Organic contaminants in urban sediments and vertical leaching in road ditches
Paper in proceedings, 2006
This is a study of the environmental impact of organic contaminants emitted from urban traffic and road infrastructure in Göteborg, Sweden. The vertical leaching of organic contaminants in road ditches, and the occurrence of organic contaminants in stormwater sediment, urban soil and shallow groundwater, have also been investigated.
A total of 80 specific organic contaminants were analysed in the stormwater sediment sample, and of these as many as 40 specific organic contaminants were identified. The concentration of total semi-volatiles, alkylbenzenes, aliphatics, 4-nonylphenols, total of mono- and di-nonylphenol ethoxylates, carcinogenic US EPA polycyclic aromatic hydrocarbons PAH–16, diethyl hexylphthalate DEHP and several brominated flame retardants, were all analysed in high concentration.
Depth profiles, in clay, clay/sand and sand road ditches, at four places along highway E20, were analysed for a total of 40 specific organic compounds. In the soil profiles, total semi-volatiles (< 2,300 mg∙kg-1dw) and carcinogenic PAH-16 (< 1.0 mg∙kg-1 dw) were identified in high concentrations. In one of the clay/sand profiles, total semi-volatiles were identified in decreasing concentrations but until a depth of 1 m, and the carcinogenic PAH-16 until 1.5 m. In reference surface soil samples, taken in the centre of Göteborg, total semi-volatiles and carcinogenic PAH-16 were also analysed in high concentrations. Even in the Göteborg urban shallow groundwater, total semi-volatiles (< 1400 μg∙l-1), and carcinogenic PAH-16 (< 0.4 μg∙l-1) were identified in remarkably high concentrations.
The occurrence of total semi-volatiles and carcinogenic PAH-16 deep in road ditches, and the high levels in urban groundwater, show the need for efficient construction of road ditches or efficient treatment of road runoff water in urban and traffic-related areas to prevent contamination. The high levels of total semi-volatiles in all samples show that most of the contaminants occurring in urban environments are still unidentified compounds with unknown environmental effects. The relative composition of the specific PAH-16 indicates rubber tyres, vehicle exhausts and asphalt materials to be the main sources of PAH contamination.