Walid Bouhamra

Measurement and prediction of ozone levels around a heavily industrialized area: a neural network approach

Abstract This paper presents an artificial neural network model that is able to predict ozone concentrations as a function of meteorological conditions and precursor concentrations. The network was trained using data collected during a period of 60 days near an industrial area in Kuwait. A mobile monitoring station was used for data collection. The data were collected at the same site as the ozone measurements. The data fed to the neural network were divided into two sets: a training set and a testing set. Various architectures were tried during the training process. A network of one hidden layer of 25 neurons was found to give good predictions for both the training and testing data set. In addition, the predictions of the network were compared to measurements taken during other times of the year. The inputs to the neural network were meteorological conditions (wind speed and direction, relative humidity, temperature, and solar intensity) and the concentration of primary pollutants (methane, carbon monoxide, carbon dioxide, nitrogen oxide, nitrogen dioxide, sulfur dioxide, non-methane hydrocarbons, and dust). A backpropagation algorithm with momentum was used to prepare the neural network. A partitioning method of the connection weights of the network was used to study the relative % contribution of each of the input variables. It was found that the precursors carbon monoxide, carbon dioxide, nitrogen oxide, nitrogen dioxide, and sulfur dioxide had the most effect on the predicted ozone concentration. In addition, temperature played an important role. The performance of the neural network model was compared against linear and non-linear regression models that were prepared based on the present collected data. It was found that the neural network model consistently gives superior predictions. Based on the results of this study, artificial neural network modeling appears to be a promising technique for the prediction of pollutant concentrations.

A NOVEL AIR CONDITIONING SYSTEM Membrane Air Drying and Evaporative Cooling

Anovel system for air conditioning is proposed which combines membrane air-drying and an indirect/direct evaporative cooling (M/ID) system. This combination extends the operating range of the evaporative cooler for small differences of dry and wet bulb temperatures. The study investigates the feasibility of operating the proposed system for the cooling of ambient air to an outlet temperature of 19°C and a relative humidity of 90%. The analysis is performed for the summer weather data of Kuwait, which varies from extremely hot and dry conditions (50°C and less than 20% relative humidity) to warm and humid conditions (35°C and more than 60% relative humidity). System analysis shows limitations imposed on air cooling by the direct evaporative cooler (DEC), the indirect evaporative cooler (IEC), and the indirect/direct evaporative cooler (ID). For ambient temperatures above 35°C, operation of the ID system requires relative humidity values below 30%. Operation of the DEC or the IEC systems is limited to temperatures below 30°C and relative humidity below 50%. The ID system operates at temperatures above 45°C and relative humidity below 50%. The M/ID operation covers a relative humidity range between 30–100% and a temperature range between 25–45°C. Energy consumption for various cooling combinations, including mechanical vapour compression (MVC), is evaluated by the energy efficiency rating (EER). The M/ID system shows savings of up to 86.2% of the energy consumed by the stand-alone MVC system. Also, the combined systems of MVC/IEC and the MVC/ID show savings of 49.8 and 58.9% over the conventional MVC.

Predicting ozone levels : A statistical model for predicting ozone levels in the Shuaiba Industrial Area, Kuwait.

This paper presents a statistical model that is capable of predicting ozone levels from precursor concentrations and meteorological conditions during daylight hours in the Shuaiba Industrial Area (SIA) of Kuwait. The model has been developed from ambient air quality data that was recorded for one year starting from December 1994 using an air pollution mobile monitoring station. The functional relationship between ozone level and the various independent variables has been determined by using a stepwise multiple regression modelling procedure. The model contains two terms that describe the dependence of ozone on nitrogen oxides (NOx) and nonmethane hydrocarbon precursor concentrations, and other terms that relate to wind direction, wind speed, sulphur dioxide (SO2) and solar energy. In the model, the levels of the precursors are inversely related to ozone concentration, whereas SO2 concentration, wind speed and solar radiation are positively correlated. Typically, 63 % of the variation in ozone levels can be explained by the levels of NOx. The model is shown to be statistically significant and model predictions and experimental observations are shown to be consistent. A detailed analysis of the ozone-temperature relationship is also presented; at temperatures less than 27 °C there is a positive correlation between temperature and ozone concentration whereas at temperatures greater than 27 °C a negative correlation is seen. This is the first time a non-monotonic relationship between ozone levels and temperature has been reported and discussed.

Characterization of Particulate Matter for Three Sites in Kuwait

Abstract Many studies have shown strong associations between particulate matter (PM) levels and a variety of health outcomes, leading to changes in air quality standards in many regions, especially the United States and Europe. Kuwait, a desert country located on the Persian Gulf, has a large petroleum industry with associated industrial and urban land uses. It was marked by environmental destruction from the 1990 Iraqi invasion and subsequent oil fires. A detailed particle characterization study was conducted over 12 months in 2004–2005 at three sites simultaneously with an additional 6 months at one of the sites. Two sites were in urban areas (central and southern) and one in a remote desert location (northern). This paper reports the concentrations of particles less than 10 µm in diameter (PM10) and fine PM (PM2.5), as well as fine particle nitrate, sulfate, elemental carbon (EC), organic carbon (OC), and elements measured at the three sites. Mean annual concentrations for PM10 ranged from 66 to 93 µg/m3 across the three sites, exceeding the World Health Organization (WHO) air quality guidelines for PM10 of 20 µg/m3. The arithmetic mean PM2.5 concentrations varied from 38 and 37 µg/m3 at the central and southern sites, respectively, to 31 µg/m3 at the northern site. All sites had mean PM2.5 concentrations more than double the U.S. National Ambient Air Quality Standard (NAAQS) for PM2.5. Coarse particles comprised 50–60% of PM10. The high levels of PM10 and large fraction of coarse particles comprising PM10 are partially explained by the resuspension of dust and soil from the desert crust. However, EC, OC, and most of the elements were significantly higher at the urbanized sites, compared with the more remote northern site, indicating significant pollutant contributions from local mobile and stationary sources. The particulate levels in this study are high enough to generate substantial health impacts and present opportunities for improving public health by reducing airborne PM.

Source apportionment of fine particles in Kuwait City

This study investigated major sources of PM2.5 in the atmosphere of Kuwait based on a sampling program conducted between February 2004 and October 2005. Three source identification techniques were used in this study: (1) a positive matrix factorization model; (2) backward trajectory profiles; and (3) concentration rose plots. Five major sources of PM2.5 were estimated. These were sand dust (sand storms), oil combustion (power plants), petrochemical industry (fertilizer, nylon or catalyst regeneration facilities), traffic (vehicle emissions and road dust) and transported emissions (emissions from outside Kuwait, such as those from automobiles, road dust or smelters). The estimated contributions to PM2.5 of these sources were: 54% from sand dust, 18% from oil combustion, 12% from petrochemical industry, 11% from traffic and 5% from anthropogenic sources transported from outside the country. Oil combustion, petrochemical industry and traffic were found to emanate from local sources, whereas sand dust and some emissions from traffic, and possibly smelters, appeared to originate from sources outside of Kuwait (transported). The PM2.5 levels in Kuwait during our previous sampling study averaged 53μg/m(3). More than half of the measured PM2.5 appears to have been due to crustal material, much originating outside of the country. However, the relatively high levels of PM2.5 contributed by anthropogenic local sources, such as oil combustion, petrochemical industry emissions, and traffic indicated that there may be great opportunities for Kuwait to improve public health. The application of cost-effective emission controls and development of forward looking environmental health policies have the potential to significantly reduce emissions, population exposures to PM2.5 and the burden of mortality and morbidity from air pollution.

Description of outdoor air quality in a typical residential area in Kuwait

Abstract This paper presents a statistical analysis of the data collected by the air pollution mobile laboratory operated by Kuwait University. The experimental work was based on operating the mobile laboratory in the Mansouriya residential area for a period of 1 month (May 1994). The site was selected to represent a typical residential area which is impacted mainly by the heavy traffic into and out of Kuwait city. The levels of carbon monoxide (CO), nitrogen oxide (NO), nitrogen dioxide (NO 2 ) and ozone (O 3 ) were selected for analysis. These are the pollutants likely to result from traffic movement in any urban area. Sulphur dioxide (SO 2 ) was also monitored during the same period. The measured variables include some meteorological parameters such as temperature, relative humidity, atmospheric pressure, solar radiation, wind speed and wind direction, which were also recorded at the same time. The study investigates the atmospheric levels of pollutants in the Mansouriya area and the expected source contributing to these pollutants. The objective of this work was to measure the atmospheric levels of pollution in terms of NO, CO, NO 2 , SO 2 and O 3 and to compare with the international standard limits for urban areas. Another objective of the study was to study the diurnal variations of these pollutants. The results of this study indicate that the levels of air pollutants are within the recommended range for residential areas according to US Environmental Protection Agency standards. The distribution of CO was correlated with heavy traffic movement during rush hours. However, SO 2 levels also followed a similar pattern. This was attributed to heavy diesel operational equipment and trucks at the highway construction site near the area of study. The hourly distributions of CO, NO and NO 2 were also compared over the days of the week. The results show that no morning peaks were detected for these gases during weekends. Correlation between O 3 levels and NO and NO 2 was also carried out. The O 3 levels show a peak at the early morning hours and a major peak during midday. This is attributed to the photochemical reactions during the month of May which is the real start of summer in this area.

DIURNAL VARIATIONS OF AIR POLLUTION FROM MOTOR VEHICLES IN RESIDENTIAL AREA

This paper employs the air quality data assembled by the Kuwait University mobile air pollution monitoring laboratory (Chemical Engineering Department). The experimental work has been conducted in the urban atmosphere of Khaldiya residential area in Kuwait University during 1997. The site was selected to represent a typical residential area which is mainly under high traffic influences. The data collected consist mainly of measurements of carbon monoxide (CO), nitrogen oxides (NOx), non‐methane hydrocarbon (NMHC) and Ozone (O3). It is important to determine the behavior of these pollutants relative to meteorological parameters. Wind speed and direction were monitored simultaneously. The first objective of this paper is to measure the atmospheric levels of these pollutants and then compare their values with the international standard limits for an urban area. The second objective is to understand the diurnal and monthly variations of these pollutants. The third objective is to study the distribution levels of these pollutants with respect to meteorological parameters such as wind speed and direction. The results showed that the levels of NMHC and NOx exceeded the proposed ambient air quality standard for residential areas in Kuwait. The monthly mean distributions of NMHC, CO and NOx showed distinct patterns with the lower concentrations during the summer period (July and August). The distribution of O3 was different from the other gases. The maximum was seen in July and August. The hourly mean distribution of pollutants reported two types of concentration variations. The hourly mean distribution of NMHC, CO and NOx were generally characterized by three peaks which were associated with the traffic loads on the main streets. On the other hand, the variation corresponding to O3 revealed the occurrence of two daily maxima. The main distribution of the various pollutants according to wind speed indicated a marked drop with stronger winds and this was common to NMHC, CO and NOx. The mean O3 level with the wind speed showed an opposite picture.

Performance of Evaporative Condensers

Experimental investigation is conducted to study the performance of evaporative condensers/coolers. The analysis includes development of correlations for the external heat transfer coefficient and the system efficiency. The evaporative condenser includes two finned-tube heat exchangers. The system is designed to allow for operation of a single condenser, two condensers in parallel, and two condensers in series. The analysis is performed as a function of the water-to-air mass flow rate ratio (L/G) and the steam temperature. Also, comparison is made between the performance of the evaporative condenser and same device as an air-cooled condenser. Analysis of the collected data shows that the system efficiency increases at lower L/G ratios and higher steam temperatures. The system efficiency for various configurations for the evaporative condenser varies between 97% and 99%. Lower efficiencies are obtained for the air-cooled condenser, with values between 88% and 92%. The highest efficiency is found for the two condensers in series, followed by two condensers in parallel and then the single condenser. The parallel condenser configuration can handle a larger amount of inlet steam and can provide the required system efficiency and degree of subcooling. The correlation for the system efficiency gives a simple tool for preliminary system design. The correlation developed for the external heat transfer coefficient is found to be consistent with the available literature data.

Sorption of volatile organic compounds on typical carpet fibers

Measurements of adsorption isotherms for three volatile organic compounds (VOCs) (toluene, 1,2-dichlorobenzene and 1,1,1-trichloroethane) on polyacrylonitrile carpet fibers over the temperature range 25-45 degrees C were carried out in a thermogravimetric analyzer (TGA). Linear isotherms were observed in all cases with values of the Henry coefficient ranging from 0.063 to 0.941 mm. The results of additional experiments carried out in a simple test chamber containing a single source of VOC showed that the carpet fibers acted as a significant sink causing a prolonged elevation of VOC concentration in the air within the chamber. An unsteady-state model is presented, which adequately described the adsorption and desorption phenomena occurring in the test chamber and yielded realistic values of the adsorption and desorption rate constants. There was good agreement between the equilibrium and kinetic constants obtained in the TGA and test chamber experiments.

Estimation of optimum requirements for indoor air quality and energy consumption in some residences in Kuwait

Contrasting effects of the dilution of indoor generated pollutants and the energy efficiency of heating and ventilating air conditioning systems (HVAC) for indoor air quality (IAQ) and thermal comfort were studied for 10 Kuwaiti residences. The levels of volatile organic compounds (VOCs) and the calculated cooling load of the HVAC systems were used as indicators for the IAQ and for the energy consumption, respectively. Air exchange rates and VOCs levels (both indoor and outdoor) were measured. It was found that the outdoor VOC concentrations were always less than the indoor values. Therefore reduction of indoor VOC levels can be accomplished either by increasing the ratio of the makeup air to the recirculation air of the HVAC system or by increasing the infiltration airflow rate through openings. A single compartment IAQ model, modified by the authors, was used to test for the variation in the above two dilution modes and to test the performance sensitivity. Hence, the optimum parameters in terms of IAQ and energy consumption were determined. The results indicated that it was necessary to increase the ratio of the makeup air to the recirculation air from its typical design value of 0.5 to a range of 0.7-1.3 in order to reduce indoor VOC to acceptable levels.