Mercury Dispersion through Streams Draining The Mt. Amiata District, Southern Tuscany, Italy

Abstract The Mt. Amiata area hosts the 3 rd largest Hg district in the world, overlapping with a present-day geothermal system that is exploited for energy production. Mining activity ceased in 1980; remediation of mining areas was only partial, and is still under way. A significant transport of mercury is documented in the streams draining the district. By far the largest output occurs to the southeast in the Paglia River catchment; this river is tributary of Tiber River, the largest river of central Italy. A much smaller transport occurs to the north, in the Orcia-Ombrone catchment. Most transport is in particulate form; mercury is temporarily stored in stream and overbank sediments, and can be significantly mobilized and redistributed by extreme events such as flash floods. Transfer to the biosphere and food chain is not negligible, as some fish in Paglia and Tiber Rivers show Hg contents that may be harmful for human consumption. The overall output from the Monte Amiata district represents a significant contribution to the Mediterranean Sea budget of this metal

Experimental simulation of arsenic desorption from Quaternary aquifer sediments following sea water intrusion

Alluvial sediments from the coastal area in southern Tuscany (Italy) characterized by a significant As anomaly (As >500 mg/kg) are subjected to seawater intrusion due to groundwater exploitation. Sequential extractions and kinetic experiments were carried out on Quaternary alluvial sediments to quantify the interaction between As oxianions (adsorbed on mineral surfaces) and Clâ\u88\u92in solutions and to establish if this mechanism may contribute to the release of As in groundwater. The natural water-rock interaction in the aquifer was simulated in two experiments by saturating the samples with four solutions with increasing chlorinity for different time. Firstly, a rapid change in the aquifer salinity (e.g. fast seawater intrusion, groundwater over pumping) was simulated by an interaction sediment/solution of 24 h. Solutions with Clâ\u88\u92â\u89¤2000 mg/L extracted up to 76 μg/kg of As, while seawater (Sol 4(24): Clâ\u88\u92â\u88¼18,500 mg/L) extracted up to 161 μg/kg of As. In a second experiment, the ingression of water with increasing salinity in the acquifer, followed by the withdrawal of the water after progressively longer interaction times with the aquifer sediments, was simulated. The timing of the As-Cl reaction was constrained by saturating the samples with four solutions with increasing salinity (Sol1(84): Clâ\u88\u92â\u88¼0 mg/L; Sol2(84)Clâ\u88\u92= 250 mg/L; Sol3(84)Clâ\u88\u92= 2000 mg/L; Sol4(84): Clâ\u88\u92= 15,886 mg/L) that interacted with the sediment samples for longer saturation times (up to 21 days for each solution). After saturation with the previous three solutions up to 62 μg/kg of As were extracted by seawater, following a salinity increase from 2000 mg/L Cl to a chlorinity close to seawater, representing â\u88¼60% of the exchangable As fraction in the sediments. Our results constrained the timing of sediment/solution interaction of As desorption and showed that after a rapid intrusion of seawater or after a relatively long period of interaction with saline solutions an aquifer with similar geology releases in groundwater concentrations of As exeeding the 10 μg/L limit for drinking water. Also, this study estimated the potential effects caused by the ingression of seawater in lowland alluvial coastal areas induced by groundwaters exploitation or by extreme weather events. Such information is crucial for management authorities to mitigate and predict the effects of As hazard in groundwater driven by changes in the environmental aquifer conditions (e.g. seasonal fluctuations of the water table and/or changes in salinity of coastal aquifers), which are becoming increasingly frequent as consequence of climate change

Marble slurry impact on groundwater: the case-study of Apuan Alps karst aquifers (Italy)

Modern sawing techniques employed in ornamental stones’ exploitation produce large amounts of slurry that can be potentially diffused into the environment by runoff water. Slurry produced by limestone and marble quarrying can impact local karst aquifers, negatively affecting the groundwater quality and generating a remarkable environmental and economic damage. A very representative case-study is that of the Apuan Alps (north-western Tuscany, Italy) because of the intensive marble quarrying activity. The Apuan Alps region extends over about 650 km2; it hosts several quarries, known all over the world for the quality of the marble extracted, and a karst aquifer producing about 70,000 m3/day of high-quality water used directly for domestic purposes almost without treatments. In addition, Apuan Alps are an extraordinary area of natural and cultural heritage hosting many caves (about 1200), karst springs and geosites of international and national interest. During intense rain events, carbonate slurry systematically reaches the karst springs, making them temporarily unsuitable for domestic uses. In addition, the deterioration of the water quality threatens all the hypogean fauna living in the caves. This paper provides preliminary insights of the hydrological and biological indicators that can offer information about the impact of the marble quarrying activities on groundwater resources, karst habitats and their biodiversity