Physicochemical parameters and stable isotope composition of water in Northern Mara Sub-Goldfield, Tanzania: Implications for groundwater-surface water interaction

Justine L Myovela,Mohamedi Salimu,Godson Godfray

doi:10.5194/egusphere-egu22-1280

Abstract

&lt;p&gt;This study focuses on water quality assessment and hydrological aspects around northern Mara Sub-Goldfield (Tanzania). A total of 26 water samples were collected from different sampling sites for physicochemical characterization and H-O isotopes analysis. Parameters such as pH, electrical conductivity (EC), Total Dissolved Solids (TDS), Total Suspended Solids (TSS), and total hardness were analyzed for each water sample. The &lt;sup&gt;18&lt;/sup&gt;O/&lt;sup&gt;16&lt;/sup&gt;O and&amp;#160;&lt;sup&gt;2&lt;/sup&gt;H/&lt;sup&gt;1&lt;/sup&gt;H ratios were measured in water samples and expressed as&amp;#160;&amp;#948;&lt;sup&gt;18&lt;/sup&gt;O and&amp;#160;&amp;#948;&lt;sup&gt;2&lt;/sup&gt;H relative to Vienna Standard Mean Ocean Water (V-SMOW). The study revealed that the majority of drinking water sources meet the recommended World Health Organization (WHO) and Tanzania Bureau of Standards (TBS) levels. Drinking water from Kegonga community borehole (pH=6.62, EC=1690 &amp;#181;s/cm, TDS=1080 mg/l), shallow well east of Ingwe Dam (pH=7.32, EC=1720 &amp;#181;s/cm, TDS= 1000mg/l), shallow well south of tailings dams (pH=7.6, EC=2670 &amp;#181;s/cm, TDS=1780 mg/l) and traditional well (pH=5.76) are not suitable for drinking purposes. Isotopic values of studied water samples have shown a wide variation from -28.5 to 21.4 &amp;#8240; for &amp;#948;&lt;sup&gt;2&lt;/sup&gt;H, -5.37 to 2.37 for &amp;#948;&lt;sup&gt;18&lt;/sup&gt;O &amp;#8240;, and -3.7 to 16.08 &amp;#8240; for D-excess values. The slope of Local Meteoric Water Line (&amp;#948;&lt;sup&gt;2&lt;/sup&gt;H = 5. 9 &amp;#948;&lt;sup&gt;18&lt;/sup&gt;O + 5.51; R&lt;sup&gt;2&lt;/sup&gt;=0.94) is slightly lower than the slope of Global Meteoric Water Line (&amp;#948;&lt;sup&gt;2&lt;/sup&gt;H = 8.2 &amp;#948;&lt;sup&gt;18&lt;/sup&gt;O + 11.27; R&lt;sup&gt;2&lt;/sup&gt;=1), which indicates that the majority of studied water samples have been isotopically modified. The study demonstrated that the majority of groundwater has been recharged by more evaporated sources likely wastewater from tailings dams. This finding is supported by the consistency of isotopic signature and physicochemical parameters of several groundwater sources with those of surface water discharged from the mines.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Keywords&lt;/strong&gt;: groundwater-surface water interaction; water quality; stable isotopes; d-excess; Tanzania&lt;/p&gt;

Full Text