Concentrations and migration forms of strontium in groundwater used for drinking within the Moscow artesian basin (Russia, Bryansk region)

The geochemical features of stable strontium distribution in groundwater of the Upper Devonian hydrogeological complex within the southwestern flank of the Moscow artesian basin used for centralized drinking water supply in the northeastern part of the Bryansk region were considered in order to detail the potential influence of additional geochemical factors on the manifestation of endemic decease caused by natural iodine deficiency.

Strontium concentration in water samples varied from 0.21 to 28.8 mg/l (median (Me) = 1.03 mg/l, n=34). The analysis of strontium distribution with considering the genetic features of water-bearing rocks showed no significant differences in the content of this element in the waters of depositions of the Frasnian (Me=0.86 mg/l, n=25) and Famennian stages (Me=1.09 mg/l, n=9) (p<0.01). The main sources of strontium in investigated groundwater are strontium-containing minerals (celestine) or strontium impurities in limestones of varying degrees of gypsification associated with the Upper Devonian carbonate rocks (Sr correlation with SO₄: r_<0.05=0.78). The maximum levels of strontium, which significantly exceed the Russian hygienic standard for drinking waters (7 mg/l), were detect in groundwater of Famennian sediments of the Rognedinsky district of the Bryansk region (>20 mg/l). Given the lack of significant correlation between strontium content and water salinity, which is usually observed for strontium-enriched artesian waters of regional hydrogeochemical provinces (Kraynov et al., 2012) it can be explained by the existence of natural local strontium anomaly in this area (Сa/Sr <7).

Membrane filtration of water samples allowed suggesting that strontium migrate in fresh and low-salinity waters mainly within dissolved fraction of groundwater (divalent cation and complexes with sulfate, chloride and hydrocarbonate) with sizes not exceeding 0.45 µm.

The presence of a local anomaly of strontium-containing waters within the Moscow artesian basin, which impair the quality of drinking water in this area, can be a factor of potential risk to the health of the local population living under conditions of iodine deficiency.

 

The reported study was funded by the Vernadsky Institute federal budget (research task #0137-2019-0006). The Field work was partly funded by RFBR and BRFBR project #20-55-00012 and BRFBR project # Х20Р-386.