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Comparative Assessment of Ambient Air Quality in Rabia Area for Years 2001 and 2004 in the State of Kuwait

The hourly air pollutants concentrations were measured continuously by fixed ambient air stations located over the polyclinics in Rabia area in Capital Governorate in the State of Kuwait. The focus of this investigation is to determine the pollution levels of SO2, NO2 and O3 in year 2001 and 2004 to assess the pollution trends. The recorded data are used in identification of the most probable sources of these pollutants. The pollutants levels were compared to evaluate exceedances of Kuwait Environmental Authority Standards. The diurnal patterns were also analyzed for different seasons for two years 2001 and 2004. Weekdays and weekend variation on Ozone pollution has been thoroughly investigated. It is observed that SO2, NO2 and O3 levels were higher in year 2001 as compare to year 2004 due to the application of various mitigation strategies such as relocation of car auction market and transport depot, which were located in the northwestern side of Rabia area with distance of 2 km. The traffic volume all over the country has increased by substantial amount increasing NOx and ozone precursor emissions, which showed the complex balance of NOx and O3. The O3 levels of the daytime hours from April to September period has shown high buildup on weekend as compare to weekdays due to the least traffic density on the roads.


INTRODUCTION
The air pollution causes persistent smog and health risk to the inhabitants of developing countries such as the state of Kuwait. Since the concept of pollution has existed for a long time, there has been progressing concern about air quality in urban communities. The state of Kuwait is an OPEC member, produces almost two million barrels of oil per day, and has numerous petroleum refineries, petrochemical plants, petroleum dispensing centers, power stations, and oil related industries, and apart from all that, has highly congested roads, with a heavy flux of traffic. The state of Kuwait is located in the Arabian Gulf has a hot dry climate, consists of large uninhabited desert area, with the temperature varying between 40oC and 50oC for at least six months of the year. Therefore, the energy consumption in Kuwait is one of the highest, increasing at an average rate of 7.7%, as compared to developing countries, where this rate is around 2-3 % [1] . Since the state of Kuwait depends mainly on the desalination of seawater to provide its citizens with drinking water, and fulfill the growing demand of electrical power, five major power stations were set up, which work continuously.
The government of Kuwait established the Kuwait Environmental Public Authority (KEPA) in 1995, to safeguard the environment from air pollution due to heavy industrialization. Kuwait EPA established a number of fixed monitoring stations (six stations), to be updated with the air quality in the urban areas, through a monitoring network. These stations continuously measure the levels of pollutants such as SO 2 , NO 2 , CO, NO, CO 2 , H 2 S, O 3 , and TSP (total suspended particles) in the air, the increasing levels of which effect human health, apart from eroding materials [2] .
Bouhamra [3] have reported VOCs concentrations in ambient air after the largest manmade environmental disaster occurred in Kuwait, exploding over six hundred wellhead by the retreating Iraqi army. He reported low concentration but prolonged exposure of these compounds has substantial health risk to Kuwaiti population. Bouhamara et al., [4] have identified large number of organic compounds in indoor and outdoor air of various Kuwaiti houses using GC/FID with Tenax TA cartridge. The concentrations of various contaminants were reported between 100 and 5000g m-in the current study will focus on them. Rigakarandinos and Saitanis [6] conducted a study comparing the air quality of two Mediterranean coastal cities in Greece, Volos, and Patras, and their results showed that the O3 levels in Volos were higher than those in Patras during the period of April -September 2004, and the SO2 levels higher in Patras than in Volos. A comparative study of variation in daily ozone maxima between the different days of the week in big French cities over the summer period of 1994-1996 indicates a difference of almost 20% between the highest values of ozone concentration measured on weekdays and over the weekend, while traffic levels vary by more than 40% especially between Fridays and Sundays [7] . In Italy the levels of ozone concentration in the weekend was higher in the two cities of Milan and Varenna, either Milan is higher, or both are high [8] . Also, Pont and Fontan have wrote that as a reducing traffic to the normal weekend regime the concentration of ozone (O3) on the next day will increase all over the country in the Belgium [7] .

Fig. 1: location of Rabia area in Kuwait state
Geographical data: Rabia area is located in the southwest of central Kuwait, with a total area of 2456 km2 and is mainly flat land. The fixed monitoring station for Rabia is located above the polyclinic, in the center of the area. There are two major highways passing adjacent to it, fifth ring road to the north, and sixth ring road from the south. There is an industrial area, Shuwaikh industrial consisting mainly of garages and workshops for the repair of cars located to the north of Rabia. The International Airport of Kuwait is located to the southeast, where daily many planes take off and land at regular intervals. Rabia is also flanked by two power stations, Doha to the northwest, and Subyia to the northeast, and a wastewater treatment plant located to the southwest, in Ardiya. Form Kuwait Municipality the total population of Rabia is about 30000 to 35000. The total locality is divided into five blocks, consisting of 320 houses, 7 schools, a polyclinic, a police station, 14 co-operative stores, 20 main electrical distribution stations, two petrol stations one to the east, and the other to the west. There is a wedding hall, a restaurant and a training institute of the public authority for agriculture and fish resources, which is located to the east. Traffic moves in and out of Rabia through many main streets, to the center of the city. The rush hours are 7:00 to 9:00 am in the morning, and around 5:00 to 8:00 pm in the evening. Most of the pollution resulting form traffic is due to heavy vehicles that use diesel as fuel, and light vehicles using gasoline as fuel.

Meteorological Data and methods: The Kuwait
Environmental Protection Authority (KEPA) Fixed an Air pollution monitoring (APM) station that consists of direct reading instruments for measuring major air pollutants as well as meteorological parameters, is located over the polyclinic Building in Rabia. The data were obtained from KEPA for year 2001 and year 2004 and consisted of the hourly averages of continuous measurements of the concentration of the pollutants SO2 (ppm), NO2 (ppm), CO (ppm), NO (ppm) and O3 (ppm) and meteorological data.

Discussion:
The investigation of this study shows the comparison between the trend of three primary pollutants SO 2 , NO 2 and O 3 using a fixed monitoring station located above the polyclinic at a height of about 6m in the Rabia residential area in Kuwait state using hourly data for the four seasons in two years 2001 and 2004 (Fig. 1). This work covers a thorough analysis of the trends in air pollution levels of SO 2 , NO 2 and O 3 and their most probable sources in Rabia area in the State of Kuwait. In order to assess the air quality in this area, measured concentration values of these pollutants have been analyzed and compared with the specified SO 2 sources: SO 2 is released in the air during the exploration, transportation, and consumption of fuel. The main contribution is from the oilfields, during exploration, production and transportation of oil, to refineries and other related industries, during refining, processing, flaring, and transport industry, which is one of the end users, and power stations that use oil to generate electric power. These sources and their emissions are directly related to the operational conditions of the machinery involved, and the prevailing weather conditions that ultimately determine the fate of sulphur dioxide released to the environment. There was no observed violation exceeding 170 ppb, the specified limit of KEPA for SO 2 concentration in this period. The maximum hourly SO 2 concentration was around 134 ppb at 11:00Hr on 5 th September where the corresponding temperature was 47.6ºC, relative humidity 13.78%, wind speed 2.43 ms -1 from NW direction (299 o ). The most probable source was the Doha power station, confirming the fact that the power plants run at peak loads during summer. The maximum daily mean SO 2 concentration for this period was 16.02ppb, corresponding to 5 th September. The monthly average SO 2 concentration in July was 1.4±0.62σ ppb, where σ =0.175, August 1.3±0.7σ ppb, where σ =0.163 and in September was 3.7±0.66σ ppb, where σ =0.395.

Autumn:
The available values for recorded SO 2 hourly concentrations in autumn period (October to December) for year 2004 was 63.53 % and there was no obvious violation exceeding 170 ppb specified limit of KEPA for SO 2 concentration in this period. The maximum hourly SO 2 concentration was around 23.25 ppb at 11:00Hr on 27 th December where the corresponding temperature was 12.6ºC, relative humidity 55.2%, wind speed 3.01 ms -1 from WNW direction (290 o ). The most probable source is the Doha power station, working in peak load in the summers, using heavy fuel containing 4% sulphur. The maximum daily mean SO 2 concentration for this period was 9.53ppb, corresponding to 11 th December. The monthly average SO 2 concentration in October was 2.8±0.91σ ppb, where σ =0.166, and in December was 3.4±0.81σ ppb, where σ =0.279.
The available values for recorded SO 2 hourly concentrations in this period for year 2001 was approximately 98.45%, and there was no observed violation exceeding 170 ppb specified limit of KEPA for SO 2 concentration in this period. The maximum hourly SO 2 concentration was around 114.7 ppb at 20:00Hr on 21 st November where the corresponding temperature was 20.7Cº, relative humidity 52.5%, wind speed 0.73 ms -1 from SE direction (142.5 o ). The most probable source is the high traffic load at the junction of the Gazalli expressway, and 6 th ring road. The maximum daily mean SO 2 concentration for this period was 35.68ppb, corresponding to 21 st November. The monthly average SO 2 concentration in October was 2.8±0.63σ ppb, where σ =0.307, November 4.2±0.35σ ppb, where σ =0.68 and in December was 1.4±0.84σ ppb, where σ =0.97.
Overall, it can be seen that the overall SO 2 concentration for the year 2001 was greater than 2004. This can be credited to the growing environmental awareness that has prompted changes like the use of cleaner fuel, treatment prior to discharge, etc. In the year 2004, the trend is opposite, with the highest concentration detected in summer, followed by autumn, spring and lastly winter. This is explained by the growing demand of power to meet the requirements of the nation. With an increased investment in real estate and a boom in the construction business, power requirements have become gargantuan. The summer temperatures escalate the need for comparative cooling causing the power stations to be running at peak loads, and in spite of the favorable dispersion conditions the concentration noticed are comparatively high. In the year 2001, however, the highest concentration detected was in the winter period, followed by autumn, and then spring and lastly summer. This is because the winters in Kuwait portray a low temperature, low inversion layers, lesser wind movements, which do not promote the dispersion of pollutants, as compared to summers, which have high temperature, high inversion layers, high wind movements and effective distribution and dilution of pollutants._-O 3 sources: It is a secondary pollutant, created in the presence of sun light, NOx and a pre-curser VOCs. It is complimentary in its action along with NOx, in that in the presence of sunlight, the available concentration of NOx is consumed and used in generation of ozone, while in the absence of sunlight, the reversible reaction prevails, reducing the O 3 concentrations, and enhancing the NOx concentrations. The analysis of ozone during the daytime was found to be significantly due to high O 3 precursor concentrations generating substantial O 3 levels than that of nighttime where only neutralization occurs due to fresh NO production [9] . In the case of NO 2 , the overall concentrations were higher in 2001, as compared to 2004. In 2004, the highest concentration detected was in summer, followed by winter, then spring, and lastly autumn. In the year 2001, the highest concentration was seen in autumn, followed by summer, winter, and lastly spring. This is simply because the increase in the number of vehicles over the years, have scaled up the production of NO, subduing the ozone production, which inevitably subdues NO 2 formation.
To asses the air quality in Rabia area, air pollution data for two years, 2001 and 2004 for this area in the state of Kuwait were obtained from a monitoring station located at the top of polyclinic. The pollutants under observation were O 3 , SO 2 , NO 2 , CO and NO. When considering the sources of these pollutants, the location of Rabia is very crucial. It is flanked by three major highways on three of its sides, 5 th ring road to the north, 6 th ring road to the south, and Gazalli highway to the east, while the fourth side is shared with Ardiya area, which houses transport offices that have come up substantially over the years. These offices mobilize goods using heavy transport vehicles and trailers. Further north, is the industrial areas of Rai and Shuwaikh, which house numerous garages, and metal processing workshops. There are two large power plants, Doha complex 16km to the northwest and Subyia power plant 25km to the northeast, which use heavy oil for the production of power that contains about 4% sulfur. Also, there is airport 8km to the southeast. The east and west boundaries accommodate two fuel dispersing stations. In the close vicinity of the monitoring station is also located a restaurant that use coal fires for the roasting of meat as part of its daily activities. Taking all these sources into consideration, the stress on the air quality in this area is quite significant. In order to understand the impact on the environment a detailed examination of the seasonal and diurnal variations was carried out, the results of which are quite crucial.
With respect to the standards set by the Kuwait EPA Table (1), all pollutants come within the set limits with no observations of any violations during the study period. All of the primary pollutants show higher concentration levels in winter months as compared to the summer months except in the case of NO 2 in the year 2004. This can be attributed to the fact that high temperatures, high winds, high inversion layer, and a very significant dispersion rate of pollutants characterize the summer in the state of Kuwait. Winter season is characterized by the exact opposite features, namely low temperatures, low winds; a low set inversion layer, and poor dispersion of pollutants. Kuwait ranking as one of the highest oil producing countries in the world also has a large number of related industries for the refining and processing of this oil and its various fractions. This is the main source of SO 2 , along with power stations, and vehicle emission. The SO 2 emissions also show high concentrations in summer, when the power stations are running at peak load to meet the power needs of the country. NO 2 , CO and NO are also released by the same sources. The major sources of SO 2 emission in Kuwait are the electrical power generation stations and water desalination plants. The prevailing wind in Kuwait is almost from northwest, so that the Doha complex, which consists of Doha east and Doha west power stations located near the residential areas, makes the highest contribution of about 49% of the total SO 2 emitted in Kuwait [10] .
In the 24-hour trend for these pollutants Fig. (2-a,  2-b), we see two distinct peaks, which is a characteristic feature of urban regions. The first one occurs between 6:00hr and 8:00hr, which represents the traffic congestion caused by people commuting to work, and children commuting to school. The second peak is comparatively longer, from 16:00hr to 21:00hr, and represents people driving out to meet friends, shopping malls, or just out for some fresh air. O 3 on the other hand, being a secondary pollutant, with a high dependence on photochemical oxidation shows a single stretched peak limited to the daytime, and two characteristic troughs. This is linked to the antagonistic behavior of O 3 towards NO, where the NO concentrations are depleted in the presence of NO concentrations are depleted in the presence of sunlight and O 3 precursor gases. The reverse is true in the absence of sunlight. NO concentrations nose dive after the first morning peak, with increasing solar radiation, remains dormant until 16:00hr and then begins to climb of the second peak. These concentrations remain elevated with fresh emissions from vehicles and reverse conversion of ozone to NO, until 7:00hr the next day morning.
Another characteristic feature in the observations for the two years data is the higher values of SO 2 in the year 2001 as compared to the year 2004. This is due to the rising awareness towards the environment that has brought about radical changes, which can be seen in the use of better quality of oil in all the various processes, as well as treatment processes to curb the discharges. The same is the case for NO 2 , and CO, but the reduction is comparatively mild. This is because of the increase in the number of vehicles over the years, personal, as well as commercial, which is of importance to this area, since numerous transport offices with strong fleets of goods carriers have come up in neighboring Ardiya. This increase is reflected quite strongly in the case of NO, where the concentrations have nearly doubled. The concentrations remain unchanged in the case of O 3 , considering that it thrives totally on photochemical oxidation, and there are no alterations in the prevalent climatic conditions in this region.   deposition that results into decrease in O3 levels with reduction in NOx emissions as compare to VOCs. In VOCs sensitive region, (abundance of NOx relative to VOCs) O 3 levels show an increase with the decrease in NOx levels due to reduced titration and HNO3 deposition reactions.
Blanchard and Tanenbaum [15] have discussed O 3 levels increase in VOCs limited zone and is supported from the results of Riga-Karandinos et al., [6]   The concentration of ozone gradually increases due to the photo dissociation of nitrogen dioxide (NO 2 ), mainly coming from automobile exhaust and because of combination of atomic oxygen (O) and molecular oxygen (O 2 ) which is present abundantly in the atmosphere [16] . The building up of ozone (O 3 ) commences when the mixing ratios of ozone (O 3 ) and nitrogen oxide (NO) are equal and is known as termination of the morning inhibition period [11,14] . The accumulation rate of ozone (O 3 ) can be calculated from the slope of ozone (O 3 ) concentration profile reacting to the highest value. This data analysis for ozone (O 3 ) and nitrogen oxide (NO), showed that, the high rate of ozone accumulation (O 3 ) was in summer period (April -September) in both years Fig. (4). As shown in Fig. (4), the crossover in year 2001 occurs about 45 minutes earlier than year 2004 for Rabia area. Riga-Karandinos and Saitanis [6] have presented O 3 and NO mixing ratio in two Mediterranean coastal cities. The crossover in Volos area has occurred about one hour earlier than Patras area. The difference in the crossover time between two years came from the high rate of NO in year 2004 compared to year 2001. The reduction of NO from its peak value to the corresponding point took a longer time but in year 2001, the value of NO is lower than year 2004 hence taking lesser time to reduce NO to crossover point.
As shown in the Fig. (4), the high rate of accumulation of O 3 value for year 2001 occurred faster between 8:00hr and 11:00hr and followed by a slow increase between 11:00hr to 15:00hr, reaching to the highest value at 15:00hr. For year 2004, the O 3 accumulation was identical to year 2001 reaching the maximum value at 15:00hr. The rate of accumulation of Ozone in year 2001 was slightly higher than year 2004. The accumulation rate of ozone (O 3 ) and nitrogen oxide (NO) showed similar trend as observed by Riga-Karandinos and Saitanis [6] .

CONCLUSION
The results of this study show that the concentration of all the pollutants for the year 2001 was greater than 2004 and the levels of pollutants in autumn and winter period are higher than summer and spring period for Rabia area. In the year 2001, however, the highest concentration of SO 2 detected was in the winter period. This is because the winters in Kuwait portray a low temperature, low inversion layers, lesser wind movements, which do not promote the dispersion of pollutants as compared to summers, which have high temperature, high inversion layers, high wind movements and effective distribution and dilution of pollutants. In the year 2004, the trend is opposite, with the highest concentration detected in summer. This can be explained by the highest demand of power generated from power plants to meet the requirements of the nation resulting into high emissions.
Overall, the concentration of ozone in 2001 is greater than 2004 so that the increasing number of cars increase NOx emissions that neutralize O 3 resulting to lower values. In 2001, the highest concentration of O 3 was in summer and for year 2004; the highest concentration recorded was in spring. This is because O 3 being a product of photochemical oxidation, is highly dependant on solar radiation, and O 3 precursor concentrations. In winter, days are short and are cloudier, leading to lower photo-oxidation reactions. In the case of NO 2 , the overall concentrations were higher in 2001, as compared to 2004. In 2004, the highest concentration detected was in summer and in year 2001; the highest concentration was in autumn. This is simply because the increase in the number of vehicles over the years, have scaled up the production of NO, subduing the ozone production, which inevitably subdues NO 2 formation.
Weekdays/weekend effect on O 3 and NO has been investigated for both years 2001 and 2004 for the day hours from 7:00hr to 21:00hr for April to September periods. It was found that on weekend, O 3 levels are high due to lower volumes of traffic while on weekdays O 3 was neutralized by the excessive NO produced by high traffic density.