A study of iodine concentration in soils and drinking waters of the Mountainous Crimea

Iodine deficiency is the most common cause of endemic goiter and other diseases, largely due to the geographical features of the regions. Iodine deficiency diseases can occur not only in inland regions and high-altitude areas, but also in those regions where iodine is poorly involved in the food chains of the local population. Thus, for some territories, an important factor of iodine deficiency may be the diversity of rocks and the difference in soils and aquifers caused by them.

The purpose of the article is to identify the contrast in the concentration of iodine content in the soil cover and natural drinking waters in the Mountainous Crimea, on different rocks. Soil and water samples collected in several regions of the Mountainous Crimea, mostly in Bakhchisarai, were examined.

Samples of natural drinking water (n=34) were taken in three districts of the Mountainous Crimea (Bakhchisarai, Alushta and Simferopol) from various sources (rivers, wells, ponds, aqueduct) in 2017. Soil samples (n=23) were taken in the Bodrak River valley (Bakhchisarai district) from the upper horizons (sampling depth up to 20 cm) in 2019. Iodine was determined by kinetic thiocyanate-nitrite method in the laboratory of the Institute of Geochemistry of the Russian Academy of Sciences.

The iodine content in the surveyed drinking water sources corresponds to the existing standards (2-10 μg/l), however, for some sources, extremely low values of iodine content are observed (both for wells 0.89 μg/l and for private pumps and aqueduct 1.11 μg/L), which can be determined primarily by the composition of the water-bearing rocks. The highest median values are marked for springs (Me=5.34 μg/L; n=8) and rivers (Me=6.77 μg/L; n=8), the lowest for aqueduct (Me=1.74 μg/L; n=7). The high variability of iodine in the soils of the automorphic landscapes of the Crimean Mountains was established from 0.43 mg/kg (mountain cambisols) to 15.4 mg/kg (regosols), depending on the humus content and the pH. The highest median values are marked for regosols (Me=5.6 mg/kg; n=13) and cambisols (Me=1.7 mg/kg; n=6), the lowest for fluvisols (Me=1.1 mg/kg; n=4).

The dependence of the iodine content in the upper horizons of different types of soils, primarily on the content of humus and soil pH-water, has been established. It has been confirmed that the content of iodine in natural waters is primarily determined by the difference in aquifers. The study was carried out without financial support, with the partial support of the Laboratory of Biogeochemistry of the Russian Academy of Sciences, which provided equipment for measuring iodine.