This study analyzed manganese in Finnish groundwater using the national geological survey database: about 5300 single samples from private wells and about 4600 repeated samples from monitoring sites. Drilled bedrock wells had much higher manganese than springs and dug wells, and concentrations at a single well could vary greatly between years and seasons. The authors conclude that one measurement may not reveal a well’s manganese status and that total and dissolved manganese should both be measured.
Key numbers
- Combined data, median (maximum): drilled bedrock wells 26.8 µg/L (5800 µg/L; n = 2671); dug wells 5.93 µg/L (5330 µg/L; n = 2771); springs 0.56 µg/L (3760 µg/L; n = 2195); captured springs 1.59 µg/L (2530 µg/L; n = 657); tube wells in clay-covered aquifers 2.49 µg/L (6560 µg/L; n = 241) (Table 1, p. 1198).
- Single samples from bedrock wells: median 28.4 µg/L, mean 100 µg/L, SD 224, 98th percentile 638 µg/L, maximum 5800 µg/L (n = 2291) (Table 2, p. 1199).
- Exceedances in single samples: about 41% of bedrock wells and 17% of wells in Quaternary sediments exceeded the Finnish quality recommendation of 50 µg/L; 28% and 11% exceeded the 100 µg/L maximum recommendation for small units and private wells (Results, p. 1196). For wells in Quaternary sediments, 3% exceeded 400 µg/L (p. 1199).
- Monitoring wells: bedrock well water in Kemijärvi ranged 114 to 352 µg/L, dug well water in Hämeenkoski 8.77 to 2640 µg/L (Abstract).
- Detection limit 0.02 µg/L by ICP-MS/AES (Methods, p. 1195).
- Values as reported by the paper: the Finnish recommendation is technical and aesthetic, there is no Finnish health-based standard, and the World Health Organization health-based value is 400 µg/L, for which WHO did not derive a formal guideline (Introduction, p. 1195).
Methods (brief)
Data came from the Geological Survey of Finland groundwater database. All included samples (after 1991) were analyzed by ICP-MS or ICP-AES with a 0.02 µg/L detection limit. Field pH and dissolved oxygen were recorded for subsets. Statistics were nonparametric, with Spearman correlations.
Evidence fitness
The paper supports national occurrence data for manganese in private well and spring water in Finland, differences by well type, the inverse association with dissolved oxygen, and large year-to-year variation. It does not assess intake or health outcomes, and municipal supplies are outside its scope.
Limitations
Samples from springs and dug wells may reflect well construction, and bedrock samples taken from taps may reflect plumbing and pressure tanks. Acid sulfate coastal areas with high manganese are not covered by the monitoring network. Bedrock geology was not examined in detail.
Related evidence
- Manganese
- Water
- ICP-MS — Inductively coupled plasma mass spectrometry
- ICP-OES — optical emission spectrometry
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