Skip to main content

A week of automated continuous measurements of temperature, pH and specific conductance in a mining-polluted river in Sardinia (Italy): The effect of rainfall as a case of serendipity Cover

.blurhash-client-img { display: none !important; }

A week of automated continuous measurements of temperature, pH and specific conductance in a mining-polluted river in Sardinia (Italy): The effect of rainfall as a case of serendipity

Volume 57 (2026): Issue 1 (January 2026)

By: Franco Frau

Open Access

|Jul 2026

Figures & tables

Figures & Tables

Schematic map of the Arburese mining district (black square in the inset with Sardinia) showing the location of the Casargiu mine, the sampling site CAS1 at the water outlet from the Casargiu mining gallery, the sampling sites from RIV1 to RIV9 along the Rio Irvi, and the RIV10 sampling site after the confluence of Rio Irvi with Rio Piscinas. The latter was completely dry during the sampling period.

(a) Water outlet from the Casargiu mining gallery (CAS1); (b and c) the RIV3 sampling site in the Rio Irvi where “green rust” formation is evident; (d) “Green rust” on 0.45-µm filter collected filtering water from the Rio Irvi at the RIV3 sampling site; (e) same filter as d after 24 h where the colour change is due to oxidation of Fe(II), present in the composition of the “green rust”, to Fe(II).

(a, b and d) The RIV10 sampling site in the Rio Irvi where precipitation of Fe(III)-hydroxides (HFO) is evident; (c) HFO collected on 0.45-µm filter filtering water from the Rio Irvi at the RIV10 sampling site.

Comparative patterns of temperature and specific conductance at the two sites RIV3 and RIV10 throughout the period of measurements with the multi-parameter sondes.

Comparative patterns of temperature and pH at the two sites RIV3 and RIV10, throughout the period of measurements with the multi-parameter sondes.

Measured and simulated pH patterns at the RIV10 site during a rainfall period.

Simulated variation of the saturation index (SI) of sulphate green rust at the RIV3 site as a consequence of dilution due to rainfall.

Comparative patterns of pH (a), temperature (b) and specific conductance (c) at the two sites RIV3 and RIV10 throughout the period of measurements with the multi-parameter sondes.

Chemical composition of Rio Irvi at the two sampling points RIV3 and RIV10

Old name		CAS4	CAS9
New name		RIV3	RIV10
Flow	L/s	55	58
T	°C	24.3	28.7
Eh	mV	183	498
pH		6.29	3.89
Cond	mS/cm	4.11	4.19
O₂	mg/L	7.23	7.36
TDS	g/L	5.43	5.27
Ca	mg/L	390	370
Mg	mg/L	252	246
Na	mg/L	78	93
K	mg/L	15	18
Cl	mg/L	87	132
Alk	mg/L	65
SO₄	mg/L	3,525	3,450
SiO₂	mg/L	17.5	19.2
Fe	mg/L	152	108
Mn	mg/L	70	68
Zn	mg/L	775	770
Cd	µg/L	2,110	1,940
Pb	µg/L	140	660
Ni	µg/L	2,480	2,320
Sb	µg/L	0.37	0.21
Co	µg/L	1,480	1,375

Ca	meq/L	19.46	18.46
Mg	meq/L	20.72	20.23
Na	meq/L	3.39	4.04
K	meq/L	0.38	0.46
Cl	meq/L	2.45	3.72
Alk	meq/L	1.07	0.00
SO₄	meq/L	73.44	71.88
Fe	meq/L	5.44	3.87
Mn	meq/L	2.55	2.48
Zn	meq/L	23.71	23.56
Σcat	meq/L	75.67	73.10
Σan	meq/L	76.96	75.60
Δ		−0.02	−0.03

Articles in this issue

DOI: https://doi.org/10.2478/mipo-2026-0004 | Journal eISSN: 1899-8526 | Journal ISSN: 1899-8291

Journal RSS Feed

Language: English

Page range: 36 - 47

Submitted on: Jan 23, 2026

|

Accepted on: Jun 14, 2026

|

Published on: Jul 8, 2026

Published by: Mineralogical Society of Poland

In partnership with: Paradigm Publishing Services

Publication frequency: Volume open

Keywords:

automated continuous measurements,

hydrogeochemical serendipity,

mining-polluted river,

rainfall effects

Related subjects:

© 2026 Franco Frau, published by Mineralogical Society of Poland
This work is licensed under the Creative Commons Attribution 4.0 License.

Volume 57 (2026): Issue 1 (January 2026)

Previous article