Polycyclic aromatic hydrocarbon in rain and street runoff in Amman, Jordan

Concentrations of polycyclic aromatic hydrocarbons (PAHs) were determined in the rain and street runoff samples from two sites in the vicinity of Amman City during the pluvial period 1999-2000. The results showed that elevated levels of PAHs were detected in the city center (site 1) than the residential area (site 2) and that the levels were higher in street runoff than rain samples of the same sites. The highest concentration of PAHs in both street runoff and rain samples were observed in the first rainy month (November 1999) which indicated a wash out effect of PAHs originating from vehicular emission accumulated during the long dry summer season before sampling. Within the investigated cold winter seasons, fluctuations in PAHs concentration were observed. The variation was attributed to the fossil combustion for heating purposes and to intervals between rainfalls: as the longer the intervals between rains were, the higher the PAH concentration were. Removal of PAHs from the atmosphere through precipitation over the investigated period varied with time and places depending on the amount of rainfall where higher rainfall removed higher amount of PAHs from the atmosphere. The amount of PAHs washed out through precipitation was estimated to be around 14.8 mg/m2 and 21.1 mg/m2 for sites 1 and 2 respectively.