Overview
Arsenic contamination of drinking water wells in Northern Italy’s Po Plain frequently exceeds the WHO guideline and EU drinking water directive limit of 10 µg/L, posing a health risk to local populations who rely on groundwater for potable supply. This study characterizes the microbial communities in six arsenic-contaminated wells and investigates the phylogenetic and functional potential of arsenic-transforming bacteria, particularly arsenic oxidizers, to understand the geomicrobiological drivers of arsenic mobilization in Alpine Pleistocene sediments.
Key numbers
- All six wells had arsenic concentrations above 10 µg/L (the EU drinking water limit under Directive 98/83/EC implemented in Italy as D.Lgs. 31/2001).
- Well sites: Brembio (LO), Paderno Ponchielli (CR1), Redondesco (MN, 182 m depth), Somma Lombardo (VA, 92 m depth), Pontevico (BS, 50 m depth), Pescarolo ed Uniti (CR2, 210 m depth).
- Well uses included potable supply (MN, VA, CR2), irrigation (CR1, BS), and livestock (LO).
- Arsenic speciation conducted by HPLC-ICP-MS on anion exchange column with As(III), As(V), and methylated arsenic species measured. Iron species measured spectrophotometrically.
- Arsenic mobilization attributed to dissimilatory reduction of As(V) and Fe(III) under low-redox, anaerobic conditions driven by organic matter decomposition.
- Pseudomonas was the most abundant genus at the most contaminated site; arsenic oxidase (aioA), arsenate reductase (arsC), and dissimilatory arsenate reductase (arrA) genes quantified by qPCR.
Methods (brief)
HPLC-ICP-MS (Bruker AURORA M90) with PRP-X100 anion exchange column for arsenic speciation; filtered (0.22 µm) non-acidified samples. 16S rRNA gene sequencing on Illumina MiSeq. qPCR quantification of functional arsenic genes (aioA, arsC, arrA, arsM). In situ measurement of pH, Eh, DO, EC. CARD-FISH for microbial community visualization.
Implications
Certification: Documents arsenic concentrations exceeding WHO/EU drinking water limits in Italian potable water wells. Relevant to supplier water quality audits in regions relying on Po Plain groundwater.
Courses: Illustrates the geomicrobiology of arsenic mobilization in sedimentary aquifers; relevant to water supply risk and irrigation water quality in European food production areas.
App: Drinking water from unmonitored wells in Northern Italy should be treated as a potential iAs exposure source, particularly in Po Plain agricultural areas.
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Update history
The five most recent substantive edits to this page, classified major (evidence or structure moved), correction (a published value or statement was wrong and has been fixed), or minor (narrative rewritten without changing the underlying evidence). Each description is derived from what the edit did to this page; the linked commit is the authoritative record, routine regeneration passes are excluded, and the full version history lives in git. When DOI minting comes online (see schema docs), each entry below will also link to a version-pinned DataCite DOI.
| Commit | Date | Change | Description |
|---|---|---|---|
| e317189 | 2026-08-11 | correction | 6 sections added; narrative text revised |