Natural background levels for chemicals in Icelandic aquifers

Abstract

Information about natural background levels (NBLs) of chemicals in source waters allows water utilities to identify trends in drinking water contamination. We estimate NBLs for chemicals in source waters for Icelandic water utilities at both national levels with all data pooled, and according to geological regime. NBLs were derived by collecting samples from 79 aquifers considered largely unimpacted by human activities. The aquifers were categorized into four geological settings that are representative of the geology of Iceland. NBLs were calculated as 90%iles of all aquifers in each setting and in all pooled. There was a statistical difference between the geological settings in 11 parameters of 37 tested. The 90%ile for nitrate for all aquifers pooled was 1.36 mg/l, indicating little anthropogenic influence on water used for public water supply in Iceland. The results were compared to the chemical status of 60 European aquifers, collected for the European Union's Sixth Framework Program Background Criteria for the Identification of Groundwater Thresholds project, revealing lower dissolved solids concentration for Icelandic groundwater than that from other parts of Europe. The explanation is likely due to high permeability of young geology settings and low population density in Iceland whereas there is a long history of agriculture and industry in most European countries.

Chemical quality and regulatory compliance of drinking water in Iceland

“…Estimates of natural background levels (NBLs) from a recent study of 79 Icelandic aquifers were added (Gunnarsdottir et al, 2015c).…”

“…In the Reykjanes peninsula median concentration for the elements abundant in sea; chloride, sodium, sulphate, potassium, magnesium, sulphur and strontium is four to ten times higher than median for all data. Natural origin includes also high alkalinity, especially in Pleistocene aquifers (Gunnarsdottir et al, 2015c). Chromium and selenium are usually higher in the younger geological areas compare to other areas and aluminum is significantly higher in the Pleistocene areas (Gunnarsdottir et al, 2015c).…”

“…Natural origin includes also high alkalinity, especially in Pleistocene aquifers (Gunnarsdottir et al, 2015c). Chromium and selenium are usually higher in the younger geological areas compare to other areas and aluminum is significantly higher in the Pleistocene areas (Gunnarsdottir et al, 2015c). Mercury is found in geothermal steam that can travel long distances and has been detected in Iceland (Olafsson, 1992).…”

“…Analysis of water from 79 aquifers in Iceland demonstrated TDS between 4 and 140 mg/l with median 75 mg/l, hardness is 90% of the time below 2,8°dH and the average temperature is 4.6°C with the range between 2 to 10°C (Gunnarsdottir et al 2015c). This TDS would be classified according to the EU mineral water directive as "very low" to "low mineral content" (EC, 2009).…”

“…In general groundwater from basaltic rock has lower chemical concentrations of major elements compared to many other rock types (Reimann et al 1996) and Icelandic groundwater has low chemical content compared to many other countries, it is also very soft and has low temperature. The concentration of total dissolved solids (TDS) is higher in the geologically young regions (Postglacial) were there is higher content of glassy rocks than in other regions (Sigurðsson and Sigurbjarnason, 1989;Gíslason et al, 1996;Oskarsdottir et al, 2011;Gunnarsdottir et al, 2015c). Precipitation with marine components has considerable incluence on chemical status of groundwater in Iceland due to meteorological conditions (Sigurdsson & Einarsson, 1988) and proximity of aquifers to the sea.…”