Potential risk from the use of mine-contaminated sediments for road and rail embankments: preliminary data from Central Italy

Mercury contamination of stream sediments in the Paglia and Tiber river catchments (Central Italy) from the abandoned Monte Amiata mining district has long been documented (Rimondi et al., 2019, and references therein). Along the river courses, fluvial sediments have been quarried for decades to obtain sand and gravel for several industrial uses, including construction of road and rail embankments. Although specific information is not available, there is a high chance that some of this material was used for two major Italian transport routes, the A1 Expressway, and the Alta Velocità (=high speed; AV) railroad.

A preliminary survey was conducted near the city of Orvieto (Umbria region, Central Italy) by taking soil samples in proximity of the embankments of A1 and AV. Both constructions occurred in the 1960s-1970s, when the Monte Amiata mines were still active; specifically, the A1 section Chiusi-Orvieto was completed in 1964, and the AV section Città della Pieve-Roma was completed in 1977. Samples from the embankment of the older railroad Orvieto-Orte (completed in 1874, when mining at Monte Amiata was just beginning) were also taken for comparison.

Samples near the A1 and AV embankments show Hg contents ranging from 1.4 to 9.2 mg/kg, and 2.7 to 5.8 mg/kg, respectively. All these values exceed the limit (1 mg/kg) established by Italian regulations for public green and civil use soil; some also exceed the limit (5 mg/kg) for industrial soil. By contrast, samples from the old railroad show values of 0.3-0.4 mg/kg, below the law limits.

The immediate risk to local inhabitants is deemed low; however, these preliminary results indicate a potential contamination of highway and railroad embankments from mine-impacted sediments, and suggest the opportunity of a more systematic study.

Rimondi V., et al. (2019) – Environmental Pollution 255, 113191