Effects of the November 2012 Flood Event on the Mobilization of Hg from the Mount Amiata Mining District to the Sediments of the Paglia River Basin

Giulia Pattelli,Pierfranco Lattanzi,Antonella Colica,Marco Benvenuti,Massimo Rinaldi,Francesco Benedetto,Valentina Rimondi,Pilario Costagliola,Mario Paolieri,Laura Chiarantini

doi:10.3390/min4020241

Giulia Pattelli, Pierfranco Lattanzi + Show 8 more

Open Access

https://doi.org/10.3390/min4020241

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Journal: Minerals	Publication Date: Apr 9, 2014
Citations: 27	License type: CC BY 4.0

Affiliation: University of Cagliari, University of Florence

Abstract

The Mount Amiata mining district (southern Tuscany, Italy) was, for decades, one of the world’s largest mercury (Hg) producing regions, where mining activity lasted until the 1980s. The Paglia River drains the eastern part of the district and is also the main western tributary of the Tiber River. Recent studies show that, still today, high total Hg contents severely affect the downstream ecosystems of these rivers. In November 2012, a major flood event occurred in the Paglia River basin, which drastically changed the river morphology and, possibly, the Hg concentrations. In the present work, stream sediment was sampled before and after the flood to evaluate possible changes in sediment total Hg concentrations as a consequence of this event. The comparison between pre- and post-flood Hg concentrations shows that Hg content increased up to an order of magnitude after the flood, suggesting that this event triggered Hg mobilization in the basin rather than its dilution.

Highlights

In recent decades, human civilization and a concomitant increase in industrial activity have gradually redistributed many toxic metals from the Earth’s crust to the environment, increasing the possibility of human exposure
The concentration of Hg in stream samples collected from the Paglia and Tiber rivers in 2012 pre-flood and in the 2013 post-flood campaigns is reported in Tables 1 and 2, respectively
Stream sediment with the lowest Hg concentrations (0.1 to 0.5 μg/g) are those collected from the eastern section of the Tiber River, which does not receive runoff from the Hg mines of the Mount Amiata mining district (MAMD) (Figure 2)

Summary

Introduction

Human civilization and a concomitant increase in industrial activity have gradually redistributed many toxic metals from the Earth’s crust to the environment, increasing the possibility of human exposure. The Paglia River has a key role in the transport of Hg, because it drains the south-eastern part of the MAMD, collecting water from different mines located at the head of its tributaries (Figure 2). This river has a torrential regime, especially in the upper mountain part [21], and in association with intense rainy events, flash floods are often documented [22]. In spite of its importance, until recently, no investigations have been carried out in the Tiber River basin to determine the impact of Hg transported by the Paglia River and to quantify the amount of Hg that is delivered to the Mediterranean Sea

Sample Collection

Sample Analysis

Results and Discussion

Conclusions