to be emitted at the start of this disaster: the plumes of these pollutants are passing. Solar radiation received on the Earth's surface is hydrocarbons, HC = 450 t d - 1 attenuated by the terrestrial atmosphere, and the nitrogen oxide, NOx = 4500 t d extent of attenuation depends on the pollution level in the atmosphere. This attenuation is caused by: (a) carbon particulates = 600 t d - 1. scattering by molecules (Rayleigh scattering); (b) selective absorption by gases, particularly 03, 02, H 2 0 and CO2; (c) scattering and absorption by aer600 osol particles (dust, smoke, pollen, etc.); and (d) scattering and absorption by cloud masses. 500 i E In the city of Riyadh, uniformly dispersed dark 400 plumes were frequently observed in the sky at high £ altitudes. They were indeed dark clouds of soot paro 3oc ticles generated by the combustion process in the oil 200 fields. Such a fact was confirmed by the presence of 0 dense soot particles in water droplets during rainy 0 I00 days. 0 Soot particles are one of the major atmospheric lorch Aprit May June absorbers. ~ e y are very small and fluffy, and may be M o n t h - 199(3 transported over thousands of kilometres, which indicates that the impact of soot on climate is not limited 700 to the source regions (Kuwait) but may be extended to 600 ~ ................................................ far distances. :& 5 0 0 ................................................................................................................................ ..,.~ Unfortunately, complete information on the polE .o 400; ........... lutants at different altitudes (constituencies, concen& 300 ........................................................................::.............. trations, etc.) were not available directly at the end of 200 .................................................................................................the Gulf war. Nevertheless, there still remains the 0 0 I00 ...............................................................................................................possibility ... of indirectly drawing some interesting in0 I I formation on the evolution of the air quality by March Apri L May June utilizing the measured total and direct normal solar M o n t h - 1991 fluxes. .=!- Fine (0-25/~) -i-Coarse (3-15/z1 --e- Total T H E E F F E C T O N I N C I D E N T SOLAR E N E R G Y

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Environmental impact of the Gulf war

objectives of the present investigation were selected, some of which are presented. If any clouds appeared during a given period, the results for this day were excluded. The presence of clouds was carefully detected by visual means and checked by the daily meteorological report in the city of Riyadh. Figure 6 shows the theoretically calculated flux of solar energy through a horizontal surface using a standard method (ASHRAE, 1985) and the measured values for the days 17, 20, 23 and 28 June 1991. During these days the weather was completely dry with relative humidities of 38, 41, 41 and 26%, respectively, and no clouds whatsoever at any altitude. Therefore Fig. 6 shows only the effect of pollutants (gases and soot and fine particulate) in the atmosphere at varying concentrations. On these days, the air pollution resulting from the Gulf war reduced the total available solar energy fluxes only 59, 55, 56 and 37% of those available in the absence of pollutants.

Measurement of total horizontal and direct normal solar

fluxes The total horizontal solar flux was measured by means of an Eppley pyranometer directly after calibration. The pyranometer is part of a complete Meteorological Tower (Series 3000 Modular Meteorological Systems, Texas Electronics). The signal from the pyranometer is received by a signal conditioner, then passed to an "ADAM II" data acquisition system, controlled by a microcomputer where the data are processed and averaged over the required span of time, then recorded on a magnetic tape and/or printed out. The direct normal solar flux was measured by means of a pyrheliometer. All solar measurements were conducted during dry weather and a completely clear sky. This is to exclude the effect of clouds on the attenuation of solar energy. The measurements were continuously conducted and only those satisfying the

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M.S. EL-SHOBOKSHYand Y. G. ALoSAEDI

Statistics of reduction of solar radiation of the whole test period, are indeed more informative and would help in drawing accurate figures. This was, unfortunately, not possible because clouds with varying intensities were covering the sky during many days. The reduction of solar radiation due to fire smoke could only be detected during days when the sky was free of clouds and the prevailing wind was blowing from north to northeast. Figure 7 shows a comparison between theoretical and measured total solar energy flux through a ho~i-zontal surface on 3 and 4 July 1991. These were very clear days with south to southwest winds and a relatively humidity of 25%, i.e. very dry weather. The figure shows also the excellent agreement between the calculated and the measured total horizontal solar energy flux. The direct normal solar insolation received in Riyadh decreased in a similar manner.

Measurements of the power output from the photovoltaic power plant To demonstrate the effect of air pollution from the Gulf war in a qualitative manner on available power from solar energy, measurements were taken in the photovoltaic power plant at AI-Jubailah, 50km northwest of Riyadh. The plant utilizes 160 photovoltaic arrays to receive solar energy during daylight hours and convert that energy into direct current (d.c.) electricity. The array field cover 40,000 m z, and tracks the sun through an automatic control system. The site is provided with an automatic weather and solar data gathering system. The rated power of the plant is 350 kW d.c. at a solar insolation 800 W m - 2 40oc ambient air temperature and wind speed < 1.0 m s - 1. Each array tracks the sun by means of 100 W motors, and if the normal solar

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Environmental impact of the Gulf war

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insolation is less than 200 W m -2, the arrays stop tracking the sun and no power is generated from the whole system. Data were collected in a continuous manner and only the results for the same days are presented. Typical output data which were obtained from the plant data collection system for direct normal inolation and associated output power are shown in Fig. 8. The output power loss due to air pollution may be estimated from Fig. 9, where the actual power is plotted against the expected values based on the direct normal insolation of dry and clear days. Figure 9 shows that only 16, 48, 20 and 16% of the possible power were available during the test days 17, 20, 23 and 28 June 1991, respectively. It has to be emphasized that these representative days were selected to show the effect of atmospheric pollutants on solar energy, whereas all cloudy days

(which may also be highly polluted) were not considered in this investigation.

C O N C L U D I N G REMARKS

The Gulf war, which was started in January 1991 to liberate the state of Kuwait, has left various impacts on the environment of the Gulf area, and possibly further afield than would be expected. The environmental problems created due to this war are very complicated and the effects too many to be investigated in a single paper. However, the present paper investigates only the resulting particulate pollution problem and the associated reduction in the received solar energy. The main achievements of the study and the conclusions can be summarized as follows:

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Environmental impact of the Gulf war

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• The wind speed levels in the city of Riyadh (500 km southwest of Kuwait) noticeably increased during the few months just after the war, when compared with those for similar months of the previous year. • The desert surface in the battle field was rigorously disturbed by tanks and war machines and favourable conditions for more dust storms have been created. • As a result of disturbing the desert surface and the increased wind speed, larger amounts of fine dust have been entrained by winds of relatively low speeds. • The concentration of inhalable dust particulates ( < 1 5 ~ m diameter) has increased during the months following the war. A comparison between the measured concentration during March-June 1991, and the similar months of 1990 confirm this fact. • The large amount of soot emitted from the oil-field fires was observed in the atmosphere of Riyadh. • The total horizontal and direct normal solar energy flux was significantly reduced over many days after the war. This was due to the absorption of solar radiation mainly by soot particulates and also by other pollutants in the atmosphere. • A loss of power generated from the 350 kW photovoltaic power plant in Riyadh has been observed during the days where northerly winds transport large amounts of soot particulates and other pollutants. This loss of power is estimated to be about 50-80% of the amount that would be generated during dry days with clear sky. It is emphasized that there are many other environmental problems which were created by the war, such as gaseous air pollution, acid precipitation, etc. Such problems need extensive studies, and the monitoring

of air pollutants all over the Arabian area is urgently required.

REFERENCES

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