2018 Volume 53 Issue 3 Pages 79-87
It is difficult to widely cover air pollution in roadside areas with a limited number of air pollution monitoring stations. Therefore, we focused on the biomonitoring technique using leaves from the roadside trees. In this study, Ginkgo leaves sampled along major arterial roads in Osaka city in the spring, summer and autumn of 2014, 2015 and 2016 were used as the biomonitor. The chemical composition of the particles retained on the leaves was quantified by PIXE (Particle-induced X-ray emission) analysis. The total mass of the particles on the leaves increased with the time between the foliation and sampling date. The particles on the leaves were affected by traffic related sources, with a greater influence by yellow sand in the spring than in the other seasons. The elemental ratios of road dust, brake wear dust and automobile exhaust gas were similar to that of the particles on the leaves. This result suggested that the biomonitoring method in this study captured the characteristics of the roadside air pollution. The elemental ratio obtained by the biomonitoring had different characteristics from that of the SPM (Suspended Particulate Matter) measured at the neighboring roadside monitoring station, because particles larger than 10 μm in diameter can be captured by the leaves and water soluble particles on the leaves can be washed away by the rain. The biomonitoring result using Zelkova leaves shared common characteristics with that of Ginkgo leaves, indicating that the biomonitoring technique can be applied to other species of plants. These results showed that the biomonitoring technique is a potentially effective method to assess roadside air pollution.
