The Fate of Pollutants in Porous Asphalt Pavements, Laboratory Experiments to Investigate Their Potential to Impact Environmental Health

Abstract

Pervious Paving Systems (PPS) are part of a sustainable approach to drainage in which excess surface water is encouraged to infiltrate through their structure, during which potentially toxic elements, such as metals and hydrocarbons are treated by biodegradation and physical entrapment and storage. However, it is not known where in the PPS structure these contaminants accumulate, which has implications for environmental health, particularly during maintenance, as well as consequences for the recycling of material from the PPS at the end-of-life. A 1 m3 porous asphalt (PA) PPS test rig was monitored for 38 months after monthly additions of road sediment (RS) (367.5 g in total) and unused oil (430 mL in total), characteristic of urban loadings, were applied. Using a rainfall simulator, a typical UK rainfall rate of 15 mm/h was used to investigate its efficiency in dealing with contamination. Water quality of the effluent discharged from the rig was found to be suitable for discharge to most environments. On completion of the monitoring, a core was taken down through its surface, and samples of sediment and aggregate were taken. Analysis showed that most of the sediment remained in the surface course, with metal levels lower than the original RS, but higher than clean, unused aggregate or PA. However, even extrapolating these concentrations to 20 years’ worth of in-service use (the projected life of PPS) did not suggest their accumulation would present an environmental pollution risk when carrying out maintenance of the pavement and also indicates that the material could be recycled at end-of-life.

Technological Review of Permeable Pavement Systems for Applications in Small Island Developing States

“…PPS have been commended by numerous studies [67,74,93,141,142] for the trapping of sediments and other pollutants during infiltration of stormwater runoff. However, this process can result in the clogging of the pavement surface leading to reduced infiltration rates.…”

“…[145] In a study conducted on 52 permeable pavement sites, Nichols and Lucke [146] found that particle size distribution (PSD) curves could not be used as a stand-alone tool to infer PICP clogging processes but found that fine particles of sizes 251 to 550 µm contributed to lower infiltration rate measurements. Charlesworth et al [142] found that after three years of monitoring, the majority of the sediments were located in the surface layer of a porous asphalt laboratory test rig.…”

The Influence of Geotextile Type and Position in a Porous Asphalt Pavement System on Pb(II) Removal from Stormwater

“…These pollutants include suspended solids, organic matter, nutrients, heavy metals, oils and even polycyclic aromatic hydrocarbons (PAHs) [3,4]. To mitigate these negative effects, and potentially start using stormwater as a resource instead of a waste product, low impact development (LID) options such as permeable pavement systems (PPS), are seeing an increase in implementation in low-traffic areas in place of impermeable surfaces [5][6][7].…”

Porous Concrete for Pedestrian Pavements

“…They are treated by biodegradation and physical entrapment and stored over the long term; heavy metals are stored inside the structure for the service life of the pavement. Charlesworth et al [36] investigated the potential impacts of released contaminants on the environment and human health during maintenance procedures and found that their accumulation does not imply an environmental pollution risk when carrying out pavement maintenance and rehabilitation work. Moreover, the materials could be recycled at end of life.…”

“…The capillary network of pedestrian areas distributed throughout the city could have a strategic role in mitigating flood risks. Despite the punctual approach of water squares [36,37] and water retention chambers [38,39], which are large underground storage facilities, a porous pavement offers a continuous and distributed system to manage rainwater.…”