1. Leaching of PAHs from Hot Mix Asphalt Pavements.
- Author
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Birgisdóttir, H., Gamst, J., and Christensen, T. H.
- Subjects
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ASPHALT pavements , *ROAD construction , *POLYCYCLIC aromatic hydrocarbons , *SOIL quality , *AROMATIC compounds , *SOIL leaching , *BITUMINOUS materials , *ENVIRONMENTAL protection - Abstract
Asphalt has been widely used as the primary bound road construction material, both as road base material and wearing course. Polycyclic aromatic hydrocarbons (PAHs) have commonly been observed in soils near and under roads. However, the contribution from PAH leaching from asphalt to the actual contamination of the soil adjoined to the road has been poorly described. Leaching of the 16 U.S. EPA PAHs from bitumen-based asphalt was investigated for four asphalt specimens and modeled for general road constructions scenarios. The total content of PAHs in the asphalt specimens was for three of four asphalt specimens below the Danish soil quality criteria. The availability of the sum of the 16 U.S. EPA PAHs was found to be in the range 3–11% of the total content. The experiments involved a 64-day tank leaching test based on the Dutch NEN 7345 standard and a new column-based availability test corresponding to a liquid-to-solid ratio of 100 L kg−1. The tank leaching test indicated that leaching of PAHs was diffusion controlled, although our experiment statistically could document this for only 7 of the 16 U.S. EPA PAHs. Overall, the effective diffusion coefficients for all specimens were within a factor of 100 (one exception) showing no correlation with the number of rings in the PAHs. This suggests that for practical purposes it might be acceptable to use one single diffusion coefficient for all PAHs in asphalt. Scenario calculations indicated that only a minor part of the PAHs present in the asphalt is leached out during 25 years of leaching (0.004–1.1% for five PAHs) corresponding to only of 0.5 mg m−2 of surface in contact with water. Concentrations of PAHs that are found above the Danish soil quality criteria near roads paved with bitumen-based asphalt in Denmark are very unlikely to be caused by leaching of PAHs from the asphalt. [ABSTRACT FROM AUTHOR]
- Published
- 2007
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