Ecotoxicological risk of asphalt pavements to aquatic animals associated with pollutant leaching.

Contaminants such as heavy metals and polycyclic aromatic hydrocarbons (PAHs) can be released from asphalt pavement and transported through stormwater runoff to nearby water bodies, leading to water pollution and potential harm to living aquatic animals. This study characterizes the heavy metal and PAH leaching from various asphalt paving materials and their potential ecotoxicological effects on zebrafish Danio rerio. Artificial runoffs were prepared in the laboratory concerning the effects of water, temperature, and traffic. The concentrations of heavy metals and PAHs in the leachates were quantified, while the toxicity assessment encompassed mortality, metal stress, PAH toxicity, inflammation, carcinogenicity, and oxidative damage. Gene expressions of related proteins or transcription factors were assessed, including metallothionines, aryl hydrocarbon receptors, interleukin-1ß, interleukin-10, nuclear factor-κB, tumor necrosis factor-α, tumor suppressor p53, heat shock protein 70, and reactive oxygen species (ROS). The findings demonstrate that leachates from asphalt pavements containing waste bottom ash, crumb rubber, or specific chemicals could induce notable stress and inflammation responses in zebrafish. In addition, potential carcinogenic effects and the elevation of ROS were identified within certain treatment groups. This study represents the first attempt to assess the ecotoxicity of pavement leachates employing a live fish model, thereby improving the current understanding of the environmental impact of asphalt pavements.

Leaching characteristics of metals and Polycyclic Aromatic Hydrocarbons (PAHs) from asphalt paving materials.

Asphalt pavement, a major type of road surface, may contain hazardous elements depending on its specific composition. A growing concern has developed regarding the potential leaching of these hazardous constituents from asphalt pavements, particularly when incorporating waste materials and additives. This study investigates the presence of heavy metals and polycyclic aromatic hydrocarbons (PAHs) in leachates from six commonly employed asphalt paving materials. A comprehensive laboratory leaching experiment was conducted on three key sample scales: asphalt binder, asphalt mortar, and asphalt mixture. The impact of the leachates was assessed by the heavy metal pollution index and the toxic equivalency factor based on the benzo[a]pyrene equivalent concentration. The results reveal that leaching tests at the binder and mortar scales provided fundamental insights into leaching characteristics within a relatively short timeframe, while the mixture-scale test was more capable of representing pollutant leaching in near-true scenarios. In addition, the results indicate potential adverse health implications associated with the incorporation of hazardous waste, such as bottom ash, into asphalt pavement. These findings hold significant implications for promoting environmentally responsible practices of asphalt pavement.

Kinetics and toxicological potential of heavy metal leaching from asphalt pavements.

The leaching of heavy metals from asphalt pavement has attracted increasing attention due to its associated environmental risks. Comprehending the leaching process is crucial for ensuring the safe utilization of asphalt pavement. This study investigates heavy metal leaching kinetics from asphalt pavements using tank-leaching tests and dynamic simulations employing both first and second-order kinetic models. Furthermore, this study reveals the toxicological potential of heavy metal leaching from asphalt pavement by assessing its temporal metal accessibility based on the obtained kinetic attributes. Six distinct asphalt mixtures were prepared and tested, each exhibiting two different gradations. The findings demonstrated that both kinetic models effectively elucidated the leaching process. Notably, the relatively stable final leaching stages primarily adhered to first-order kinetics, while the second-order kinetics provided a superior description of the more intricate initial leaching stages. In terms of toxicological potential, the results indicated that recycled waste-incorporated asphalt pavements, specifically bottom ash-incorporated asphalt and asphalt rubber, exhibited excessive heavy metal leaching for varying durations, ranging from several days to months under specific conditions. This study has provided valuable insights into the metal leaching kinetics of asphalt pavements and their associated toxicological impact, significantly advancing the current understanding of the consequences of heavy metal leaching from asphalt pavements.