Concentrations of nitrogen dioxide throughout the state of Bahrain.

A comprehensive field study of atmospheric NO2 was conducted throughout the state of Bahrain, using passive diffusion tube samplers. A total of 319 tubes were used, and all sites were chosen to include residential, heavy and low traffic roads, industrial, airport and commercial areas. The results of the survey revealed marked spatial variations in NO2 concentrations. The weekly mean NO2 values varied from 76 microg m(-3) in the north-eastern part of Bahrain island to 13 microg m(-3) in the south-east of Muharaq island. Generally, NO2 values decreased from the north to the south, where traffic volume and density also decreased. In addition, the results indicated that high traffic areas revealed higher NO2 levels compared with airport and industrial areas. The highest NO2 concentrations were measured in roads characterized by being narrow and confined, with many traffic lights and roundabouts, indicating the influence of road geometry on NO2 levels. The results provide valuable baseline information for future investigators, especially since the study was conducted at the start of the Gulf War, which was accompanied by substantial emissions of NO2 from jet fighters and burning of about 600 oil fields.