New Research Article by Horstmeyer et al. 2018

For the infiltration of runoff from traffic areas, a tailored pretreatment is recommended that is considering the site-specific contamination level, e.g., by using a vegetated topsoil in accordance with the German Standards DWA-A 138 and DWA-M 153. Following this approach, the contamination level of the runoff is categorized by the annual average daily traffic (AADT). Earlier studies determined that further factors such as stop-and-go traffic, junctions, and guardrails should be consi- dered for the determination of the pollution and the design of vegetated infiltration swales. The analysis of 262 soil samples from 35 infiltration swales revealed that the heavy metals lead, cadmium, chromium, copper, and zinc are retained at differ- ent depths and distances from the roadway. For copper and zinc contents, which correlate with the organic carbon content, a significant decrease as a function of depth and distance from the traffic area was determined. The migration of cadmium in deeper layers is particularly important for operation and maintenance of infiltration swales to avoid any adverse effects on groundwater quality. Revealing a general service life of the topsoil used in infiltration swales is not possible because of the heterogeneity of the soils and the varying site-specific conditions.

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