Heavy metals can directly harm public health by entering the body via soil and dust, dermal contact or breathing. The typical elements Cd, Pb, Zn, and Cu in the roadside soils, coming from traffic activity, can be transported through the food chain into the human body and thus be very toxic to people.
Roadway runoff can include breakdown products from asphalt emulsifiers since a significant metal concentration is found in the polar fraction of asphalt binders as measured on the Schieff scale.
This article reviews the runoff from asphalt roadways as a source of pollution to drinking water and proposes a scheme for measuring and quantifying the amounts of metals in their source materials used to bind asphalt used in making roads.
The use of bench top EDXRF to characterize binders before blending them into asphalt cements is possible because the metal values are in the 10s – 1000s of ppms and are readily monitored. The data generated in this study was collected on a Xenemetrix X-Cite Benchtop using the Analytix software package which has both empirical and fundamental parameter processes for evaluating data.
XRF is a very cost effective method for characterizing the metal content in asphalt and asphalt related materials. Relatively simple sample preparation steps and sophisticated matrix correction methods can lead to highly accurate and precise results. Cross checking by ICP would be a good practice for any large scale XRF monitoring program. Essentially well characterized samples that are products of round robin analysis that run through the Federal Highways Department can serve as check standards in XRF protocols.
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