Volume 28 (2022): Edition 3 (December 2022)

For the present study, geochemical ages were derived from radiocarbon and radiokrypton age calibration with ground-water chemical contents (Na⁺, K⁺, Mg²⁺, Ca²⁺, Cl⁻, SO₄²⁻, HCO₃⁻). Geochemical ages may fill the dating gap (40–150 ka) between the isotope techniques mentioned. A case study of groundwater in the Baltic Artesian Basin has involved geochemical age calibration, data filtering (such as regional subdivision of the basin for more accurate results) and geochemical dating of groundwater of unknown age. Various approaches to interpretations of geochemical age results could be used. Bicarbonate and sulphate are sensitive to the hydrochemical environment and should be omitted from geochemical age calculations. Modern fresh groundwater samples should also be excluded from calibration in order to obtain more reliable trend lines. Calcium-sodium cation exchange occurs in deep aquifers and may be used for geo-chemical age determination of fossil groundwater.

Seen in the light of increasing anthropogenic impacts on the environment and a growing demand for potable water, pollution of groundwater is a very important issue, especially in large city areas. The present research includes analyses of the chemical composition at 109 measuring points in the Wrocław area, and of the spatial distribution of groundwater components with regard to land use, geological structure and hydrogeological conditions. Based on spatial analyses, it has been noted that changes depend mainly on land use and the kind of activity carried out in close proximity of water intake. Shallow groundwater in Wrocław is characterised by a great variability of main components. Factor analysis has made it possible to distinguish these components and determine the degree of their influence on the chemical composition of shallow groundwater in the entire study area. The current research demonstrates the high sensitivity of aquifers to pollution and emphasises the role of human activity in levels of groundwater pollution in urban areas.

The Shifting Sand is a barchan dune in Ngorongoro Lengai Geopark in Arusha, Tanzania. The geopark, a UNESCO World Heritage Site, is protected by the Ngorongoro Conservation Area Authority. The dune ranks amongst the main geosites that have been attracting numerous tourists; it formed as a result of volcanic ash eruptions that led to tephra deposition on a palaeosol (palaeosurface) in the Ootun area. The easterly winds modified the ash into dunes and headed to the Olduvai Gorge area. The age of the Shifting Sand dune is not known in detail. In the present study, we employ the radiocarbon (¹⁴C) dating method to date a subsurface palaeosol bed in the Ootun area where the tephra (i.e., original Shifting Sand materials) was originally deposited. An Accelerator Mass Spectrometer was used to determine the carbon-14 date of the palaeosol so as to estimate the age of the Shifting Sand dune, and an Energy Dispersive X-ray Fluorescent Spectrometer to determine the chemical composition of the Shifting Sand material and the tephra bed for correlative purposes. A radiocarbon (¹⁴C) date of 2510 ± 30 years BP for the Ootun palaeosol was obtained to estimate the minimum age of the Ootun subsurface tephra deposited in the area; since then, this started to move westwards towards the Olduvai Gorge area, where it is today defined as the Shifting Sand. The current findings add educational value to the Shifting Sand in Ngorongoro Lengai Geopark and improve our understanding of the eruption history of the Gregory Rift volcanoes.