Abstract
Measurements of 16 polycyclic aromatic hydrocarbon (PAH) congeners (particles and vapour) have been made at three sites over a distance of 230 km on the Red Sea coast of Saudi Arabia. The data have been pooled with an earlier dataset from three sites in the city of Jeddah, with one urban site common to both studies. The concentrations and congener profiles are broadly similar for the two measurement campaigns at the common site. Coefficients of Divergence have been calculated and show more substantial differences between the sites within the city of Jeddah than are found between the sites to the north of the city which emphasises the strong concentration gradients within Jeddah in comparison to those found in the atmosphere of the coastal sites to the north of the city. A sub-set of data corresponding to days on which the air mass travelled from the northwest parallel with the Red Sea coast, hence linking the three sites, showed a progressive reduction in concentrations as the air mass travelled towards the southeast, which is attributed to emissions from a large source area to the northwest of the sampling sites and either atmospheric dilution or chemical reaction accounting for a progressive reduction in concentrations with advection of the air mass. The congener profile is very similar to that identified in earlier work relating to oil refinery emissions and is consistent with the major petrochemical installation at Yanbu contributing substantial emissions to the atmosphere which are advected to downwind sites.
•PAH (particles and vapour) measured at three sites over 230 km.•Concentration data from six sites are analysed.•Spatial differences are greater within Jeddah than between rural sites.•Samples moving parallel to the Red Sea Coast are analysed.•A major petrochemical plant is the most probable PAH source.