The acidic waters in Italy: a brief overview

The present study is aimed at providing a brief overview of the Italian acidic waters based on literature and unpublished data. Acidic waters in Italy, as elsewhere, are relatively common and associated with extremely variable geological settings. Owing to their peculiar features, these waters may seriously affect the environment and the ecosystems. Along the Apennine belt, the western and inner sectors of the Italian peninsula record an anomalous geothermal gradient, mostly overlapping with the Neogene-to-present magmatism, that explains the presence of a huge amount of CO2(H2S)-rich gas and thermal water discharges, geothermal fields (e.g. Larderello and Mt. Amiata) and ore deposits (e.g. Fe- and polymetallic sulfides, e.g. Elba Island and Colline Metallifere). Acidic waters (pH ≤5) from volcanic and geothermal areas show outlet temperatures and Total Dissolved Solids (TDS) from 10 to 96°C and <1 to ≈30 g/L, respectively, with a chemical composition usually belonging to the Ca-SO4, NH4-SO4 or Na-Cl facies. Frequently, they are related to bubbling and boiling pools due to the interaction between deepsourced gases and shallow aquifers or meteoric waters. Concentrations of heavy metals and metalloids are in most cases high. Extremely high contents of metals are also recorded for those acidic waters that characterize the main Italian mining districts, mostly located in Sardinia (not included in the present study), Tuscany and NW Alps, where they are related to Acid Mine Drainage l.s. or Acid Rock Drainage. The pH values are as low as 2.08, with variable TDS concentrations. Compositionally, they are Na-SO4, Ca(Mg)-SO4, and/or Mg(Ca)-SO4 waters, prevalently due to oxidative processes affecting polymetallic sulfides.

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Small-scale field evaluation of geochemical blending of waste rock to mitigate acid rock drainage potential

Geochemistry Exploration Environment Analysis ◽

10.1144/geochem2021-066 ◽

2021 ◽

pp. geochem2021-066

Author(s):

S.J. Day

Keyword(s):

Acid Rock Drainage ◽

Field Evaluation ◽

Waste Rock ◽

Small Scale ◽

Proof Of Concept ◽

Acidic Water ◽

Acid Rock ◽

Acid Generation ◽

Acidic Waters ◽

Critical Consideration

Blending of potentially acid generating (PAG) waste rock with non-PAG waste rock to create a rock mixture which performs as non-PAG is a possible approach to permanent prevention of acid rock drainage (ARD) for PAG waste rock. In 2012, a field weathering study using 300 kg samples was implemented at Teck Coal's Quintette Project located in northeastern British Columbia, Canada to test the prevention of acid generation in the PAG waste rock by dissolved carbonate leached from overlying non-PAG waste rock and direct neutralization of acidic water from PAG waste rock by contact with non-PAG waste rock.After eight years of monitoring the experiments, the layered non-PAG on PAG barrels provided proof-of-concept that as the thickness of the PAG layer increases relative to the thickness of the non-PAG layers, acidic waters are more likely to be produced. The PAG on non-PAG layering has resulted in non-acidic water and no indications of metal leaching despite accelerated oxidation in the PAG layer shown by sulphate loadings. The study has demonstrated that the scale of heterogeneity of PAG and non-PAG materials is a critical consideration for providing certainty that rock blends designed to be non-PAG will perform as non-PAG in perpetuity. This is contrary to the standard paradigm in which an excess of acid-consuming minerals is often considered sufficient alone to ensure ARD is not produced.

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Effects of acid mine drainage on clay minerals suspended in the Tinto River (Río Tinto, Spain). An experimental approach

Clay Minerals ◽

10.1180/000985599546118 ◽

1999 ◽

Vol 34 (1) ◽

pp. 99-108 ◽

Cited By ~ 41

Author(s):

E. Galan ◽

M. I. Carretero ◽

J . C. Fernandez-Caliani

Keyword(s):

Acid Mine Drainage ◽

Mine Drainage ◽

Drainage Basin ◽

Acid Rock Drainage ◽

Chemical Degradation ◽

Acid Rock ◽

Tinto River ◽

Acid Mine ◽

Mineral Stability ◽

Water Ph

AbstractThe Tinto river is one of the most polluted stream environments in the world, as a result of both acid mine drainage and natural acid rock drainage. Two representative samples from the phyllosilicate-rich rocks exposed in the drainage basin (Palaeozoic chlorite-bearing slates and Miocene smectite-rich marls) were treated with acid river water (pH = 2.2) for different times to constrain the effects of extreme hydrogeochemical conditions on clay mineral stability. Illite and kaolinite did not show appreciable variations in their crystal chemistry parameters upon treatment. Chlorite underwent an incipient chemical degradation evidenced by the progressive loss of Fe in octahedral positions coupled with a shortening of the b unit-cell parameter, although no weathering products of chlorite were observed. Smectite and calcite were rapidly and fully dissolved thus neutralizing the water acidity, and subsequently Fe and Al oxy-hydroxides and opaline silica precipitated from the aqueous solution, together with a neoformed amorphous silicate phase largely enriched in Al and Mg.

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Acid mine drainage mitigation: A review

Ingeniería Industrial ◽

10.26439/ing.ind2020.n039.4917 ◽

2020 ◽

pp. 97-118

Author(s):

Daniel Lazo

Keyword(s):

Acid Mine Drainage ◽

Large Scale ◽

Mine Drainage ◽

Acid Rock Drainage ◽

Human Beings ◽

Mining Operations ◽

Aquatic Life ◽

Acid Rock ◽

Sulphide Minerals ◽

Acid Mine

Acid mine drainage (AMD) or acid rock drainage (ARD) refers to the effluents from coal and metal mines. AMD is a common phenomenon which occurs naturally as a process of rock weathering, but is increased in large scale due to human activities such as construction contracts (transportation corridors, dam build, etc.) and mining operations. This phenomenon denotes the acidic water that is produced during exposure of sulphide minerals (mainly pyrite) to air and water through a natural process, and creates sulphuric acid. AMD is a hazard to animals, aquatic life and human beings as it increases the acidity and dissolves metals. Preventing and treating AMD is an important issue in a mine site not only during operation life but also after the mine is abandoned.

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