BERmon20 Cumulative geological, regional and site-specific factors affecting groundwater quality in domestic wells in Finland
Korkka-Niemi Kirsti, 2001.
Monographs of the Boreal Environment Research No. 20, p. 98.
URN:ISBN:9521109424. The publication is available also in printed form (ISBN 952-11-0942-4).
Groundwater quality in domestic wells and the reasons for problems in this respect are described on the scale of an individual household well using an extensive database of 1421 wells. The water quality in these wells is compared with that reported in the late 1950’s in order to assess longterm changes, and a comparison is made between the dug wells (N = 1096) and the bedrock wells (N = 325). The possibility of seasonal changes is assessed by comparing analyses of water taken from the same 423 wells at three seasons of the year.
Only 37.2 % of the wells fulfilled all the hygienic and technical requirements and recommendations for drinking water. Statistical evaluation of the water quality analyses and background data obtained from questionnaires and geological maps points to five water quality factors contributing to the conclusions reached in the survey: salinity, redox, pH, pollution and contamination. These correspond to a combination of specific geological, regional and site-specific factors which together are manifested as cumulative effects operating at particular locations. All the layers of factors are represented to various extents in each well.
Well owners can modify the site-specific factors and ameliorate their effects by keeping their wells in a good state of repair, addressing problems of insufficient aeration and eliminating any nearby sources of pollution. Such measures can affect the microbiological quality of the well water, the amounts of nitrogen compounds contained in it, its turbidity, KMnO4 consumption and in part its Al, Fe and Mn concentrations, but it is not possible to influence the state of oxidation in the aquifer (affecting turbidity, colour, KMnO4 consumption, Fe and Mn, SO4 and NO3 ) or any of the extra-regional factors such as the chemical composition of the soil and bedrock or present or relict marine influence (F, Al, SO4 ,Cl, Na, K, Mn, Fe, alkalinity, pH and total hardness). The seasonal variation in quality variables in individual wells is likely to be greater than the seasonal variation in the aquifers, which emphasises the vulnerability of the wells.