Determination of trace elements in ground drinking water in Norway

Abstract

Drinking water is essential for life. However, unless standard quality of drinking water is maintained, water can be associated with health risks. The present study was conducted to determine primarily inorganic elements in Norwegian ground drinking water in a nationwide investigation including 201 well works. In addition, indicators of water quality such as pH, conductivity, alkalinity, turbidity, and color were also determined. Water samples were collected from the source (raw water) and from distribution network (clean/treated water) and analyzed for 64 inorganic elements using inductively coupled plasma-Mass spectrometry (ICP-MS). Anions (F-, NO3- and SO42-) were measured using Ion chromatography (IC). The results show that aluminum (Al), manganese (Mn), copper (Cu), iron (Fe), nickel (Ni), and arsenic (As) had concentrations exceeding the Norwegian drinking water regulation limits. While the concentration of sodium (Na), boron (B), calcium (Ca), selenium (Se), antimony (Sb), cadmium (Cd), and chromium (Cr) were within the regulation limits. Moreover, the concentration of uranium (U) was higher than WHO and US drinking water guidelines at three waterworks and at seven waterworks compared to Canada water guideline. Among anions, fluoride (F-) concentration was higher than the regulation limit at four waterworks. Considering water quality indicators, color was within the regulation limit set by heath authorities in Norway. However, 40 out of 201 (20%) of the waterworks, 91 out of 201 (45%) waterworks, and 1 out of 201 (0.5%) waterworks, had levels above the regulation for conductivity, alkalinity, and turbidity, respectively. Moreover, the pH was lower than the regulation limit at six waterworks. In general, the geological composition of bedrock and quaternary aquifers are among the factor affecting the level of elements. In particular, the concentrations of trace elements, such as Ni, Cd, Pb, As, Cr, and Sb were high in bedrock aquifers from mica schist, augengneiss, tonalite, and amphibolite, phylite, and granite rocks. Similarly, higher concentration of elements such as Al, Zn, Mn, and Cu was found in Quaternary aquifers such as marine deposits and fluvial deposits compared to bedrock aquifers. The concentrations of F- and U were high in bedrock aquifers were gneiss, granites, amphibolite and granite to tonalities rocks dominant. Drinking water samples from bedrock aquifers in coastal areas had high concentration for elements such as Na, I, Br, B, SO42-, and Cl. The concentration of Na and Cl, Br and I increase in coastal marine derived areas and decrease with the distance to ocean. Multivariate statistical analyses such as principal component analysis (PCA) was applied to 34 elements from clean water (treated water) and 33 elements from raw water analyzed by ICP-MS from 201 waterworks .PCA were used in order to describe the variability of measured elements. 51 % of the variability among the waterworks were explained by PC1 (35%) and PC2 (16 %) for clean water, and 58 % of the variability were explained by PC1 (39%) and PC2 (19 %) for raw water. Correlation loadings plot suggests high correlation exist between Al and REE, between the elements Cu, Zn and Mn and between U, K, Na and Cs.