| Title | Sources of geogenic arsenic in well water associated with granitic bedrock from Nova Scotia, Canada |
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| Author | Maciag, B J ;
Brenan, J M; Parsons, M B; Kennedy, G W |
| Source | Science of the Total Environment vol. 887, 163943, 2023 p. 1-11, https://doi.org/10.1016/j.scitotenv.2023.163943 |
| Image |  |
| Year | 2023 |
| Alt Series | Natural Resources Canada, Contribution Series 20220520 |
| Publisher | Elsevier |
| Document | serial |
| Lang. | English |
| Media | paper; digital; on-line |
| File format | pdf |
| Province | Nova Scotia |
| NTS | 10M; 11D; 11E; 20P; 21A; 21H |
| Area | Port Mouton |
| Lat/Long WENS | -65.9981 -62.0372 45.1231 43.1453 |
| Subjects | Science and Technology; general geology; hydrogeology; mineralogy; arsenic; bedrock geology; groundwater pollution; groundwater; cordierite; pyrite; South Mountain Batholith; Port Mouton
Pluton |
| Illustrations | location maps; charts; cross-plots; satellite imagery; graphs; tables; diagrams |
| Program | Environmental
Geoscience Program Management |
| Released | 2023 05 06 |
| Abstract | Arsenic toxicity in drinking water is a global issue, with chronic exposure causing cancer and other health concerns. Groundwater from geochemically similar granites from mainland Nova Scotia, Canada,
can have high and low levels of arsenic. The origin of this variation is uncertain, but different mineral hosts for arsenic could explain the disparity. The lability of arsenic from different minerals was assessed using laser ablation inductively
coupled plasma mass spectrometry combined with calculations based upon well water data. Pyrite has the highest arsenic concentration (mean: 2,300 µg/g, n=9), is unstable in the groundwater system, and can release arsenic during oxidation. However,
oxidation products replacing pyrite can adsorb arsenic, modifying the amount released. Cordierite has low arsenic concentrations (mean: 7.3 µg/g, n=5) but is abundant and relatively soluble. Thus, cordierite could be a previously unrecognized source
of arsenic in metapelitic rocks from metamorphic terranes. Pyrite from one of the granites studied was not oxidized, which in addition to the absence of cordierite in these same granites could account for the lower arsenic levels observed in
associated well water. The results of this study can be used to identify potential geogenic sources of arsenic in other granitic terranes and reduce the risk of exposure through drinking water. |
| Summary | (Plain Language Summary, not published)
This paper examines the origin of naturally occurring arsenic in well water from granitic bedrock. In Nova Scotia, more than 30% of wells developed in
granite have arsenic concentrations that exceed the Canadian Drinking Water Quality Guideline of 10 micrograms per litre (10 µg/L). Understanding the source of this arsenic is important, as exposure to arsenic levels above the drinking water
guideline can lead to adverse health effects including lung, bladder, and liver cancer. In this study, we measured the arsenic concentration in various minerals found in Nova Scotian granites associated with both high and low groundwater arsenic
concentrations. Laboratory and modeling investigations show that both pyrite and cordierite (a previously unrecognized host of arsenic) have a significant amount of arsenic and are soluble under local groundwater conditions. The results of this study
can be used to help predict arsenic contamination of well waters in granitic terranes and to mitigate the risk of exposure through drinking water. |
| GEOSCAN ID | 331356 |
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