Investigation of hydrochemistry and uranium radioactivity in the groundwater of Namaqualand, Northern Cape, South Africa
Year: 2012
Type: dissertation
Abstract: The demand for groundwater in South Africa has increased over the years, \nmainly in the arid, semi-arid and rural areas of the country. Groundwater is \ngenerally considered a safe and viable option to untreated surface water. \nGroundwater samples analyzed were limited to inorganic chemicals, stable \nisotopes and radiological constituents. Dissolved inorganic constituents and \nparameters analyzed included major anions and cations, trace metals, and \nphysico-chemical parameters. Inorganic constituents were analyzed to provide \nbasic information pertaining to water chemistry. \nThe hydrochemistry of the area indicates that groundwater evolution is taking \nplace and dissolution, ion exchange and mixing processes are the driving \nprocesses. Br-/Cl- ratio show that the salinity in the area is derived from seawater \nmixing, halite dissolution and atmospheric deposition/sea aerosol spray. Under \nexcessive evaporative regimes, as experience in the study area some of the \ngroundwater is heading towards hypersaline waters. \nIsotopes analyses disclosed two groundwater flow types, deep and shallow \ngroundwater flow. The data further revealed groundwater mixing within the \naquifer where there is no direct infiltration (the samples have undergone \nfractionation due to evaporation before infiltration), recharge in the area results \nfrom regional flow from the neighboring catchments. . The age of the \ngroundwater calculated from average tritium of the local rainfall of 28.32 TU, \nranges from 87.01 to 174.02 years. \nGross alpha and beta emitters were detected in the water samples and are likely \nattributed to naturally occurring uranium isotopes present in the water. The \nradioactivity in the area is background activity, i.e. it is very low and is from the \nrock material. \n \nUranium occurs in high concentrations in the groundwater of the study area, \nranges from 1 μg/l to 146 μg/l, which is above the WHO drinking water standard. \nData analysis show that uranium occur as UO2 \n+(c), UO2OH+, and U(OH)5 \n- \ncomplexes in the absence of other complexing agents. In the presents of \ncarbonates uranium is found in solution as UO2 \n+, UO2CO3 and UO2(CO3)2 \n2- and \nUO2(CO3)3 \n4- complexes.
Author: Joyce Leshomo
Language: English
Subfield: Geochemistry and Petrology
Field: Earth and Planetary Sciences
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W2248848031