title: Air quality in Yanbu, Saudi Arabia.
abstract: Yanbu, on the Red Sea, is an affluent Saudi Arabian industrial city of modest size. Substantial effort has been spent to balance environmental quality, especially air pollution, and industrial development. We have analyzed six years of observations of criteria pollutants O3, SO2, particles (PM2.5 and PM10) and the known ozone precursors-volatile organic compounds (VOCs) and nitrogen oxides (NOx). The results suggest frequent VOC-limited conditions in which ozone concentrations increase with decreasing NOx and with increasing VOCs when NOx is plentiful. For the remaining circumstances ozone has a complex non-linear relationship with the VOCs. The interactions between these factors at Yanbu cause measurable impacts on air pollution including the weekend effect in which ozone concentrations stay the same or even increase despite significantly lower emissions of the precursors on the weekends. Air pollution was lower during the Eids (al-Fitr and al-Adha), Ramadan and the Hajj periods. During Ramadan, there were substantial night time emissions as the cycle everyday living is almost reversed between night and day. The exceedances of air pollution standards were evaluated using criteria from the U.S. Environmental Protection Agency (EPA), World Health Organization (WHO), the Saudi Presidency of Meteorology and Environment (PME) and the Royal Commission Environmental Regulations (RCER). The latter are stricter standards set just for Yanbu and Jubail. For the fine particles (PM2.5), an analysis of the winds showed a major impact from desert dust. This effect had to be taken into account but still left many occasions when standards were exceeded. Fewer exceedances were found for SO2, and fewer still for ozone. The paper presents a comprehensive view of air quality at this isolated desert urban environment.
  
  
  CONCLUSIONS
  Frequent VOC-limited conditions are found at Yanbu in Saudi Arabia that increase ozone pollution if NOx is are reduced. In this desert environment, increased nightlife produces the highest levels of VOCs and NOx at night rather than the day. The effects increase during Ramadan. Fine particles peak twice a day-the morning peak is caused by traffic and increases with decreasing wind, potentially representing health concerns, but the larger afternoon peak is caused by the wind, and it increases with increasing wind speeds. These features suggest that exposure to pollutants must be redefined for such an environment.
authors.affiliation: a Department of Physics , Portland State University , Portland , Oregon , USA.|b Department of Meteorology, Faculty of Meteorology , Environmental and Arid Land Agriculture, King Abdulaziz University , Jeddah , Saudi Arabia.
authors.forename: M A K
authors.initials: MA
authors.lastname: Khalil
authors.affiliation: a Department of Physics , Portland State University , Portland , Oregon , USA.
authors.forename: Christopher L
authors.initials: CL
authors.lastname: Butenhoff
authors.affiliation: a Department of Physics , Portland State University , Portland , Oregon , USA.|d Department of Civil and Environmental Engineering , Massachusetts Institute of Technology , Cambridge , Massachusetts , USA.
authors.forename: William C
authors.initials: WC
authors.lastname: Porter
authors.affiliation: b Department of Meteorology, Faculty of Meteorology , Environmental and Arid Land Agriculture, King Abdulaziz University , Jeddah , Saudi Arabia.
authors.forename: Mansour
authors.initials: M
authors.lastname: Almazroui
authors.affiliation: b Department of Meteorology, Faculty of Meteorology , Environmental and Arid Land Agriculture, King Abdulaziz University , Jeddah , Saudi Arabia.
authors.forename: Abdulrahman
authors.initials: A
authors.lastname: Alkhalaf
authors.affiliation: c Presidency of Meteorology and Environment , Jeddah , Saudi Arabia.
authors.forename: Mohammed Saleh
authors.initials: MS
authors.lastname: Al-Sahafi
mesh_terms: D000393:Air Pollutants / Q000032:analysis* / Q000592:standards; D000397:Air Pollution / Q000706:statistics & numerical data*; D003469:Culture; D009589:Nitrogen Oxides / Q000032:analysis / Q000737:chemistry; D010126:Ozone / Q000032:analysis / Q000737:chemistry; D012529:Saudi Arabia; D055549:Volatile Organic Compounds / Q000032:analysis / Q000737:chemistry; D014887:Weather
chemical_list: D000393:Air Pollutants; D009589:Nitrogen Oxides; D055549:Volatile Organic Compounds; D010126:Ozone