Petroleum hydrocarbons in urban runoff from a commercial land use area

Abstract

Storm runoff effluent from a shopping mall parking lot was monitored for petroleum hydrocarbons and suspended solids during six storms over a 10-month period. The load of suspended solids (SS) and petroleum hydrocarbons in urban runoff varies widely during the progress of a storm. The highest concentrations and loads of SS and hydrocarbons in each storm are associated with the first major peak in flow rate, the first flush. Upon integration of the loads over time, a total hydrocarbon and SS load was calculated for each storm. The loading relationship was essentially linear with total rainfall, implying that the supply of solids available for incorporation in the runoff had not been exhausted in storms up to 4.06 cm (1.60 in.). There are indications, however, that the supply of hydrocarbons may be approaching a limit in storms greater than 4.82 cm (1.90 in.) of rainfall. The petroleum hydrocarbons were largely associated with particulate material, and the particulate fraction of the hydrocarbons accounted for 83 to 93% of the total. Hydrocarbons associated with these particles accounted for 1.7 to 3.3% of the total mass of the solids.