Toward a Cost-Efficient Method for Monitoring of Traffic-Derived Pollutants with Quartz Sand Boxes

摘要

This study aims at understanding characteristics of current traffic pollution at roadsides and to assess the use of magnetic parameters for a cost-efficient monitoring concept. We conducted a systematic monitoring study of roadside pollution at three sites in southern Germany and one site at Lanzhou/China For this purpose, we installed ground-based monitoring boxes filled with clean quartz sand at different distances (1, 2, and 4 m) from the road. Mass-specific magnetic susceptibility (chi), heavy metal (HM) contents, and polycyclic aromatic hydrocarbon (PAH) concentrations all showed decreasing values with distance to the roadside. The temporal variations over 2 years of monitoring reveal an overall increasing trend but differences in depth migration due to seasonal effects (i.e., precipitation). A magnetite-like phase turned out to be responsible for the enhancement of chi. Significant positive correlations between chi and total PAHs as well as HMs for the Gennan sites suggest that chi-which can be measured fast and convenient-can be used as a proxy for traffic-derived. PAH and HM pollution. However, in the much drier region of Lanzhou, the relationship of chi with HMs is much weaker, which might be caused by specific materials used in road construction and heavy vehicles. From the obtained results, we conclude that an appropriate roadside monitoring procedure based on magnetic signatures should best use a single thin (1-2 cm) layer of clean quartz sand protected against lateral material translocation.